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Bassman 100 Tube head - two questions

Discussion in 'Amps and Cabs [BG]' started by Eric Cioe, Dec 9, 2005.


  1. Eric Cioe

    Eric Cioe

    Jun 4, 2001
    Missoula, MT
    Hey guys.

    Is there anything I need to keep a particular eye out for when looking for one? I found one in a local shop, and it looks like it is in good shape (plus, it has one of those diamond 4x12s ... but it only had 3 speakers). Four power tubes, 6L6s that looked pretty new. Took one out to look at the number, and they seemed very clean. Tolex was in good shape, the knobs were smooth. I just didn't have a chance to play through it, though I plan on taking The Plow (modded MIM fretless jazz with MM humbucker in the neck) in next week with my Avatar 2x10 (not an ideal cabinet, I'm sure, but it's what I have to work with for now) to try it out with all of my stuff. Guy said $400, and if I can talk him down at all, I will. I think it will be a trade, so we'll see.

    I guess the two questions are - is there anything in particular I should keep my eye out for? And - I know 6L6s, EL34s and 5881s are more or less interchangeable, and that 6550s and KT88s are more or less interchangeable. Is there a mod that one could do to make a 6L6 amp take 6550s for the extra power?

    Thanks guys.
     
  2. Theoretically, you could put a big block Chevy engine into a Volkswagon bug....

    Is it practical?

    Probably not in this case. First, the 6550 takes a lot more current for each heater. The power transformer most likely can't handle it.

    Secondly, the power transformer is also limited in the amount of power as well as the B+ voltage for the power tubes. So realistically a bigger power transformer is required. And if B+ is increased, change a number of capacitors too, to handle the higher voltage. And modify the bias circuit.

    Finally, the output transformer would be undersized...so add a new output transformer.

    None of these mods are cheap or easy. So you'll spend at least another $400 making these changes, which incidentally also would destroy most of the resale value of the amp.

    For the same money, buy a bigger amp to start with...say a used Mesa 400.
     
  3. Eric Cioe

    Eric Cioe

    Jun 4, 2001
    Missoula, MT
    It definitely isn't a make or break thing with the 6550s/KT88s. More curiousity than anything else. If an Ampeg V-4 is loud enough for small gigs and things, I'm sure this will be plenty loud for my purposes (mostly recording, these days).

    Is $400 a fair price?
     
  4. As a previous owner of the 4x12, I'd highly recommend factoring that cabinet out of the price.

    Mike
     
  5. An Ampeg V4 has got a lot more oomph than the Bassman 100, IMHO.

    The old V4's have a very beefy power supply and output transformer, and they could run 6550's with just a rebias (though I kept 7027's in mine).

    The Bassman probably would do great for recording with a proper speaker cab, but I suspect you may be disappointed at its volume for gigging. Of course, YMMV...
     
  6. AGCurry

    AGCurry

    Jun 29, 2005
    Kansas City
    +1. The Bassman 100 is just not a very good amplifier IMO. I've had one, and I would not buy another. And Fender made virtually NO good bass speakers until a few years ago.