How to attenuate signal in an effect loop (guitar)

Hi Guys!

I have a problem I tried to solve but didn't come far, maybe you have an idea.
I`m using an effects precessor (50k input impedance) inside a tube buffered effects loop (max 10k output impedance) and when I switch to clean channel, I overdrive the unit due to the large dynamics of a clean sound. I would like to put a switched attenuator before the unit to get rid of some dB in that case.
I tried a pot, but it takes away high frequency when turned down.
Is there any other possibility to get rid of some level without loss?
I would like to do that with passive components...

Thank you very much!
Best,
Steaan

maybe a small cap across the pot to bypass the highs
like in gtrs ?

I thought of that, too, but I think it's difficult to compensate linearly...

> I tried a pot, but it takes away high frequency when turned down.

Use a lower-value pot?

have you tried putting a cap across two legs of the pot? This will retain some of the signal. Try something like a 150 picofarads. These are what fender uses as bright caps.

Here is some reference info on tube buffered effects loops..

http://www.diyguitaramp.com/fxloop.html
There is alot of info on effects loops at the forums at:

http://www.ax84.com/bbs/index.php

Just do a search for effects loops.
If you have a 12ax7 tube that both sides are used for the in/out buffer of the loop...you can try a 12at7 which will lower the output a bit.

Thanks for your help!
I'm just looking for something that is only switched in the signal path to take away some dB when playing clean stuff, using a different tube would affect all
channels...

PostPosted: Sat Jun 14, 2008 2:25 am Post subject:
> I tried a pot, but it takes away high frequency when turned down.

Use a lower-value pot?

Click to expand...

Is it OK to go lower than 200k when the load impedance is already 50k. I don't want to load the tube to much...

What about active electronics...could I use another tube buffer or something like that?