Is anyone using a variac?

Most power tubes for audio amps, yup, 6.3V.

Tube heater/filament voltage=tube number for many American tubes

12A**= 12V
6L6, 6V6= 6.3V
5AR4, 5U4 etc.= 5V

el34, el84= 6.3V
KT88= 6.3V

Bias affects plate voltage-plate voltage affects bias-wall voltage changes both plate and bias voltage in preamp and power amp.
 
No, the heater voltage is not going to have any effect on the sound. It is, after all, not in any way involved with the signal path. It is just there to keep the tubes warm.
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Exactly.... tubes sound different at different temperatures... so when they run "cool", they have a distinctive (sometimes called "Brown") sound.

The heater voltage may not be involved in the signal path, but the tubes sure as hell are.
 
turnitdown said:
Exactly.... tubes sound different at different temperatures... so when they run "cool", they have a distinctive (sometimes called "Brown") sound.

The heater voltage may not be involved in the signal path, but the tubes sure as hell are.
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When people talk about tubes running cool or hot, they are talking about the bias voltage, not heater temperature. Changing the bias voltage allows more or less current to flow at idle, which will affect the temp of the plate. Like when you see a poorly biased amp with glowing plates. :eek: Too hot!

The heater heats the cathode, so it frees up electrons, which pass to the plate. Too low heater/cathode temp results in cathode stripping- the material of the cathode is damaged as electrons are pulled from it to the plate. The heater causes the cathode to release electrons without damage, that's all.
 
turnitdown said:
Exactly.... tubes sound different at different temperatures... so when they run "cool", they have a distinctive (sometimes called "Brown") sound.
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ps-

When tubes are biased "cooler" the sound is usually described as sterile/too clean, not brown or warm.
 
Thanks... I learn something every day.... :D

All this talk makes me glad that I'm happy w/ a Mesa Quad preamp (tubes) and a TubeWorks MosValve power (solid state) amp!!! ;)

In all my years of messing w/ different equipment and amps, I have never actually used a Variac.... had a few custom Marshalls, MetalTronix, Fender etc....

Thanks again...
 
turnitdown said:
All this talk makes me glad that I'm happy w/ a Mesa Quad preamp (tubes) and a TubeWorks MosValve power (solid state) amp!!! ;)
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Whoa, Tubeworks, rock on! I have owned a lot of their gear. Good rig to be happy with. :)
 
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