I know there isn't much interest in these amps anymore, but wanted to post my findings regarding thermals. I spent around 3 hours yesterday testing the one I have in for repair to evaluate whether these run cooler with no heatsink, heatsink only, or heatsink with a spreader bar to tie it to the top cover. @johnwmclean had at one point suggested that he thought these might run cooler without. I forget which user suggested and implemented a spreader bar, which for them resulted in lower temps.
I used a thermocouple with the covers on to do this test. For the 1st case (no HS), I put the thermocouple on top of the upper right transistor in the L- channel. For the other two tests, the thermocouple was touching the collector tab. I tried to wait long enough for things to stabilize completely, which never really happened. Even after an hour or more, the temp would go up 0.1 ÂșC every minute or so. Here are the results:
bare 91.8 (shortest test, around 45 minutes)
HS only 92.6 (approx 1 hour +)
HS w/spreader 87.1 (1 hr 20 min)
all temps in ÂșC. Ambient temp 22.1 ÂșC.
It appears that w/spreader is the winner. That temp was going up slower than the other two, so I would guess that the margin is a bit larger. i made the spreader with a couple of pieces of 1/8" and 1/16" thick aluminum x 1" stock.