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Vintage Kalamazoo Bass 30...a good starter project?

Discussion in 'Amps [BG]' started by BurningSkies, Jan 22, 2014.

  1. BurningSkies

    BurningSkies

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    Background:
    So back in the distant TB past, I posted a thread about a friend giving me a 60's Kalamazoo Bass 30 combo amp. Its a double 10" speaker 30w tube amp, with minimal circuitry. It came nearly original (minus a hole cut in the rear of the cab), and working. It has the original 2 prong cord and unmolested electronics.

    Looks like this one:
    [​IMG]

    And this is a shot of the actual amp from behind and opened:

    [​IMG]


    Its definitely not a bass amp these days, but really is a great sounding guitar amp, especially when you drive the front end. Sort of like a mini-marshall vibe.

    It needs a grounded power cord. It also should have the caps done, as it grumbles a bit when turned on. It doesn't have any other apparent problems (buzzing, etc.), or at least didn't about a year ago, when I last turned it on. I have an awesome tech, but don't have the expendable cash for 'low priority' projects. I've also wanted to start a basic tube project and get at least a little experience and understanding in.

    Is this a good way to start down that road?

    Here's one that's obviously been updated:

    [​IMG]


    And here's the schematic:

    [​IMG]

    Comments, pointers, advice?

    Parts to change out besides the power cord?

    Things I need to do, tools I need to have on hand besides my fairly decent soldering skills, strong respect for tube amp voltages and the usual disclaimers about dangers and safety?
  2. pfox14

    pfox14

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    Kalamazoo guitars, basses and amps were made by Gibson so they can be surprisingly good. Yours probably dates to the mid to late 60s. If you say it sounds good as a guitar amp, then why change anything?
  3. BurningSkies

    BurningSkies

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    It definitely needs a grounded power cord and is deathlike in a live band setting, or even in our practice room if there are live mics around. We've 'tested it' and as I believe this is a death-cap amp, I can say that at the very least, that cap has failed, and I certainly don't need that creepy buzzy feel of 'that could have blown you across the room' feeling ever again.

    The fact that it 'grumbles' a bit when you first turn it on for about 15 minutes suggests that the caps are either on the way out or done. I would love for this amp to be a viable player for either recording or general use at some point. I have a 135w Twin that covers 'real live guitar amp' situations. I feel like its work that needs doing and if I can do it and learn at the same time, I can't image it would be a bad idea.
  4. nashvillebill

    nashvillebill

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    All the electrolytics, all the coupling caps, and all the carbon comp resistors should take care of the grumbling. (There's no "mojo" in noisy components).

    Oh, if those diodes are selenium, replace with silicon, use a dropping resistor to get bias voltage right.
  5. BurningSkies

    BurningSkies

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    Thanks. Seems like a worthwhile project for a beginner to take on? That sounds like what would amount to the 'standard' laundry list for old amp upkeep.
  6. BurningSkies

    BurningSkies

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    Any input from the evening/after work tube amp crew? As a first project I may need to lean on the experience of the TB massive.
  7. Steve Dallman

    Steve Dallman Supporting Member

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    The bass player in the first band I played in in 1967 started on one of these. I ended up with the cabinet years later, in which the amp had been removed. The Jensen speakers (I still have one of them) were great guitar speakers, but not so great for bass.

    The tubes are still available. I see that the amp has been extensively worked on...I see metal oxide/film resistors, new power caps, a lot of orange drop coupling caps.

    The design is a valid one, but for bass, not much going on.
  8. morebass!

    morebass! Supporting Member

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    My first amp in the mid-70's. It was pretty beat but sounded great at low volume. I bought it and a Kalamazoo bass for $65 total. The pickguard looked as if it were painted by Grace Slick. :cool:
  9. BurningSkies

    BurningSkies

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    Yeah, the internal pic shown is not mine... Just a rough example of one that he'd been updated. Mine is original with no updating. When I got it, it appeared to be unopened. The only 'mod' is that someone opened the back of the cab (that pic IS mine). It has the original tubes and original speakers. I'd like it to be useable for guitar duties, especially recorded.
  10. BurningSkies

    BurningSkies

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    Nice. This one was trash picked, believe it or not... Still in good shape!
  11. B-string

    B-string Supporting Member

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    Are you going for bass use (as in not through the built-in speakers)?
  12. BurningSkies

    BurningSkies

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    That's an interesting question. I had only really thought about guitar use. Do you think it is worth thinking about it as a low wattage tube amp through a modern cab? It seems like it isn't all that suited to bass in a modern sense?
  13. Rick Wolfe

    Rick Wolfe

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    Great thread as my first amp was an old Kalamazoo Model Two with a ten inch speaker and an old Lyndell guitar bought in 1972 for $50. The amp was from the 60's. My dad said "this is the biggest waste of money" as many Dads do. I still have that amp and it screams...worth almost 10 times what I paid for it too I'll bet! I even saved up and eventually bought the Kalamazoo guitar (strat copy, red with white pick guard) that is long gone. Lifetime of music that even put me through undergrad in college. I still like to razz my old man about that "crappy purchase" from time to time. I'm just gentler now that he's quite old. Thanks for allowing me to highjack this thread for a minute.
  14. B-string

    B-string Supporting Member

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    It would be interesting to explore anyway? Try changing the roll off on the first stage, sub a 25mfd on the cathode (not sure if it would support a 35mfd). Blocking caps to the 7591's to a 0.1uf.
  15. Interceptor

    Interceptor Supporting Member

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    Worthwhile to work on. I played through one of those in Jazz settings for a few weeks when my Standel was down for service back in the '70's. It was usable against a tame drummer. It sounded fine, just lacked umph. These days, I could see it being great as a guitar amp, or as a mic'd bass amp.

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