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QSC-RMX-2450, Amp not loud

1422 Views 2 Replies 2 Participants Last post by  -Pjackso
Hi all,
I bought a used pro-amp QSC-RMX-2450 to powering my subwoofers.
I have (2) Ultimax UM18 subwoofers, each box is sealed and wired at 4 ohms each box.

I have an old Sony home theater amp for the main theater.
I connected the Sony sub-out (RCA) connector to the QSC-RMX amp via an (RCA to 1/4") adapter.
All dip switches are set correctly, clip-off, filter off, stereo, not-bridged.

When I turn on the system, I have to turn the QSC to maximum-gain to get any output. And when I do, it's lacking.
I know the RCA cable is sending the signal, because it works great when (temp) connected to my PE Bash 500 watt plate amp. (LOUD!)
When I move the cables to the QSC - the sound is there - but nowhere near where it should be for a 750watt @ 4 ohms. (It sounds puny, like 60 watts)
Both channels are the same.

I'm starting to think it's the input voltage.
Is there a mismatch between (RCA) input voltage and (1/4" / XLR) input voltage?
It's like the QSC isn't coming alive, due to the volume being too low.

Any ideas? If so, any solutions?
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Aphex 224, Samson S convert, Art cleanbox etc. Wire the subs in series for 8 ohm final load after correcting for low input signal, and drive the subs bridged.
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Ah, thanks.
This is my first Pro-Amp, so I'm learning as I go.

So there is a difference in input signals between consumer electronics (RCA) and professional electronics (1/4" / XLR).
See Wikipedia for 'Line_level'. Line level - Wikipedia

So my suspicion is correct, my consumer amp is sending consumer input signals, which is way-underrated for professional input requirements.
Hence, the consumer amp signal is too low (effectively low-volume) for professional equipment. Which is why my amp isn't loud.

As per John's response, there are consumer-to-professional converter boxes available, most around $100. (Yikes!)
Are there any converter boxes that are cheaper?

I appreciate the help.
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