Using the Maestro GA1RT as a stand alone Reverb/Tremolo

Discussion in 'Glowing Bottle Tube Amp Forum' started by Tomm Williams, Jun 28, 2019.

  1. Tomm Williams

    Tomm Williams Tele-Afflicted

    Posts:
    1,025
    Joined:
    Jun 11, 2016
    Location:
    USA
    97E5338E-EA17-4972-93F0-CA6E412C4A2A.jpeg 077D39AD-BF7F-4FF5-BD09-CAD9345E6E62.jpeg I have an addiction towards vintage stand-alone reverb units and had to pick this thing up from a Music Go Round. I'm not so interested in that it also functions as an amp but rather that it can be slaved to another amp and then becomes a stand alone effects unit. Has anyone ever messed with one?
    I'm thinking it will go perfect with my Lessman Accordion amp that was modded by Fargen but has no reverb or tremolo.
     
  2. Wally

    Wally Telefied Ad Free Member

    Posts:
    32,159
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Nice unit, Tom. How does it interface to function as only an effects unit rather than as an amp? I do not see a jack that would send in effect a preamp line out, and I don’t see a salve out, which some Gibson amps have on the front panel. The schematic I found does not show either of these capabilities. Of course, Gibson is famous for not having schematics that match reality, right?

    https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga1rvt.pdf

    This reminds me I need to get my Gibson GA 4RE reverb/trem unit going.
     
  3. brucerbc

    brucerbc TDPRI Member

    Posts:
    42
    Joined:
    Oct 11, 2013
    Location:
    A little below the middle, BC, Canada
    From TGP (https://www.thegearpage.net/board/index.php?threads/maestro-ga-1-rt.1891385/):

    "The most interesting part of the amp is the reverb circuit - or rather, the fact that there is a reverb pan but NO reverb circuitry, other than the wooden footswitch for on/off. The input of the reverb pan is a long zipcord cable with 2 alligator clips. The output goes to the input of the amp. You attach the alligator clips to the speaker leads of another amp. This other amp actually drives the reverb tank, and the reverb output is controlled by the volume knob on the Maestro.

    The results? You have a wet/dry setup with the "driver" amp as your dry signal and the Maestro as your "wet" signal. Since the Maestro also has tremolo, this effect is applied AFTER the reverb effect, which yields a cool sound. Add the inherent overdrive of the Maestro gain circuit, which allows you to distort the reverb and trem effects, and you have a pretty unique little beast that is a lot of fun to play around with."

    Very interesting!
     
    Tomm Williams likes this.
  4. Wally

    Wally Telefied Ad Free Member

    Posts:
    32,159
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Thanks for that link, Bruce. However, the schematic I linked shows something very different from that description. The 7199 pentode section is the input stage of the GA1RVT. The triode section of the 7199 is the reverb driver while a triode of the 6EU7 is the reverb recovery. So, there is a complete reverb circuit there...with an on/off switch. Otherwise, it would not be an RVT...reverb/tremolo amp in Gibson model designation.
    One might wonder if the amp in the TGP thread was ‘whole’ or had been modified. The schematic shows no output of any sort for effects being sent outboard. Just curious I am...
     
    Pierce likes this.
  5. radiocaster

    radiocaster Poster Extraordinaire

    Posts:
    5,260
    Joined:
    Aug 18, 2015
    Location:
    europe
    There is a video of one, I remember watching it. Apparently you can also use it as a regular amp, but I think you don't get the effects.
     
  6. Wally

    Wally Telefied Ad Free Member

    Posts:
    32,159
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    My apologies....I looked at the RVT circuit instead of the earlier RT circuit....and so I go back and look at the GA1RT, and it does show a Reverb tank with no driver and return with two leads going out. This is tapped off of the input signal before the first input stage.
    Sorry for my confusion....

    https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga1rt.pdf
     
    Tomm Williams likes this.
  7. Tomm Williams

    Tomm Williams Tele-Afflicted

    Posts:
    1,025
    Joined:
    Jun 11, 2016
    Location:
    USA
    I found a description of it's function on another site that states it has a 2 conductor cable with alligator clips that you attach to the speaker of another amp. That amp then acts as the reverb driver for the pan in the GA1. I might be oversimplifying it a bit but supposedly that's how it functions.

    Oooops…………..just saw your correction.
     
  8. Wally

    Wally Telefied Ad Free Member

    Posts:
    32,159
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Tomm, I am in the middle of my GA4RE right now. Thanks for posting about this GA1RT....it drove me to do this long neglected chore. I am about to refill the oil tank with the oil I bought for this purpose long ago. Oil can Reverbs are new territory for me as far as repairs go. When my parents bought me my first big amp...a Rickenbacker B16 Supersonic...I got a new GA4RE and a great Turner mic with a stand, too. But that Gibson unit left me long ago.

    I need to school myself on how to move pics from my new I Pad Air to forums.
     
    Paul in Colorado likes this.
  9. Tomm Williams

    Tomm Williams Tele-Afflicted

    Posts:
    1,025
    Joined:
    Jun 11, 2016
    Location:
    USA
    I’ve come across a few oil cans that keep catching my interest. Gibson apparently has a real neat one too.
     
    Last edited: Jun 29, 2019
  10. Wally

    Wally Telefied Ad Free Member

    Posts:
    32,159
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Well, I have this Gibson GA4RE oil can unit recapped with a grounded plug. I am ready to fill the can up with the oil and see what it does.....maybe manana. It has been 50 years or so since I have played through one. I am excited to hear it in front of the premier Super 88 I just got going...what an amp!!!! Magnificent, imho.
     
  11. Tomm Williams

    Tomm Williams Tele-Afflicted

    Posts:
    1,025
    Joined:
    Jun 11, 2016
    Location:
    USA
    I’m jealous....... I took a Multivox Premier 90 into Ben Fargen to have worked on and he coincidentally (?) mentioned to me he really didn’t care to work on oil cans. I think he was heading me off at the pass before I dragged one in:lol::lol:
     
  12. Tomm Williams

    Tomm Williams Tele-Afflicted

    Posts:
    1,025
    Joined:
    Jun 11, 2016
    Location:
    USA
    Wally how did that GA4 turn out? I started reading about those awhile back, neat unit.
     
  13. Pierce

    Pierce Tele-Holic

    Posts:
    543
    Joined:
    Mar 4, 2003
    Location:
    skull island
    that's the problem with gibson.. there are more than a couple schematics for their amps out there
     
    Wally likes this.
  14. Wally

    Wally Telefied Ad Free Member

    Posts:
    32,159
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    Tomm, I am at the point where I need to put the oil in the tank and reassemble, then, I will know what is what there.
     
    Tomm Williams and Pierce like this.
  15. Paul in Colorado

    Paul in Colorado Telefied Ad Free Member

    Posts:
    23,189
    Joined:
    Mar 17, 2003
    Location:
    Fort Collins, CO
    FYI. Uncle Doug on You Tube has done a few oil can repairs and has posted videos. They might help if you have to do some trouble shooting.



     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.