Four 6V6's = 50 watts?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by rockon1, Mar 14, 2006.


  1. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Just read here that a 6V6 will only produce about 6 watts. My Stealth GT50 H head which is powered by four 6V6's I presumed was 50 watts.Am I mistaken? Thanks Bob
     
  2. Mickey_C

    Mickey_C The Original Racketeer Gold Supporting Member

    Messages:
    1,527
    Joined:
    Mar 28, 2003
    Location:
    Sedona, AZ
    Up to 14 watts per 6V6. Your amp could easily be 50 watts, at the more conservative rating of 12 per tube.

    Who said 6?
     
  3. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Thanks. I thought 6 watts seemed to small. At any rate I dont think I want to name names. Ive read a lot of his posts and they seem very knowledgeable.
     
  4. Scumback Speakers

    Scumback Speakers Gold Supporting Member

    Messages:
    9,575
    Joined:
    Oct 6, 2003
    Location:
    Los Angeles, Ca
    Depends on the amp class design. Although I know it sounds/projects louder than it's rating of 9 watts (actually 10.8 watts RMS at a volume of 2, clean signal, 8 ohm setting), my Capt. Crunch model (dual 6V6 Single Ended Class A) amp easily competes with Deluxe Reverbs (22 watts) and 18 watt style amps. But my amp designer is ULTRA conservative about his ratings, too.

    The Major Crunch (quad 6V6 SE Class A) amp he rates at 19 watts RMS at a volume of 2, and about 25 watts RMS "pushed". Yet I have guys with Super Reverbs and JTM 45's telling me I'm as loud as they are.

    My guess is that some designs project more than others.
     
  5. Mickey_C

    Mickey_C The Original Racketeer Gold Supporting Member

    Messages:
    1,527
    Joined:
    Mar 28, 2003
    Location:
    Sedona, AZ
    I went back and read it.. surprised I missed that! My eyes probably refused to believe it ..guess he never saw a Fender deluxe reverb... 22 watts out of a pair of 6V6.

    Like I said, I wish the builder of that amp would get to speak to it all himself.

    I was scolded in here for recommending a dual bias circuit as an easy and cheap answer to tube matching (especially since tubes go unmatched so quickly in usage) so my opinion is that you should do research and not take anything here as the law. Much of it is just simply wrong.

    Mickey
     
  6. mbratch

    mbratch Member

    Messages:
    2,389
    Joined:
    Nov 3, 2003
    Location:
    Webster, NY
    I've never read 6 watts for a 6V6, but it's interesting that a Fender Champ has one 6V6 and is rated at 6 watts (I think). Not sure why that is.
     
  7. Scumback Speakers

    Scumback Speakers Gold Supporting Member

    Messages:
    9,575
    Joined:
    Oct 6, 2003
    Location:
    Los Angeles, Ca
    That's because in single ended Class A amps (Champ, Gibsonette GA-8, & my single ended amps) the tubes do not work as efficiently as in a push/pull circuit. What they lack in raw power output they make up for in sounding "bigger" for their wattage, and having sweeter tone since they don't cancel the even order harmonics which a push/pull amp will do.

    I've gone round and round with my amp circuit guru on this, and you lose more on the SE style amps for power than any other. I've read the oscilloscope, and A/B'd the Fender Deluxe to my Capt Crunch amp. On an o-scope the Deluxe is "technically" louder. I'm just glad I use my ears, and not an o-scope to determine the tone I want.
     
  8. Reeek

    Reeek Member

    Messages:
    1,208
    Joined:
    Feb 1, 2005
    Location:
    Reno, NV
    Circuit design classes and trannies, etc. can affect that I believe. I can easily see a single 6V6 amp at 6-7 watts in class A for instance. My Hi Mu is 7 watts but it only had 5 watts until the builder upgraded the OT to an air-gap trannie that upped the output to 7 watts.
     
  9. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    AHHHH...Probably was reading about a CLASS A application for a 6V6! Thanks guys. Im suire the Stealth is probably not class A!
     
  10. GuitarsFromMars

    GuitarsFromMars Member

    Messages:
    11,395
    Joined:
    Jun 7, 2004
    Location:
    playing in traffic...
    Geeeeeeeeeeeeeeeeeeeeeeeee,ya think?????;)

    ...somehow when I saw this thread I figured you'd be here Dr. Pure Evil Incarnate...Robin Amps guy says about 12 watts per...oops,gotta go,got something brewing in MY lab with one of my critters....GFM
     
  11. Mickey_C

    Mickey_C The Original Racketeer Gold Supporting Member

    Messages:
    1,527
    Joined:
    Mar 28, 2003
    Location:
    Sedona, AZ
  12. Beer

    Beer Member

    Messages:
    108
    Joined:
    Jan 21, 2002
    Location:
    Westbrook, CT
    Wattage in tube amplifiers is sorta kinda a little bit nutty. It doesn't seem to mean a whole hell of a lot for "nominal" wattage in most amplifiers. It gives you a pretty basic idea of the amount of "power" but even that is quite difficult to nail down as to whether it's "peak power" or "maximum sustainable power" or "theoretical power" or "acoustical power" or "electrical power". And then it becomes more confusing when you translate that to actual volume and combine it with "clean headroom" and what are we really talking about in an amplifier that can be defined by one single number? Basically, the way I've come to think of it, is that it is simply a number that has only the thinnest of meanings. It is "nominal" as far as I'm concerned and sort of puts the amplifier into a category I can understand. Especially since using the maximum power in an amplifier (everything on 10) is so very rare for most people.
     
  13. mbratch

    mbratch Member

    Messages:
    2,389
    Joined:
    Nov 3, 2003
    Location:
    Webster, NY
    Thanks OTm, that was helpful. So, it looks like the first three choices under 6V6GTA roughly correspond to Champ, Princeton, and Deluxe. And choice #4 would be like a Tone King Meteor. :)
     
  14. Mickey_C

    Mickey_C The Original Racketeer Gold Supporting Member

    Messages:
    1,527
    Joined:
    Mar 28, 2003
    Location:
    Sedona, AZ
    Hey, so that angela circuit is just a 5F2A princeton, 1 6v6 circuit. There's a typo, but the amp is cool - I've played the weber kit.

    He really meant to say it's "ONE 5 watt" amp, as in "This here's ONE kicka$$ little 5 watt amp."

    Having done my community service, I am off to the guitar trade papers...

    :RoCkIn
     
  15. John Phillips

    John Phillips Member

    Messages:
    13,080
    Joined:
    Mar 17, 2002
    Location:
    Scotland
    Without exceeding the tube ratings, you can only get:

    Up to half the tube rating in single-ended Class A with one tube.
    Up to the tube rating of one tube from a pair in parallel-single-ended or push-pull Class A.
    Up to twice the rating of one tube from four tubes in push-pull Class A.
    Up to twice the rating of one tube from a pair in push-pull Class AB (this is achieved when the bias point is as close to Class B as possible without causing crossover distortion).
    Up to four times the rating of one tube in parallel push-pull Class AB (typical four-tube amps).
    Audio amps do not use Class B because you can't avoid crossover distortion.

    So for 6V6s, the maximum power outputs are:

    6W for 1 tube in SE
    12W for 2 tubes in Class A
    24W for 4 tubes in Class A
    24W for 2 tubes in Class AB
    48W for 4 tubes in Class AB

    These are theoretical limits assuming 100% efficiency in the OT, which obviously doesn't occur, so the real-world numbers are about 10% less - and assuming the tubes are run within the design limits, which many guitar amps deliberately exceed - but you can't go much over before tube life is seriously shortened.

    This is also for clean output power. You can stretch the figures by allowing more distortion - eg 5% rather than 1% or 0.1%.

    So 50W from 4 6V6s is certainly possible, provided you run the tubes at or just over their dissipation rating, and allow more distortion than would be considered acceptable for a true clean output power rating.


    You will also notice that 33W from four EL84s (also 12W tubes) is not possible in Class A ;).
     
  16. Scumback Speakers

    Scumback Speakers Gold Supporting Member

    Messages:
    9,575
    Joined:
    Oct 6, 2003
    Location:
    Los Angeles, Ca
    Or more...in the JCM 800 series manual they list the Studio 15 (dual 6V6) as putting out:
    15 watts RMS into 8 ohms at 1% THD (Total Harmonic Distortion)
    20 watts RMS into 8 ohms at 10% THD
    29.5 watts RMS into 8 ohms at 40% THD (maximum amplifier saturation)

    Sheesh 40% THD...I'm just about to get my Studio 15 out of the repair shop (yep, I know 18 months later) with a new power tranny, and a Mercury Magnetics Axiom output tranny (cloned/upgraded from my still original OT).

    I wonder if I can get more than 40% THD? That might be a real chewy tone...huh? :RoCkIn
     
  17. Scumback Speakers

    Scumback Speakers Gold Supporting Member

    Messages:
    9,575
    Joined:
    Oct 6, 2003
    Location:
    Los Angeles, Ca
    I can, and when the Studio 15 is back in action, I'll see if it produces that tone, too. :AOK
     
  18. John Phillips

    John Phillips Member

    Messages:
    13,080
    Joined:
    Mar 17, 2002
    Location:
    Scotland
    Not after they've passed through the OT you can't ;).

    Scope both sides of the OT and you will have a very good visual proof of one of the main reasons overdriven tube power stages sound good and overdriven solid-state ones don't - and why SS is much harder on speakers than tube when it's pushed too hard.

    :)
     
  19. TheAmpNerd

    TheAmpNerd Member

    Messages:
    1,063
    Joined:
    Sep 23, 2004
    Location:
    Tejas
    How fun,

    I was wondering what to do with my scope today.
     
  20. lastwinj

    lastwinj Member

    Messages:
    297
    Joined:
    Mar 17, 2006
    Location:
    livonia, MI
    don't sweat it.

    germ
     

Share This Page