Official Word On D-Moll Tube Types

[ubermetaldood]

Neither the manual or website say anything about which tubes can be substituted in the D-Moll. Does it only take KT77/EL34 types, or can other types like 6V6 OR KT66 be used? If so, do you recommend certain bias settings or something?

 

[Peter Diezel]

[No message]

 

[ubermetaldood]

Cool, thanks Peter. So I guess the D-Moll doesn't accept other kinds of tubes like the Einstein or other models do? What about EL34's and bias recommendations for that type? Also, why JJ's? I have been looking at Tung-Sol and Sino KT77's. What do you think about those as well?

 

[Peter Diezel]

Our amps accept other tubes too but we are a company
that needs reliable tubes. At the moment we are happy
with our stock tubes because of minimum warranty repairs.

To calculate your bias current:

Our amps have a plate voltage of 460 to 480 volts.
Let´s say it´s 470 volts average.

Maximum power (plate dissipation) of the tube X 0,7 / 470 volts

For example: 25 watts X 0,7 / 470 volt = 37,2 mA each tube.

To bias for 60% would result in more tight response but decreasing the clean sound.

25 watts X 0,6 / 470 volt = 31,9 mA each tube.

So we are happy to recommend 35 mA

Best,
Peter

 

[ubermetaldood]

Our amps accept other tubes too but we are a company
that needs reliable tubes. At the moment we are happy
with our stock tubes because of minimum warranty repairs.

To calculate your bias current:

Our amps have a plate voltage of 460 to 480 volts.
Let´s say it´s 470 volts average.

Maximum power (plate dissipation) of the tube X 0,7 / 470 volts

For example: 25 watts X 0,7 / 470 volt = 37,2 mA each tube.

To bias for 60% would result in more tight response but decreasing the clean sound.

25 watts X 0,6 / 470 volt = 31,9 mA each tube.

So we are happy to recommend 35 mA

Best,
Peter

Exactly what I wanted to know. Thanks.

 

[adr1anos]

FYI the Plate Dissipation (max) of the various tube types can be quickly referenced to here:
http://www.audiomatica.com/tubes/kt77.htm

 

[ubermetaldood]

So if KT77's are 25w and EL34's are also 25w plate dissipation then there's no need to rebias for EL34's?

 

[esizer]

So if KT77's are 25w and EL34's are also 25w plate dissipation then there's no need to rebias for EL34's?

In theory...yes. In practice, I always rebias. FWIW, I'm running the recommended tube list in my D-Moll and it sounds glorious.

 

[esizer]

And Peter, my D-Moll's plate voltage was right around 500 volts. Is that something to be concerned about?

 

[cheftie]

So if KT77's are 25w and EL34's are also 25w plate dissipation then there's no need to rebias for EL34's?

Not quite so, I am afraid.

In fact, it is strongly recommended you bias each time you install power tubes even if they have been the same tube type and brand.

 

[Peter Diezel]

And Peter, my D-Moll's plate voltage was right around 500 volts. Is that something to be concerned about?

No concerns, you have a good wall supply.

 

[ubermetaldood]

And Peter, my D-Moll's plate voltage was right around 500 volts. Is that something to be concerned about?

No concerns, you have a good wall supply.

This brings to mind some questions. First of all, does the power from a standard wall socket differ from home to home or don't they all supply the same voltage? Also, if some are stronger and some are weaker, then I guess that means it increases the plate voltage? I thought higher plate voltages means that you have to have higher volume to juice the tubes. Does that mean the more powerful your wall socket is, thus increasing the plate voltage, the louder you have to play your amp to get a good tone?