The amps are a fairly straightforward version of the 25W T8s as described in Audio Reality, constructed as a pair of mirror-image monoblocks. I made a few modifications here and there, but nothing of any great consequence - the circuit is still 95% as in Bruce's book. The changes I did make were mainly to the power supply.
I used two custom wound 240V primary toroidal transformers from Torema Transformers in each chassis. One has 4 secondaries - filiment heaters, driver B+, and output bias. The other just has one secondary which is the output B+. This is overspecified by 50% compared with the Avel transformer in the standard parts list. The transformers come with core resin "potting" and electrostatic shielding.
I decided to separate the two heater circuits rather than run the drivers and output valves from the same supply, as shown in the schematic. The output valves have a 20V/5A supply and were still wired as per the book, but I used a separate 12V/1A secondary for the driver filiments. This goes to a LM317T adjustable regulator and provides a regulated 12.6V for the driver, splitter and buffer stages. It intuitively seemed a good thing to do, but maybe it's just overkill.
The 550V circuit is as per the book, as is the bias circuit. I didn't see any point in messing around with these. The polarised B+ for the output valves has C-L-C filtering instead of the simple capacitor smoothing shown in the book (this is actually provided as an optional modification for the factory assembled T8 amplifiers). I used Hammond chokes and Sprague capacitors in the filter. The capacitors are smaller in value than those specified in the book, but there are more of them. Total supply capacitance is 7,200uF.
