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Peavey AlphaBass 8 Ohm tap?

Discussion in 'Amps and Cabs [BG]' started by Rockbobmel, Oct 15, 2017.


  1. I found a 4 ohm tap on my old Sunn 2000S from some research. It was originally 8 and 16 ohm. So, the Alphabass has a 4 and 2 ohm output, I see it's going in the opposite direction, but there are more wires coming from the tranny. I'll never use the 2 ohm output.
     
  2. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I’m not sure what you are asking here. Are you wondering if there might be an 8Ω tap that’s unused?
     
  3. Yes. I should have been clearer.
     
  4. Nobuddy?
     
  5. Passinwind

    Passinwind I am Passinwind and some of you are not. Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    What did Peavey tech support say when you called them? Yel_wink.
     
    BassmanPaul likes this.
  6. Well, that's a novel idea I didn't think of. I called and the tech guy was real nice and knew the amp and it's history being made of leftover "Mace" parts. He said the amp, or any tube amp don't give a rat's A$$ what load is there as long as it sees one.
    Hmmm, Not what I expected to hear.
     
  7. bobcruz

    bobcruz

    Mar 10, 2004
    CA
    I don't know jack about tube amps but that sounds really, really wrong to me, since proper load matching is supposed to prevent transformer meltdowns. Maybe @BbbyBld can answer since he used to work there. Good luck, Bob
     
  8. That’s not what I understand to be okay either. I only have one cab that is 8ohm anyway and I can top that one with an 8 ohm tweeter box so it’s really 4 total. My Berg is 4 ohm and my 2 Ag gs112s come to 4 ohm also.
     
  9. I had an Alphabass back in the 90s and I thought it did have an 8 Ohm tap. Hmm, googled it up and the speaker jack say "4 Ohms minimum" and "2 Ohms minimum" so I guess I assumed at the time that I could plug a single 8 Ohm cab into the "4 Ohms minimum" jack and I did do just that for a couple of years with no issues. The schematic indicates that there are only 2 taps on the OT, called out as 4 and 2 Ohms on the sheet.

    The above is at least partly true as most tube amps use transformers spec'd to handle at least a 100% impedance mismatch in either direction and Peavey is not known for making finicky, easy to damage gear so I'd say it probably isn't a critical issue to run an 8 Ohm cab off it. My guess is that they designed the transformer with this in mind if they labeled the outputs that way.
     
  10. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    A tube output stage works best into a load that matches the tap selected. It’s SS amps that don’t care as long as the load is above it’s minimum.
     

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