Calling all tube amp Gurus

Discussion in 'Amps and Cabs [BG]' started by Skorzen, Nov 15, 2003.

  1. Skorzen


    Mar 15, 2002
    Springfield MA
    I picked up an old Baldwin tube amp out of a church I was working on. They had two of them that were once used for an organ I presume, but were no longer used. What I would like to do with this is make a small combo type amp. My problem is that in my searching so far I can find no info on this amp. It is a baldwin model "PC" amp. If any of you know any thing about this amp or where I might be able to get info on it it would be much appreciated. here are a couple pics:
  2. Skorzen


    Mar 15, 2002
    Springfield MA
    and the whole thing:
  3. bassmantele


    Jul 22, 2003
    Boston MA USA
    Interesting amp. You'll probably have to find an old organ tech to help out. I couldn't find any schematics online. You might try the Ampage amp page - some guys there have pulled amps out of organs in the past. Get as much information on the amp as possible before you post - tube type and number, any transformer info, controls, etc. Good luck - it looks like a good find.
  4. notanaggie

    notanaggie Guest

    Sep 30, 2003
    Well, if you have enough electronic smarts to convert it to a combo amp, you probably can trace it out and draw up the schematic yourself.

    That's if it isn't pasted on somewhere, like on the cabinet it came out of.

    The nice thing about old tube amps is its usually all out there for you to secret inside layers on PC boards, etc.

    You need a tube reference to be sure of the basing...the Groove tubes one isn't bad, if you can find that. It has most of the common and less common tubes, although the organ amps I have seen tended towards odder tubes than most guitar and bass amps.

    But it looks heavy....might be some combo amp....sure you don't want to make it a head?
  5. Can you post the tube lineup? Looks like (2) 5U4GB's, (4) 6L6GC's, and (1) 6SN7. Is that right? You'll probably need to throw in another preamp tube to get sufficient gain, but that's no prob at all. Add in a 12AX7 set up like the front of an Ampeg V4-B and you're probably good to go.

  6. Skorzen


    Mar 15, 2002
    Springfield MA
    Thanks for the suggestions so far, It is a bit heavy, but as far as I can tell it only puts out 40 watts so that was why I was thinking a combo type thing. There was no cabinet really the amp was just bolted down to a self in the attic of this church. The tube are 4X 6L6 2X SU4 G and 1X 6SL7.
  7. I think throbbinut nailed the tube complement with the exception of the 6LS7 (which looks a LOT like a 6NS7 anyway.) The two big tubes are 5U4 rectifiers. There is no "S"U4.

    I'm interested in the large transformer next to the multi-pin input. If you can get a pinout for the input, that transformer might be an input voltage booster and you wouldn't need to mess with adding another gain stage.

    If the amp works, all you need to do is trace which line eventually feeds that 6LS7 and whatever pin it's attatched to will be your "hot" input. About the only mod the amp should need might be an input jack. If you're feeling adventurous, you could insert a tone stack for EQ, but I don't recommend it.

    Most old organ amps do pretty well for bass and amost guitar amp conversions are to get them to distort or otherwise sound like a guitar amp. As-is, if you've got a bass with active electronics or a cheapie preamp (even a stompbox) all you should need to do is install an input jack.
  8. Skorzen


    Mar 15, 2002
    Springfield MA
    Your right, I look at it too quickly, and the ink on the chassis is a little smeared.

    The transformers are only identified by numbers, I assum this is a part number. The are: largest on the right in the photo is 512-14512E, The one next to that above the input is marked 512-13926B, and the last one is marked 512-14633D.

    One other thing that may not be obvious in the photo is a pot marked gain next to the 6SL7.

    I opened the case and took a few pics, I don't know if this will help or not because it is a little hard to see exactly where thing go, but here it is:
  9. Cool. Do what Psycho said. Try it like that and you may not need to do anything else, but I think you'll end up needing some more gain. That thing was probably being fed about 1V or so from the headend electronics of the organ. Another option is to run a preamp in front of it.

    That transformer next to the 5U4's is a choke, so you've got a nice choke-filtered supply.

  10. jokerjkny


    Jan 19, 2002
    NY / NJ / PA

    the interior is pretty clean. i like the fact its got relatively little wiring. nothing too crazy or jumbled to mess with the tone coming from the tubes.

    at 40 watts, maybe it'd be better off as a clean jazz amp?

    once you get it working, how 'bout some sound clips? :D