'61 brownface Fender Deluxe

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Laurent Brondel, Mar 7, 2015.

  1. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME
    I just go this amp (sans speaker) and put a Celestion G12H80 in it, the speaker sounds very good, has tight, powerful and controlled bass, nice flat mids and trebles, but I am looking more for a mini-Marshall type of vibe, any speaker recommendation?

    The layout shows 365v on the plates, mine is at 445v with a bias of 35mA (I installed an adjustable bias pot). It sounds great and the electrolytics can take the voltage, but is this common? Original PT BTW.
     
  2. slider313

    slider313 Silver Supporting Member

    Messages:
    7,436
    Joined:
    Jul 28, 2005
    Location:
    NC
    I'm running mine with a 5Y3GTB/6087 rectifier. I'm getting 400v with the bias at 20ma. They ran these amps hot from the beginning. The bias is set at -26. I believe this was to compensate for the "wiggle bias" tremolo.

    I have a '61 alnico Rola reconed with Webers' Blue Dog cone and 75 watt voice coil in mine.
     
  3. zenas

    zenas Member

    Messages:
    5,979
    Joined:
    Jul 1, 2011
    If the amp is running right (with fresh electrolytics) it will get that mini Marshall thing with the volume knob cranked up.
    If it's too loud for you cranked up get rid of that speaker. You need somethng with lower effientency. You might have to look for an old speaker to get the volume down enough.

    Newer speakers are great but they really ad alot of volume. That can be good or bad.
     
  4. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME
    Is it safe to run a 5Y3 in this amp? How's the bass response with the 5Y3 on yours, still tight, no flub?
    Yes, the G12H80 is pretty efficient, I do not know the specs but it is probably close to 100dB.
    I am looking for a speaker that has a nice controlled bass response with maybe more agressive mids, less efficient is OK too.
     
  5. zenas

    zenas Member

    Messages:
    5,979
    Joined:
    Jul 1, 2011
    5Y3 will be fine I'd highly recommend a USA one either NOS or pull one out of an old radio or something.
     
  6. Chandler

    Chandler Member

    Messages:
    201
    Joined:
    Jul 11, 2005
    Location:
    Media, PA
    I like a Weber Silver Bell (ceramic) for that tone. You call talk to them and have it built to your specs. Efficiency can be tweaked by voice coil and magnet sizes etc.
     
  7. slider313

    slider313 Silver Supporting Member

    Messages:
    7,436
    Joined:
    Jul 28, 2005
    Location:
    NC
    The bass response is the same, just slightly more compressed.

    A Greenback is 97db and will sound great. If you want to go alnico then an old Jensen P12P would be the ticket.
     
  8. ked

    ked Supporting Member

    Messages:
    893
    Joined:
    May 18, 2006
    I'm surprised you're not killing those 6v6 tubes running at 445v and 35ma bias point. That is over 100%.
     
  9. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME
    I have a '79 Deluxe reverb that runs hotter.

    Of course a lower bias increases the voltage even more…
    What can I do, besides switching to a 5y3 rectifier, to lower the voltage?
     
  10. swiveltung

    swiveltung Member

    Messages:
    14,567
    Joined:
    Feb 5, 2011
    Location:
    PNW
    Yes, it's pretty normal for the plate voltage to run real high. My BFDR runs in excess of 455V. I'm not saying it's good though. I would go to JJ power tubes or you may end up with a trashed Output Transformer. You can also go to a 5V4 rectifier to get a little lower on the plate voltage. But maybe only 10 volts or so.
    I used a GB in my BFDR for a while, It might get you where you want to go. A Weber Silver Bell sounds pretty good too. For smooth top end a 50 watt with screen dust cap will help on that.
     
  11. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME
    Is the 5U4GB OK for an amp designed to use a GZ34 rectifier?
     
  12. pdf64

    pdf64 Member

    Messages:
    5,147
    Joined:
    Aug 9, 2008
    Location:
    Staffordshire, UK.
    Maybe; a 5U4 draws more heater current (3 amps compared to 2), so if the PT is marginal then it may not be a good idea.
    A 5R4 may be a better choice, as it drops a lot of voltage (perhaps more than a 5U4) but has a 2 amp heater.
     
  13. slider313

    slider313 Silver Supporting Member

    Messages:
    7,436
    Joined:
    Jul 28, 2005
    Location:
    NC
    I would pick up a GE 6087. These are indirectly heated 5Y3GB mil-spec tubes.
     
  14. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME
    Yes, this is what concerned me, it is a '61 after all and it would be a shame to burn the PT. Is the 5R4 between a 5Y3 and a 5U4GB, sort of?

    So the specs are the same as a 5Y3?
     
  15. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME
    Imagining that household voltages were a bit lower in the '60s (117v?), this amp would have run hot from the beginning, no?
     
  16. zenas

    zenas Member

    Messages:
    5,979
    Joined:
    Jul 1, 2011
  17. slider313

    slider313 Silver Supporting Member

    Messages:
    7,436
    Joined:
    Jul 28, 2005
    Location:
    NC
    Look at the schematic. The 6G3 Deluxe is fixed bias set at -26v from the factory. To compare the AB763 non reverb Deluxe is fixed adjustable bias set at -35v from the factory. I believe it's (running hotter) to compensate for the bias variable trem circuit.
     
  18. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME
    Thanks, yes… If I run mine at -26mA the voltages are even higher, over 450v! The bias tremolo is more pronounced with a "cold" bias of course, but that means higher voltage on the plates.

    What is worse for the amp, higher voltage or hotter bias? Am I assuming correctly that a hotter bias will shorten tube life, but not negatively affect the PT like higher voltages may do? Or am I totally missing it?
     
  19. swiveltung

    swiveltung Member

    Messages:
    14,567
    Joined:
    Feb 5, 2011
    Location:
    PNW
    I wouldn't run a 5U4GB in that amp... you risk the power Transformer as that tube draws a bunch of current.
    The hierarchy is generally:
    5AR4
    5V4
    5U4GB
    5R4
    5Y3
    I have a list with other specs, email me if you want it.
     
  20. Laurent Brondel

    Laurent Brondel Supporting Member

    Messages:
    2,093
    Joined:
    Dec 9, 2011
    Location:
    West Paris, ME

Share This Page