Description
Accuphase C-240 Preamplifier used 1978 Stereo Control Center Working MaintainedDescription Type Stereo control centerFrequency Response High Level Input: 20Hz to 20000Hz +0 -0.2dBDisc input: 20Hz to 20000Hz ±0.2dBHarmonic distortion ratio 0.005% (between 20Hz and 20kHz, rated output)Input sensitivity/input impedance DISC1, 2(Head Amp OFF):2.0mV/100?, 47k?, 82k?, 150k? selectableDISC1, 2 (Head Amp ON):0.1mV/100? fixedTuner, AUX, Tape Play1, 2: 126mV/50k?Rated Output/Output Impedance(Volume max., Rated input) Output:2.0V/2?Tape Rec1, 2:126mV/500?Headphone Output Impedance:0.3?Output (8? load): 0.25W, 1kHz, distortion 0.01Maximum output level (20Hz to 20kHz): 10V or more, distortion 0.005Max. disc input Head Amp OFF: 400mVrms, 1kHz, 0.005% distortionHead Amp ON: 20mVrms, 1kHz, 0.005% distortionMinimum load impedance Outputs:1k?Tape Rec: 10k?GainFrom Tuner, AUX, Tape Play?Tape Rec: 0dBOutputs: 24dBHeadPhones: 20dBFrom DISC (Head Amp OFF)?Tape Rec: 36dBOutputs: 60dBHeadPhones: 56dB(+26dB when DISC input HEAD AMP ON)S/N / Input Converted Noise(Input short, IHF-A,Rated Input) High Level Input: 110dB/-128dBVDisc input (Head Amp OFF): 85dB/-139dBVDisc input (Head Amp ON): 72dB/-152dBVTone control 8-step push-switch selectableBass: 500Hz: ±8dB(50Hz)200Hz:±8dB(20Hz) 2dB step2dB stepHighs 2kHz:±8dB(20kHz)7kHz:±8dB(50kHz) 2dB step2dB stepLoudness compensator COMP1:+6dB(50Hz)COMP2:+9dB(50Hz)COMP3: +10dB(50Hz), +6dB(20kHz)(Volume control, at -30dB)Disc height trimming DISC1, DISC2, 0dB to -8dB continuously variable (at 20kHz)Attenuator -10dB, -20dB, -30dB switchableSubsonic filter 17Hz, 12dB/octSemiconductor used 159Tr, 10FET, 102DiPower supply 100V, 117V, 220V, 240V, 50/60HzPower consumption 80WDimensions Width 466 x Height 188 x Depth 391mmWeight 18kg Stereo control amplifier designed for top-of-the-line audio systems. The panel layout is unique, using push-switches throughout, and the circuit configuration consists of a Class-A DC system with symmetrical push-pull drive for all amplification stages, and the highest quality elements that affect sound quality are also used. The panel face consists of 4 rotary knobs, 1 lever switch, and 57 push switches.The input selector, in particular, is electronically controlled by relays in the circuit and can be switched by a feather touch.The head amp switching can be stored ON/OFF exclusively for each of the DISC1 and DISC2 cartridges, taking advantage of the electronic control system, thus improving operability.In addition, in order to improve the contact resistance of push switches and relays, which determines sound quality and durability, everything is configured using a two-circuit array. A fully symmetrical push-pull circuit is used in all amplifier stages, from the headphone amplifier inlet to output, as well as in all amplifier stages dedicated to headphones. This circuit has excellent linearity and the best distortion ratio is obtained with a small amount of NFB. As a result, TIM (transient intermodulation) distortion, which is a factor in sound quality degradation, is improved.The head amp, equalizer amp, high-level amp, and headphone amp are all DC amplifiers. The DC-cut capacitors in the NF loop, which require large capacitance, are removed, and the input capacitors are also removed to improve the sound quality. The head amplifier has a differential input push-pull configuration and uses a RET (ring-emitter transistor) specially developed for small signals, contributing to improved sound quality. Furthermore, the output impedance is lowered by driving a large current in the output stage, and the input conversion noise is kept low by setting a low feedback voltage divider resistance.In addition, the head amplifier is modularized to ensure stable operation over temperature changes without humidity. The equalizer amplifier consists of a symmetrical push-pull configuration with a FET buffer at the input and all amplification stages thereafter.The equalizer output uses a ring-emitter transistor (RET) for high-frequency power amplification, and a low output impedance is achieved by driving a large Class-A current and setting a low feedback voltage divider resistance. At the same time, by using a high gmFET in the input buffer, an input conversion noise level close to the ideal limit can be obtained. The high-level amplifier (flat amplifier) uses the DC servo system (PAT, PEND) to operate as a DC amplifier even when the tone control is in use, and DC drift is suppressed to almost zero.The DC servo system also eliminates the need for an output capacitor, so there is no DC cutoff capacitor from the Tuner and AUX terminals to the output. The amplifier dedicated to headphones is equipped with a pure-con headphone amplifier. The volume uses a sliding element configured on 18 brushes, and the resistive element consists of a conductive plastic element with a mirror finish.The film resistive element is made of a continuous array of conductive particles molded into a thermosetting resin insulator to form a smooth, strong film surface.The contact resistance is theoretically as low as 1/18 due to the use of 18 sliders and conductive plastic elements, resulting in a stable volume over a long period of time. Electromagnetic cartridges have a peak characteristic in the high frequency range due to the resonance of the vibration system, coil inductance, and wiring tray capacity.To adjust the high-frequency characteristics of such cartridges, HF trimming is provided, which can be continuously varied from flat to -8dB at 20kHz.The control is dedicated to DISC1 and DISC2 and can be adjusted for each cartridge. The tone control turnover switching is 500Hz and 200Hz for bass and 2kHz and 7kHz for treble, with 200Hz and 7kHz turnover for heavy bass and highest frequency control. Switching is in 2dB steps. A loudness compensator switch is provided to compensate for low volume and balance the energy.Three different curves can be selected according to the playback level and listening room characteristics. Only a 17Hz, 12dB subsonic filter is provided for filter practicality.A CR is added to the input element of the high-level amplifier to form an active filter.Since no dedicated active elements are added, there is no deterioration in sound quality. Two tape recorders can be connected, and an independent copy switch allows mutual dubbing while listening to other program sources.An ON-OFF switch for the recording output is provided for convenient cutting of unneeded programs.This switch is also useful for preventing distortion that occurs when the tape recorder is turned off because the input circuitry becomes a load on the control center. An attenuator switch is provided for finding the starting point of a record or for changing records. In addition to this, a level switch is provided to select between three different attenuation levels: -10dB, -20dB, and -30dB. The mode switch has a Blend position in addition to Stereo, Rev, and Mono.This is for use when the speaker spacing is too wide, or when playing a source that plays an unnaturally separate program source, and the left/right spread is narrowed to 10dB for a more natural spread. One of the three outputs has a Cannon output connector. Shipping FedEx?or DHLInternational Buyers - Please Note:Import duties, taxes, and charges are not included in the item price or shipping cost. These charges are the buyers responsibility. Please check with your countrys customs office to determine what these additional costs will be prior to bidding or buying. Thank you for your understanding.
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