6DJ8 Linestage

[morfeas]

i've got to ask a silly question bout the heaters.

say i've got a silly transfomer lying around that only has one 6.3v filament taping. i was thinking of raising the heater voltage to the upper valve's voltage, would this prove detrimental to the lower valve?

Violate the max Vkh of the valve is not good practice either way. Regarding noise heater should more + than cathode. It also depends on type, brand, make. Some tend to make more noise than others.

 

[Shoog]

If using a totem pole design with one heater supply, and a twin triode such as the ECC88, these triodes are designed for such operation. Reading the datasheets will tell you that one triode is designed to sit at the top of a totem pole and the other at the bottom. It will also tell you the potential the top triode is allowed to be above the heater DC potential (usually around a 100V). If you stick to these instructions heater potential becomes a none issue (ie ground the heater and forget about it). If you think you will exceed the top triodes cathode to heater potential, then consider raising the potential of the heater by an amount which will bring the top triodes cathode back into its allowed range, this will have the added benefit of reducing heater induced hum within the bottom triode.

I have done this with no issues at all. Trying to use a different tube for the upper and lower triodes will create far more issues than the method I suggest.

Shoog

 

[hacknet]

cool. i'm thinking of raising the heater to somewhere inbetween but if you say that such triodes were built that way, then i'll just go ahead with grounding the heater..!

 

[Zen Mod]

cool. i'm thinking of raising the heater to somewhere inbetween but if you say that such triodes were built that way, then i'll just go ahead with grounding the heater..!

you better elevate heaters to some 40V;
all you need is two resistors and one cap

 

[Shoog]

Not all twin triodes will necissarily be designed this way, so the important thing is to read the datasheet for your chosen tube. The ECC88 is definately designed for this operation, I know this because I am using them in a totem pole.
Remember that one triode is designed to go at the bottom and one is designed to go at the top. Reverse them and you are going to lose the benefit and put your valve under strain.

Shoog

 

[lt cdr data]

aha the aikido, ok, but simple is better, sounds too clean and unmusical to my ears anyway.