Results 1 to 6 of 6

Thread: 78' Pro Reverb - does popping the master volume super-drive V2?

  1. #1
    Forum Member
    Join Date
    Feb 2020
    Posts
    3

    78' Pro Reverb - does popping the master volume super-drive V2?

    My Pro Reverb is I believe a 1978 model - 40 or 45 watt w/ tube rectifier - I've had since 'bout 1980.
    When ever it's needed servicing, I've taken it in, but became wiser last week when simply switching the tubes between V4 (1/2 Vib channel gain, 1/2 reverb) and V5 (Vibrato) completely cured a bad noise floor...

    So after having the amp dang near forever, I'm getting to know her a little better.

    Snagged a pair of test-good Sylvania green lettering 7025, and a pair of NOS Sylvania JAN 5751 to play around with.

    *I'm assuming only the output 6L6 need to be biased, correct? So away I go with looking for a cleaner sweeter sound.
    Last time in the tech put a few new GT 12AX7 in, as well as JJ outputs (she ran dirty for my taste). Research for a gigging amp tends to say running vintage tubes in the output doesn't gain much sound quality compared to keeping vintage tubes in the preamp section.

    Anyway, I'm rambling.
    So my question: I generally play clean, enjoy the light "texture" this amp has when happy; but do, on occasion, turn the preamp volume to 10, and pop the master for a full distortion.
    ? Is popping the master out simply sending the preamp tube in V2 to the cleaners? Or is it nailing V4? Should I be careful putting nice NOS tubes through that torture?

    Thanks, Joe (new kid on the block).

  2. #2
    Forum Member
    Join Date
    Feb 2020
    Posts
    3

    Re: 78' Pro Reverb - does popping the master volume super-drive V2?

    Well, spent the afternoon reading endlessly (so it seems), and came up with these bits. Figured I'd share for others.
    Me thinks I'll pack a pedal for gigs I think might need a screamer near night's end.
    _______

    https://www.harmonycentral.com/forum...are-so-crappy/

    Some of the SF Fender Twin's and Pro's had a pull master volume.
    In the "normal" (not pulled position) they were just a pre-power amp master volume.
    which produced little if any distortion with using a pedal to distort the preamp.

    In pulled mode, they used a part of the reverb driver circuit to produce the distortion.
    Clearly designed by an Engineer (with no guitarist participation).
    Maybe it looked good on an oscilloscope scope, but in real life it sounded like A$$.
    -------------------------

    https://www.thegearpage.net/board/in...-reverb.97940/

    The pull knob on the MV turns on a crude distortion circuit fed from the reverb drive. If it does absolutely nothing,
    check that the reverb drive tube hasn't failed (you'll get no reverb either) - these amps are also quite hard on this tube which is run very hot.

    You probably won't want to have it working though - it sounds horrible.
    To get much distortion you need to have the vibrato channel volume (and usually the midrange) most or all of the way up,
    and then it sounds harsh and scratchy.

    IMO it's much better to use these amps for what they do extremely well - a very loud, clear, bell-like clean tone.

  3. #3
    Forum Member Kap'n's Avatar
    Join Date
    Sep 2002
    Location
    Where phony hippies meet
    Posts
    19,769

    Re: 78' Pro Reverb - does popping the master volume super-drive V2?

    A Pro Reverb is a nice rig. Plenty of clean for modern gigs, and moves air without necessarily being loud. You'll need some sort of dirt pedal to bring the rock. As for the pull-boost, just say "no" and it'll be fine.

    What guitars you playing through that amp?
    Several guitars in different colors
    Things to make them fuzzy
    Things to make them louder
    orange picks

  4. #4
    Forum Member Don's Avatar
    Join Date
    Jul 2002
    Location
    Massachusetts
    Posts
    11,288

    Re: 78' Pro Reverb - does popping the master volume super-drive V2?

    Quote Originally Posted by Goldenvoice View Post
    *I'm assuming only the output 6L6 need to be biased, correct?
    This is correct. You can play with preamp tubes without worrying about setting bias.

    If you want the amp to sound a little bolder, pull V1 if you're using the Vibrato input (pull V2 if you're using the Normal input). It changes the bias of V2 (Hey wait a minute! I just said you didn't have to worry about preamp tube bias!) and makes the amp sound a little bolder. It's free to try.

  5. #5
    Forum Member
    Join Date
    Feb 2020
    Posts
    3

    Re: 78' Pro Reverb - does popping the master volume super-drive V2?

    I'll give removing V1 a try - certainly not something I would've thought to try myself. So doing so lets more current to V2?


    What guitars you playing through that amp?
    I'm still gigging mostly with my 58' Gibson 175D - natural yellow with the original dual PAFs.
    Also use an Ibanez AD202 analog delay - Western and Rockabilly.

  6. #6
    Forum Member ch willie's Avatar
    Join Date
    May 2008
    Location
    Tennessee
    Posts
    8,163

    Re: 78' Pro Reverb - does popping the master volume super-drive V2?

    Quote Originally Posted by Goldenvoice View Post
    I'll give removing V1 a try - certainly not something I would've thought to try myself. So doing so lets more current to V2?
    I'm still gigging mostly with my 58' Gibson 175D - natural yellow with the original dual PAFs.
    Also use an Ibanez AD202 analog delay - Western and Rockabilly.

    Ooh a 175. I'd love to see photos if you can post them.
    If we'd known we were going to be the Beatles, we'd have tried harder.--George Harrison

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •