Audio Database


Accuphase M-100
500,000 yen(one set, the July, 1981 release)


Monophonic power amplifier which thought as important "the Output load impedance of an open-loop is low", and "a large current supply power source and an output stage", and was developed in quest of the ideal of power amplifier in order to carry out the ideal drive of the speaker.

The output stage constitutes the broadband bipolar transistor of Pc(collector loss)200W from a 12 parallel push pull (a total of 24 output transistors). Thereby, all the electric power capacities were set to 4.8kW, and have obtained sufficient margin.

In order that an output transistor may improve the heat dissipation effect, it is divided into 2 sets and attached to the large-sized heat sink on either side. Since heat combination is not carried out, if it becomes imbalanced thermally, the tendency will be accelerated, only one side is overheated, and both of heat sinks develop into destruction of an element. In order to prevent such thermal unbalance, the bias balance circuit is adopted. This circuit attaches to the other party's heat sink the element connected to the base of an output element, detects temperature, has the structure of controlling bias current, and is carrying out operation stabilized by considering it as the mutual almost same temperature.

The drive stage consists of MOS FET for electric power magnification which is the original of an Accuphase, and it has performed a low impedance large current drive and improved the characteristic of a high region sharply collectively.
Moreover, since a heat characteristic works in the direction which stabilizes a bipolar transistor, the bias current of an output stage is stabilized. for this reason -- it is possible to make emitter resistance of an output stage low -- 12 [ furthermore, ] -- parallel more, equivalent emitter resistance became low with 1/12, and the switching distortion of it generated in order that the bias of an output transistor may cut off is almost lost.
The predrive stage consists of cascode connection push pulls, and is reconciling the outstanding high region characteristic and large amplitude operation without a Miller effect.
Moreover, comparatively big bias current is given to 24 output elements, and Output 5W has become a pure Class-A operation domain.

The circuit is constituted from all the traditional magnification stage push pulls of an Accuphase, and has improved many characteristics of an open-loop to a limit.
The input is received by dual FET and has adopted cascode bootstrap differential push pull composition. While obtaining the big profit by cascode bootstrap, the high region characteristic has been improved, and the distorted increase by the rise (change of an input level control) of input impedance is prevented.

By the push pull input circuit by dual FET, a direct current did not occur to an input but the input capacitor can be removed. However, in this state, when the large preamplifier of direct-current leak is connected, direct current occurs in an output, and it has a bad influence on a speaker.
In M-100, while intercepting a direct current, applying a direct-current return with direct-current servo amplifier, direct-current drift generated in a circuit is also suppressed.

The peak power Direct-reading equipment by a digital system is begun in the world, and it carries in power amplifier.
In this circuit, the output signal of amplifier was changed into the magnification which is easy to read with a range changeover switch (Attenuator), and is inputted into the peak wave detector. All the ripples by the side of + and - are arranged with the direction of the + side here, the peak value of a signal is held at the following step, the peak value is sent into a 12-bit A/D converter, and it changes into a digital signal. A digital signal is inputted into a 4-bit microprocessor, converts voltage into electric power by a microprocessor, and displays the peak within a definite period of time on a choice and LED.
Moreover, the signal which tells what a setup and the reset signal which newly starts a hold of hold time were generated, or the signal and display range of a range change exceeded is also outputted from the microprocessor.
A range change is four, x1, x0.1, x0.01, and x0.001, and, thereby, can carry out the Direct reading of between 0.001W - 999W in triple digits.
It is 3/30 kind, and for 0.5 second and 3 seconds, if a range is used for 30 minutes, the hold time can read the peak value of record one side, it is comparing with the standard signal of a test record, and can know the maximum cutting level.

The outside 磁 type precision large-sized meter which can supervise an output with dB and a watt value other than a digital display is carried.
Even -60dB (0dB=500W, -60dB=0.0005W) can be read with a logarithm compression type.

25 contact rotary switch for communication machines and the full-scale step type Attenuator by high precision metal tunic resistance are carried.
-23dB, -26dB, -30dB, and -infinity can be chosen in the accuracy of ±0.1dB 0 - the 1dB step between -20dB, and henceforth.

The low filter which cuts a low-pass unnecessary noise is carried.
The cutoff frequency can choose four kinds, 10Hz of a subsonic-speed domain, 17Hz, 30Hz that demonstrates power by business use, and 50Hz. Moreover, as for the slope characteristic, all are -12 dB/oct.
These changes attached the relay only for each frequency in the substrate circuit, and have controlled this relay with the switch of the front panel.

The phase switch which reverses the phase of an output signal to an incoming signal is carried. It is possible for this to unite the phase between channels.
Moreover, bridge connection can be constituted using M-100 of two per channel, and it can upgrade for 1.6kW of 8-ohm loads.

When using two or more M-100, the hold start timing of a digital display will shift.
The synchronized signal terminal for synchronizing this and carrying out a simultaneous start is carried. Thereby, the timing of a relay of the output circuit at the time of power-source ON-OFF can also be united with a digital display.
A 1.5m cable with a connector is attached, and there is also a 5m cable as an option.

The input terminal carries the business-use canon type connector besides the usual phono jack.

When installing in the bad place of the heat dissipation effect, or when performing the Oide power drive over a long period of time, the optimal fan for heat dissipation is an option.
The fan can attach with a rear panel.

The wood panel of persimmon finishing of 24mm thickness is an option.

At Rear
Internal Drive

Rating of a mode
Form Monophonic power amplifier
Continuation average output
(20Hz - 20kHz, 0.01% of distortion)
1000W (2ohms)
800W (4ohms)
500W (8ohms)
250W (16ohms)
THD (20Hz - 20kHz) 0.01% (between 2ohm-16ohm, 0.25W - a continuation average output)
IM distortion (EIA) 0.003%
Frequency response 20Hz-20kHz±0dB (at the time of a continuation average output level control MAX)
0.5Hz-400kHz+0 -3 dB (at the time of 1W output level control MAX)
0.5Hz-140kHz+0 -3 dB (at EIA, the time of 1W output level-control 6dB)
Gain 28dB
Load impedance 2ohm-16ohm
Dumping factor (EIA) 300 (50Hz, 8ohms)
Input sensitivity/impedance 2.6V/20kohm (at the time of a continuation average output)
0.12V/20kohm (at the time of EIA and 1W output)
Input level adjustment Step type Attenuator
Attenuation: They are [ 0 - the 1dB step between -20dB, and ] 25 contacts of -23dB, -30dB, and -infinity henceforth.
Error: Less than ±0.1dB
S/N (A compensation) 130dB (at the time of a continuation average output input short-circuit)
100dB (at EIA, the time of 1W output input 1kohm)
A low filter 10Hz/17 Hz/30 Hz/50 Hz, -12 dB/oct
Power output meter A logarithm compression peak directions type, -60dB-+3dB, and an output Direct-reading scale
Digital power display
Form : It is a watt display about the peaking capacity at the time of 8-ohm load.
Display digit number : Triple figures
Display range : It is a Direct reading about 0.001W-999W by range change.
Range 0.001: 0.001-0.999W
0.01: 0.01-9.99W
0.1: 0.1-99.9W
Hold time : 0.5 second, 3 seconds, 30 minutes
Frequency response : 20Hz-20kHz+0 -0.2 dB
Pulse reply error : It is +0 about 100Hz one wave. -0.4 dB
The semiconductor used Transistor: 57 pieces
FET: Five pieces
IC: 21 pieces
Diode: 65 pieces
Power supply voltage AC100V/117V/220V/240V, 50Hz/60Hz
Power consumption 175W (at the time of no inputting)
490W (Electrical Appliance and Material Control Law)
780W (at the time of 8-ohm load 500W output)
Dimensions the width 480x height 232(piece -- it includeds) x depth of 476mm
Weight 41.5kg
Attachment Timing cable (1.5m)
Option Side wood A-14 (one set with attachment lug, 16,000yen)
Fan for heat dissipation O-81 (one set, 8,000yen)
Timing cable TC-11 (10m, 3,000yen)