Kingrex T20 type T amp. I bought this to use as an amp for computer audio but I never used it. This does not come with the PSU and is not the USB models. This unit has gold plated RCA in. I have heard these amp with the supplied converter and with the PSU and I heard absolutely no difference so I did not order the $300 PSU. Most of the reviews that go on and on about how much better they sound with the PSU are really based on the manufacturer giving free PSUs with the review sample of the amp and the reviewer thanking the manufacturer with the review to help them double their revenue. The converter is not a wall wart type but rather a sizable in line type. The amp sounds splendid on its own. I equate raving about the PSU improvements to people raving about how much better a speaker sounds if you add a $1000 solid gold spade to the cable to replace a $15 solid silver spade or spending hundred os dollars for little wood blocks that hold the speaker cables off the floor- utter nonsense and I have been an audiophile since the early 70s and I am a musician as well with perfect pitch. Retail on these $399 (for one) in 2007 Inputs RCA Gold PlatedOutputs- Banana Plug Gold Plated Included Power Supply 100-240 V output 12V 3ATHD+N 0.03% @ 10W 4 OhmTHD+N 0.1% @12 W 4 OhmIHF-IM 0.18% @1W 4 OhmOutput 22W@4 Ohm, 10% THD+N, VDD=13.5 V 13W@8 Ohm, 10% THD+N, VDD=13.5VEfficiency 88%@12W 8 Ohm 81%@20W 4 OhmDynamic Range = 99dBOver current and over temperature protection6 mm thickness aluminum face plate and aluminum knob with audio grade capacitor 6 Moons review and additional review links below Reviewer: David Kan Digital Source: Philips DVP-9000S, Apple PowerBook G4, Acer TravelMate 3010 notebook Preamp: Audio Zone Pre T-1, Dared SL-2000A Speakers: Loth-X BS-1, Klipsch Synergy F2, Dynaudio Facette Cables: Luscombe LBR-35 interconnect, Clear Audio Silver Line interconnect, OCOS speaker cables by Dynaudio Power Cords: stock power cords, Unity Audio Link [on loan] Power Line Conditioning: Monster Power HTS-1000 MkII Room Size: 15 x 13.5 x 8 diagonal set up Part I: KingRex T20U U for ubiquitous. U for unprecedented. U for unbelievable. U for USB. The KingRex T20U is basically the same as the Tripath-based T20 integrated amp but with an onboard USB interface and DAC. USB has plugged into our so-called modern living and taken over. Audio devices with USB interface are becoming commonplace. Weve seen tube amps and outboard converters with USB inputs. But combining a USB DAC with a Tripath amp is definitely unprecedented. It makes so much sense that one should ask, what took you. The fact that the T20U is priced at $245, a mere 25 bucks more than the T20, is absolutely unbelievable. Opening up the black boxes to quickly compare the two further hammered home one simple mathematical fact: theres no way I would take the trouble to build my own USB DAC even if you paid me 25 smackers.Before we actually look at the DAC portion of the T20U, lets see whats wrong with computer sound cards from an audiophiles perspective. Why would we need the U in the T20? If one wanted to play music from a computer through a mainstream audio system, simply connecting the audio-out of the computer to an input of the audio system will give sound. Alas, the sound card or audio device installed in the computer is not - um, dedicated enough. In the audiophiles cookbook, theres no multi-tasking. Duo core do more? No, thank you. For audiophiles, less is more! A typical sound card these days (or the AC97 chip mounted to the motherboard) is hardly just stereo. Whether you like it, need it or ever use it, it comes with 5.1 or 7.1 capability for gaming and movies, a synthesizer and MIDI interface for music making, analog-to-digital conversion for recording and digital-to-analog conversion for playback. For audiophiles, anything but the latter are unnecessary evils and unsolicited sources of interference. To shut off these back doors to block unwanted noise and distortion, an outboard digital-to-analog converter that receives digital signals via USB seems a welcome proposition. Instead of creating another standalone DAC that takes up extra space and one more AC power outlet, KingRex took a shortcut and build the DAC inside the T20 Tripath amp - shortcut in the sense that it saves you a pair of interconnects (could you buy a decent pair with $25?). Shortcut in the sense that the signal path from the DACs output stage to the Tripath chip is as short as five centimeters. Fitting snugly inside the same compact chassis of 180 x 138 x 45mm, the amp and DAC come to you all in one piece - plus a free USB cable and the standard AC/DC adapter.Sitting side by side with their bonnets removed, one can easily spot that in addition to the DAC circuit, the original Tripath amp section has been modified. The two input coupling capacitors have been changed from electrolytics to metalized polypropylene films for better frequency response. There are also four high-current inductors for demodulating the switching waveform into the audio signal. The high-current type ensures more headroom for the Tripath chip to perform with maximum output capabilities. What kind of DAC does $25 buy you? The heart of the T20U DAC is the Burr-Brown PCM2702E, a familiar choice for USB-ready amps including Dareds MP-5 and its many OEM reincarnations. Lets face it, the PCM2702E has very conservative specs. Its merely a 32/44.1/48kHz ready 16-bit stereo DAC with USB interface, on-chip clock generator, 8 times oversampling digital interpolation filter and analog low-pass output filter. Knowing that the AC97 chip supports 96kHz/20-bit stereo resolution, these seven-years old specs might give techno freaks cold feet. Not me. One of my reference CD players, the Restek Radiant, is also a 44.1kHz/16-bit affair and more than 14 years old. . Yet its still putting a lot of newer players to shame. The best part of the KingRex design is the use of a 12MHz crystal resonator as the clock source for the PCM2702E. It works with the on-chip crystal oscillator to generate a stable low-jitter clock for internal PLL and DAC operation from the USB interface audio data, freeing them from the computers inferior anti-audio clock. As we said, the PCM2702E is dedicated to stereo and we like it that way. In terms of measurable typical performance, the PCM2702E renders a set of numbers that satisfies the Redbook requirement: 100dB dynamic range, 105dB S/N ratio (both A-weighted) and 103dB channel separation. By the way, the PCM2702E is USB 1.0 compliant. The DAC chip has a large internal storage buffer to store up audio packets and you wont need the higher speed USB 2.0 so even less up-to-date computers can plug n play. Leaving the DAC chip via the low-pass filters, the analog two-channel signals are handed over to the Burr-Brown OPA2134 operational amplifier which acts as output stage preamp and low-pass filter, taking out the residual digital garbage and turning the audio signal into the analogue stream. To make sure the audio signals are clean without a DC stage, a pair of Texas TL072 low-noise dual JFET op amps are assigned to the DC servo circuit. Every DIYer knows how changing the op amp will change the sonic characteristics. KingRex adeptly left that option open by making it a plug-in feature on the circuit board. In addition to the USB interface, the T20U has one set of line inputs. Both the input sockets and toggle switch are located on the rear panel, keeping the front panel as clean as the T20s. Input selection is electronically executed by a relay. Chip rolling Last time, KingRex kindly sent me two T20s and two PSUs for bi-amping per my request. This time, they sent me two T20Us and two updated PSUs without asking and added two extra Burr-Brown OPA2604 op amps to roll with the factory-fitted OPA2314. I soon realized that I could not bi-amp with USB. PC or Mac, I could select but one audio output device. (The USB hub would still connect to one randomly). Still, I could enjoy the convenience of comparing the OPA2314 and OPA2604 by setting up two amps with different op amps. KingRex chief engineer James Lee told me to switch on the T20U before booting up the computer to insure that the USB device would be recognized. I followed his instruction but thought he might be too precautionary. Both PC and Mac detected the T20U without problem even if I booted up the computer first. On my PowerBook, when two amps were connected via two USB ports, both were detected as Burr-Brown Japan PCM2707 USB. On my Acer laptop, they were recognized as USB speaker and USB speaker (2). The PowerBook had no problem switching between the two. Even with music playing continuously, switching back and forth required merely a click. The Acer was more temperamental. Sometimes it switched after the music stopped or it wouldnt switch at all unless rebooted. Using a USB switch connected to one USB port was slightly better at times. The USB switch is not a USB hub but a push-button selector. The USB hub didnt help. It just connected me to one USB interface. By the way, the operation system on the PowerBook is Mac OS 10.3.9. On the Acer, its Windows XP Professional. Would Vista recognize the USB better? Perhaps. ames also advised me to disable the computer sound card or audio device to avoid interference. That was possible only with my PC. Apple only selects one audio output device at a time. Theres no option for enabling or disabling other devices. Does that mean the remainder is automatically disabled? Im clueless. After the USB audio output is selected, volume and L/R channel balance can still be adjusted. That probably indicates that the volume and balance settings are carried out in the digital domain. It is therefore wise to set the volume to maximum to optimize the 16-bit word length. So, this was the setup: Mac PowerBook, two USB cables, T20U with OPA2134 and T20U with OPA2604 both running on PSU, each driving a pair of identical Loth-X BS-1. I conducted a blind comparison by labeling the chips on the back of the amps and then shuffling them. During the audition, they were identified as chip A and chip B. Their identity was only revealed at the end. Since I always have my Loth-X stacked in DAppolito arrays, I just left them like that and hooked up chip A to the top pair, chip B to the bottom pair for direct comparison. I swapped the speaker connections at random to make sure placement (the top pair was higher and inverted) would not play tricks on my ears. I picked five CDs, selected a few tracks from each, ripped them to MP3 and WAV, saved them to the hard disk of the PowerBook and compared the different file formats with the original CDs played on the PowerBook super drive. One CD in particular was also converted to FLAC and EAC for more extensive comparison with the original CD played from the PowerBook as well as from the Philips DVP-9000S SACD/CD player – for the sake of USB DAC vs. Philips DSD upsampling. The Philips was only connected to the line input of one of the T20U since that didnt involve the OPA2134 or OPA2604. If thats not too complicated, lets continue, shall we? hat somehow made the caressing passages in Barcarola more intimate. Chip B cleared up vocal and piano separation. Sonic elements were distilled and reasonably well-defined. The piano came to life with leaping, galloping and bouncing notes so characteristic of Rossini as in Lorgia and La pastorella. CD playback on the PowerBook showed further improvements. Vocals were silky and piano sounded like pearly droplets. Better soundstage and layering turned the simple home gathering into a musical event. The difference between chip A and chip B was almost indiscernible except that the piano in La danza: Tarantella seemed more sparkling. Gavin Bryars The Sinking of the Titanic [Point Muisc 446-061-2] could be the tribute to the band that kept on playing the hymn Autumn as the ship went down in the North Atlantic. This Episcopal hymn played here on three violas and two cellos forms the base upon which other materials are superimposed - including fragments of interviews with survivors, sound effects reconstructed according to survivors and speculations (the impact of the iceberg, engine room sounds and bagpipers aboard) and realized on various instruments, from bass clarinet to Korg keyboard. Though monothematic yet full of imaginations and noble humanity, the music is strangely peaceful. I picked five tracks: Opening, Titanic Hymn, Titanic Lament, Last Hymn and Coda. MP3 playback was again disappointing. There was almost insufficient resolution to distinguish the subtleties between stringed instruments above water and underwater. Miscellaneous sound effects had no details. The WAV files shed more lights on the nuances. That luminous sheen on the strings above water was restored. The hollow strings under water once again reverberated in the more sound-efficient medium. The dark hue over the sound effects was removed. Original CD playback on the PowerBook further exemplified the true magic of this very quiet recording full of nuances. Woodblocks, tam-tam, bells, marimba, water gongs and the very occasional electric guitar, no matter how subtle, were faithfully and meticulously presented. Chip A versus chip B was almost pointless at any level except that B, for some unknown reason, seemed to be louder and delivering more energy in the mid to lower frequencies. GianCarlo Menotti who just passed away in February this year at the age of 96, was the most performed operatic composer of his era. Yet his ballet Sebastian [ASV CD DCA 741] was unjustly neglected. This is probably the only recording available thanks to conductor José Serebrier and the London Symphony Orchestra. Menotti painted this hauntingly beautiful ballet with romantic melodies, operatic drama and inventive orchestration. Sebastian is the love story about the Prince and notorious Venetian courtesan whose evil sisters conspire to intercept the alliance with black magic by piercing a wax image of their sister with arrows. Sebastian the Moorish slave, secretly in love with the courtesan, substitutes himself for the wax figure, takes the lethal arrows and breaks the evil power. The ballet is only 36 minutes long and hardly contains one inane note. MP3 playback depicted a compressed sound image even though Menottis ingeniously appointed tonal palette was somewhat preserved. The WAV file improved the soundstage dramatically. With chip A, instrument placement was well articulated across the breadth of the stage but fell flat from front to back. Chip B opened up the soundstage even more and defined front to back layering more proficiently if not superbly. CD playback on PowerBook had the soundstage fully restored to 3D, with chip A being more dynamic and chip B more detailed. As in Barcarolle, string bowings and harp plucking were vividly portrayed. Time for the final show down between the $25 USB DAC and the $1,000 CD/SACD player. Marianne Thorsen/TrondheimSolistenes Mozart Violin Concertos [2L 38] was chosen to be the reference software for two simple reasons: artistic brilliance and sonics extraordinaire. While most Mozart interpreters try too hard to please by portraying Mozart as a wide-eye innocent porcelain doll, the young Norwegian violinist dares to tell it like it is. This is the most original Mozart with true zest for life. However, MP3 playback on chip A did no justice to this superb recording. The strings sounded coarse. Chip B sounded marginally more refined. WAV saw little improvement, with chip A still sounding lightweight and chip B just adding minor body. On the whole, WAV sounded impatient and strung up. Then I tried FLAC. This is the technical part I could use help with. Correct me if Im wrong. When converting approximately 750MB of audio data to MP3, file size is reduced to roughly 1/3rd. WAV and EAC are the same as the original. FLAC is about half. Yet FLAC sounds way better than WAV and EAC. It might have something to do with the software I used to play back FLAC. FLAC -- Free Lossless Audio Codec -- is basically encoded WAV in a lossless but compressed file. I used Amadeus II for playback. Even when the Sound Characteristics were set to the original 16-bit/44.1kHz, the FLAC playback outperformed WAV and EAC with decisively more mellowness and finesse. At times, I even might say that it outperformed the original CD playback on the PowerBook. If you still follow, let me further complicate the picture by saying that the difference between chip A and chip B was more evident with FLAC, with B offering richer harmonics and finer texture. Yet this is not the complete story of FLAC. Original CD playback through the Philips was clearly the winner with its DSD upsampling at work. Superb 2-channel multi-channel SACD playback, excellent Red Book performance plus selectable upsampling to 24-bit/96KHz or DSD bit-stream only found on machines ten times its price make this piece of exceptional hardware the most desirable hybrid player of all times. Why Philips pulled it off the market in under one year has me befuddled. But prepare yourself for more mind-boggling phenomena. Back to FLAC. The Amadeus II is a sound recording and editing software for Mac only. One of its many functions is recoding the sampling size and rate. I used that to upsample the FLAC audio data to 24-bit/96kHz and played it back on chip B. Guess what, the result was so close to the Philips DSD upsampling, the latter only excelled by a smidgen of resolution. I was puzzled at first. How on earth could the upsampled 24/96 FLAC audio data have any effect on the 16/44 DAC and churn out such awesome performance? Then I thought of the EMI 24-bit digital remastered CDs, the Japanese K2 series and the like. By the same token, the final making of these CDs is all in Red Book format but the prior upsampling remastering process somehow improves the sound. The real difference is from FLAC to KingRex USB/DAC - pure digital transmission skipping the error-inducing injection molding of pits and bumps and laser tracking mechanism. Time to reveal the op amp identity. Chip A was OPA2134 and chip B was OPA2604, the latter being regarded as the better op amp by DIY consensus. As a low-pass filter, the OPA2604 enjoys a reputation of being very analog sounding, with refined resolution and musicality. Its great news that after I completed my first course in chip-rolling, KingRex decided on the OPA2604 as production standard. In fact, any low-noise JFET or CMOS dual input op amps that fit the 8-pin DIP socket can be rolled. Its been reported that OPA2227 and LM4562 are very good choices so its just a matter of finding one to suit your tastes. Even so, the $25 DAC didnt beat the Philips SACD/CD player but we knew that to be an unfair comparison right from the start. However, any CD player no matter how advanced will devolve into obsolescence the day you put your money down. With the KingRex T20U, you are buying into more than a chip-rolling USB DAC. You are opening up the unlimited realm of many newer and more advanced audio codecs and playback softwares to come. FLAC and Amadeus II are only the two I know of - and I am such a computer idiot. The latest Amadeus II and Amadeus Pro are equipped with 24-bit/192kHz upsampling. Im sure more options already exist for both Mac and PC. And more are bound to follow.Part I: Conclusion I have given my highest commendation to the KingRex T20 by honoring it with the Blue Moon Award for heart-warming tube sound from a cold-running Class-T amp. The T20U is the same amp, only more truthful to the category of integrated amp by offering a second input via its USB interface. If you fancy listening to music from your computer and upgrading your listening pleasure, simply think of the T20U as the best $245 USB DAC money can buy - and the award-winning Tripath amp comes with it gratis. For curiositys sake, I did compare the line input of the T20U with the T20 but have nothing to report. Not only is the difference itself negligible and meaningless, the need for reporting it is pointless. You either need USB or you dont. If you are sure youll never need USB, save yourself $25. If you are not sure, the extra $25 pays for a good insurance policy. https://www.diy-audio-guide.com/kingrex-t20u-review.html https://www.hifivision.com/threads/kingrex-t20u-review.22380/ https://www.tnt-audio.com/ampli/kingrext20_e.html

Kingrex T20 type T amp. I bought this to use as an amp for computer audio but I never used it. This does not come with the PSU and is not the USB models. This unit has gold plated RCA in. I have heard these amp with the supplied converter and with the PSU and I heard absolutely no difference so I did not order the $300 PSU. Most of the reviews that go on and on about how much better they sound with the PSU are really based on the manufacturer giving free PSUs with the review sample of the amp and the reviewer thanking the manufacturer with the review to help them double their revenue. The converter is not a wall wart type but rather a sizable in line type. The amp sounds splendid on its own. I equate raving about the PSU improvements to people raving about how much better a speaker sounds if you add a $1000 solid gold spade to the cable to replace a $15 solid silver spade or spending hundred os dollars for little wood blocks that hold the speaker cables off the floor- utter nonsense and I have been an audiophile since the early 70s and I am a musician as well with perfect pitch. Retail on these $399 (for one) in 2007 Inputs RCA Gold PlatedOutputs- Banana Plug Gold Plated Included Power Supply 100-240 V output 12V 3ATHD+N 0.03% @ 10W 4 OhmTHD+N 0.1% @12 W 4 OhmIHF-IM 0.18% @1W 4 OhmOutput 22W@4 Ohm, 10% THD+N, VDD=13.5 V 13W@8 Ohm, 10% THD+N, VDD=13.5VEfficiency 88%@12W 8 Ohm 81%@20W 4 OhmDynamic Range = 99dBOver current and over temperature protection6 mm thickness aluminum face plate and aluminum knob with audio grade capacitor 6 Moons review and additional review links below Reviewer: David Kan Digital Source: Philips DVP-9000S, Apple PowerBook G4, Acer TravelMate 3010 notebook Preamp: Audio Zone Pre T-1, Dared SL-2000A Speakers: Loth-X BS-1, Klipsch Synergy F2, Dynaudio Facette Cables: Luscombe LBR-35 interconnect, Clear Audio Silver Line interconnect, OCOS speaker cables by Dynaudio Power Cords: stock power cords, Unity Audio Link [on loan] Power Line Conditioning: Monster Power HTS-1000 MkII Room Size: 15 x 13.5 x 8 diagonal set up Part I: KingRex T20U U for ubiquitous. U for unprecedented. U for unbelievable. U for USB. The KingRex T20U is basically the same as the Tripath-based T20 integrated amp but with an onboard USB interface and DAC. USB has plugged into our so-called modern living and taken over. Audio devices with USB interface are becoming commonplace. Weve seen tube amps and outboard converters with USB inputs. But combining a USB DAC with a Tripath amp is definitely unprecedented. It makes so much sense that one should ask, what took you. The fact that the T20U is priced at $245, a mere 25 bucks more than the T20, is absolutely unbelievable. Opening up the black boxes to quickly compare the two further hammered home one simple mathematical fact: theres no way I would take the trouble to build my own USB DAC even if you paid me 25 smackers.Before we actually look at the DAC portion of the T20U, lets see whats wrong with computer sound cards from an audiophiles perspective. Why would we need the U in the T20? If one wanted to play music from a computer through a mainstream audio system, simply connecting the audio-out of the computer to an input of the audio system will give sound. Alas, the sound card or audio device installed in the computer is not - um, dedicated enough. In the audiophiles cookbook, theres no multi-tasking. Duo core do more? No, thank you. For audiophiles, less is more! A typical sound card these days (or the AC97 chip mounted to the motherboard) is hardly just stereo. Whether you like it, need it or ever use it, it comes with 5.1 or 7.1 capability for gaming and movies, a synthesizer and MIDI interface for music making, analog-to-digital conversion for recording and digital-to-analog conversion for playback. For audiophiles, anything but the latter are unnecessary evils and unsolicited sources of interference. To shut off these back doors to block unwanted noise and distortion, an outboard digital-to-analog converter that receives digital signals via USB seems a welcome proposition. Instead of creating another standalone DAC that takes up extra space and one more AC power outlet, KingRex took a shortcut and build the DAC inside the T20 Tripath amp - shortcut in the sense that it saves you a pair of interconnects (could you buy a decent pair with $25?). Shortcut in the sense that the signal path from the DACs output stage to the Tripath chip is as short as five centimeters. Fitting snugly inside the same compact chassis of 180 x 138 x 45mm, the amp and DAC come to you all in one piece - plus a free USB cable and the standard AC/DC adapter.Sitting side by side with their bonnets removed, one can easily spot that in addition to the DAC circuit, the original Tripath amp section has been modified. The two input coupling capacitors have been changed from electrolytics to metalized polypropylene films for better frequency response. There are also four high-current inductors for demodulating the switching waveform into the audio signal. The high-current type ensures more headroom for the Tripath chip to perform with maximum output capabilities. What kind of DAC does $25 buy you? The heart of the T20U DAC is the Burr-Brown PCM2702E, a familiar choice for USB-ready amps including Dareds MP-5 and its many OEM reincarnations. Lets face it, the PCM2702E has very conservative specs. Its merely a 32/44.1/48kHz ready 16-bit stereo DAC with USB interface, on-chip clock generator, 8 times oversampling digital interpolation filter and analog low-pass output filter. Knowing that the AC97 chip supports 96kHz/20-bit stereo resolution, these seven-years old specs might give techno freaks cold feet. Not me. One of my reference CD players, the Restek Radiant, is also a 44.1kHz/16-bit affair and more than 14 years old. . Yet its still putting a lot of newer players to shame. The best part of the KingRex design is the use of a 12MHz crystal resonator as the clock source for the PCM2702E. It works with the on-chip crystal oscillator to generate a stable low-jitter clock for internal PLL and DAC operation from the USB interface audio data, freeing them from the computers inferior anti-audio clock. As we said, the PCM2702E is dedicated to stereo and we like it that way. In terms of measurable typical performance, the PCM2702E renders a set of numbers that satisfies the Redbook requirement: 100dB dynamic range, 105dB S/N ratio (both A-weighted) and 103dB channel separation. By the way, the PCM2702E is USB 1.0 compliant. The DAC chip has a large internal storage buffer to store up audio packets and you wont need the higher speed USB 2.0 so even less up-to-date computers can plug n play. Leaving the DAC chip via the low-pass filters, the analog two-channel signals are handed over to the Burr-Brown OPA2134 operational amplifier which acts as output stage preamp and low-pass filter, taking out the residual digital garbage and turning the audio signal into the analogue stream. To make sure the audio signals are clean without a DC stage, a pair of Texas TL072 low-noise dual JFET op amps are assigned to the DC servo circuit. Every DIYer knows how changing the op amp will change the sonic characteristics. KingRex adeptly left that option open by making it a plug-in feature on the circuit board. In addition to the USB interface, the T20U has one set of line inputs. Both the input sockets and toggle switch are located on the rear panel, keeping the front panel as clean as the T20s. Input selection is electronically executed by a relay. Chip rolling Last time, KingRex kindly sent me two T20s and two PSUs for bi-amping per my request. This time, they sent me two T20Us and two updated PSUs without asking and added two extra Burr-Brown OPA2604 op amps to roll with the factory-fitted OPA2314. I soon realized that I could not bi-amp with USB. PC or Mac, I could select but one audio output device. (The USB hub would still connect to one randomly). Still, I could enjoy the convenience of comparing the OPA2314 and OPA2604 by setting up two amps with different op amps. KingRex chief engineer James Lee told me to switch on the T20U before booting up the computer to insure that the USB device would be recognized. I followed his instruction but thought he might be too precautionary. Both PC and Mac detected the T20U without problem even if I booted up the computer first. On my PowerBook, when two amps were connected via two USB ports, both were detected as Burr-Brown Japan PCM2707 USB. On my Acer laptop, they were recognized as USB speaker and USB speaker (2). The PowerBook had no problem switching between the two. Even with music playing continuously, switching back and forth required merely a click. The Acer was more temperamental. Sometimes it switched after the music stopped or it wouldnt switch at all unless rebooted. Using a USB switch connected to one USB port was slightly better at times. The USB switch is not a USB hub but a push-button selector. The USB hub didnt help. It just connected me to one USB interface. By the way, the operation system on the PowerBook is Mac OS 10.3.9. On the Acer, its Windows XP Professional. Would Vista recognize the USB better? Perhaps. ames also advised me to disable the computer sound card or audio device to avoid interference. That was possible only with my PC. Apple only selects one audio output device at a time. Theres no option for enabling or disabling other devices. Does that mean the remainder is automatically disabled? Im clueless. After the USB audio output is selected, volume and L/R channel balance can still be adjusted. That probably indicates that the volume and balance settings are carried out in the digital domain. It is therefore wise to set the volume to maximum to optimize the 16-bit word length. So, this was the setup: Mac PowerBook, two USB cables, T20U with OPA2134 and T20U with OPA2604 both running on PSU, each driving a pair of identical Loth-X BS-1. I conducted a blind comparison by labeling the chips on the back of the amps and then shuffling them. During the audition, they were identified as chip A and chip B. Their identity was only revealed at the end. Since I always have my Loth-X stacked in DAppolito arrays, I just left them like that and hooked up chip A to the top pair, chip B to the bottom pair for direct comparison. I swapped the speaker connections at random to make sure placement (the top pair was higher and inverted) would not play tricks on my ears. I picked five CDs, selected a few tracks from each, ripped them to MP3 and WAV, saved them to the hard disk of the PowerBook and compared the different file formats with the original CDs played on the PowerBook super drive. One CD in particular was also converted to FLAC and EAC for more extensive comparison with the original CD played from the PowerBook as well as from the Philips DVP-9000S SACD/CD player – for the sake of USB DAC vs. Philips DSD upsampling. The Philips was only connected to the line input of one of the T20U since that didnt involve the OPA2134 or OPA2604. If thats not too complicated, lets continue, shall we? hat somehow made the caressing passages in Barcarola more intimate. Chip B cleared up vocal and piano separation. Sonic elements were distilled and reasonably well-defined. The piano came to life with leaping, galloping and bouncing notes so characteristic of Rossini as in Lorgia and La pastorella. CD playback on the PowerBook showed further improvements. Vocals were silky and piano sounded like pearly droplets. Better soundstage and layering turned the simple home gathering into a musical event. The difference between chip A and chip B was almost indiscernible except that the piano in La danza: Tarantella seemed more sparkling. Gavin Bryars The Sinking of the Titanic [Point Muisc 446-061-2] could be the tribute to the band that kept on playing the hymn Autumn as the ship went down in the North Atlantic. This Episcopal hymn played here on three violas and two cellos forms the base upon which other materials are superimposed - including fragments of interviews with survivors, sound effects reconstructed according to survivors and speculations (the impact of the iceberg, engine room sounds and bagpipers aboard) and realized on various instruments, from bass clarinet to Korg keyboard. Though monothematic yet full of imaginations and noble humanity, the music is strangely peaceful. I picked five tracks: Opening, Titanic Hymn, Titanic Lament, Last Hymn and Coda. MP3 playback was again disappointing. There was almost insufficient resolution to distinguish the subtleties between stringed instruments above water and underwater. Miscellaneous sound effects had no details. The WAV files shed more lights on the nuances. That luminous sheen on the strings above water was restored. The hollow strings under water once again reverberated in the more sound-efficient medium. The dark hue over the sound effects was removed. Original CD playback on the PowerBook further exemplified the true magic of this very quiet recording full of nuances. Woodblocks, tam-tam, bells, marimba, water gongs and the very occasional electric guitar, no matter how subtle, were faithfully and meticulously presented. Chip A versus chip B was almost pointless at any level except that B, for some unknown reason, seemed to be louder and delivering more energy in the mid to lower frequencies. GianCarlo Menotti who just passed away in February this year at the age of 96, was the most performed operatic composer of his era. Yet his ballet Sebastian [ASV CD DCA 741] was unjustly neglected. This is probably the only recording available thanks to conductor José Serebrier and the London Symphony Orchestra. Menotti painted this hauntingly beautiful ballet with romantic melodies, operatic drama and inventive orchestration. Sebastian is the love story about the Prince and notorious Venetian courtesan whose evil sisters conspire to intercept the alliance with black magic by piercing a wax image of their sister with arrows. Sebastian the Moorish slave, secretly in love with the courtesan, substitutes himself for the wax figure, takes the lethal arrows and breaks the evil power. The ballet is only 36 minutes long and hardly contains one inane note. MP3 playback depicted a compressed sound image even though Menottis ingeniously appointed tonal palette was somewhat preserved. The WAV file improved the soundstage dramatically. With chip A, instrument placement was well articulated across the breadth of the stage but fell flat from front to back. Chip B opened up the soundstage even more and defined front to back layering more proficiently if not superbly. CD playback on PowerBook had the soundstage fully restored to 3D, with chip A being more dynamic and chip B more detailed. As in Barcarolle, string bowings and harp plucking were vividly portrayed. Time for the final show down between the $25 USB DAC and the $1,000 CD/SACD player. Marianne Thorsen/TrondheimSolistenes Mozart Violin Concertos [2L 38] was chosen to be the reference software for two simple reasons: artistic brilliance and sonics extraordinaire. While most Mozart interpreters try too hard to please by portraying Mozart as a wide-eye innocent porcelain doll, the young Norwegian violinist dares to tell it like it is. This is the most original Mozart with true zest for life. However, MP3 playback on chip A did no justice to this superb recording. The strings sounded coarse. Chip B sounded marginally more refined. WAV saw little improvement, with chip A still sounding lightweight and chip B just adding minor body. On the whole, WAV sounded impatient and strung up. Then I tried FLAC. This is the technical part I could use help with. Correct me if Im wrong. When converting approximately 750MB of audio data to MP3, file size is reduced to roughly 1/3rd. WAV and EAC are the same as the original. FLAC is about half. Yet FLAC sounds way better than WAV and EAC. It might have something to do with the software I used to play back FLAC. FLAC -- Free Lossless Audio Codec -- is basically encoded WAV in a lossless but compressed file. I used Amadeus II for playback. Even when the Sound Characteristics were set to the original 16-bit/44.1kHz, the FLAC playback outperformed WAV and EAC with decisively more mellowness and finesse. At times, I even might say that it outperformed the original CD playback on the PowerBook. If you still follow, let me further complicate the picture by saying that the difference between chip A and chip B was more evident with FLAC, with B offering richer harmonics and finer texture. Yet this is not the complete story of FLAC. Original CD playback through the Philips was clearly the winner with its DSD upsampling at work. Superb 2-channel multi-channel SACD playback, excellent Red Book performance plus selectable upsampling to 24-bit/96KHz or DSD bit-stream only found on machines ten times its price make this piece of exceptional hardware the most desirable hybrid player of all times. Why Philips pulled it off the market in under one year has me befuddled. But prepare yourself for more mind-boggling phenomena. Back to FLAC. The Amadeus II is a sound recording and editing software for Mac only. One of its many functions is recoding the sampling size and rate. I used that to upsample the FLAC audio data to 24-bit/96kHz and played it back on chip B. Guess what, the result was so close to the Philips DSD upsampling, the latter only excelled by a smidgen of resolution. I was puzzled at first. How on earth could the upsampled 24/96 FLAC audio data have any effect on the 16/44 DAC and churn out such awesome performance? Then I thought of the EMI 24-bit digital remastered CDs, the Japanese K2 series and the like. By the same token, the final making of these CDs is all in Red Book format but the prior upsampling remastering process somehow improves the sound. The real difference is from FLAC to KingRex USB/DAC - pure digital transmission skipping the error-inducing injection molding of pits and bumps and laser tracking mechanism. Time to reveal the op amp identity. Chip A was OPA2134 and chip B was OPA2604, the latter being regarded as the better op amp by DIY consensus. As a low-pass filter, the OPA2604 enjoys a reputation of being very analog sounding, with refined resolution and musicality. Its great news that after I completed my first course in chip-rolling, KingRex decided on the OPA2604 as production standard. In fact, any low-noise JFET or CMOS dual input op amps that fit the 8-pin DIP socket can be rolled. Its been reported that OPA2227 and LM4562 are very good choices so its just a matter of finding one to suit your tastes. Even so, the $25 DAC didnt beat the Philips SACD/CD player but we knew that to be an unfair comparison right from the start. However, any CD player no matter how advanced will devolve into obsolescence the day you put your money down. With the KingRex T20U, you are buying into more than a chip-rolling USB DAC. You are opening up the unlimited realm of many newer and more advanced audio codecs and playback softwares to come. FLAC and Amadeus II are only the two I know of - and I am such a computer idiot. The latest Amadeus II and Amadeus Pro are equipped with 24-bit/192kHz upsampling. Im sure more options already exist for both Mac and PC. And more are bound to follow.Part I: Conclusion I have given my highest commendation to the KingRex T20 by honoring it with the Blue Moon Award for heart-warming tube sound from a cold-running Class-T amp. The T20U is the same amp, only more truthful to the category of integrated amp by offering a second input via its USB interface. If you fancy listening to music from your computer and upgrading your listening pleasure, simply think of the T20U as the best $245 USB DAC money can buy - and the award-winning Tripath amp comes with it gratis. For curiositys sake, I did compare the line input of the T20U with the T20 but have nothing to report. Not only is the difference itself negligible and meaningless, the need for reporting it is pointless. You either need USB or you dont. If you are sure youll never need USB, save yourself $25. If you are not sure, the extra $25 pays for a good insurance policy. https://www.diy-audio-guide.com/kingrex-t20u-review.html https://www.hifivision.com/threads/kingrex-t20u-review.22380/ https://www.tnt-audio.com/ampli/kingrext20_e.html

Kingrex T20 type T amp. I bought this to use as an amp for computer audio but I never used it. This does not come with the PSU and is not the USB models. This unit has gold plated RCA in. I have heard these amp with the supplied converter and with the PSU and I heard absolutely no difference so I did not order the $300 PSU. Most of the reviews that go on and on about how much better they sound with the PSU are really based on the manufacturer giving free PSUs with the review sample of the amp and the reviewer thanking the manufacturer with the review to help them double their revenue. The converter is not a wall wart type but rather a sizable in line type. The amp sounds splendid on its own. I equate raving about the PSU improvements to people raving about how much better a speaker sounds if you add a $1000 solid gold spade to the cable to replace a $15 solid silver spade or spending hundred os dollars for little wood blocks that hold the speaker cables off the floor- utter nonsense and I have been an audiophile since the early 70s and I am a musician as well with perfect pitch. Retail on these $399 (for one) in 2007 Inputs RCA Gold PlatedOutputs- Banana Plug Gold Plated Included Power Supply 100-240 V output 12V 3ATHD+N 0.03% @ 10W 4 OhmTHD+N 0.1% @12 W 4 OhmIHF-IM 0.18% @1W 4 OhmOutput 22W@4 Ohm, 10% THD+N, VDD=13.5 V 13W@8 Ohm, 10% THD+N, VDD=13.5VEfficiency 88%@12W 8 Ohm 81%@20W 4 OhmDynamic Range = 99dBOver current and over temperature protection6 mm thickness aluminum face plate and aluminum knob with audio grade capacitor 6 Moons review and additional review links below Reviewer: David Kan Digital Source: Philips DVP-9000S, Apple PowerBook G4, Acer TravelMate 3010 notebook Preamp: Audio Zone Pre T-1, Dared SL-2000A Speakers: Loth-X BS-1, Klipsch Synergy F2, Dynaudio Facette Cables: Luscombe LBR-35 interconnect, Clear Audio Silver Line interconnect, OCOS speaker cables by Dynaudio Power Cords: stock power cords, Unity Audio Link [on loan] Power Line Conditioning: Monster Power HTS-1000 MkII Room Size: 15 x 13.5 x 8 diagonal set up Part I: KingRex T20U U for ubiquitous. U for unprecedented. U for unbelievable. U for USB. The KingRex T20U is basically the same as the Tripath-based T20 integrated amp but with an onboard USB interface and DAC. USB has plugged into our so-called modern living and taken over. Audio devices with USB interface are becoming commonplace. Weve seen tube amps and outboard converters with USB inputs. But combining a USB DAC with a Tripath amp is definitely unprecedented. It makes so much sense that one should ask, what took you. The fact that the T20U is priced at $245, a mere 25 bucks more than the T20, is absolutely unbelievable. Opening up the black boxes to quickly compare the two further hammered home one simple mathematical fact: theres no way I would take the trouble to build my own USB DAC even if you paid me 25 smackers.Before we actually look at the DAC portion of the T20U, lets see whats wrong with computer sound cards from an audiophiles perspective. Why would we need the U in the T20? If one wanted to play music from a computer through a mainstream audio system, simply connecting the audio-out of the computer to an input of the audio system will give sound. Alas, the sound card or audio device installed in the computer is not - um, dedicated enough. In the audiophiles cookbook, theres no multi-tasking. Duo core do more? No, thank you. For audiophiles, less is more! A typical sound card these days (or the AC97 chip mounted to the motherboard) is hardly just stereo. Whether you like it, need it or ever use it, it comes with 5.1 or 7.1 capability for gaming and movies, a synthesizer and MIDI interface for music making, analog-to-digital conversion for recording and digital-to-analog conversion for playback. For audiophiles, anything but the latter are unnecessary evils and unsolicited sources of interference. To shut off these back doors to block unwanted noise and distortion, an outboard digital-to-analog converter that receives digital signals via USB seems a welcome proposition. Instead of creating another standalone DAC that takes up extra space and one more AC power outlet, KingRex took a shortcut and build the DAC inside the T20 Tripath amp - shortcut in the sense that it saves you a pair of interconnects (could you buy a decent pair with $25?). Shortcut in the sense that the signal path from the DACs output stage to the Tripath chip is as short as five centimeters. Fitting snugly inside the same compact chassis of 180 x 138 x 45mm, the amp and DAC come to you all in one piece - plus a free USB cable and the standard AC/DC adapter.Sitting side by side with their bonnets removed, one can easily spot that in addition to the DAC circuit, the original Tripath amp section has been modified. The two input coupling capacitors have been changed from electrolytics to metalized polypropylene films for better frequency response. There are also four high-current inductors for demodulating the switching waveform into the audio signal. The high-current type ensures more headroom for the Tripath chip to perform with maximum output capabilities. What kind of DAC does $25 buy you? The heart of the T20U DAC is the Burr-Brown PCM2702E, a familiar choice for USB-ready amps including Dareds MP-5 and its many OEM reincarnations. Lets face it, the PCM2702E has very conservative specs. Its merely a 32/44.1/48kHz ready 16-bit stereo DAC with USB interface, on-chip clock generator, 8 times oversampling digital interpolation filter and analog low-pass output filter. Knowing that the AC97 chip supports 96kHz/20-bit stereo resolution, these seven-years old specs might give techno freaks cold feet. Not me. One of my reference CD players, the Restek Radiant, is also a 44.1kHz/16-bit affair and more than 14 years old. . Yet its still putting a lot of newer players to shame. The best part of the KingRex design is the use of a 12MHz crystal resonator as the clock source for the PCM2702E. It works with the on-chip crystal oscillator to generate a stable low-jitter clock for internal PLL and DAC operation from the USB interface audio data, freeing them from the computers inferior anti-audio clock. As we said, the PCM2702E is dedicated to stereo and we like it that way. In terms of measurable typical performance, the PCM2702E renders a set of numbers that satisfies the Redbook requirement: 100dB dynamic range, 105dB S/N ratio (both A-weighted) and 103dB channel separation. By the way, the PCM2702E is USB 1.0 compliant. The DAC chip has a large internal storage buffer to store up audio packets and you wont need the higher speed USB 2.0 so even less up-to-date computers can plug n play. Leaving the DAC chip via the low-pass filters, the analog two-channel signals are handed over to the Burr-Brown OPA2134 operational amplifier which acts as output stage preamp and low-pass filter, taking out the residual digital garbage and turning the audio signal into the analogue stream. To make sure the audio signals are clean without a DC stage, a pair of Texas TL072 low-noise dual JFET op amps are assigned to the DC servo circuit. Every DIYer knows how changing the op amp will change the sonic characteristics. KingRex adeptly left that option open by making it a plug-in feature on the circuit board. In addition to the USB interface, the T20U has one set of line inputs. Both the input sockets and toggle switch are located on the rear panel, keeping the front panel as clean as the T20s. Input selection is electronically executed by a relay. Chip rolling Last time, KingRex kindly sent me two T20s and two PSUs for bi-amping per my request. This time, they sent me two T20Us and two updated PSUs without asking and added two extra Burr-Brown OPA2604 op amps to roll with the factory-fitted OPA2314. I soon realized that I could not bi-amp with USB. PC or Mac, I could select but one audio output device. (The USB hub would still connect to one randomly). Still, I could enjoy the convenience of comparing the OPA2314 and OPA2604 by setting up two amps with different op amps. KingRex chief engineer James Lee told me to switch on the T20U before booting up the computer to insure that the USB device would be recognized. I followed his instruction but thought he might be too precautionary. Both PC and Mac detected the T20U without problem even if I booted up the computer first. On my PowerBook, when two amps were connected via two USB ports, both were detected as Burr-Brown Japan PCM2707 USB. On my Acer laptop, they were recognized as USB speaker and USB speaker (2). The PowerBook had no problem switching between the two. Even with music playing continuously, switching back and forth required merely a click. The Acer was more temperamental. Sometimes it switched after the music stopped or it wouldnt switch at all unless rebooted. Using a USB switch connected to one USB port was slightly better at times. The USB switch is not a USB hub but a push-button selector. The USB hub didnt help. It just connected me to one USB interface. By the way, the operation system on the PowerBook is Mac OS 10.3.9. On the Acer, its Windows XP Professional. Would Vista recognize the USB better? Perhaps. ames also advised me to disable the computer sound card or audio device to avoid interference. That was possible only with my PC. Apple only selects one audio output device at a time. Theres no option for enabling or disabling other devices. Does that mean the remainder is automatically disabled? Im clueless. After the USB audio output is selected, volume and L/R channel balance can still be adjusted. That probably indicates that the volume and balance settings are carried out in the digital domain. It is therefore wise to set the volume to maximum to optimize the 16-bit word length. So, this was the setup: Mac PowerBook, two USB cables, T20U with OPA2134 and T20U with OPA2604 both running on PSU, each driving a pair of identical Loth-X BS-1. I conducted a blind comparison by labeling the chips on the back of the amps and then shuffling them. During the audition, they were identified as chip A and chip B. Their identity was only revealed at the end. Since I always have my Loth-X stacked in DAppolito arrays, I just left them like that and hooked up chip A to the top pair, chip B to the bottom pair for direct comparison. I swapped the speaker connections at random to make sure placement (the top pair was higher and inverted) would not play tricks on my ears. I picked five CDs, selected a few tracks from each, ripped them to MP3 and WAV, saved them to the hard disk of the PowerBook and compared the different file formats with the original CDs played on the PowerBook super drive. One CD in particular was also converted to FLAC and EAC for more extensive comparison with the original CD played from the PowerBook as well as from the Philips DVP-9000S SACD/CD player – for the sake of USB DAC vs. Philips DSD upsampling. The Philips was only connected to the line input of one of the T20U since that didnt involve the OPA2134 or OPA2604. If thats not too complicated, lets continue, shall we? hat somehow made the caressing passages in Barcarola more intimate. Chip B cleared up vocal and piano separation. Sonic elements were distilled and reasonably well-defined. The piano came to life with leaping, galloping and bouncing notes so characteristic of Rossini as in Lorgia and La pastorella. CD playback on the PowerBook showed further improvements. Vocals were silky and piano sounded like pearly droplets. Better soundstage and layering turned the simple home gathering into a musical event. The difference between chip A and chip B was almost indiscernible except that the piano in La danza: Tarantella seemed more sparkling. Gavin Bryars The Sinking of the Titanic [Point Muisc 446-061-2] could be the tribute to the band that kept on playing the hymn Autumn as the ship went down in the North Atlantic. This Episcopal hymn played here on three violas and two cellos forms the base upon which other materials are superimposed - including fragments of interviews with survivors, sound effects reconstructed according to survivors and speculations (the impact of the iceberg, engine room sounds and bagpipers aboard) and realized on various instruments, from bass clarinet to Korg keyboard. Though monothematic yet full of imaginations and noble humanity, the music is strangely peaceful. I picked five tracks: Opening, Titanic Hymn, Titanic Lament, Last Hymn and Coda. MP3 playback was again disappointing. There was almost insufficient resolution to distinguish the subtleties between stringed instruments above water and underwater. Miscellaneous sound effects had no details. The WAV files shed more lights on the nuances. That luminous sheen on the strings above water was restored. The hollow strings under water once again reverberated in the more sound-efficient medium. The dark hue over the sound effects was removed. Original CD playback on the PowerBook further exemplified the true magic of this very quiet recording full of nuances. Woodblocks, tam-tam, bells, marimba, water gongs and the very occasional electric guitar, no matter how subtle, were faithfully and meticulously presented. Chip A versus chip B was almost pointless at any level except that B, for some unknown reason, seemed to be louder and delivering more energy in the mid to lower frequencies. GianCarlo Menotti who just passed away in February this year at the age of 96, was the most performed operatic composer of his era. Yet his ballet Sebastian [ASV CD DCA 741] was unjustly neglected. This is probably the only recording available thanks to conductor José Serebrier and the London Symphony Orchestra. Menotti painted this hauntingly beautiful ballet with romantic melodies, operatic drama and inventive orchestration. Sebastian is the love story about the Prince and notorious Venetian courtesan whose evil sisters conspire to intercept the alliance with black magic by piercing a wax image of their sister with arrows. Sebastian the Moorish slave, secretly in love with the courtesan, substitutes himself for the wax figure, takes the lethal arrows and breaks the evil power. The ballet is only 36 minutes long and hardly contains one inane note. MP3 playback depicted a compressed sound image even though Menottis ingeniously appointed tonal palette was somewhat preserved. The WAV file improved the soundstage dramatically. With chip A, instrument placement was well articulated across the breadth of the stage but fell flat from front to back. Chip B opened up the soundstage even more and defined front to back layering more proficiently if not superbly. CD playback on PowerBook had the soundstage fully restored to 3D, with chip A being more dynamic and chip B more detailed. As in Barcarolle, string bowings and harp plucking were vividly portrayed. Time for the final show down between the $25 USB DAC and the $1,000 CD/SACD player. Marianne Thorsen/TrondheimSolistenes Mozart Violin Concertos [2L 38] was chosen to be the reference software for two simple reasons: artistic brilliance and sonics extraordinaire. While most Mozart interpreters try too hard to please by portraying Mozart as a wide-eye innocent porcelain doll, the young Norwegian violinist dares to tell it like it is. This is the most original Mozart with true zest for life. However, MP3 playback on chip A did no justice to this superb recording. The strings sounded coarse. Chip B sounded marginally more refined. WAV saw little improvement, with chip A still sounding lightweight and chip B just adding minor body. On the whole, WAV sounded impatient and strung up. Then I tried FLAC. This is the technical part I could use help with. Correct me if Im wrong. When converting approximately 750MB of audio data to MP3, file size is reduced to roughly 1/3rd. WAV and EAC are the same as the original. FLAC is about half. Yet FLAC sounds way better than WAV and EAC. It might have something to do with the software I used to play back FLAC. FLAC -- Free Lossless Audio Codec -- is basically encoded WAV in a lossless but compressed file. I used Amadeus II for playback. Even when the Sound Characteristics were set to the original 16-bit/44.1kHz, the FLAC playback outperformed WAV and EAC with decisively more mellowness and finesse. At times, I even might say that it outperformed the original CD playback on the PowerBook. If you still follow, let me further complicate the picture by saying that the difference between chip A and chip B was more evident with FLAC, with B offering richer harmonics and finer texture. Yet this is not the complete story of FLAC. Original CD playback through the Philips was clearly the winner with its DSD upsampling at work. Superb 2-channel multi-channel SACD playback, excellent Red Book performance plus selectable upsampling to 24-bit/96KHz or DSD bit-stream only found on machines ten times its price make this piece of exceptional hardware the most desirable hybrid player of all times. Why Philips pulled it off the market in under one year has me befuddled. But prepare yourself for more mind-boggling phenomena. Back to FLAC. The Amadeus II is a sound recording and editing software for Mac only. One of its many functions is recoding the sampling size and rate. I used that to upsample the FLAC audio data to 24-bit/96kHz and played it back on chip B. Guess what, the result was so close to the Philips DSD upsampling, the latter only excelled by a smidgen of resolution. I was puzzled at first. How on earth could the upsampled 24/96 FLAC audio data have any effect on the 16/44 DAC and churn out such awesome performance? Then I thought of the EMI 24-bit digital remastered CDs, the Japanese K2 series and the like. By the same token, the final making of these CDs is all in Red Book format but the prior upsampling remastering process somehow improves the sound. The real difference is from FLAC to KingRex USB/DAC - pure digital transmission skipping the error-inducing injection molding of pits and bumps and laser tracking mechanism. Time to reveal the op amp identity. Chip A was OPA2134 and chip B was OPA2604, the latter being regarded as the better op amp by DIY consensus. As a low-pass filter, the OPA2604 enjoys a reputation of being very analog sounding, with refined resolution and musicality. Its great news that after I completed my first course in chip-rolling, KingRex decided on the OPA2604 as production standard. In fact, any low-noise JFET or CMOS dual input op amps that fit the 8-pin DIP socket can be rolled. Its been reported that OPA2227 and LM4562 are very good choices so its just a matter of finding one to suit your tastes. Even so, the $25 DAC didnt beat the Philips SACD/CD player but we knew that to be an unfair comparison right from the start. However, any CD player no matter how advanced will devolve into obsolescence the day you put your money down. With the KingRex T20U, you are buying into more than a chip-rolling USB DAC. You are opening up the unlimited realm of many newer and more advanced audio codecs and playback softwares to come. FLAC and Amadeus II are only the two I know of - and I am such a computer idiot. The latest Amadeus II and Amadeus Pro are equipped with 24-bit/192kHz upsampling. Im sure more options already exist for both Mac and PC. And more are bound to follow.Part I: Conclusion I have given my highest commendation to the KingRex T20 by honoring it with the Blue Moon Award for heart-warming tube sound from a cold-running Class-T amp. The T20U is the same amp, only more truthful to the category of integrated amp by offering a second input via its USB interface. If you fancy listening to music from your computer and upgrading your listening pleasure, simply think of the T20U as the best $245 USB DAC money can buy - and the award-winning Tripath amp comes with it gratis. For curiositys sake, I did compare the line input of the T20U with the T20 but have nothing to report. Not only is the difference itself negligible and meaningless, the need for reporting it is pointless. You either need USB or you dont. If you are sure youll never need USB, save yourself $25. If you are not sure, the extra $25 pays for a good insurance policy. https://www.diy-audio-guide.com/kingrex-t20u-review.html https://www.hifivision.com/threads/kingrex-t20u-review.22380/ https://www.tnt-audio.com/ampli/kingrext20_e.html

Kingrex T20 type T amp. I have 2 of these. I bought these to use as amps for computer audio but I never used them. These do not come with the PSU and are not the USB models. These units have RCA in. Retail on these $399 (for one) in 2007 Inputs RCA Gold PlatedOutputs- Banana Plug Gold Plated Included Power Supply 100-240 V output 12V 3ATHD+N 0.03% @ 10W 4 OhmTHD+N 0.1% @12 W 4 OhmIHF-IM 0.18% @1W 4 OhmOutput 22W@4 Ohm, 10% THD+N, VDD=13.5 V 13W@8 Ohm, 10% THD+N, VDD=13.5VEfficiency 88%@12W 8 Ohm 81%@20W 4 OhmDynamic Range = 99dBOver current and over temperature protection6 mm thickness aluminum face plate and aluminum knob with audio grade capacitor 6 Moons review and additional review links below Reviewer: David Kan Digital Source: Philips DVP-9000S, Apple PowerBook G4, Acer TravelMate 3010 notebook Preamp: Audio Zone Pre T-1, Dared SL-2000A Speakers: Loth-X BS-1, Klipsch Synergy F2, Dynaudio Facette Cables: Luscombe LBR-35 interconnect, Clear Audio Silver Line interconnect, OCOS speaker cables by Dynaudio Power Cords: stock power cords, Unity Audio Link [on loan] Power Line Conditioning: Monster Power HTS-1000 MkII Room Size: 15 x 13.5 x 8 diagonal set up Part I: KingRex T20U U for ubiquitous. U for unprecedented. U for unbelievable. U for USB. The KingRex T20U is basically the same as the Tripath-based T20 integrated amp but with an onboard USB interface and DAC. USB has plugged into our so-called modern living and taken over. Audio devices with USB interface are becoming commonplace. Weve seen tube amps and outboard converters with USB inputs. But combining a USB DAC with a Tripath amp is definitely unprecedented. It makes so much sense that one should ask, what took you. The fact that the T20U is priced at $245, a mere 25 bucks more than the T20, is absolutely unbelievable. Opening up the black boxes to quickly compare the two further hammered home one simple mathematical fact: theres no way I would take the trouble to build my own USB DAC even if you paid me 25 smackers.Before we actually look at the DAC portion of the T20U, lets see whats wrong with computer sound cards from an audiophiles perspective. Why would we need the U in the T20? If one wanted to play music from a computer through a mainstream audio system, simply connecting the audio-out of the computer to an input of the audio system will give sound. Alas, the sound card or audio device installed in the computer is not - um, dedicated enough. In the audiophiles cookbook, theres no multi-tasking. Duo core do more? No, thank you. For audiophiles, less is more! A typical sound card these days (or the AC97 chip mounted to the motherboard) is hardly just stereo. Whether you like it, need it or ever use it, it comes with 5.1 or 7.1 capability for gaming and movies, a synthesizer and MIDI interface for music making, analog-to-digital conversion for recording and digital-to-analog conversion for playback. For audiophiles, anything but the latter are unnecessary evils and unsolicited sources of interference. To shut off these back doors to block unwanted noise and distortion, an outboard digital-to-analog converter that receives digital signals via USB seems a welcome proposition. Instead of creating another standalone DAC that takes up extra space and one more AC power outlet, KingRex took a shortcut and build the DAC inside the T20 Tripath amp - shortcut in the sense that it saves you a pair of interconnects (could you buy a decent pair with $25?). Shortcut in the sense that the signal path from the DACs output stage to the Tripath chip is as short as five centimeters. Fitting snugly inside the same compact chassis of 180 x 138 x 45mm, the amp and DAC come to you all in one piece - plus a free USB cable and the standard AC/DC adapter.Sitting side by side with their bonnets removed, one can easily spot that in addition to the DAC circuit, the original Tripath amp section has been modified. The two input coupling capacitors have been changed from electrolytics to metalized polypropylene films for better frequency response. There are also four high-current inductors for demodulating the switching waveform into the audio signal. The high-current type ensures more headroom for the Tripath chip to perform with maximum output capabilities. What kind of DAC does $25 buy you? The heart of the T20U DAC is the Burr-Brown PCM2702E, a familiar choice for USB-ready amps including Dareds MP-5 and its many OEM reincarnations. Lets face it, the PCM2702E has very conservative specs. Its merely a 32/44.1/48kHz ready 16-bit stereo DAC with USB interface, on-chip clock generator, 8 times oversampling digital interpolation filter and analog low-pass output filter. Knowing that the AC97 chip supports 96kHz/20-bit stereo resolution, these seven-years old specs might give techno freaks cold feet. Not me. One of my reference CD players, the Restek Radiant, is also a 44.1kHz/16-bit affair and more than 14 years old. . Yet its still putting a lot of newer players to shame. The best part of the KingRex design is the use of a 12MHz crystal resonator as the clock source for the PCM2702E. It works with the on-chip crystal oscillator to generate a stable low-jitter clock for internal PLL and DAC operation from the USB interface audio data, freeing them from the computers inferior anti-audio clock. As we said, the PCM2702E is dedicated to stereo and we like it that way. In terms of measurable typical performance, the PCM2702E renders a set of numbers that satisfies the Redbook requirement: 100dB dynamic range, 105dB S/N ratio (both A-weighted) and 103dB channel separation. By the way, the PCM2702E is USB 1.0 compliant. The DAC chip has a large internal storage buffer to store up audio packets and you wont need the higher speed USB 2.0 so even less up-to-date computers can plug n play. Leaving the DAC chip via the low-pass filters, the analog two-channel signals are handed over to the Burr-Brown OPA2134 operational amplifier which acts as output stage preamp and low-pass filter, taking out the residual digital garbage and turning the audio signal into the analogue stream. To make sure the audio signals are clean without a DC stage, a pair of Texas TL072 low-noise dual JFET op amps are assigned to the DC servo circuit. Every DIYer knows how changing the op amp will change the sonic characteristics. KingRex adeptly left that option open by making it a plug-in feature on the circuit board. In addition to the USB interface, the T20U has one set of line inputs. Both the input sockets and toggle switch are located on the rear panel, keeping the front panel as clean as the T20s. Input selection is electronically executed by a relay. Chip rolling Last time, KingRex kindly sent me two T20s and two PSUs for bi-amping per my request. This time, they sent me two T20Us and two updated PSUs without asking and added two extra Burr-Brown OPA2604 op amps to roll with the factory-fitted OPA2314. I soon realized that I could not bi-amp with USB. PC or Mac, I could select but one audio output device. (The USB hub would still connect to one randomly). Still, I could enjoy the convenience of comparing the OPA2314 and OPA2604 by setting up two amps with different op amps. KingRex chief engineer James Lee told me to switch on the T20U before booting up the computer to insure that the USB device would be recognized. I followed his instruction but thought he might be too precautionary. Both PC and Mac detected the T20U without problem even if I booted up the computer first. On my PowerBook, when two amps were connected via two USB ports, both were detected as Burr-Brown Japan PCM2707 USB. On my Acer laptop, they were recognized as USB speaker and USB speaker (2). The PowerBook had no problem switching between the two. Even with music playing continuously, switching back and forth required merely a click. The Acer was more temperamental. Sometimes it switched after the music stopped or it wouldnt switch at all unless rebooted. Using a USB switch connected to one USB port was slightly better at times. The USB switch is not a USB hub but a push-button selector. The USB hub didnt help. It just connected me to one USB interface. By the way, the operation system on the PowerBook is Mac OS 10.3.9. On the Acer, its Windows XP Professional. Would Vista recognize the USB better? Perhaps. ames also advised me to disable the computer sound card or audio device to avoid interference. That was possible only with my PC. Apple only selects one audio output device at a time. Theres no option for enabling or disabling other devices. Does that mean the remainder is automatically disabled? Im clueless. After the USB audio output is selected, volume and L/R channel balance can still be adjusted. That probably indicates that the volume and balance settings are carried out in the digital domain. It is therefore wise to set the volume to maximum to optimize the 16-bit word length. So, this was the setup: Mac PowerBook, two USB cables, T20U with OPA2134 and T20U with OPA2604 both running on PSU, each driving a pair of identical Loth-X BS-1. I conducted a blind comparison by labeling the chips on the back of the amps and then shuffling them. During the audition, they were identified as chip A and chip B. Their identity was only revealed at the end. Since I always have my Loth-X stacked in DAppolito arrays, I just left them like that and hooked up chip A to the top pair, chip B to the bottom pair for direct comparison. I swapped the speaker connections at random to make sure placement (the top pair was higher and inverted) would not play tricks on my ears. I picked five CDs, selected a few tracks from each, ripped them to MP3 and WAV, saved them to the hard disk of the PowerBook and compared the different file formats with the original CDs played on the PowerBook super drive. One CD in particular was also converted to FLAC and EAC for more extensive comparison with the original CD played from the PowerBook as well as from the Philips DVP-9000S SACD/CD player – for the sake of USB DAC vs. Philips DSD upsampling. The Philips was only connected to the line input of one of the T20U since that didnt involve the OPA2134 or OPA2604. If thats not too complicated, lets continue, shall we? hat somehow made the caressing passages in Barcarola more intimate. Chip B cleared up vocal and piano separation. Sonic elements were distilled and reasonably well-defined. The piano came to life with leaping, galloping and bouncing notes so characteristic of Rossini as in Lorgia and La pastorella. CD playback on the PowerBook showed further improvements. Vocals were silky and piano sounded like pearly droplets. Better soundstage and layering turned the simple home gathering into a musical event. The difference between chip A and chip B was almost indiscernible except that the piano in La danza: Tarantella seemed more sparkling. Gavin Bryars The Sinking of the Titanic [Point Muisc 446-061-2] could be the tribute to the band that kept on playing the hymn Autumn as the ship went down in the North Atlantic. This Episcopal hymn played here on three violas and two cellos forms the base upon which other materials are superimposed - including fragments of interviews with survivors, sound effects reconstructed according to survivors and speculations (the impact of the iceberg, engine room sounds and bagpipers aboard) and realized on various instruments, from bass clarinet to Korg keyboard. Though monothematic yet full of imaginations and noble humanity, the music is strangely peaceful. I picked five tracks: Opening, Titanic Hymn, Titanic Lament, Last Hymn and Coda. MP3 playback was again disappointing. There was almost insufficient resolution to distinguish the subtleties between stringed instruments above water and underwater. Miscellaneous sound effects had no details. The WAV files shed more lights on the nuances. That luminous sheen on the strings above water was restored. The hollow strings under water once again reverberated in the more sound-efficient medium. The dark hue over the sound effects was removed. Original CD playback on the PowerBook further exemplified the true magic of this very quiet recording full of nuances. Woodblocks, tam-tam, bells, marimba, water gongs and the very occasional electric guitar, no matter how subtle, were faithfully and meticulously presented. Chip A versus chip B was almost pointless at any level except that B, for some unknown reason, seemed to be louder and delivering more energy in the mid to lower frequencies. GianCarlo Menotti who just passed away in February this year at the age of 96, was the most performed operatic composer of his era. Yet his ballet Sebastian [ASV CD DCA 741] was unjustly neglected. This is probably the only recording available thanks to conductor José Serebrier and the London Symphony Orchestra. Menotti painted this hauntingly beautiful ballet with romantic melodies, operatic drama and inventive orchestration. Sebastian is the love story about the Prince and notorious Venetian courtesan whose evil sisters conspire to intercept the alliance with black magic by piercing a wax image of their sister with arrows. Sebastian the Moorish slave, secretly in love with the courtesan, substitutes himself for the wax figure, takes the lethal arrows and breaks the evil power. The ballet is only 36 minutes long and hardly contains one inane note. MP3 playback depicted a compressed sound image even though Menottis ingeniously appointed tonal palette was somewhat preserved. The WAV file improved the soundstage dramatically. With chip A, instrument placement was well articulated across the breadth of the stage but fell flat from front to back. Chip B opened up the soundstage even more and defined front to back layering more proficiently if not superbly. CD playback on PowerBook had the soundstage fully restored to 3D, with chip A being more dynamic and chip B more detailed. As in Barcarolle, string bowings and harp plucking were vividly portrayed. Time for the final show down between the $25 USB DAC and the $1,000 CD/SACD player. Marianne Thorsen/TrondheimSolistenes Mozart Violin Concertos [2L 38] was chosen to be the reference software for two simple reasons: artistic brilliance and sonics extraordinaire. While most Mozart interpreters try too hard to please by portraying Mozart as a wide-eye innocent porcelain doll, the young Norwegian violinist dares to tell it like it is. This is the most original Mozart with true zest for life. However, MP3 playback on chip A did no justice to this superb recording. The strings sounded coarse. Chip B sounded marginally more refined. WAV saw little improvement, with chip A still sounding lightweight and chip B just adding minor body. On the whole, WAV sounded impatient and strung up. Then I tried FLAC. This is the technical part I could use help with. Correct me if Im wrong. When converting approximately 750MB of audio data to MP3, file size is reduced to roughly 1/3rd. WAV and EAC are the same as the original. FLAC is about half. Yet FLAC sounds way better than WAV and EAC. It might have something to do with the software I used to play back FLAC. FLAC -- Free Lossless Audio Codec -- is basically encoded WAV in a lossless but compressed file. I used Amadeus II for playback. Even when the Sound Characteristics were set to the original 16-bit/44.1kHz, the FLAC playback outperformed WAV and EAC with decisively more mellowness and finesse. At times, I even might say that it outperformed the original CD playback on the PowerBook. If you still follow, let me further complicate the picture by saying that the difference between chip A and chip B was more evident with FLAC, with B offering richer harmonics and finer texture. Yet this is not the complete story of FLAC. Original CD playback through the Philips was clearly the winner with its DSD upsampling at work. Superb 2-channel multi-channel SACD playback, excellent Red Book performance plus selectable upsampling to 24-bit/96KHz or DSD bit-stream only found on machines ten times its price make this piece of exceptional hardware the most desirable hybrid player of all times. Why Philips pulled it off the market in under one year has me befuddled. But prepare yourself for more mind-boggling phenomena. Back to FLAC. The Amadeus II is a sound recording and editing software for Mac only. One of its many functions is recoding the sampling size and rate. I used that to upsample the FLAC audio data to 24-bit/96kHz and played it back on chip B. Guess what, the result was so close to the Philips DSD upsampling, the latter only excelled by a smidgen of resolution. I was puzzled at first. How on earth could the upsampled 24/96 FLAC audio data have any effect on the 16/44 DAC and churn out such awesome performance? Then I thought of the EMI 24-bit digital remastered CDs, the Japanese K2 series and the like. By the same token, the final making of these CDs is all in Red Book format but the prior upsampling remastering process somehow improves the sound. The real difference is from FLAC to KingRex USB/DAC - pure digital transmission skipping the error-inducing injection molding of pits and bumps and laser tracking mechanism. Time to reveal the op amp identity. Chip A was OPA2134 and chip B was OPA2604, the latter being regarded as the better op amp by DIY consensus. As a low-pass filter, the OPA2604 enjoys a reputation of being very analog sounding, with refined resolution and musicality. Its great news that after I completed my first course in chip-rolling, KingRex decided on the OPA2604 as production standard. In fact, any low-noise JFET or CMOS dual input op amps that fit the 8-pin DIP socket can be rolled. Its been reported that OPA2227 and LM4562 are very good choices so its just a matter of finding one to suit your tastes. Even so, the $25 DAC didnt beat the Philips SACD/CD player but we knew that to be an unfair comparison right from the start. However, any CD player no matter how advanced will devolve into obsolescence the day you put your money down. With the KingRex T20U, you are buying into more than a chip-rolling USB DAC. You are opening up the unlimited realm of many newer and more advanced audio codecs and playback softwares to come. FLAC and Amadeus II are only the two I know of - and I am such a computer idiot. The latest Amadeus II and Amadeus Pro are equipped with 24-bit/192kHz upsampling. Im sure more options already exist for both Mac and PC. And more are bound to follow.Part I: Conclusion I have given my highest commendation to the KingRex T20 by honoring it with the Blue Moon Award for heart-warming tube sound from a cold-running Class-T amp. The T20U is the same amp, only more truthful to the category of integrated amp by offering a second input via its USB interface. If you fancy listening to music from your computer and upgrading your listening pleasure, simply think of the T20U as the best $245 USB DAC money can buy - and the award-winning Tripath amp comes with it gratis. For curiositys sake, I did compare the line input of the T20U with the T20 but have nothing to report. Not only is the difference itself negligible and meaningless, the need for reporting it is pointless. You either need USB or you dont. If you are sure youll never need USB, save yourself $25. If you are not sure, the extra $25 pays for a good insurance policy. https://www.diy-audio-guide.com/kingrex-t20u-review.html https://www.hifivision.com/threads/kingrex-t20u-review.22380/ https://www.tnt-audio.com/ampli/kingrext20_e.html

Ich verkaufe meinen kleinen, feinen Kingrex-Verstärker, um auf ein anderes Gerät umzusteigen. Er funktioniert einwandfrei. Detaillierte Testberichte sind hier zu finden:https://www.fairaudio.de/test/test-vollverstaerker-kingrex-king-rex-t20-1-dwt/https://www.diy-audio-guide.com/kingrex-t20u-review.html Lieferumfang:Kingrex T20U NetzteilAnleitungUSB-Anschlusskabel