Amplifier Power Consumption Problem

Serendipity

As some of you may know, I run the PA at my church and it basically consists of pro cabinets driven by an Adcom GFA-535 amplifier. The unit has clip LED's which rarely light up even when driving low-impedance loads.

I also have a Radio Shack MPA-250 with output power level LED's and noticed something interesting:

On songs # 1, 3, and 4 the power output can be low while achieving a high dB output. On songs # 2, 5, and 6 the amplifier can easily be driven into clipping without producing much output.
1. http://www.youtube.com/watch?v=2CJvO6WaoKc
2. http://www.youtube.com/watch?v=oEauWw9ZGrA&ob=av2e
3. http://www.youtube.com/watch?v=_4FpUhtfbBY
4. http://www.youtube.com/watch?v=do5-9C6LaH4
5. http://www.youtube.com/watch?v=f7VoXvRr86A
6. http://www.youtube.com/watch?v=rJYcmq__nDM

What exactly is the reason for this? The second song (pon de replay) is especially hard on ANY amplifier, and it concerns me that both the Adcom and RS MPA-250 are showing high power output without much audible output.

What gives?

Serendipity

The Adcom GFA-535 and Radio Shack MPA-250 are both rated down to 4-ohm operation. Load is a single pair of Ramsa PA cabinets, which run at 8 ohms, and should not present a problem to the Adcom. At home I have the MPA-250 hooked up to a pair of Polks as outdoor speakers, and a second pair of small HTiB speakers on the "B" speaker outputs.

What's strange is the Hayley Williams song can have TONS of output with only 3 bars lit on the Radio Shack amplifier, but others (like Rihanna) will totally make the amp go to 0 pretty quickly.

Does listening to the songs on your setup produce similar results?

messiah

I think God doesn't like you playing Rihanna in church lol :rolleyes:

Serendipity

Never said it was. The Adcom, mixer, and pre are all mine - donated from many years ago - so I do get to use them once in a while. When you spent many summers mowing lawns to be able to afford the gear, then you should be able to borrow it back on occasion.