BSIAB2 brightness

[GGBB]

I built a BSIAB2-Pinnacle hybrid the other day and find that it really enhances the finger squeak noise - to the point where it's just too much. I know that isn't uncommon for distortion pedals, but this is different - it's very high frequency like someone turned the high presence all the way up. Playing with the tone or contour can alleviate it but that changes the sound character in a negative way, so it's hard to dial in a good tone without the squeak. This is my first JFET distortion pedal build so is that a usual thing with them or with the BSIAB2 circuit?

Background - stock BSIAB2 with Pinnacle input stage (everything before the first JFET), Pinnacle tone and contour (brightness switch is off) and output buffer (everything after Q5). And one other difference - I used noiseless biasing for the two µ-amps - 47k + 47k divider with 470k bias resistors.

http://gaussmarkov.net/layouts/bsiab2/bsiab2-schem.png
http://i1272.photobucket.com/albums/y384/jawnypublic/pinnaclelastversion_zps55e23dc2.jpg

[PRR]

Verify R4 R5 C12 C13.

Take out C7 and C9.

No, it is certainly not "a JFET thing". But this circuit uses all the tricks to drive JFETs wild.

[amz-fx]

Raise the value of C4 to 0.22uF or larger (gaussmarkov schematic).

The BSIAB is derived from one of my old circuits, so take a look at some of the original values from the old schematic:

http://www.diystompboxes.com/pedals/booster25.JPG

Best regards, Jack

[GGBB]

Thanks guys - interesting. All my values were okay. Bumping C4 didn't really rein in the top end, but it did add some whomp to the bottom end. I'll have to play around with that some more - there are some interesting tonal possibilities there. Taking out C7 changed the character of the pedal too much for my liking, but removing C9 helped. I added a 1nF cap between drive lugs 1 and 2 and that seems to be working pretty well although I need to play with the value some more. I'm going to change the tone stack too - I'm not crazy about the Wampler stack and that contour is really just a high mid and treble shelf filter - I don't find it terribly versatile - too heavy handed. I'll probably try your presence control, Jack, as well as the stock BSIAB2 stack.