WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
Heatsinks on tubes may actually make them run hotter, since they intercept the normally radiated radiant heat and have poor thermal contact with the glass. Probably were used to keep the surrounding components from getting hot by converting all the radiant heat to vertical convected hot air instead. A fan could help, but that would likely work even better without the heatsink in the way.
Morgan Jones wrote about valve heat sinks in Building Valve Amplifiers (The blue book)
I dont have the book to hand at the moment but I think I remember him quoting some source saying that just keeping the envelope temperature down can extend life.
I can see that radiated heat from the anode would be partly absorbed by the glass because it does not completely pass IR. Also the black anodising on the heatsink will absorb the rest of the IR and as long as it has enough surface area for conduction/convection to the air will prevent heating of other devices around it.
I think I saw some the same as in the book at Ask Jan First. The Pearl ones look good if a bit pricey.
Pearl Tube Coolers do in fact work, especially the newer ones (without the fibre sleeve).
Though you could also experiment with thin section aluminum extrusion which you can buy be the foot, cut it to desired length then hand roll them to dia. over an appropriately sized dowel rod (od a dead tube of the specific type). Use eithe Viton or Silicone "O" rings to hold to the tube wall.
Just to be curious: what magical thing are you designing with these wonderful tubes??? Please tell us it is a Wavebourn OTL!!!!!
Sounds like an incredible way to use the 6S19P. A home theatre system seems like an interesting way to use them. What is the max output you get from them? How do they sound?
My worry is that the tubes may not tolerate the increased dissipation even with the heat sinks. Tried that with mil-spec 6N8S and found them becoming noisy after around 100 hours even though I had a dedicated fan blowing on it with glass temp not exceeding 80 deg Celsius. Let us know the results of your experiments.
I have always been puzzled by valve heatsinks. Unless silicon grease is used, they will make only patchy contact with the glass so there will be cool spots and the rest hot - a recipe for problems? Glass is a poor conductor of heat, so even the contact points won't cool it very much. Most of the heat gained by the heatsink will be radiant heat, which was already outside the valve anyway!
The solution to valve cooling is either ceramic valves or air flow. Air does contact the whole glass fairly uniformly so it can take the heat away. Maybe Wavebourn should be looking for a very quiet fan?
I would have to agree with DF96- I cannot see the electrode structure of a valve as anything other than a blackbody radiator with very little direct conduction. Is it possible, however, in this case, that because of the very high heater current,1-1.1A for a relatively small envelope that there is significant conduction to the glass via the heater pins? I must say that I liked MJ's solution of mounting 6528 double triode on a fan guard of a low noise fan with the fan blowing from underneath.
Maybe the glass will be cooler ( better convection ) , but the temperature of the plate will rise because some of the radiated heat will be reflected back from the heatsink , wich is very close and not a perfect black body to absorbe all radiation ...