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Testing output of power amp...

Discussion in 'Amps and Cabs [BG]' started by Scotius2001, Oct 28, 2005.

  1. Anybody know a simple way to test the output of a power amplifier to see if it's putting out what it's suppoed to? I have a PLX3402 that has always seemed underpowered to me and have always been curious to check it. Is this something you can get a cursory read on without sophisticated test equipment? (by just using a current/voltmeter in some particular arrangement). Just curious...

  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    No simple way. You can measure the voltage it will produce across an 8 ohm resistor large enough to handle the power involved, but 700 watt resistors don't grow on trees. The likelyhood that it isn't producing full power is very slim in any event. Need more volume? Get better speakers.
  3. Dan1099

    Dan1099 Dumbing My Process Down

    Aug 7, 2004
    Are you running it in bridged mode? Have the speaker cable set up correctly for bridged mode?
  4. Thanks. Couldn't I then just measure the voltage across a speaker cab? Not so much that I need more volume, more that I just don't have the headroom I would expect from this amp. I've heard much lower rated heads that sound the same or slightly louder than this amp which always had me scratching my head. Not a big deal though and I like tinkering with his kind of stuff...
  5. Passinwind

    Passinwind I Know Nothing Supporting Member

    One thing you might be able to test is current draw from the wall socket, if you have the right meter. If you're not happy with the output of the amp, it might pay off to look at what you're feeding it. How much other stuff is on the service you run your amp on, typically?
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You can if you have a sine wave source and don't mind the possibility of toasting your speakers.
  7. maybe your not giving it a decent input ?

    ie, the gain on your preamp is too low, a common example of this mistake happens with the Tech21 RBI unit, one of the outputs is -20dB while the other is 0dB, and people dont notice
  8. Nope. Stereo mode, 700W/1100W per side (depending on cab config). I'm up on all the filter and mode settings in the back so that's not an issue. I've demoed significantly lesser wattage heads that sound as loud as this amp so that's always had me wondering. I'm not looking to knock walls down, just have ample headroom. Just bought a Schroeder 1212 so I'm sure that's gonna help with efficiency ;) (previously using Epi NCY 115/210) It's more a curiosity than a problem...
  9. Yeah, I've had this discussion with Bob Lee but I don't believe that's an issue. I'm driving the amp on average to just below clipping (last green l.e.d. below red is usually lit) so I don't think the preamp gain is the issue. I may just have higher than realistic expectations of this amp. Not playing insanely loud by any means but woulda thought I could get my necessary levels with this amp without driving it that hard...
  10. Passinwind

    Passinwind I Know Nothing Supporting Member

    The last LED is 10dB down, so you're only at 1/10th power at the point where it just comes on, assuming it's calibrated correctly. I've had similar experiences with my PLX 2402, but putting it into bridged mono through Schroeder radically changed my perception of how loud it can get. Judicious use of a compressor makes a big difference too, in my experience.
  11. Cool Thanks. ;)