Express build question

[moselle]

Hello.
I have an Express built.
Everything is typical values.
It sounds very good until I roll down the amp volume (maybe 7 on the dial or below) and it sounds extremely bright to the point of sounding not very nice.
In the build I have substituted a 250K treble pot because I have no 1M.
Is this a problem?

[marcoloco961]

That 250k pot will make a difference. Whether it is that big of a difference, is a matter of opinion. I would go ahead and change it to a 1M when you have a chance. The 500pf cap entering the bright switch can be lowered to take away some of the treble. You might try a 330pf or a 250pf instead of the 500pf.

I have found that the 100k resistor entering the tone stack has a big effect on the overall tone. Marshall uses a 33k there to get their sound. I have installed a switch on my last build to go between 100k and 47k.

With the 100k in place, it has the great trainwreck cleans. Really crisp and clear, but as you turn up the treble, the attinuation on the low end is severely cut. With the 47k, you do not lose the lows as bad when the treble is turned up. You do lose a little of the good cleans when using the 47k, so I just made mine switchable between the two. The 47k mode is also good for a really nice "grunge rock" type of overdriven sound.

[moselle]

Excellent.
I'll dig around and see if I can find a 1M.
I bet that is the problem because the treble pot seems to be doing next to nothing.
33K resistor swap is a good idea.
I give it a shot.
Thanks for the advice.