• 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.

triode=>pentode

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Lico

Member
Joined 2003
I've been listening to this amp for a few months now and I want to change something. Nothing's wrong, but maybe I can make it better ;)
How would I change this to run the 6v6 in pentode mode, or I guess it would be tetrode wouldn't it? I think I just connect the other grid to B+ through a resister, but how do I figure out the value?
Thanks,
Andy
 

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bournville

Member
Joined 2003
I agree with Tim, but remember that in tetrode mode the HT consumption of the 6V6 will be higher than in triode mode, so check that your power supply and output tranny are up to it.

Depending on how sensitive your speaker (or ears!) are to third harmonic transients you might like to try the effect of a small capacitor wired across the primary of the output tranny - 0.001uf or 0.002uf of at least 750v working would be suitable. Larger values will affect the treble resonse.
 
Sch3mat1c

Sch3mat1c

Member
Joined 2003
seventransistorlabs.com/
Actually the screen and plate voltages are nearly exactly the same. Quiescently, the tube can't tell if its screen is on the plate or +V.

BTW, I wouldn't blame you if you think it sounds like crap...high Zo and distortion and all. By moving the screen connection you've removed the local NFB that keeps things in line. This is usually remedied with global NFB, but that's another can of worms that you can look for posts on...

Tim
 
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