Technik > Tech-Talk Amps

Less gain in valve jr mods

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bea:
The loudness of the amp is entirely determined by the last stage, i.e. the EL84 and to some degree on its working parameters (load impedance, screen voltage, anode voltage). If You reduce gain You need a higher input voltage to achieve the maximum power. On this level of argumentation it will not matter how the gain is reduced - by tubes with lower gain, by voltage dividers or by NFB (just to name some examples).

One simple and cheap method to reduce gain might be the removal of *all* cathode capacitances. This will add local NFB to each stage and, as a drawback, increased output resistance of that stage. Unfortunately we do not know what You mean by "all the mods" - some of the proposed mods might be contradicting.

BTW: changing tubes was the first of my modifications. Later on i restored the original tubes.

Beate

larsthestrat:
hi,

Thanks!

I did the mods mentioned in the DIY section of Tube Town, so adding a gain stage, tone-stack, new tranny, JJ tubes, etc.

grt lars

Caisa:
Why did you added a gainstage when you aim for extended clean headroom  ???

bea:
So the next thing to do might be to remove the gain stage You added, won't it? And then You might have a lokk into the forum. Some users, among them i, have modded the amp in the direction You like to have. This is documented in almost every detail - simply read the stuff and pick the ideas You like.

Beate

larsthestrat:
okay I have a second epiphone valve junior with a bitmo mod (tonepot). I will try to mod this one to these new specs you refer to (and use the hammond tranny from the first one). Do you have the post on when to look for these mods?

I'm not able to find them.....

grt. lars

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