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V4 Ampeg 154 watts????

Discussion in 'Amps and Cabs [BG]' started by Tim1, Apr 4, 2006.


  1. Tim1

    Tim1

    Sep 9, 2005
    New Zealand
    I just saw this on our local ebay - is this really possible? " V4-bh ampeg head has been upgraded to be 154watts output over the normal 100 which really means about 80"
    Not considering buying it really as it is overpriced, but has anyone heard of such a mod - I thought tube amp power was fixed by the number and type of tubes. I will ask the seller some questions but thought I would ask here first in case there is some common mod of which I am unaware.
     
  2. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    umm... don't think so. I went through a rebuild of a 70's V4B last year. IIRC, it did 125 or so on the bench after serious tweaking. WHen I played through it, there was no question in my mind but that it was a very string 100 watt amplifier. Very, very strong and totally not me. Interesting experience though. Passinwind did the rebuild and Metron grabbed it from me. Still had it last I knew. No way a V4 derivative is putting out 150 wattts unless they rate it at 80 % THD (just kidding) or add tubes. The gut's aren't in the chassis to support that... this fellow is blowing smoke, or his amp is, or will ...
     
  3. 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
    The fairly common mod to vintage is to substitute 6550 tubes for the stock 7027A ones. Do a google search and you'll see plenty of info on that.
     
  4. But does the 6550 mod increase the wattage that significantly?
    Isn't output wattage RMS directly related to output transformer?
     
  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
    Well, the power supply is often the primary limiting factor in my experience, but many power supplies have a healthy bit of margin built in. The output transformer could easily be the bottleneck in many cases too. In a well designed amp the (stock) tubes should be the limiting factor though IMHO, since they're readily replaceable. I haven't worked on many Ampegs, so I'm not really sure which case holds here, given the substitution of a more robust tube.

    The V4B mentioned above did about 110 watts at onset of clipping with properly biased 6550s, and maybe 120 or so at 10% THD (guesstimated using my scope). 156 watts sounds like a crackhead's pipe dream, unless new transformers or a scary rewiring for a mismatched primary voltage were part of the mods.:eyebrow: You could ask for a screenshot of the scope trace used to confirm the measurements, but it could be pretty easy to fake that I guess.
     
  6. metron

    metron Supporting Member

    Sep 12, 2003
    Denver
    Ahh the V-4B mentioned above. :D Thanks guys I had fun with it. When I had it of course. Its now sitting in some studio in Denver.
     

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