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Will using both channels on my amp hurt it?

Discussion in 'Amps and Cabs [BG]' started by Fieldflower, Oct 1, 2005.

  1. Hi all You experts out there!

    I have a -73 Kustom K250-4, one of those tuck'n'roll SS beasts, with matching 2x15 cab.
    The 250's have 2 channels that are both on simultaneously. Channel 1 is voiced more for bass, and channel 2 is voiced more for guitar.
    Since mine is a model 4 it has fuzz, wah, reverb and tremolo.
    The fuzz is only connected to channel 2, and not really intended for bass.

    What I've tried just now is to connect my bass into both channels (by using a 1x6,3 -> 2x6,3 adaptor and a short cable).
    My goal was to get subtle fuzz without loosing the bottom, and it worked really well! Channel 1 supplies the round tone with the bottom, and channel 2 supplies the fuzz.
    With the volumes blended together I get a real nice tone, and variable at that...
    Since the fuzz can be switched on/off by a footswitch it's a pretty useful feature in band settings also.

    I noticed a small decrease in volume when I plugged in also channel 2, but I think that's just because the basses output gets divided into the 2 circuits, right...?

    The big question is: Will this hurt my amp in any way?
    Could it make it run significantly hotter, thus risking damage?
    I really like the tone I got, but I like the amp more...

  2. No, I do not believe this will not hurt it. I also have an old K250, though I've got the pure-bass version...

    The two channels are inputs that are summed together before they go into the power amp. The guy I bought my amp from--the original owner-said he used a Y adaptor to do exactly what you described.

    Each channel has two input jacks--did you know one jack has more gain than the other jack, though they're not labelled? (I can't remember which one, I stopped gigging with mine a couple of years ago) Possibly going into the higher (or lower) gain jack may get you a different sound too.

    These amps do run hot, one of their few design flaws IMO was the way they stuck the output transistors inside the (completely sealed) amp. I've read some people take the steel chassis lid off so the amp can get a little fresh air.
  3. These are 2 input channels, right? The output still goes to 1 speaker?

    It won't hurt anything. Its made for 2 inputs, and it has no way of knowing if you've got a guitar and a bass plugged in (is that the orignal intent for the 2nd channel?) or 2 basses, or if the signal for both channels comes from the same bass.

  4. Correct, two input channels, one power amp....

    The schematics may be available on the VintageKustom site by now.

    Unfortunately some of the transistors, as well as a few other goodies like the pushbutton power switch, are obsolete and no longer available.
  5. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    No, you won't hurt the amp.
  6. might want a new power amp tho, so you can actually push more of the sound u want out
  7. Yes, it's 2 input channels (separate preamps I guess) that go to the same output power stage, and only one output jack into one cabinet.

    In the literature from back then it says the model 4 is for guitar, but channel 1 is definitely voiced for bass.
    I'm sure it can also produce a nice round tone for clean guitar, or a full tone for organ for that matter.
    I think Kustom made pretty much one amp and just stuck more or less effects into them, calling the one without effects "Bass" and the one with all the effects "Guitar".
    Nashvillebill: Does Your 250-1 have deeper voicing on the top channel than one the bottom one?

    I like what You're both saying, that it won't hurt the amp!
    That definitely means I'm taking the beast to the rehearsal tomorrow! I've got this 70's rock band where it'll fit right in... :)

    Top input is quieter and bottom is louder on each channel.
    I've heard somewhere that the logic is high input = high damping, low input = low damping, but that's just what I've heard...
    I don't percieve any real difference in tone between them. I just use the louder input with the band and the quieter at home.

    I have thought about removing the top plate, but if I do that I will lose it for sure...
    Since the top plate is still there it has probably been there for the last 32 years. I'm kinda hoping it'll keep working that way. Is that a stupid hope - should I remove the top plate "or else"?

    Will running both channels make it go even hotter, or is it just the output stage that generates the serious heat?

  8. I think it'll keep up..
    I have been using my Carlsbro 90Watt 1x15 combo in the band so far and it has kept up OK in volume (Yeah I know it sounds like a joke, but the rehearsal room is pretty boomy).
    Having more than twice the power and twice the speaker area will be nice though... :)

  9. I actually found that the schematics glued to the inside of the top plate when I took it apart for a look-over... :)
    I don't know if that has something to do with mine having been sold new in Sweden, running 230V, and therefore being special in the power department.
    Probably because of this the power and polarity switches are bypassed, but I got them lighted again at least. :)

    Almost everything is hard to come by on these...
    I had to make a cab handle from wood (still had the metal thingy) because it was impossible to find one.
    Can't find an original 4-switch pedal for the effects, so I bought one from another brand and rewired it.

    But 30+ years later and it works!!

  10. It's just the power amp--the output stage--that generates the serious heat, there's also a little from the power transformer, but virtually no heat from the preamp channels.

    It appears from the schematics that your thinking is indeed correct: there are two basic preamps (channel one and channel two) and the power amp, and these components are commonamong all models. The preamp schematics show where the in/out connection points are to go to the fuzz and reverb boards (though I don't have schematics for the fuzz/reverb boards, since I only needed the preamps and power amp schematics when I got them....)

    I measured around 125 to 130 watts RMS on mine when the sine wave started clipping on my scope. Not a huge amount of power by today's standards, but for country and classic rock, it did fine as long as I wasn't competing with a Marshall stack and a loud drummer!! I've got the 2x15 cab, now it's loaded with Eminence Deltas and it's definately got the old school tone going on.