1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

Riviera 725 by Pepco

Discussion in 'Shock Brother's DIY Amps' started by Mongo Park, Apr 18, 2021.

  1. Mongo Park

    Mongo Park Tele-Afflicted

    Posts:
    1,117
    Joined:
    Nov 28, 2010
    Location:
    Winnipeg
    I was looking at this amp, Riviera 725 by Pepco, a early 70's amp made in Canada. It was a head. This is what I found on TDPRI.
    "The 725 can vary from around 20 watts (more like a Deluxe clone in head form) to 50 watts (more like a Bassman), so be sure of what you're getting. These have zero collector's mojo, even in Canada, in spite of being great amps, so keep your eyes open on Kijiji and in pawn shops for cheap deals. People sometimes mistake them for Garnets (as did the former owner of mine), so get to know the distinctive signs of Pine/ Pepco to help you spot them."
    The thing that I noticed is the description that the 20 watts version is decried as a Deluxe clone. I don't think it looks like a 5E3, but might be interesting to build anyways. It looks kinda fenderish on the front end but has something going on after the tone stack. It might even do well with a master volume.
    Anybody have any advice from building one of these things.





    [​IMG]
     
  2. David Barnett

    David Barnett Doctor of Teleocity

    Age:
    64
    Posts:
    14,723
    Joined:
    Mar 17, 2003
    Location:
    The Far-Flung Isles of Langerhans
    Circuit looks pretty normal, apart from being drawn upside down and backwards in parts.
     
    Nickfl likes this.
  3. Dan German

    Dan German Doctor of Teleocity

    Posts:
    11,452
    Joined:
    Feb 21, 2008
    Location:
    Left of the Left Coast
    Not to distract, but what’s the deal with Canadian amps? I had a Raven I picked up cheap in a Winnipeg pawn shop. It actually sounded amazing, but something went “Foof” and it stopped making noise, and it wasn’t worth the fixing. Also, it was probably not safe. But it sounded good.

    Never seen or heard of a Pepco, though.
     
    Flip G likes this.
  4. J. Bonkosky

    J. Bonkosky Tele-Meister Silver Supporter

    Posts:
    458
    Joined:
    Sep 7, 2014
    Location:
    Seattle Washington
    Looks like a Blackface input and tone stack with an added gain stage post EQ recovery with a cathodyne inverter. Probably very tweed like not much headroom. I would probably move the gain stage before the tone stack and give it a volume control. A little more controllable that way.
     
  5. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,045
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    I don’t see a tweed there. It looks like an AB165 Bassman Normal channel preamp with a cathodyne PI and fixed bias. It should be a hot little amp with a BF flavor. fwiw, the way that third gain stage into the PI is drawn has my head twisted.
     
    Paul G. likes this.
  6. Mongo Park

    Mongo Park Tele-Afflicted

    Posts:
    1,117
    Joined:
    Nov 28, 2010
    Location:
    Winnipeg
    All of this sounds great, I think I will give it a try. I will have to see if I have the parts to make I it go or if I have to order something. I have a 5U4 rectifier tube but maybe not a transformer to run the heater for it. I am thinking a head like some of the originals. Also point to point for room to try a few mods once the original schematic it built and used a bit.
    Thanks for the input about moving the tone stack.
    Also cheers to the insight of the schematic. All things pushing me towards a build. Yes Winnipeg home of the Gar Garnet amps, they are for sale right regular, course I have not seen a Herzog for sale, but that can also be built, but that is another topic. These amps are around and nobody ever connects the word collectable with them. They are considered ye old workers amp of guitar players until they can trade up to something more glamorous, but I think this will be a great amp with some quality parts to really bring it alive.
     
  7. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,045
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    The Herzog is in essence is a 5F1 Champ with a line out built into it...best little distortion unit ever. I built a line out into the top of the chassis of a 5F1 long ago. The owner’s friend had borrowed and hogged out a crude hole in the top of the chassis or I never would have done it. It was a great little amp. It did not have to be driven into distortion as Bachmann did in order to be of service. The young owner played Billy Bob’s in Ft. Worth several times with it running into the board....country band in the world’s largest dance hall.
    Good luck with the build.
     
  8. David Barnett

    David Barnett Doctor of Teleocity

    Age:
    64
    Posts:
    14,723
    Joined:
    Mar 17, 2003
    Location:
    The Far-Flung Isles of Langerhans
    Essentially a blackface Princeton-Amp with no trem, no feedback, and a treble peaker before the third gain stage.
     
    NTC and Wally like this.
  9. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,045
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    except a BF Princeton does not have a third gain stage. The Normal channel of that AB165 Bassman does. Hot preamp.
     
  10. David Barnett

    David Barnett Doctor of Teleocity

    Age:
    64
    Posts:
    14,723
    Joined:
    Mar 17, 2003
    Location:
    The Far-Flung Isles of Langerhans
    Okay, then a Princeton Reverb with no trem and no reverb.

    I consider the third stage part of the power amp, not preamp, since a split-load has no gain.
     
    Wally likes this.
  11. Wally

    Wally Telefied Ad Free Member

    Posts:
    39,045
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    David, the AB165 Bassman has three gain stages...just as do the Fender reverb amps do. The difference is that the Bassman does not have the tone sucking drag of the reverb and the tremolo to weaken that signal, so they are hot. Now, as you and I noted, the schematic around that third triode prior to that cathodyne phase inverter is oddly drawn, but if that is a gain stage as I suspect then this is a hot preamp...hotter than the Fender reverbs....since it is more akin to that Bassman. I am not considering the phase inverter in the gain formula.....I don’t wonder about that too much if it a LTP. I am just talking about those first three triodes.
    Now, if someone can explain exactly what is going on with that third triode and why it is drawn the way it is drawn, I am here to learn.
     
  12. David Barnett

    David Barnett Doctor of Teleocity

    Age:
    64
    Posts:
    14,723
    Joined:
    Mar 17, 2003
    Location:
    The Far-Flung Isles of Langerhans
    My guess is that the schematic was drawn from a layout. They've clustered three plate resistors together where they all tap off the power supply.

    I'll re-draw it tomorrow at work, we have a scanner there. The only thing that's really different from standard Fender practice here is the RC network on the grid of the third triode, and the lack of global feedback around the power amp. Also there's no cathode bypass cap on the second stage.
     
    Wally likes this.
  13. NTC

    NTC Tele-Holic

    Posts:
    593
    Joined:
    Mar 17, 2003
    This really is like a standard BF/SF preamp connected to a cathode biased Princeton output section. The third gain stage is the one you normally have with a cathodyne pi. The odd parts are the cathode bias resistor for the output (probably due to high voltages), the cap in parallel with the 2.2M resistor (gain dumping but with a bright cap) and the 68k resistors in the cathodyne instead of the customary 56k. No negative feedback around the output, so it will behave like a 5E3. Sort of a 5E3 with a full tone stack of a later period. And the bass and treble lables are swapped.
     
    Wally likes this.
  14. printer2

    printer2 Poster Extraordinaire

    Posts:
    7,288
    Joined:
    May 24, 2010
    Location:
    Canada
    Other than the 2.2M and mystery cap with it the stage is a normal 1.5k-100k gain stage. The cap used to give a rising treble response and the resistor to bypass some lows around it. The 2.2M resistor and the 1M across the grid acts as a voltage divider, cutting down the signal by third. Because of the hot signal due to the extra gain stage as Wally said they dump some signal there as well as not bypass the second stage and the output cathode resistor. If the amp plays well I don't see any reason to change stuff. If not, it gives a few possibilities. Trying to remember the amp with the extra triode thrown in, Divide By 13, CJ11.

    [​IMG]
     
  15. David Barnett

    David Barnett Doctor of Teleocity

    Age:
    64
    Posts:
    14,723
    Joined:
    Mar 17, 2003
    Location:
    The Far-Flung Isles of Langerhans
    Yeah, if you remove the master volume and change a few values, the ÷13 and the Pepco are essentially the same thing. Beats the hell out of my sloppy sketch on post it notes:

    pepco.jpg

    And I forgot the wiper on the bass control and the grid leak on the 3rd stage.
     
  16. NSB_Chris

    NSB_Chris Tele-Meister

    Age:
    56
    Posts:
    463
    Joined:
    Sep 2, 2017
    Location:
    New Smyrna Beach Florida
    The bass and treble pot lables on the tone stack in post #1 appear to be reversed.
     
  17. Mongo Park

    Mongo Park Tele-Afflicted

    Posts:
    1,117
    Joined:
    Nov 28, 2010
    Location:
    Winnipeg
    Printer2 thanks for posting the schematic of the Cee Jay 11. Never herd of this company before now, amazing what is out there just waiting to be discovered. I think the Cee Jay fits my tastes a little more. It is not as loud, the Riviera is really loud, it has no clean without a Master Volume. So I think I am jumping ship and moving in the Cee Jay direction. I will print both schematics and let them both sink on before ordering parts. Close examination may reveal why one is so much louder than the other. I know the MV does suck out a little volume but couldn’t be that much. The Riviera barely gets past three on the volume indoors.
    Thanks also to David for drawing thing out in mellow yellow.
     
  18. NTC

    NTC Tele-Holic

    Posts:
    593
    Joined:
    Mar 17, 2003
    Perhaps adding negative feedback like a Princeton Reverb has would tame it...
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.