Description
FINALE DI POTENZA NAD 2155 - 55 W su 8 Ohm - MAGIA DEL SUONO ANNI 80 Made in Japan Acquistato nel 1985 ed utilizzato fino al 1999 quando fu sostituito da un integrato a valvole di ESTRO ARMONICO.Riutilizzato dal settembre 2020, dopo controllo e manutenzione effettuati da Lorenzo Betti di ESTRO ARMONICO, fino a dicembre 2022 quando è stato sostituito da un un QUAD 303 costruito dieci anni prima di lui. Le condizioni estetiche sono ottime (qualche segno su un fiancata e i segni di 4 feltrini che vi erano incollati).Tutti i pezzi sono originali compreso il cavo di alimentazione. Tutto è perfettamente funzionante con qualità musicale magica ed inimitabile di prodotti di quegli anni. Sotto le caratteristiche tecniche e il contenuto del manuale, in inglese, trovati in rete. POWER AMP SECTIONContinuous output power into 8? * 55W (17.4dBW)Rated distortion (THD 20Hz - 20kHz) 0.03%Clipping power (maximum continuous power per channel) 65WIHF Dynamic headroom at 8? +3dBIHF dynamic power (maximum short term power per channel) 8? 100W 4? 100W 2? 130WDamping factor (ref. 8?, 50Hz) >50Input impedance 22k?Input sensitivity (for rated power into 8?) 1.3VTHD (20Hz - 20kHz) <0.03% Bridged ModeContinuous output power into 8? * 125W (21dBW)IHF Dynamic headroom at 8? +2.5dBIHF dynamic power (maximum short term power per channel) 8? 2 50W PHYSICAL SPECIFICATIONSDimensions (W x H x D) 420 x 108 x 380mmNet weight 7.8kg Power consumption (120 ~ 240V, 50/60Hz) 340W * Minimum power per chnnel, 20Hz - 20kHz, both channels driven with no more than rated distiortion.Dimensions are of unit’s cabinet without attached feet; add up to 18mm for total height.Dimension depth excludes terminals, sockets, controls and buttons. 2155Power AmplifierDateof manufacture : Jan 85 - Jan 87• Poweroutput conservatively rated at 55 watts per channel into 8 or 4 ohms.• +3dB IHF Dynamic Headroom for peaks: 110 W/ch at 8 ohms, 130 W/ch at 4ohms.•High-currentoutput stage, able to deliver peak currents up to 40 amperes forprecise control of voice coil motion with speaker impedances as lowas 2 ohms.•Bridgingcircuit yields 150 watts continuous power, 250 watts IHF dynamicpower.•ExclusiveNAD impedance selector optimises power delivery to either high or lowspeaker impedance.• SoftClipping™ minimises distortion at output levels above the ratedpower.NADleads the audio industry in producing amplifiers with high-headroomcircuitry and high current output stages, precisely the qualitiesneeded for musically accurate reproduction of todays wide-rangeanalogue and digital recordings. The 2155 power amp is one of thefinest in a long tradition of highly praised NAD amplifiers, withincreased power, improved reliability, and numerous refinements insound quality. As a high-current high-headroom power amplifier itdrives even difficult loudspeakers to surprisingly highvolume levels with clean, solid, full-bodied musical sound thatremains refreshingly free from distortion even in transient peaks.The2155, which is simply the power amplifier section of the 3155 and7155 packaged on a separate chassis,is NADs building-block amp, offering a variety ofconvenient and economical approaches to up-grading a stereo systemfor higher performance and power. The 2155 is an obvious choice ifyou want to upgrade from a low-powered receiver or integrated amp, orif you are using a separate preamplifier. If you need still higherpower, a pair of 2155s in the bridged mode deliver nearlythree times as much power output for only twice the cost.The2155 delivers substantially more than its conservatively rated 55watts/channel into the complex and varying impedances of realloudspeakers. In the bridged monophonic mode this amplifier is ratedconservatively at 150 watts continuous output. And these amplifiersmaintain a full 3 dB of IHF dynamic headroom (2.5 dB in bridgedmode), meaning that they deliver twice their rated power in briefbursts:over110 watts/channel in stereo and about 250 watts in bridgedconfiguration. This headroom for peaksis crucially important for reproducing the uncompressed transients inmodern digital and DBX encoded recordings.Whencombined as a bridged stereo pair, these amplifiers function as a 150W/ch stereo amplifier with 250 watts per channel of short-termoutput. That power, together with the remarkable flexibility andflawless sonic performance of the 7155 or 3155s preamplifiersection, make these combinations remarkable best-buy systems.HighCurrent and Headroom: Designing for Real-Use ConditionsSinceamplifiers are usually rated in terms of a few standardspecifications (e.g. 8-ohm power and THD), many designers concentrateon optimising test-bench performance. But in the real world,amplifiers are connected to loudspeakers with complex impedances, notto 8-ohm test resistors, and they are used to play music, notsine-wave test tones. In NAD amplifiers every circuit is designed todeliver full performance under real-use conditions. While manyspecific engineering goals follow from this principle, two have beenthe cornerstones of every amplifier in NAD history (including thelegendary Model 3020): graceful handling of dynamic transients thatexceed the amplifiers rated power, and the ability to deliver largebursts of output current to the loudspeakers. Electricalpower is the product of voltage and current, but it is the currentflowing through the voice coil that causes a loudspeaker cone tovibrate and reproduce sound. As NAD engineers have always known andother manufacturers have lately begun to realise, to obtain preciseelectromagnetic control of the speakers motion the amplifier must beable to supply high peak currents upon demand, unconstricted bytransistor protection circuits. The NAD 2155 amplifiercircuit produces peak currents of up to 40 amperes per channel.Loudspeakerimpedance matching Standard lab tests of amplifiers use 8-ohmresistors in place of loudspeakers. But most loudspeakers have alower and more complex impedance that increases the requiredamplifier output current. (And if you connect two pairs ofloudspeakers, the effective impedance of the pair is halved.) Forthis reason the 2155 amplifier is designed to deliver its maximumpower into low impedances of 4 or even 2 ohms.Butthe exclusive NAD impedance selector allows you to re-optimise theamplifier circuit to produce greater output voltage, for the mosteffective delivery of power to loudspeakers whose true impedance is 8ohms or higher.SoftClipping NADs trademarked Soft Clipping circuit gently limits thewaveform when the amplifier is driven beyond its maximum powerrating. By preventing the out-put transistors from being driven fullyinto saturation, the Soft Clipping reduces the harshness that isnormally heard when an amplifier is over driven. Because of this andthe amplifiers high dynamic headroom, the sound remains clean andmusical even at very high sound levels, rather than becoming harsh asin other amplifiers.ExceptionalPerformance and Value The NAD 2155 is a superb general-purpose poweramplifier with an unusually attractive ratio of performance and powerto price, and it is also the core of the unique NAD building-blockconcept that allows the stereo system to evolve with your needs oryour budget, now and in the future
| 
Live search