SVT-VR power draw?

Discussion in 'Amps and Cabs [BG]' started by Forrrest, Apr 19, 2014.


  1. Forrrest

    Forrrest

    Mar 10, 2013
    I know the amp pushes 300watts, but how many watts does the amp pull from the wall?

    It must be higher then 300watts because I'm hitting distortion, and there's also power that's wasted in heat and other things...
     
  2. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    About 2 amps at idle due to the heaters. 2 amps is 240W if you assuming the line voltage is exactly 120V. About 8 amps at full power, 300W output, or 960W input.
     
  3. BassmanPaul

    BassmanPaul Inactive

    if you own an SVT it should give the maximum power draw on the back plate close to the power cable inlet.
     
  4. Forrrest

    Forrrest

    Mar 10, 2013
    There's nothing written there.

    ok, this is good to know. and would 100% explain why running two SVT's are jumping a 15amp breaker... out of curiosity, how did you come to this figure?
     
  5. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    You can buy an inexpensive meter called a Kill A Watt at some hardware stores or through amazon. There are different models, you want the latest. Plug your amp into that and it will show you exactly what the power usage is, the line voltage, current, etc. It is a handy tool to have. Nice when you are at a gig to check that the line voltage isn't too low. This can damage your amp.

    If you are poping the circuit breaker, you should try to run each amp on its own breaker. Sometimes you need to carry some extension cords to reach another plug that is on a different circuit.
     
  6. f.c.geil

    f.c.geil

    May 12, 2011
    According to Ampeg, an SVT-CL pulls 450 watts. A VR would be more, but I have trouble believing it's over 900. I've run two, along with a channel strip and mixer, on a power strip rated at 1800 watts with no trouble.
     
  7. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The problem at a venue is that there may be other pieces of equipment on the circuit that you don't know about. Bad wiring can cause the breaker to pop sooner. Even an old tired breaker can cause an issue.
     
  8. Forrrest

    Forrrest

    Mar 10, 2013
    My practice space is on one breaker, can't get around that without renting a second room.... at least the maintenance guys don't mind resetting the breaker when we jump it (it's only happened twice so far), (we've also blown the breaker at a venue in the past, yet they admitted to needing to get their breaker box completely redone)
    I'm posting about this particularly today because at a show yesterday my SVT-VR would go into standby when the band got loud and only go green during the quiet parts. The venue ran on two breakers but the soundguy wouldn't plug me into the second circuit since it was kept to the console & PA (understandable). I know the VR has a safety feature built in where it goes into standby when the voltage drops below a certain threshold. I know I could bypass this with a mod, but I'd rather not risk my amps life over a gig...

    I'm gong to buy myself a kill-a-watt unit and use it to help figure out a solution. once I diagnose the problem and fix my needs I wonder how big of a UPS (uninterrupted powersupply) I need to get to make sure I never have this problem again...
     
  9. B-string

    B-string Supporting Member

    That would be an average draw, at roughly 50% efficiency (about the best you might hope for) that would allow output power of 225 watts (160 rms).
     
  10. f.c.geil

    f.c.geil

    May 12, 2011
    Whatever you say. Good to know that Ampeg don't know how their amps work.
     
  11. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    Apparently they don't. B-string knows what he's talking about, and so do I. Guys, I've seen it first hand. Unless the ammeter on my variac is waaay off, a vintage SVT pulls about 8 amps full tilt. That's almost 1000 watts. The things pull about 240 watts at idle just due to the heater current.

    Don't believe me? Fine. You're not hurting my feelings any. Buy a $20 kill-a-watt as beans suggested and prove me wrong.

    Oh, and Forrrest - I didn't see your other question. P = V * I. P (power, watts) = V (input voltage, 120VAC) times I (current, amps).
     
    Last edited: Apr 20, 2014
  12. f.c.geil

    f.c.geil

    May 12, 2011
    I said it was good to know that.
     
  13. Forrrest

    Forrrest

    Mar 10, 2013
    K-Thanks!



    are these accurate as advertised? 20$ seems really cheap for accurate readings. (either I'm ordering one because I want to read the voltage coming out of the wall when I play shows.)
     
  14. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    Oh, I'm sorry man. I thought you were implying that B-string was full of BS. Can't tell someone's tone on the interwebz.
     
  15. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    It seems to be pretty darn accurate. JohnK_10 and many others on here have come to the same conclusion.
     
  16. f.c.geil

    f.c.geil

    May 12, 2011
    No worries. I'm not choosing my words wisely today, sorry.
     
  17. B-string

    B-string Supporting Member

    I actually laughed. :)
    It is not that they don't know their product, it is that they are publishing only what industry rules require. A little knowledge lets you weed through those published specs. I think QSC actually goes above and beyond with published specs listing power draw by output and duty cycle.
    Average SVT is being run below half it's potential.
     
  18. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    I just laughed at "Average SVT"...
     
  19. B-string

    B-string Supporting Member

    LOL, yes SVT did become a marketing badge. Should have specified all tube "SVT's".
     
  20. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Hmmmmmmmmm..........

    The current for the filaments is at 6V..... so you need to divide that by 20 to get the 120V current. The SVT VR and similar would draw about a half amp or a bit more due to heater current.

    And, all the "current" that is drawn by an amplifier is not equal to "power". For various engineering reasons*, there can be more current drawn than the actual power would indicate. That is true of amplifiers, motors, and many other things electrical. Not true of heaters.... amps is proportional to watts for heaters.

    *A consideration known as "power factor" affects the proportion of current that corresponds to actual power
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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