Capacitors in Cary PH302 phono amp

The caps appear to be mounted too close to the 6SL7 tubes as Dover has noted. However, the glass envelope of the 6SL7 is where most of the heat is. The base just houses the pin-out, so your mounting position is probably fine.

FYI- An old trick when replacing passive components that take up room is to mount from the underside of the circuit board. Sometimes taller standoffs are needed to raise the board a sufficient height to fit the part. This would allow you to keep the leads short. ( and mount away from the tubes.

Reb, Dover, thanks for the concern. I had read about the Mundorf caps not liking heat, so I checked things out before mounting.

I've given the caps a little tweak - the distance to the 6SL7 tubes is 4mm. As you noted the caps are opposite the brown tube bases, not the glass envelope, and they approach the round base on a tangent. I think that gives plenty of breathing room.

If we were talking about a power tube in a hot amplifier chassis it might be different, but the envelopes on these tubes only run warm to touch.
You can read the specs for the 6SL7 here.
As you can see the plate dissipation for the tube is 1W max and the heater is using <2W - so <3W total per tube (most of which will dissipate from the glass envelope - which has substantially more area than say a similarly rated 12AX7, hence the lower glass temp I guess).
The PH302 has a rather big case with plenty of breathing room and the case itself gets barely warm...and that's only above the 5AR4 rectifier tube.

I don't believe this environment should pose any issue for any reasonably designed electronic component.

FWIW, the PH302's PCB mounts onto shallow standoffs to the bottom of the chassis - definitly no room to mount a cap like this on the bottom of the PCB.

Once again thanks for the input.

A closer look at the cap to tube distance after a little tweak to the left:

Mundorf silver/oil cap

Tobes,

I would buy a roll of automotive gasket material (the grey multi-ply sheet) Cut a square and stand it up between the capacitor and tube. In a tube cd player mod that I installed Mundorf caps close to the tubes. The gasket material blocked the heat. Without the gasket material, just too hot for the long term.

Hi Tobes - we must sound like a bunch of old women with our comments. Next step if you want to go further would be to replace any Solen's in the signal path. Even the MIT will easily surpass these in speed, timing, dynamics and your pre will just get better and better.