BSIAB2....is this normal?

Discussion in 'Effects, Pedals, Strings & Things' started by FLYING V 83, May 12, 2008.

  1. FLYING V 83

    FLYING V 83 Pedal Trading Guru Silver Supporting Member

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    Recently got a BSIAB2 in trade.
    It doesn't "get going" until both volume & gain are cranked about 3/4 over, and has a digital "fizz" to the decaying sound. It also dies off rapidly with little sustain. Is this normal for this pedal?
    I like it's overall sound, very cranked-Marshall, but the lack of sustain and having no volume or gain until either pot is past 1/2way bothers me.
    Looked inside and saw there's a combination of 2n5457s & J201s, would it be worth it to swap them all out? I've read they can sometimes be bad but don't know the symptoms.
    Just getting into building pedals but not too keen on diagnosing trannys yet. All wiring seems to be in order, and adjusting the trimpot yields no improvement.
    Or should I just send it off to Chad at CMATMODS for repair?

    Any advice/thoughts is appreciated.
     
  2. nibus

    nibus Supporting Member

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    I have a Brownie and there is no "digital fizz" on the decay. It sounds like there is something wrong with the build. You could try switching the chips but it might not help the problem if there is some other flaw.
     
  3. LVE

    LVE Member

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    I've built half a dozen of those. Your symptoms sound like it could be the FETs. I think JD's build guide at GGG has reference voltages on it. You might have a loook at that to see if your voltages are in the ball park.
     
  4. FLYING V 83

    FLYING V 83 Pedal Trading Guru Silver Supporting Member

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    Thanks guys.
    I'm just getting into building pedals, and I'm not sure whether I can check voltages with the pedal assembled. Would I check across the soldered side or on the legs themselves?
    I didn't build this pedal, but have built the LPB2 and have some idea of the components and have a digital multimeter.

    I also emailed Chad at CMATMODS to ask about him repairing it.
    Or replacing the guts with his Brownie with the "fr8trane" mods.

    I repainted the box on the BSIAB2 so I don't want to lose that work:
    [​IMG]

    Hopefully I'll have this fixed or upgraded before to long....
     
  5. fendergeek

    fendergeek Member

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    I don't know much about building pedals, but I know a good looking pedal when I see one. Nice job! I'm not sure about those knobs with that pedal though. Hope you get it up and running!!
     
  6. B_of_H

    B_of_H Member

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    I wish I could help. I've built two of these one from a kit and the other on perfboard. It's a great pedal that I gig with and blew away my OCD and Tonebone classic head to head.
     
  7. fr8_trane

    fr8_trane Member

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    There's a trim pot inside that adjusts the bias for the final transistor stage. If its not set near the sweet spot it'll make the pedal sound bad. Mess with that and see if you can tune it by ear. If that doesn't work I would say you have 1 or more bad transistors.

    By the way my "mod" is just swapping lower gain transistors for the stock values. Nothing more nothing less.
     
  8. FLYING V 83

    FLYING V 83 Pedal Trading Guru Silver Supporting Member

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    Thanks Fr8, I've tried turning the trimpot.
    Only one spot along it's sweep where the pedal is it's loudest, everywhere else it produces no sound at all.
    Even after finding that sweet spot, it still doesn't produce sound until both vol & gain are beyond 1/2, which just isn't right to me.
    Unity gain on volume is at 2 o'clock, and the gain knob doesn't get mean until at least 3 o'clock, then a huge volume jump with both at 3/4.

    But the fizz bothers me, I like smooth gain structures.
     
  9. FLYING V 83

    FLYING V 83 Pedal Trading Guru Silver Supporting Member

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    Thanks.
    The knobs are from my Red Witch Pentavocal trem, I just painted the tops with tan watercolor & clear-coated them.
    Regular cream knobs (ala Fulltone), which I prefer, don't fit (the shafts are that close together) and the black rubber ones that came with it look like crap.
    I needed to paint the chrome tops as my 52 year-old eyes ain't what they used to be.
     
  10. Ed G.

    Ed G. Senior Member

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    There's a bad FET in there somewhere.
    The problem with FETs is that sometimes, the specs on them are not very consistent.
    Are the FETs socketed? If so, order a half dozen each of J201 and 2n5457. Plug in and try them out. Usually, it's the "top" fet that isn't working along with the 'bottom' fet. (On the schematic, those are Q2 and Q4)
    If the FETs aren't socketed, solder in some sockets.

    If you don't feel like fooling with it, send it to me with return postage and I'll fix it.


    The circuit is the same as the CMATMODS Brownie. The Fr8_Trane mods are lower gain mods in some spots. If you have the fets socketed you can swap them out easily to audition them.
     
  11. FLYING V 83

    FLYING V 83 Pedal Trading Guru Silver Supporting Member

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    Thanks Ed, but after your "I want one" reply in my thread about painting this pedal,
    I'd be worried about getting it back. ;)

    Thanks for the advice on Q2 & 4.
    Would a bad jfet cause the vol & gain pots to have no signal until they're beyond 1/2way?
    I can understand the fizz being caused by it, but that part has me baffled.
    And no, they're not socketed.
     
  12. fuzzyratfarts

    fuzzyratfarts Member

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    Should be WAY louder...My BSIAB reaches unity (Gain at noon) with the volume at only 9 oclock.
     
  13. Cary Chilton

    Cary Chilton Senior Member

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    I had no digital FIZZ...check out my clips...
     
  14. atomicholiday

    atomicholiday Member

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    Hey, first time poster here. Seems like a pretty cool forum you got going on here. Anyway...
    I build one of the BSIAB2 kits last week. So far I'm loving the gain, but I'm not crazy about the tone. Not sure if everthing is ok with this thing or not.
    It just doesn't seem to have nearly enough high end or presence or something. And cranking the tone knob seems to only add upper-mids. Also, the trim pot doesn't dial enough of it out to make much difference.
    I've tried it in front of three different amps so far (Line6 Spider III, 5150 half stack, and Mesa Studio Pre-50/50 power amp) and the tone is pretty much the same. I even let a friend use it for the weekend and he said the same thing. Not nearly as much high end as all the sound clips I've heard on the web.
    Any thoughts???
    Thanks guys!
     
  15. B_of_H

    B_of_H Member

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    you have to take out c13 and c14

    they are the last two caps and you can just pull them, no need for jumpers or anything.

    this will allow a lot more high end to come through and makes the pedal sound a lot better imo.

    I also replaced q1 with a j201 instead of a 5457 which makes it less buzzy IMO. (you'll have to adjust the trimpot again if you do this)
     
  16. Axekisser

    Axekisser Member

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    I'm always surprised when I read the BSIAB doesn't have enough high-end. My self-built unit has plenty of high-end and I play it through Fenders! My tone knob never gets past high-noonish. Maybe it's the FETs that effect the amount of high end. I built mine lower gain with 201s in Q1 and Q2 and it works great, plenty of snap with somewhat reduced mids. Teams up well with a TS type pedal.
     
  17. B_of_H

    B_of_H Member

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    my feelings exactly but taking at least one of those caps off at the end really makes the pedal more articulate.

    I have my tone around 11:30 usually. Before I took the caps off it was around 12:30 or noon but was a little dull when a/b'd against my ocd.
     
  18. atomicholiday

    atomicholiday Member

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    B of H, thanks alot for the tip! I'll give it a shot when I get time and let you know how it turned out.
     
  19. Bucksears

    Bucksears Silver Supporting Member

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    I would recommend socketing C13 and C14 rather than cut them altogether. I've been playing my BSIAB II (all 2N5457's) and I'm finding now that it's very bright with those two caps clipped. I'm socketing mine soon so I can try with/without 1 or both caps.

    Awesome circuit, though.
     
  20. Ed G.

    Ed G. Senior Member

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    Smaller value caps can also affect a narrower frequency range, so it sounds like there's more high end, while still filtering out the high-frequency "hash"
     

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