Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Plucking Tubes

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


  1. TheChariot

    TheChariot

    Jul 6, 2004
    Boston, MA
    I've got an early 70's Ampeg V4B... but I'm stuck in a friggon dorm room. I really need to get it down to 50Watts, because I want to push it just to the point of distortion without it having to get really loud.

    Is there a way I can just pull out tubes? Or do I need to do some sort of re-wiring along with removing tubes?

    If anyone has experience, lemme know.

    If it makes a difference, they're 7027's.


    Thanks! :)
     
  2. Theoretically it is possible to pull a pair of tubes, but you must a) pull the correct pair of tubes, and b) flip the impedance selector switch to half (or was that twice?) of the cabinet's rating.

    Unfortunately, the amp will still be very very loud, and you still won't be able to drive it into the distortion you seek....I have a V4 myself.

    So, it's not a good idea. There was a thread that discussed this a month or so ago, Passinwind made some good observations....
     
  3. DEVILMAN

    DEVILMAN

    Nov 24, 2001
    New York,NY
    ...buy a headphone amp...

    ~S~
     
  4. brothernewt

    brothernewt Some people call me the stormtrooper of love...

    Apr 13, 2004
    Happyrock, OR
  5. godraphonic

    godraphonic

    Jun 6, 2005
    you should look for a Ampeg master volume pedal on ebay, or search on usedampegs for directions on how to make one.

    it plugs into the external amp jack and lets you turn down the 'master' while cranking the volume on the amp. its like having a master volume mod without hacking the amp.

    why not just use a good overdrive pedal?
     
  6. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    Jesus people, master volumes and overdrive pedals do not get power tube overdrive!!!! :rollno:


    What I might suggest are looking into a ZVex Nano Amp, it's a 1/4 watt clean, and a full one watt cranked. And all tube. Only about 400 bucks new too, I think.
     
  7. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    the amp uses 4 power tubes, right?
    you can certainly pull two of them.

    the output transformer matches a primary impedance to a secondary. let's call the primary "X" for now. do you know what load your amp is running now? I'm going to assume 8.

    If the transformer is currently giving the ratio X:8, when you pull two power tubes, you'll want 2X on the primary.

    this can be achieved by taking your 8ohm load and putting it on the 4ohm jack.

    if you normally use a 4ohm load, you can switch ot the 2ohm jack. (shown on the schematic, your amp does have this, right?)


    Additionally, make sure you pull the correct tubes!!!

    according to the schematic, you can pull
    EITHER V5 or V6
    AND
    EITHER V7 or V8

    (so pulling V5 and V8 is fine... don't pull V5 AND V6)


    yes, this will cut your power in half (possibly a bit more), but it probably isn't as much of a volume decrease as you're hoping for... give it a shot and see if it's ok.


    shelling out 400 bucks for a nanohead is really pretty pointless.

    a marshall powerbrake is a terrible design too. (if you're going to the attenuator route, your best bet is a weber product... either the load dump or the MASS...)

    see if pulling two tubes (and changing the output impedance setting) does it for you. if it doesn't, there are other things you can do. (especially if you can move t a single less efficient speaker).
     
  8. TheChariot

    TheChariot

    Jul 6, 2004
    Boston, MA
    That is EXACTLY the answer I was looking for. Thank you very much. I've got four 7027's.

    My cab (for now) is a 4ohm Ampeg BXT410. Lucky for me, I just sold the cab and will be shipping it out soon. I ALSO just signed the lease for my first apartment in Boston.... so I can be a LITTLE louder I guess.

    If I switch cabs to a 112 or 210 and get down to 50Watts... I think I'll be good.

    It's such a weird concept for me to be trying to get LESS power... but... that's how things are for me now.

    EDIT: Oh! My head actually had a switch to select the impedance, so I'm definately set. 2-8 ohms.
     
  9. What about a THD (i think?) hotplate?
     
  10. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    a thd hotplate is another insanely expensive idea.

    if you're going the commercial attenuator route, you should drop to two power tubes first... it'll stress the attenuator less.

    anyway, the hotplate isn't really the most reactive load on the market, so it's like sticking a big (adjustable) power resistor as a load to eat up some wattage.

    IMO, at that point, the weber load dump is a much better (and cheaper) alternative.
     
  11. Was just making a suggestion, ive never looked at the Weber, never had to worry about volume myself
     
  12. a3holerman

    a3holerman

    Nov 21, 2002
    Matt H,


    I used to be in the electronics game many years ago. Building and repairing commercial and ham stuff. Changed careers many moons ago but still have most of my stuff except my tube tester as I knew i would never need it again:rolleyes: Just took up the bass and am loving it. Have been bitten by the tube bug and am looking at at a bassman or a Ampeg v4 to rebuild. Just wanted to thank you for your very informative posts; I have enjoyed and learned much by reading them.

    Thanks
     
  13. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    Tom, thanks for the kind words. :) this if the first i've been on the board in over a week, and i find your message today! ha!

    anyway- i think it's hilarious you're from the cape, that's where I am (from and currently) visiting my family for the next few days.

    i actually have a couple of tube testers, unfortunately, they're at home. hehe