> And I think the yellow panels would be great.
> with the tubes protruding from the panel are they running hot, enough to
> either singe a hand or a patch cable

Thanks all. Nice to see someone cares enough to answer.

No, the tubes won't get hot enough to melt patchcords or burn your
fingers.
At most, they will get a little too hot to hold with your fingers for
extended periods. So don't hold them.

Convective cooling is critical here, thus the exposure. If they were
enclosed in a cabinet they would run a lot hotter.

That VCO circuit is a really cute thing. I found it in a 1964
textbook. It was called a "tuneable amplifier", even though it doesn't
even provide any gain, in fact it attenuates the input signal a LOT.
Control it with a 5C3 Vactrol, and it makes a strangely linear
VCO.....I didn't expect that!