Reusing Blues DeVille building blocks

Discussion in 'Shock Brother's DIY Amps' started by symbiotic, Jun 16, 2019.

  1. symbiotic

    symbiotic TDPRI Member

    Posts:
    73
    Joined:
    Feb 1, 2007
    Location:
    Hamilton, Ontario - Canada
    I have a 1996 made in USA Blues Deville. It has seen its share of repairs through the years - of course jacks, plate resistors and electrolytics, but also more than one relay repair. It has gone out again and I've had it. I've always felt it to be a little too stiff & sterile which contributes to not wanting to fix it again.

    Ditching the circuit would leave me with at least the chassis, tubes, iron, enclosure and speakers. I am keen to try my hand at putting together my own circuit that uses these resources as much as possible but I really want to make the thing lean more to the compressing side of things than the Blues DeVille. The question in my mind is, what might be the right way to go about using the transformers to get there. After all, it has a honking 60 watt output transformer and the B+ in the original design is 471V according to the schematic.

    Where to go from there? Cathode bias on the power tubes came to mind, to emphasize compression but, how much lower would the plate voltage need to go? The example values on the RCA data sheet for 6L6GC is based on 300V plate voltage. Where to find out what is the upper limit for that?

    I suppose zener diodes before the B+ node could knock the voltage down but how far can one take that in reality?

    All of the above is just about voltages and if I go changing that radically I will have to consider the load placed on the output tubes by the OT & speakers. I've got a lot to think about but thought I would put the voltage question out here to see what the community has to say.

    Thanks in advance!
     
  2. Nickfl

    Nickfl Tele-Afflicted

    Posts:
    1,479
    Joined:
    May 24, 2016
    Location:
    Florida
    For the most part, data sheet typical operating characteristics aren't all that useful for guitar amps. Note that the max plate voltage is 500v, also note that most classic guitar amp designs with 6l6 tubes are using plate voltage of 400 +. those 300 volt designs are for old radios and things like that.

    Based on your post I'd suggest you consider some of the classic 6l6 amps and figure out which one suits your needs and then figure out from there how you would use your transformer set to build something along those lines.
     
  3. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    35
    Posts:
    2,340
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Or, if you want to build something special, a Hammond or Classictone PT that suits your needs can be had for $100 or less. I understand the budget aspect of reusing what you have, but if you end up with a dream amp in the end, and extra $80-100 might be worth it.

    Sent from my XT1585 using Tapatalk
     
  4. Dacious

    Dacious Poster Extraordinaire

    Posts:
    6,561
    Joined:
    Mar 16, 2003
    Location:
    Godzone
    The HRDx/Dv designs are based off Bassman/Super era 6L6 amps. You could build one of those easily. Add a transformer for tube recto, drop your B+ probably 20-30 volts. The iron you have both power and output would be near-ideal.
     
  5. sds1

    sds1 Tele-Afflicted

    Age:
    42
    Posts:
    1,007
    Joined:
    May 4, 2017
    Location:
    Orlando, FL, USA
    I did a Dumble style build in a HRDeville. Came out great. I think for maximum risk management you copy the output section and power supply verbatim, but whatever preamp you want. These make great donor amps, problem is -- do you need reverb? If so, you're possibly short a tube socket. Something to think about.
     
  6. clintj

    clintj Friend of Leo's

    Posts:
    4,917
    Joined:
    Apr 4, 2015
    Location:
    Idaho
    You can add in a sag resistor if you want to drop the B+ voltage a little and give it that tube rectifier feel. Really, though, 471V is not a challenge for a 6L6GC. The blackface amps ran in that range, and the max plate voltage listed is usually around 500V IIRC.

    Sent from my Pixel 2 using Tapatalk
     
  7. symbiotic

    symbiotic TDPRI Member

    Posts:
    73
    Joined:
    Feb 1, 2007
    Location:
    Hamilton, Ontario - Canada
    Thanks to everyone who replied, particularly to Dacious who I think has set me on the right path. Cathode bias was just an arbitrary idea after all, and the suggestion to look back at classic Fender 6L6 circuits was a particularly good one. It has me thinking of a 6G6-B blonde Bassman. That's an amp I've always liked recordings of and I think it suits these parts pretty well. The B+ on the Fender schematic is 430V though, so it has me thinking of a 5V filament transformer and 5U4 or 5U4G rectifier. Wouldn't be a strict 6G6-B copy but should drop enough voltage that any further tweaks to the power rail wouldn't need to be dramatic ones.
     
    jsnwhite619 likes this.
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.