A lot of people seem to want a vero of this effect. Someone also requested a dual switch version, but I haven’t found much info on that so this is the, I guess, regular version. Let me know if it works πŸ™‚

Update (08.02.2012): Finally verified, thanks to Christian.

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33 thoughts on “Request: Xotic BB Preamp

  1. Hi guillotedivi,
    You should be fine substituting with the closest value you can get your hands on. E.g. 150pF and 47pF is probably more common.

  2. Hi, I wanted to know if I can replace the 151pf and 51pf capacitors for others, because I can not get them. Sorry for my English.

  3. It’s probably either a short circuit somewhere or possibly a wrong valued resistor (are both R25 and R26 10k?). You can measure the DC voltage at the lower leg of either R25 or R26; it should read approx. +4.5-5V. Your best bet is to double and triple check everything (check out the debugging section for some suggestions).

  4. Harald,
    Thanks for your help, I’m not much good when things don’t work, fortunately the other 3 projects I’ve done from your site have been functional.
    Your #1 supposition is correct, my voltages are way off,
    (pin1=8.53, Pin2=8.27,pin3=0.11,pin 4=0,pin5,6,7=8.29,pin8=9.31)
    Could you tell me how best to track down my dc bias issue.

  5. Steven, sounds like you’re getting close to finding the problem. If the signal enters the opamp (pin #3) but doesn’t leave it (pin #1) most likely you have either:
    1) Wrong DC bias. Measure the DC voltage on your IC’s. Apart from the power and ground pins you should see approx. half of +V on all of them (with +9V in that should be about +4.5-5V).
    2) The signal path around pin #1 (or pin #2) is shorted to ground or +V. Look for shorts, missing/misplaced components, bad pot etc. in that area.
    Hope that helps πŸ™‚

  6. I’m having a problem with no signal, I can trace it as far #3 pin of IC1, no further.
    I have good power and grounds to the IC and throughout, I’ve even replaced the IC with another RC4558.
    Shouldn’t the audio come out of IC1 pin 1 again?
    Any suggestions?

  7. If I were to guess I’d say you have a short somewhere that’s taking the pot out of the circuit equation. Check out the debugging section for some tips that might get you closer to a solution.

  8. Sorry, to be more specific turning my gain pot does nothing, even at either extreme there is no change to the signal.

  9. Hey dude, awesome pedal. Just one problem – the gain pot does nothing at all. I have an awesome booster but no crunch and I’m not sure what might be wrong. I’ve checked the gain pot, replaced the transistors and ICs and re-melted all connections. Any ideas? Thanks πŸ™‚

  10. No tonal difference between the 1N4001 and the 1N4007. The only difference is that the 1N4007 is rated for a much higher voltage (1kV).

  11. It’s been a while since I made this one but I was wondering if there would be a tonal difference with 1N4007 (which I used) instead of 1N4001?

  12. You have to make sure the ICs and transistors can handle +18v (which they probably do just fine) and you also have to make sure your capacitors, and especially the electrolytics, are rated for at least the same amount of voltage, but ideally 40-50% more; i.e. you need electrolytics rated for 25v or more.

  13. I added some fresh solder on every joint and I cleaned all the cuts.Finaly I have a good pedal!Thank you so much for your time anyway!

  14. Sounds like there’s a mis-biased gain stage somewhere. If you have an audio probe it’s a great tool for walking down the signal path looking for what stage is failing, which would help you narrowing it down. Otherwise, do general debugging, look for cold solder joints, solder bridges, missing or displaced components/cuts.

  15. Great tone!I have a problem though..it sounds good when I play lets say chords, but while playing lead notes with soft picking the tone fades out very fast and in bad way.I have normal sustain only with low gain.Anything?

  16. Thanks alot for this one! I think I am going to tweak it for more bass and more gain, with boost switches. Appreciate all of your effort posting your new layouts. Peace.

  17. Yes but with no luck.
    I’m sure I have something crossed up somewhere.
    Thanks anyways!

  18. Never run into this issue before and I’m not sure what may cause it, sorry. Have you tried googling the problem?

  19. Thanks so much for posting this!
    I’ve made one and sounds beautiful, but-

    Volume knob works properly until increased past 2o’clock, where it starts to cut volume (or treble really).
    Otherwise, works awesome
    Any ideas where to look first??

  20. I builded this. MAN I HAD A RAGINGNGNG BONER, when I played this.. Got it working on the first try.
    Don’t know what’s wrong with others problems, but my clone works πŸ˜› … Something bad about the layout: THE THING IS HARD TO FIT TO THOSE NORMAL SIZED ENCLOSURES πŸ˜› closing this pedal was a bit ANAL

  21. Hello, thanks for your great site. several builds firt time posting. I have a problem with the BB preamp. I have it working, sounds good, however if i have the volume pot at any over 25% i get a horible squellig noise, i can however silince it only by tunring down the treble. In fact i can turn the volume up all the way with no issues, but only if the treble is turned down all the way. Any ideas to check or where i can start

  22. can i use 2N3904 for 2N5088 ? any Hfe values for 2n5088? it can help me to find proper 2n3904, maybe.

    thanks, as always sorry for my english πŸ˜€

  23. just finished this and it works like a charm! i’m really digging this pedal. definitely will be using this one a lot.

    thanks again for an awesome layout, harald!


  24. Haven’t tried this myself, but looking at the schematic you should only be able to mute it with the volume, not the gain.

  25. Hi, Harold i built this today, and like it, very useful.When i back the volume and gain back to nothing, i get nothing, which is what its supposed to do, right?.
    Harald great job as always!

  26. First off, thanks for verifying the layout.
    Not sure about the volume issue. From looking at the layout it should be able to shut completely off. Have you checked all trace cuts, resistor values, component placements etc? Could this be a signal leaking into the output via a wire that’s too close or something like that? I’m afraid I can’t help you much πŸ™

  27. Hi mr Harald,
    I have built this bb preamp,and its work..the sound is nice,but the volume does not completely mute at full CCW rotation (leaks a little ),.can u help me..

  28. Thanks so much for this layout! I tried myself to make the vero on DIYLC, but it didn’t go well.. I’ll tell how it goes when I try it out.

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