With a B+ of 250V or less, the power scale kit mentioned in the last post runs cool because I can use half the winding in the power transformer and just produce less voltage. If I jumper channel 1 and 2, the amp is plenty loud at this setting. However, when using just one channel, I was finding that I needed more volume. This meant using the full winding of 550V and dropping 150V to 200V through the power scaling circuit. This produces some noticeable heat in the regulator.
Kevin reassured me that with an adequate heat sink things would be fine, and that if I was worried, a small fan would help move the heat away. If I was still concerned, he suggested the Power Scale Cascode kit. This adds another regulator to the power scaling circuit and splits the heat between them. I realize this is probably overkill, but it restored my peace of mind, so I went for it.
This really works as it's intended. Both regulators are bolted to the chassis for a heat sink, and the devices get slightly warm. The chassis heats up, so you know the heat is still being dissipated, but the heat is distributed and there are no hot spots in the circuit. A Super Lead's B+ is about 550V with 4 tubes drawing about 30 mA apiece, so this is somewhat extreme case, and I don't think the power scale cascode kit would be needed on amps with lower B+ voltages and fewer tubes.