2xEL34 Power????? (30watt vs. 80watts)

Discussion in 'Amps and Cabs' started by jamison162, Jun 23, 2006.

  1. jamison162

    jamison162 Member

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    How are some 2xEL34 amps rated only 30 watts such as the Orange Rocker 30 whereas the Bogner Shiva is rated a whopping 80 watts?
    How do you come up with a 50 watt difference utilizing just 2xEL34 power tubes.
     
  2. electronpirate

    electronpirate Member

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    Interesting question. I'm curious too.

    My guess is Output Transformers.
     
  3. afm409

    afm409 Member

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    Tubes being powered at higher voltage?
     
  4. riffmeister

    riffmeister Gold Supporting Member

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    80 watts seems a bit high, I've always been skeptical of that one.
     
  5. redjet55

    redjet55 Member

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    I'm guessing you guys don’t remember the stereo power wars....

    The numbers don’t mean much since they’re unlikely to measuring the same thing... peak power, low distortion %, continuous rms, class a, class a/b....

    They’re just numbers....
     
  6. Rusty G.

    Rusty G. Member

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    YEAH. . .I'll throw a curve ball. . .my Fargen Mini-Plexi combo uses 2 X EL34's and it's only cranking out a whopping 12 watts. It's definitely the output transformer.
     
  7. jamison162

    jamison162 Member

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    Well one of my problems and the reason for this thread is that I've always wanted a Shiva but have been told they are loud as hell. Guess I just need to find one and try it out for myself.
     
  8. bullfrogblues

    bullfrogblues Supporting Member

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    Shiva's are generally biased a little hot, might make up for the higher wattage rating(I'm no techie so I may be wrong)
    Yes, Shiva's are loud, but they do have one of the best master volumes of any amp I've played. I can get great tones at almost a whisper. Can also pump it up and blow the windows out!!

    Allan.
     
  9. carltonh

    carltonh Member

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    I don't remember much electronics, but I think power = current draw x voltage. Tubes have a maximum of each value that they can tolerate, but they can also tolerate a lot less. Amps can be designed to create less power by sending less current or voltage to the tubes. Smaller output transformers can then be used if less power is being created, but that isn't the cause of less than maximum power per tube.

    Tubes also probably last longer if they are used at less than maximum power, the smaller output transformer can let the amp weigh less, and the amp can be sweeter at lesser volumes. So plenty of reasons to design some amplifiers at less than max power per tube.

    Also, there are standard EL34s, and then there are high power EL34s that would have to be used in an amp drawing 70-80 watts for a pair.
     
  10. dhines

    dhines Member

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    I'm not sure, but the Orange amp is probably class A and the other amp might be running in class AB. AB usually puts out more power. And, the transformers do make a difference.

    That said, I do NOT believe the other amp is running 80 watts. Might get to 60, but I doubt 80. I won't say this with 100% confidence because I just don't know enough about their amp, though.

    But I will say that the majority of amp companies list their wattages and features as simple marketing tools. There is a lot of incorrect information. Over 90% of manufacturers who claim "class A" are NOT class A. Especially the guys who got famous for bringing back the term "class A." ;)

    Most companies choose to list their wattage to appeal to a certain type of player or position their product. i.e. an 18 watt amp may be listed as "15 watts" because the company doesn't want to fall in the marshall 18 watt group, even though they have a marshall design. etc....
     
  11. jakins

    jakins Member

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    +1 on the shiva master volume. I sold my shiva a while back and am considering getting another, i cant really think of another amp that rocks so hard, yet is soo versatile, too.
     
  12. drbob1

    drbob1 Silver Supporting Member

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    +1 on the marketing hype...

    The output volume of the amp is what you're concerned about. That's affected by:
    1. Speaker efficiency-this can make up as much as quadrupling the power.
    2. OT efficiency-throw power away as heat
    3. The output wattage of a power tube is dependent on a lot of things, but most noticeably the bias voltage, input voltage and B+ or plate voltage. Also whether it's being operated in pentode or (less efficient) pseudo-triode mode. By manipulating these variables the tube output can vary from 6w or less a tube to as high as 30w (I think 80w is probably peak output dimed and may still be a bit optimistic). So, the difference between a nominal 20w output El34 amp, into inneficient speakers with a wasteful OT could be as much as 16 times as much power (6 dB + 6 dB + 2 or 3 dB) or 4 times as loud perceptually.
     
  13. conundrum

    conundrum Member

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    simple answer:

    Fargen is Class A
    Orange is cathode biased AB
    Bogner is fixed biased AB

    output transformer does play into it, but not as much as the above.
     
  14. jamison162

    jamison162 Member

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    So......with all that said, I guess my question is: How loud is the Bogner Shiva really? Or does it matter...I wasn't really aware that it is a Master Volume Amp. Wonder it compares to the Orange Rockerverb 50. Output level wise, not speaking tone here.
     
  15. clothwiring

    clothwiring Supporting Member

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    I don't know it all, but what I do know is that my 40 Watt Matchless Chieftain seems to have a ton more volume (power) than my Marshall Jubilee 2558 (on 50 w setting) and that the Matchless is probably close volume wise to my 1/2 stack 2555 Jubilee (yes I know the Matchless is Class A and the Marshalls AB). I have to be real careful with my Matchless and it's volume...also the Matchless tends to cause hearing fatique easily.
     
  16. Doug

    Doug Member

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    Echo what bullfrogblues said. The Shiva's master volume works great. It does sound good at almost apartment levels. I've never had the master past 5 because of fear of damaging the building. :RoCkIn
     
  17. mmorse

    mmorse Member

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    Your average Marshall 50 watt puts out 70-80 watts overall. The 50 watt rating is how much the amp will put out before clipping occurs.
     
  18. John Phillips

    John Phillips Member

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    It's totally dependent on the circuit parameters. Just because a tube is capable of being used to produce 80W from a pair doesn't mean that it must be used to. You can run them at any power you like below the maximum.

    Actually a pair of EL34s is probably not capable of producing 80W true clean power while staying within its ratings - you can distort :) the figures by allowing more measured distortion though. I have measured up to 70W (clean) from a pair of EL34s in a Marshall JCM800 2204 before now, but never anything higher and that's really pushing the tubes too - those are the most powerful '50W' amps I know of.

    A Matchless Chieftain is not Class A. It is cathode-biased Class AB, which always sound louder for their rated power due to the attack characteristic of the notes (because the bias is dependent on signal strength).

    Speaker sensitivity and voicing is as important as output power in determining volume - if the Matchless is going through a V30/H30 pair and the Marshall Jubilee has G12T-75s, the Matchless will certainly sound louder... the sensitivity difference is 3dB, which is equivalent to doubing the amp power.
     
  19. VacuumVoodoo

    VacuumVoodoo Member

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    As John said, it's the circuit design. Plate dissipation is not the same as output power.

    Try this for 2xEL34 in class B Push-Pull:

    B+ = 800V
    Screens supply 775V
    Bias = -39V
    Idle plate current = 25mA
    Raa = 11 kOhm

    and you'll get 100W output at ca 5% distortion (onset of clipping)

    Of course with a standard OT providing "customary" 3.5 to 5kOhm plate load this will not work.

    Then there's the specs game. An amp that delivers 40W clean before clipping can theoretically put out ca 80W when fully clipping i.e. a symmetrical squarewave. BUT, for that you need a B+ supply that will hold up to current demand and a large OT that will not saturate before the tubes do. Who puts a power transformer rated at well over 200W (big & expensive) and 50% bigger than needed OT in 40W amp?

    More realistic is that an amp specified for 40W clean will output about 55W clipped.

    oh well, enough of me technobabbling...
     
  20. jhc

    jhc Senior Member

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    so if an amp is rated at 30 watts class a, switchable to 50 watts class A/B, will the A/B mode have more clean headroom?
     

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