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Ampeg watts?

Discussion in 'Amps and Cabs [BG]' started by Tom-Jens, Jul 26, 2000.

  1. Tom-Jens


    Jul 26, 2000
    Antwerp, Belgium

    There's something I don't understand:

    Ampeg says their V4B-head is rated 100 watt RMS, produced by 4 Groove Tubes 6L6-tubes.
    But Groove Tubes claims that their GT-6L6 C
    Tubes are rated at ca. 60 watt RMS each. Does that mean, if the Ampeg V4B-head uses 4 GT-6L6 C tubes, that the overall power rating of the V4b is actually ca. 240 watt RMS?

    Maybe it's a stupid question, but are Ampegs power ratings systematically understated, so that they can claim to be louder than other bass amps? Or is there something technically going on that I don't know (e.g. positive and negative tube watt ratings ...60 watt-60 watt+60 watt-60 watt= 120 watt)?
  2. timv

    timv Supporting Member

    Jun 7, 2000
    Chandler, AZ
    Where did you see that a 6L6 tube was rated at 60 watts?. I didn't think groove tubes misrepresented that horribly. Maybe a 6550 could be rated for 60 watts but the highest rating on 6l6's i've seen is maybe 30 watts a piece.
  3. Scok


    Apr 20, 2000
    Ya, I think Tim is right. 6L6's, from what I've seen are usually 25W a piece and 6550's are 50W a piece.

    Ps Tim, did you ever get to A/B your Ampeg and 400+? How's the old SVT working out for ya?

    [This message has been edited by Scok (edited July 26, 2000).]
  4. A pair of 6L6GC's is good for a maximum of 60 clean Watts RMS unless ratings are being exceeded, which is not recommended with today's tubes. (Some old Music Man amps actually run the EL34's at about 800 Volts.)

    As for Ampegs sounding louder than the rating would seem to imply, that is a characteristic of tube amps in general, just because they can go into distortion and supply more power than rated without sounding bad, and to me, actually sounding really good. My old V4B is supposedly 100W, and the last time I biased it, which was back in '94, I could get 107 Watts out of it with 7027A's into an 8 Ohm resistive load.

    Most times when you see unbelievable power ratings on older tube amps, it is because they are labeling it with Peak power, which is usually twice RMS power.

    Rules of thumb-

    pair of 6V6's max power = 15 Watts RMS
    pair of EL84's max power = 20 Watts RMS
    pair of 6L6's max power = 60 Watts RMS
    pair of EL34's max power = 60 Watts RMS
    pair of 6550A's max power = 100 Watts RMS
    pair of 211's max power = 260 Watts RMS (old radio transmitter tube at 1200VDC! smile. )

    They add normally. SVT has 3 pairs of 6550A's for 300 Watts RMS output. Most 100W amps have a quad of 6L6's or EL34's.

  5. Tom-Jens


    Jul 26, 2000
    Antwerp, Belgium
    I read it in a GT catalog from 1996, but the ratings are probably given per pair then, like throbbinnut says. Thanks for the information guys! Sorry for the stupid question!
    Do you guys think that the 100w V4B (new version) will be loud enough for most situations? Because that's the only thing about this amp what i'm worried about.

    Bassic greetings, T-J.
  6. Suusi M-B

    Suusi M-B

    Oct 15, 2006

    Just going to throw my Tuppence worth in here. I am an electronics engineer by training and just happens to play the guitar.

    I have been reverse engineering (OK attempting to reverse engineering) the original Ampeg V4 amplifiers, the ones with 6K11 tubes.

    I have programmed them into a spice simulator (an electronics simulator) to see how they work. So far successfully. I have gone back to the schematics and the original data sheets for the tubes 7027A, 6550A and 6L6GC

    Re the V4

    Firstly why 7027A output Valves for a 100 watt amplifier when 6L6GC's will do the job very well?

    Going to the schematics, the voltages sugest that the actual power output for these amplifiers is more like 152 watts RMS at full power with 7027A tubes. Switching to 6550A tubes would take the possible maximum power output up to a maximum of 182 watts RMS, provided that the power supply did not collapse too much.

    The Maximum power output sugested by the 6L6GC data sheets is 110 watts, and definitely NOT at the voltages inside an Ampeg V4 which are 100 volts higher than design maximum ratings.

    Assuming that Ampeg was pushing the limits, and the choice of 7027A tubes and the 545 volt HT voltage really points in that direction, it would place the V4 at half the power output of its more famous the SVT (300 watts RMS) This would give a proper midpoint for a product range.

    I know that there are other Ampeg amplifiers, the model numbers escape me for the moment, from that time that had a a pair of 7027A tubes for the output with 595 Volt HT's which would give a very handy 76 watts RMS output for a baby bother.

    I havent got the schematics for the re issue V4 amplifiers so I cannot comment too much on tham, BUT I gather they weigh 20 pounds less, so thay have less iron and copper in them. something that would make sence if the power output had been throttled back to 100 watts RMS and 6L6GC tubes selected for the output stage.

    Less power output needs less iron and copper in the power supply transformer and output transformer. something thats would account for the drop in weight.

    Hope that this makes a sort of sence ;) as I come from a teckky point of view rather than a musicians one. :bag:
  7. The hangman

    The hangman

    Dec 1, 2007
    came across this thread in the results of a google search, wanted to clear a few things up.

    suusi, your spice simulations are flawed. either your results are not RMS or spice is just not a good program for tube simulations.

    I've measured v-4s and vt-22s in real life. if the 7027s are good, they will hit 100-110 watts TOPS. the chage to 6550s makes no significant difference in output power. (again I've actually tested this)

    as for Vt-40s and B-25s Ive never seen one put out 75 watts. maybe 60 tops.
    keep in mind that amps like the fender bassman (two 6L6s) does not put out 60 watts. most Ive tested do not even put out 50 watts clean.
    but the ampeg VT-40 will put out 50+ watts Clean easy.

    The 7027as were used because ampeg put the 545Vdc on the plates. 7027s have a 35 watt plate dissipation rating where 6L6s are 30 watts.

    now there are many people that do not believe there is a difference between 6L6s and 7027s. I don't have an opinion about that myself, I have never done much experimentation.

    I don't know about ampegs sounding louder... but they do put out more power. compare the Twin Reverb, and the Vt-22. I've never measured more than 80watts (clean) on the output of a twin reverb (save the 100watt linear model) but routinely I measure 100watts (clean) on vt-22s.

    anyway, just wanted to chime in and clear a few things up.
  8. If you want to see some fun stuff, do a forum search on KT88's, 7027's, 7581's and 6550's.
  9. A9X


    Dec 27, 2003
    That's pretty close to the mark, and the datasheet numbers from the tube manufacturers.

    One other thing to consider with power rating discrepencies, is the point at which the measurement was taken; pro SS is typically 0.1%, hifi tube 1%, MI 5% and some MI 10%. But usually they don't tell you which they've used.

    Do you post under that moniker on the audio boards?
  10. Ryan L.

    Ryan L. Moderator Staff Member Supporting Member

    Aug 7, 2000
    West Fargo, ND
    Wow. Nothing like dredging up a thread that's over 7 years old.
  11. lowendgenerator


    Mar 26, 2006
    Double necro-posting! Sweet!
  12. A9X


    Dec 27, 2003
    LOL, I didn't even look at the dates.
  13. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    I like how Hangman joined this forum just to correct Suusi, who hasn't visited this forum in over a year.
  14. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Y'know I've read lots of PBG's posts and I've sort of dismissed the man 'cos of his sig. However the more I read the more I realize I owe him an apology. PBG please accept this as it was meant.

    Rule of thumb that I have followed is this - if a tube amp has two output tubes it is about 50W and four is 100W. Now 6550's and KT88's can double this BUT if you replace EL34's in a UK Marshall say, even if you do fix the bias voltage they are NOT going to give you more power output. Maybe even less. EL34's can run at high voltages and CAN produce 70-80 watts. However running them this hot is something I would not recommend. It's like trying to win the Indy with a stock consumer car. Y' just wouldn't do it.

    Ok, I'm done! It's nearly 2AM and I've downed a 12 pack of Creemore Springs Lager 'n' I'm tired. So goodnight to y'all. Shoot It's snowing outside!!! {Sigh} I hate Winter!

    Geeez, I'm responding to and old thread - hey that's OK I.m old too!!!!!!


    PS A9X stop laughing just 'cos it's your summer!!!!

  15. lowendgenerator


    Mar 26, 2006
    Well at least people are using the search function...

    For the record, I have no idea how my SVT-CL pumps so much power into my 4x10 and 1x18 cabs, and I don't care! Ignorance is bliss :).
  16. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Just to clear up the whole tube actual power thing, regardless of the age of the thread.......

    The original poster seems to have confused a bunch of ratings......

    The actual power limit (I'm not getting into how loud they sound here) is set by the power supply, the output transformer, and the load.

    The output tube can do a better or worse job of USING that potential power. But just because its rating is 6 watts, or 60, or 600, does not mean it can get any better than the "actual limit" as per the above. Once a tube is "good enough" (conducts enough current) to use the whole power supply voltage, you are done, that is the max power no matter what tube you replace it with.

    Using a tube that is "better", like replacing a 6L6 with a 6550 (you generally need to change the wiring) may change the wattage a small amount, and change the way the amp clips, but it won't generally make a drastic change (or even necessarily a noticeable change) in power, unless the original designer was a dunce.

    The tube power rating is what the tube can handle without melting or getting overly hot (!). There IS a relationship with the actual output power, and tubes differ in voltage rating.

    Those factors are why you can't get 100W out of a pair of 6V6 tubes...... But you CAN get 100W out of a BUNCH of 6V6 tubes, if the circuit is properly set up. It surely isn't economical, and I have not seen it done....... but it COULD be done.
  17. ...and I'll lay odds we don't hear too much, if anything, more from hangman. There are loads of dredge posts concerning tubes here. Usually a new poster will resurrect an old thread, say a couple of VERY obviously correct or incorrect technical comments and we never hear from them again. In this case, it was a dredge of a dredge, but hangman at least said that he found the thread through a Google search and didn't try to act like this was a timely conversation.

    Don't worry about it. At least you're not one the people who doesn't like me BECAUSE of what I know. ;)
  18. The hangman

    The hangman

    Dec 1, 2007
    had the thread not appeared in a google search I did for ampeg V4s I would never have bothered.
    it had nothing to do with ego, really doesn't matter if Suusi sees it at all. the point was to correct something that wasn't reality.
    so when someone else does a google search and finds this thread, they wont be misguided. I'll drudge up any 8 year old thread for that.
  19. The hangman

    The hangman

    Dec 1, 2007
    in many cases I don't know if I would recommend changing 6L6 to 6550. 6550s draw alot more heater current. 1.6 amps vs .9. in an amp like the v4 where there are 4 tubes, thats a considerable increase in current draw. the power transformer might be able to take the extra load. but there will be more heat... and in the long run, it could cost you a power transformer.

    I apologize for digging up old news on the forum. it was just kinda asking to be finished, or corrected.
    you probably wont see too much of me, too many forums to be an active member of all of them.
  20. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis

    It won't take very long....... A guy I know did it with an old Fender amp. He decided it wasn't such a good idea when the transformer started dripping out the tar it was filled with.
    I don't know if it was due to the filament current, or the fact that he also played it very distorted after the change. probably a bit of both.

    Just for the record, I don't recommend the change............. and "better" was in quotes for a reason....... because the 6550 are NOT "better", just different. "Too" different.

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