Acoustic Image amps and voltage

Discussion in 'Amps and Cabs [BG]' started by basss, Mar 29, 2005.

  1. basss

    basss Supporting Member

    Aug 27, 2001
    The other night I was using my AI Focus SA on a medium loud pop gig. I was sharing a power strip with the rest of the band (guitar, keys, DJ, PA). I didn't seem to be getting the volume I usually am able to get from the amp and the amp clipped if I turned it past 3 o'clock. I emailed Rick at AI about this and he said that it was due to low voltage. I haven't had this problem with other amps I've used. Are AI amp paticularly suseptable to voltage problems?
  2. emjazz

    emjazz Supporting Member

    Feb 23, 2003
    Boston, MA
    It's not the amp. I've had this problem once in a similar situation. It's definately due to everyone coming from the same power source. I now insist that I have my own power outlet to plug into (if possible of coarse). I always carry my own extension cord and multi plug.
  3. B String

    B String Supporting Member

    Apr 11, 2002
    Los Angeles
    I've experienced this a number of times with different amps.
    Its all about the power source, not the amp. I usually like
    to run a line directly to the nearest power plant. Yes, I know,
    a looong extention cord, but its pure power. anyway....
    Just try to get as good a power source as you can. It really
    helps low end and volume.
  4. fretlessrock

    fretlessrock Supporting Member

    Aug 8, 2002
    One thing to remember about power supplies, and especially switchers, is that you don't get out more than you put in. If the source voltage is low, the output voltage will be low. And if the output voltage is low your output power will be low.

    As for getting your own outlet, that doesn't matter if you are all on the same circuit, and all getting power form the same panel. The voltage at the wall, or at the pole for that matter, is not a guarantee. It is common for utility systems to run high, low, noisy...

    Try dropping the voltage on one circuit of a breaker box with everything paralleled to the 220v feed from the street. It ain't easy.
  5. basss

    basss Supporting Member

    Aug 27, 2001
    So do you think the AI amps are more prone to voltage problems? In most of the places I play running to a separate circuit is pretty much impossible so this is a definite issue for me.
  6. Everybody's playing by the same rules of physics, no amp should be more vulnerable than any other.

    Still, lets say the AC voltage drops 10%. 100v instead of 110. Say your power amp is normally 1600W@4 ohms. That's 80V. That drops 10% also. Now its 72V. 72v@4 ohms = 1300W. What's the difference between 1600 and 1300W?

    Less than 1db. You can't hear 1db difference. Sorry.

    Even if the AC voltage dropped to 77v from 110, cutting the power amp voltage from 80V to 56v@4ohms, that would result in 800W vs the original 1600. Even that would only be a 3db drop. You might hear that, but no way the power drooped to 77v.

    I have the furman voltage regulator that boosts low voltages, and shows you the line voltage. I've never seen it droop near 100v, rarely even to 105, and I've played some shabby clubs with horrible power. Any my 1500 W power amp could cause plenty of droopage all by itself, so its not that we're running puny amps.

    Unless you're running all your stuff plugged into Xmas light extension cords, I doubt that's what your problem is.

  7. fretlessrock

    fretlessrock Supporting Member

    Aug 8, 2002
    I've dragged my Clarus (2 different units, actually) to some of the crappiest stages in the NYC/CT/MA area and never had a problem like that. I'd even say that the high-freq switching supply is less susceptible to problems with low voltage than a linear supply. You are using the Focus SA, which is a power amp with no preamp on the front end... is there a chance that you had a problem with your preamp?

    If you are going to become a gourmet power consumer, then spring for a good A/C voltmeter, an outlet tester, and maybe a nice small digital scope. Then when the bar owner shrugs, points to the outlet next to the stage, and makes a mental note to never book you again, at least you have the high moral ground.
  8. thiessen3.14

    thiessen3.14 Supporting Member

    Nov 22, 2002
    wichita, ks
    A 3dB sound difference is definitely noticeable. If you added another amp/speaker producing the same sound pressure, you would see a 3dB increase. Essentially, doubling your rig is worth 3dB.
  9. When running sound gigs, we usually put the board, effects, and any recording gear on a UPS just to protect against spikes, surges and other crap which might be on the line. For reasons of power, we usually don't bother with FOH or monitors or anything which might be taking significant power. I wonder if using a small (400VA) UPS on a bass amp might prevent the problem decribed at the beginning of this thread…

    - Wil