Hi There,
Happy New Year folks!
I'm hoping you fellow pedal junkies might be able to offer some advice please. I've built the BB Preamp from
http://tagboardeffects.blogspot.com.au/2012/10/xotic-bb-preamp.html.
The basics are ok. Bypass works, foot switch toggled gives me huge volume boost. At almost min volume , I get close to unity :-). So it sounds like a fully cranked Marshall, which is to be expected.
The gain pot does not seem to have any effect when I play. At zero gain it's pretty high gain - and maxed it sounds no different. However without playing I can hear a bit of a difference when sweeping from min to max gain. It sounds like the hum increases slightly with gain (not a bad hum, just the kind of mild hum you would expect to hear when turning up an amp from min to max without any playing).
Also, I don't seem to hear any difference when switching between the two diode combos (I'm using an on/on dpdt)
So the issue is around the gain / volume clipping area. I built it with the 47k substituted for a 22k as suggested. Wondering whether I should sub the 151p for a 220p as suggested in the thread? Might help with the high output volume?
I swapped the Drive 1 and Sw1-5 wires at the switch as I wasn't sure if polarity mattered there?
I've scraped along all the gaps between the copper to ensure there are no bridges etc.
Any other suggestions to check before providing voltages and pics to dig deeper?
Regards,
Mark
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