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5AR4 vs. Two 5V4s in a Matchless C-30

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by MT Buckaroo, May 16, 2011.

  1. MT Buckaroo

    MT Buckaroo Silver Supporting Member

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    The amp can take either one 5AR4 or a pair of 5V4s for rectification. So what would the difference be? Would the two 5V4s produce a tighter feel with less sag (higher plate voltages?) than the 5AR4, or is the other way around? Anyone know?
     
  2. phsyconoodler

    phsyconoodler Member

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    5V4's would have less voltage,more sag.The 5AR4 is the highest voltage rectifier.
     
  3. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    I'm not so sure...

    We're comparing a single 5AR4/GZ34 with two 5V4 - the two 5V4 could supply more B+ than that single 5AR4, depending on the power section design. If it were one 5V4, that would obviously supply less.

    What does your amp manual say?

    - Thom

    edit:
    I looked and found this at the Matchless site:
    There's your answer. But the design makes me wonder...
     
  4. MT Buckaroo

    MT Buckaroo Silver Supporting Member

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    Now why couldn't I find that on the Matchless site? Thanks!

    I guess it's worth experimenting to see if I can hear or feel any difference. One KCA order, coming up...
     
  5. wyatt

    wyatt Member

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    Everything I've heard is it does loosen things up noticeably (less stiff). Doing some loose math, the voltage drop should be similar between one 5AR4 and two 5V4's (running in parallel, the voltage drop is halved), but I can't find a voltage drop co-efficient for a 5V4 and it's 2:45AM on the East Coast, so I really don't want to have to factor in current.

    However a NOS 5AR4 is $200+ and you can by NOS 5V4G's from reputable dealers for less than $15. So, the difference averages $175, that must affect one's audio perception somehow. :)
     
    Last edited: May 18, 2011
  6. Blue Strat

    Blue Strat Member

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    From dealing with dozens of xC-30 owners, the 2 5V4 option does decrease headroom and increasing sag. I was a little surprised too.
     
    Last edited: May 17, 2011
  7. drbob1

    drbob1 Silver Supporting Member

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    I thought it was related to increased internal resistance or something?
     
  8. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    I've got several Ken-Rad (and early GE) 5V4G, and several of the more common RCA 5V4G. I've noticed that the RCA "sag" much more than the Ken-Rad. I suspect the RCA are more to spec, and the Ken-Rad typically drop less B+.

    I can't quantify this observation with B+ measurements, as I've only used these rectifiers and noted the sag differences in cathode-biased amps, and have not tried the two different 5V4G makes in fixed-bias amps. The three cathode-biased amps I noted this effect in are: Vox AC30CC1, Richter tweed Bandmaster-inspired 5E7+, and Vintage 47 Amps Valco/Supro-inspired Bronson.

    I'd love to try comparing two Ken-Rad 5V4G to one standard-spec GZ34 (not current-production, below-spec Sovtek) in that C-30. I'll bet they'd be pretty close in operation, and, as noted earlier in this thread, the 5V4G are less-expensive than many NOS GZ34 options.

    - Thom
     
  9. Blue Strat

    Blue Strat Member

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    Internal series resistance is definitely it. The higher this is, the lower the output voltage and greater the sag.
     
  10. Blue Strat

    Blue Strat Member

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    Interesting...and a possible explanation for why audiophiles (who seem to use more 5V4s than guitar players) make brand distinctions.
     
  11. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    I suppose I was thinking about a parallel rectification circuit. When there are two rectifiers used at once, are they commonly in series? Or does this vary too much, from amp to amp, for a generalization? Not having such an amp, I've never looked into the topic...

    - T
     
  12. EL34

    EL34 Silver Supporting Member

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    The rectifier sockets are wired in parallel. Two 5v4's are required because a single one won't supply enough current to run the amp. The 5v4 drops more PS voltage than the 5AR4. I've tried it both ways and noticed a little more sag/give with two 5v4's.
     
  13. Blue Strat

    Blue Strat Member

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    +1. This is the only amp I've seen which offers this option and parallel operation is, sorta, required because you get double the current capability of one tube. Not so in a serial connection which would give more sag than even a single 5V4.
     
  14. Jeff West

    Jeff West Member

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    Going back a few years, 5E8-A tweed Twin and 5E6-A 4x10 Bassman had dual parallel 5U4GAs, and earlier still, at least a few 5D8 Twins supposedly called for dual 5Y3GTs. I had a '55 EV "Circlotron" audio amp with dual horizontal 5Y3GTs too. Have seen three different '67 plexi 100W heads with dual parallel full-wave bridge SS diode rectifiers as well, each with a different physical layout/configuration. Lotsa tinkering.

    J
     
  15. Blue Strat

    Blue Strat Member

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    Oh yeah, I forgot about the Twins. I was thinking of modern amps...does the low powered Tweed Twin (there's a reissue, right?) have dueling rectos?
     
  16. Jeff West

    Jeff West Member

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    Yep, the "'57 Twin RI", they had one of those on the floor for awhile at a local shop here on Poplar a couple of years ago and I got to check it out. Twin 5U4s. Said to run ok on one as well, with more sag.

    Going back still further, I recall that some of the Charlie Christian era Gibson amps designed to run on either AC or DC 110 line voltage as could commonly be found in U.S. then used at least four rectifier tubes in parallel (25Z5s). Gibson also experimented with added OA2s for voltage regulation (!) but I guess that's another thing . . .
     
    Last edited: May 18, 2011
  17. chilibatsu

    chilibatsu Supporting Member

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    I saw DC-30 with 2 different rectifier tubes yesterday.
    Seems like the amp has one 5AR4 AND one 5V4 working together........maybe I'm wrong but does the amp work like this ?
     
  18. Blue Strat

    Blue Strat Member

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    It'll definitely work. Likely, the 5AR4 will override any "contribution" of the 5V4.
     
  19. melvins

    melvins Member

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    I stand by the two 5VR4's. It gave the amp more sag which i thought it needed, especially coming from playing mostly Marshall style amps. The 5AR4 was nice, but very stiff sounding imop.
     
  20. MT Buckaroo

    MT Buckaroo Silver Supporting Member

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    Well, my most recent order from Blue Strat showed up today (super fast shipping, thanks Mike!), and so I'm going to try the two NOS 5V4s vs. a Ruby (Chinese?) 5AR4 in the Matchless this weekend.

    I have a Sylvania 5V4GA and a Philco 5V4GA to pop in the SC-30, and both test exactly the same on my B&K 700, FWIW. Tube construction looks identical, so I suspect they are the same manufacturer, just different labels on the base.

    Stay tuned for my impressions. Can the tin ear tell a difference?
     

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