An amplifier more powerful than the 25W MosFet, a 60 – 90W High Quality power amplifier design is presented here.Circuit topology is about the same of the above mentioned amplifier, but the extremely rugged IRFP240 and IRFP9240 MosFet devices are used as the output pair, and well renowned high voltage Motorola transistors are employed in the preceding stages.
The supply rails voltage was kept prudentially at the rather low value of + and – 40V. For those wishing to experiment, the supply rails voltage could be raised to + and – 50V maximum, allowing the amplifier to approach the 100W into 8 Ohm target: enjoy! A matching, discrete components, Modular Preamplifier design is available here: Modular Audio Preamplifier.
In the original circuit, a three-diode string was wired in series to R10. Two of these diodes are now replaced by a red LED in order to achieve improved quiescent current stability over a larger temperature range. Thanks to David Edwards of LedeAudio for this suggestion.
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