Hi,

I did all the mods from the TT -site (valve jr.). I really like the sound of this amp now, but I would like less gain coming from it (more headroom). Are there any mods I can do to achieve this
(different pre-amp tube, changing resistors, etc.).

grt. lars

Hello,

The easiest way would be to use a different preamptube. Instead of the normally used 12AX7/ECC83 try a 5751 which would have about 70% of the gain of a 12AX7 or try even a 12AT7 for even less gain but some more compression.

Cheers Micha

hi,

thanks!

would this make the amp less loud or will it decrease the gain. I'm looking for the last thing, decreasing the gain but the amp should give the same amount of (clean volume).
I want to use it on stage, but with less gain....

grt. lars

[EDIT:]

I would like to recommend you a 12AT7.

The  GE 5751 in V1 of my Valve Junior sounds great but you'll not notice considerably less gain than with a JJ 12AX7.

Bye
Stephan

EDIT:

To further increase the clean headroom you might try a NFB mod, discussed here. Try efficient speaker too!

hi,

and will the amp stay as loud as with the 12ax7?

thanks!

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

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

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

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

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

Just a few lines deeper in the thread listing - the GA-5 modding thread:

http://www.tube-town.de/ttforum/index.php/topic,5240.msg134910.html#msg134910 (this refers to te other extrem - a bass amp)

and of course all the pages before.

Beate

okay, I can read a little bit german, so I can figure this out maybe. Which page do I start reading?? There's a lot to read. I would like to go  for maximum clean sound, but don't want to go less loud.

The easiest approach is to adapt my approach, maybe without the tone stack.

Reading: i read everything from page 1. Initially even several times.

okay thanks!

instead of removing the second tube stage, adding a new switch for bypassing the 2nd tube is also an option and will lead to a 3-Channel micro amp.
Also check the plate resistor Ra1. Replace it with an 68k resistor. Remove or make C4 switchable.

Regards, Dirk