Audio Database


Pioneer M-70
100,000yen(1990 release)

audio-video power amplifier which carries 2ch / 4ch change functionality.

Shortest-ization of the thorough signal path is attained and the direct construction is carried.
In a direct construction, an input signal goes into the main volume unit prepared in the shortest location controlled by a brass long shaft from the part of a front direct, after passing through the selector stored in the shielding case which took the measures against a noise.
The signal by which level adjustment was carried out is led to an amplification part in the shortest distance, and is straight outputted to a speaker termination.
The circuitry layout considered so that unreasonableness might not start the fluence of this signal has realized shortest-ization of 80cm. And the using of the wire rod used as distortion of a signal or the factor of the tone-quality failure is made into the minimum.

In the power amplifier part, in order to cancel the nonlinearity of a transistor, the original super linear circuit of Pioneer is adopted.
This is pulling out the property which is combining the nonlinearity which the transistor has with another transistor which completely has a reverse property, is a flume detour way technology which negates a mutual nonlinearity and suits, and was excellent in the low distortion.
For this reason, it becomes possible to stop very slightly the amount of feedbacks in the whole amplification stage, and the number and capacity of a capacitor which have an ill effect on a tone quality are also decreasing.

In order that the noise electric current generated in a power-source part or a large-current part may prevent degrading an input signal by invading into a signal path, the clean grand system is adopted.
The power transformer and heat sink which were only being conventionally fixed to the chassis were attached as a severe insulated structure, the contact into which a noise invades was reduced as much as possible, and the path of an input signal and the break-in path of a noise are separated.
Furthermore, the it1 setups is carried out so that it may return to the power source which is a source of a noise, and the ill effect by a noise electric current is low stopped by these measures.

Various oscillations from the interior or the outside shake the circuit board, and cause the instability of a circuitry, and in order to prevent becoming a cause of a noise or a distorted occurrence, no vibrating and an absent-resonance-ized design are put into practice.
A hybrid chassis with a vinyl chloride sheet, the bottom plate which improved the periodic-damping property greatly according to the sandwich construction of the heterogeneous material of a steel plate, and a shielding case is begun,A variance and absorption effect of an oscillation are high, and the firm high-rigidity structure by the heat sink and honeycomb frame of the honeycomb form whose intensity also improved simultaneously is built.
Furthermore, five insulators which support a chassis frame directly are adopted.

By the same to each channel circuit-design and super linear circuit, direct construction, and powerful power-source part, it is at the 2ch drives time, and is at the 120W+120W and 4ch drives time, and the output of 70Wx4 (all are 6ohm) is realized.

2ch / 4ch change functionality is carried, and, also in two-line three inputs, and a speaker output, the inputs are two-line three outputs.
By an input selector, a functionality is possible as power amplifier of 2ch, 2chx2, and 4ch.

For the reason at the time of using combining digital surround field processor SP-91D etc., the auto output selector is carried.
This has a functionality of a surround field control and a Dolby prologic decode, for example in SP-91D, and placements of the speaker outputted like a processing front speaker and a center speaker, respectively differ in these two mode plays.
In an auto output selector, if the input mode to reproduce is chosen, according to it, it will switch to a processing front speaker or a center speaker automatically.

Power Electrolytic

Rating of a mode
Form audio-video power amplifier
Output power (20Hz - 20kHz)
Twoch drives : 150W+150W (4 ohm, 0.02%)
120W+120W (6 ohm, 0.01%)
100W+100W (8 ohm, 0.009%)
Fourch drives : 75Wx4 (4 ohm, 0.04%)
70Wx4 (6 ohm, 0.03%)
55Wx4 (8 ohm, 0.02%)
Dynamic power (EIAJ testing signal)
Twoch drives 2ohm: 210W
4ohm: 190W
THD (2ch drives) 0.005% (20Hz - 20kHz, 50W, 8ohm)
Input sensitivity/impedance Amp1 and 2:1V/40kohm
Frequency characteristic 5Hz-150kHz+0 -3 dB
SN ratio (A network, a short circuit) Twoch drives: 120dB
Supply voltage AC100V, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law) 320W
Dimensions Width 420x height 163x depth of 424mm
Weight 20.2kg