Here is a simple 8W Class A Amplifier. I am very pleased with the sonic results of this amplifier. It really does not disappoint. Even using fairly standard 3 way speakers in a large room, surprisingly there is ample power. What strikes me the most is the ability of this amplifier to differentiate between instruments and noises in the sound stage. This clarity is what I like most and I think this is achieved by deceptively simple and pure circuit topology.
I used the original board layout, transistors and JFETs, and made some modifications. Heat sinking was increased to approximately triple the amount recommended. Instead of using the standard bridge rectifier, capacitor bank and battery setup, I opted for a fully regulated supply with a total of 127,0000 uF capacitance per channel and a 500 VA toroid transformer.
My “regulated monster” is currently running 0.5-0.6 Amps bias per Hiraga’s recommendations in the article. I tested the power supply which you may recognize as the PCB for the John Linsley-Hood simple Class A amplifier 1996 version from Williams Hart Electronics. I have upgraded the supply with LM338K TO-3 case regulators in lieu of the original LM338T TO-220 regulators (see LM338 Voltage Regulator Calculator for more information). On the bench the supply measures very well in this configuration with below 160-200uV of ripple peak-to-peak under a 2A series load. Despite this low level of noise, I would like to try the battery supply for its huge current capability and as close to zero noise as possible.
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