Audio Database


Pioneer M-22
120,000yen(around the 1980 time)

Class-A stereo power amplifier which adopted the chassis made from die-casting as the radiator made from die-casting.

The Class-A operation is adopted as a whole page.
The Class-A operation sends many idle currents through the transistor also in the time of a non-signal, and is a scheme which uses only operating range with the sufficient linearity of a transistor.
Although a Class-A operation has a low electrical-power utilization factor and calorific value also increases, in order that the upper and lower sides may be amplified by the same wave and may obtain a synthetic output, with B class amplifier, switching distortion or crossover distortion which are not avoided do not generate two transistors of a push pull.

The Class-A operation circuitry of M-22 has DC amplifier composition which removed the capacitor of the NFB circuitry. The time constant formation of the NFB loop was lost by this DC-ization, and the stable NFB operation is realized.
A whole page Class-A operation and this DC amplifier stream composition have realized the mid-high range without a distorted feeling, and the outstanding low-pass property.

The large-sized transformer of a L/R independency and the capacitor of 33,000 micro Fx4 are adopted as a power-source part.

The construction of the whole included amplifier is used as a symmetrical form, and the power relay of a protection network is also using the power-source part by two L/R independencies. Furthermore, attention is paid to leading about of an internal wiring etc. and the cross interferencee between channels is eliminated.

The pure-copper board is adopted as the earth line from an electrolytic capacitor to a speaker termination.

In order to protect a speaker and a transistor even against an emergency outage, the reliable protection network constituted from a quick electronic circuitry of a power relay and a response is built in.
A power relay carries out parallel connection of the two contacts, and is improving the robustness.

Rating of a mode
Form Stereo power amplifier
Circuit system Two steps of differentials, PP drive, two-step Darlington, parallel PP,
Pure complimentary OCL (a Class-A operation, DC amplifier stream composition)
Effective output (both channel drive) 30W+30W (10Hz - 30kHz, 8ohm)
(10Hz - 30kHz, 8ohm)
At the time of an effective output: 0.01%
At the time of 15W output: 0.005%
At the time of 1W output: 0.005%
Cross modulation distortion
(50Hz : 7kHz = 4:1 or 8ohm)
At the time of an effective output: 0.005%
At the time of 15W output: 0.003%
At the time of 1W output: 0.003%
Output bandwidth (IHF, both channel drive) 5Hz - 100kHz (distortion 0.01%)
Frequency characteristic 2Hz-150kHz+0 -1dB (at the time of 1W output)
Input terminal Input: 1V/50kohm
Output-terminal Speaker: 8ohm
Dumping factor 60 (20Hz - 20kHz, 8ohm)
SN ratio (IHF, A network)
Short circuit
The semiconductor used Transistor: 44 pieces
Diode, other:62 piece
Supply voltage 100V, 50Hz/60Hz
Power consumption 240W (Electrical Appliance and Material Control Law)
Dimensions Width 420x height 153x depth of 370mm
Weight 22.0kg