Audio Database


Pioneer M-25
200,000yen(around the 1980 time)

The performance of amplifier is the stereo power amplifier developed by the basis of the design concept of a "magni-wide power range" that a full power play must be able to be carried out in a low distortion not only over the inside of an audio frequency band but over a super-wide band.

In order to enable the low-distortion full power play in a super-high region, ensemble transistor RET excellent in the high region switching characteristic is developed and adopted.

It carries the large-sized power-source part by the large-sized transformer of a L-R independency, and the capacitor of 22,000 micro Fx4 in order to die and to make it go over sufficient power while super-low-pass one improves a property with DC amplifier.

Even 3W is reproduced in a Class-A operation, and AB class operation is carried out with the output beyond it.
Since the utilization factor of an electrical power is a high efficiency near common B class amplifier, the peek component of a music signal also has allowance and it is being reproduced.

DC amplifier stream composition which eliminated the capacitor of the NFB circuitry is adopted.
Since the low-pass phase shift which the capacitor in a NFB loop generates owing to is canceled by this, stable NFB can be applied.

Since low-impedance-ization inside amplifier is put into practice, width is using the pure-copper board which are 12mm and 1mm in thickness for the grounding from an electrolytic capacitor to a speaker termination.
Moreover, the resistance value has adopted as the hot line from a rectifier to a speaker termination the 14th track (2.03phi Yori line) of the very thick set to one fourth of the conventional thick lines.
Furthermore, the Copper foil of the substrate was doubled in 70micro, and, as for 12mm and thickness, width has connected the collector of two power transistors with the short bar of a 1.2mm pure-copper board.

The mono-construction specification which suppressed the separation between right-and-left channels has attained the high separation.

Gilding excellent in the corrosion resistant is given to the input/output terminal.

Rating of a mode
Form Stereo power amplifier
Circuit system 3 steps of first rank differential current mirror load-intensities Darlington
Parallel push pull pure complimentary OCL circuitry
(AB class operation, DC amplifier stream composition)
Effective output (both channel drive)
8ohm : 120W+120W (5Hz - 30kHz, THD 0.01%)
120W+120W (5Hz - 80kHz, THD 0.05%)
4ohm : 120W+120W (5Hz - 20kHz, THD 0.02%)
(5Hz - 30kHz, 8ohm)
At the time of an effective output: 0.01%
At the time of 60W output: 0.01%
At the time of 1W output: 0.007%
Cross modulation distortion
(50Hz : 7kHz = 4:1 or 8ohm)
At the time of an effective output: 0.006%
At the time of 60W output: 0.005%
At the time of 1W output: 0.005%
Output bandwidth
(IHF, both channel drive)
5Hz - 45kHz (0.01% of distortion)
5Hz - 100kHz (0.05% of distortion)
Frequency characteristic 5Hz-200kHz+0 -1dB (at the time of 1W output)
Input terminal Input: 1V/50kohm
Output-terminal Speaker: 4ohm - 16ohm
Dumping factor 100 (20Hz - 20kHz, 8ohm)
SN ratio (IHF, A network)
Short circuit
Channel separation 1kHz:105dB
The semiconductor used Transistor: 55 pieces
Diode, other:53 piece
Supply voltage 100V, 50Hz/60Hz
Power consumption 280W (Electrical Appliance and Material Control Law)
Maximum electric power consumption 800W
Dimensions Width 420x height 153x depth of 370mm
Weight 22.5kg