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  Old School A/AB amplifiers 
 Date Written 
Gerritt Feb 23, 2007, 11:53pm EST Report Abuse
I have a circa late 70s/early 80s Yamaha M-80 amplifier that has a blown transistor in one bank. This unit used the Can type of transistors and had a max power output of 1250W/channel with 800W sustained. The uncorrected THD was in the range of .0003 to .0005 if I recall properly.

The last time I tried to repair this unit, oh about 10 years ago, the transistors were costing about $25 or so. I tried 3. It seems that each bank required a tuned set of transistors or the noise (THD) went off level.

The dang thing weighs a ton, but if I hit the lotto, I'd much rather have this unit and my old Klipch LaScallas back than most of the modern offerings.


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Sander Sassen Feb 26, 2007, 06:55am EST Report Abuse
>> Re: Old School A/AB amplifiers
Those amplifiers only performed well in 1kHz THD ratings, 10kHz and up would often be 1000-fold worse, if they even met with the 1kHz rating. Most of them only did at low power, if they even made the spec. Marketing was a big sales tool back then, which was amplified by the fact that such ratings could not be measured directly by magazines etc., simply because the commercially available equipment would only measure down to about 80 or 90dB which equals 0.01 ~ 0.03%.

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Sander Sassen
Editor in Chief - Hardware Analysis



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