treble bleed in fx/BMP

[m_charles]

Hi,

I had a quick question.
Did a search, learned a lot, but couldn't find this exact answer.

I wanted to see if I could retain some of the highs on my modded BMP clone when the fuzz pot (100k) was turned down.
I decided to try the treble bleed I had done on a telecaster years ago. I couldn't remember the values so I played around with caps and resistors and came up with:

A 470pf (or .001uf also good) in parallel with a 100k resistor across lugs 3 and 2 on the fuzz pot. This brightened things up nicely.

1) Now I know that the 100k has now altered the fuzz pot's value, but can someone tell me why this worked and sounded good?
2) The 100k was a total guess. Does the 100K with the 470pf even make sense?
3) is putting a treble bleed on a fuzz/gain pot even a "kosher" thing to do? I heard of them on the out pot...
4) Any other suggestions for values/caps/resistors to get a good bleed with the fuzz down?

thank you so much,

chuck

[John Lyons]

Putting a cap in parallel with a resistor makes a bypass in itself not even using a pot.
Marshall used a 470K with a 470pf across it for a treble bypass in line with the signal.

Usually a treble bypass for guitar or amp is a cap in series with a resistor across the hot lug (3) and the wiper.
Or often times just a cap. 100pf or so. Fender used 120pf in most of the silver face amps.
Adding the resistor in series alters the shelf slope of the treble bypass.

I looked up some notes and I had 130K in series with a .001 cap across the hot and wiper for guitar...

Hope this helps.

John

[zombiwoof]

Yup, if you put the cap across the outside lugs of the pot, you just changed the value of the pot.  A bypass cap goes, as the previous poster said, from the hot lug to the wiper, the same as in a guitar.  I did this on my fuzzface for the same reason, and I noticed later when I saw a schematic of Roger Mayer's Fuzzface that he does something similar.  This was on the volume pot, however, don't know how it will work on the fuzz pot.

Al