Audio Database

The

DIATONE M-A01
75,000yen(around the 1978 time)

Description
 
It is the stereo power amplifier aiming at a miniaturization, maintaining high performance.

In order to improve a low-pass phase distortion and TIM, direct-current-ization which excluded entirely the capacitor used as the damping time constant of a circuit is adopted. This has realized the characteristic [ flat / to a direct-current region ].

In order to improve the elongation of a high region, RET (ring emitter transistor) is adopted as a power transistor. furthermore, the gain before applying a negative return -- each of each stage -- the negative return which is aiming at improvement in the nakedness characteristic by distributing the optimal, and was stabilized to high frequency is made easy to apply.
The amount of negative returns in low frequency was reduced, increased the amount of negative returns in that much high frequency, and, specifically, has proposed distortion.

The characteristic is well equal to the first rank, and also gm (mutual inductance) is large, and the noise of itself has adopted extremely little original low noise dual FET. This has improved the S/N ratio.

Two filter condensers of 55V/20,000micro F and the power transformer of 250VA which efficiency carried out the cut core which can do a miniaturization highly, and it had are adopted as a power-source part. This power-source part is the magnitude which occupies about 40% of the capacity inside amplifier, and has structure with a power source powerful with small size.

The peak level indicator by the LED display of 12 single-sided channels is carried.

In order to attain a miniaturization, power supply circuits other than a power transformer and a heat sink are summarized on the printed circuit board of one sheet.
Moreover, は's [ and others ] cautions are in combination of the magnetic flux produced by a large power-source part, and in order to lose the magnetic flux combination during input and output, consideration fine also about part arrangement of an input circuit and an output circuit and leading about of a Copper-foil pattern is carried out.
Furthermore, by miniaturizing a printed circuit board, a Copper-foil pattern becomes narrow, about the problem which affects the impedance of a pattern, in proportion to the magnitude of current, a Copper-foil pattern is made large, and influence of pattern impedance is lessened.

The heat sink was exposed on the right-and-left side, and also air was taken in from the front panel lower part, the convection current was caused also inside the set, and the heat stability which also bears the Oide power is secured.

The protection circuit respectively independent of the speaker and amplifier side is carried.

Internal

Rating of a mode
Form Stereo power amplifier
Circuit system Three steps of differential amplification
Current mirror drive Darlington single PP (direct-current amplifier)
Output power 70W+70W (8 ohms, 15Hz - 20kHz, THD0.01%)
THD 0.004% (8 ohms, a rated-3dB output, 20Hz - 20kHz)
0.006% (8 ohms, 1W output, 20Hz - 20kHz)
Cross modulation distortion
(70Hz:7kHz=4:1)
0.008% (8 ohms, Output power)
0.005% (8 ohms, 1W output)
Output bandwidth 10Hz - 60kHz (8 ohms, THD 0.05%)
Frequency response direct-current-200kHz+0 -1dB
Input sensitivity/impedance 1V/50kohm
Dumping factor 100
Remains noise 80 microvolts or less
S/N 123dB
Phono Output voltage 0.1mW/W
Power source AC100V, 50Hz/60Hz
Power consumption 160W
Dimensions Width 270x height 140x depth of 243mm
Weight 10kg
Attachment PIN-PIN cord