"Master" volume in a SE guitar amp

Guys,

A friend of mine has a Matamp first lady, which is very close to the C7 , http://nicosonic.free.fr/schems/Matamp%20C7%20schem2.jpg
This little amp has no master, but has an effect loop, Can I just put a 10k Log pot between send and return in a small box, so it mimics a "master" volume ?
Or maybe a lower or highe value pot ?
The amp is small but very loud, it starts to sound nice when the volume pot is cranked up, but it's much too loud for bedroom playing.
Any ideas, infos are welcome to tame this little beast.

Regards

try a 1M log pot first.

That should work (1M). If the tone dies somewhat (eg. becomes dull) at low volumes, you could consider adding some filtering to compensate.

Better than a master volume, controls voltage to plates to retain tube gain. Look under kits for V V R.

Two versions, cathode biased and fixed bias. With fixed bias, you need to lower the bias supply as well.

http://hallamplification.com/main.html?src=%2F



Or another option is a bootstrapped master volume. Best master volume I have heard. The dual ganged pot feeds the phase inverter. No need to add capacitors like you would if you were adding a PPIMV (post phase inverter master volume), which is a fairly common type, and generally considered good. Bootstrapped is much better in my opinion.

http://ampgarage.com/forum/download.php?id=8373

http://ampgarage.com/diy/index.php?topic=8464



EDIT   doooh!!, you did say SE. For a master volume, I would go with a 1Meg pot after the last triode, after the 100n cap. Since the power section is cathode biased, probably won't need a cap after the pot (block DC from the pot making it scratchy). I really do like the VVR/power scaling systems though. Way better than a master volume.

i think you are liking the el34 distortion, as millions of americans listen to everyday on the way to work.

so, you might try a different speaker, or a speaker attn, like a power brake or something.

or, you could hammer on the output transformer and short the lams into dc saturation?

Thanks for your suggestions guys.

The amp is very compact, we try to avoid to drill the chassis, and anyway, the only free space is at the back of the amp, which is not practical for a master volume.
The send and return jacks sockets are on the front, so, I was thinking of making a small box with the pot in it and plug it on the front loop jacks. In that way the amp stays "untouched".
I'm going to try this.

Cheers

It's almost humorous the amount of ebayers selling
" Master volume " boxes for the fx loop
certainly cheap  easy and non destructive for you
if there's enough gain for your liking in the preamp
[ no harm and you can play with caps as others mentioned ]
Speaker atten as cj mentioned also no drilling and
of course give you the whole amp sound .

I like the sound of the cathode schemes for masters ,
thanks for the links above ,posters

might also want to check this out, this guy seems to really know his stuff. i've heard nothing but good things about his books.

http://www.powerscaling.com/community/index.php

CJ said:

i think you are liking the el34 distortion, as millions of americans listen to everyday on the way to work.

Click to expand...

Yeah baby!  Which is why I just built a Marshall Plexi with a single ended, single EL34 output stage (haven't quite finished it yet)

if you want to get funky, put in a super small output transformer and wear the tube out.

no wait, relam with nickel.

outoftune said:

might also want to check this out, this guy seems to really know his stuff. i've heard nothing but good things about his books.

http://www.powerscaling.com/community/index.php

Click to expand...

His books are very expensive but I was lucky to pick-up his 2nd volume on e-bay pretty cheap. Concepts are explained in a very-brief-but-to-the-point manner and it is packed with schematics. Worth every penny. However, when you think about what PRR throws here on a daily basis, the guy should be receiving royalty cheques every month.

sahib said:

[However, when you think about what PRR throws here on a daily basis, the guy should be receiving royalty cheques every month.

Click to expand...

Ain't that the truth !!!

MM.