PA Amp??
Oct 28, 2009 at 4:18 AM Thread Starter Post #1 of 7

Moontan13

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Curiosity got the better of me and I dropped $80 on an Optimus MPA-250 amp at a pawn shop. Essentially it's a 125w/ch stereo PA amp. It has twin volume controls, speaker switches and a headphone jack. While I could go on about speaker performance, the headphone output on this thing was stunningly clear and forward.
While i'd rather not spin the electric meter to run headphones, I'm considering looking at other non-consumer type audio devices.

Anybody else have some experience with low power PA amps or pre-amps? I like the idea of twin volume controls instead of one and a balance. No tone controls period is also desireable.
 
Oct 28, 2009 at 4:36 AM Post #2 of 7

eddiewalker

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Just fyi, Optimus is a Radioshack brand. Those "volume" controls are actually meant to function as somewhat permanent gain settings, and actual volume is to be controlled by a mixer. I wouldn't be surprised if the amp also popped when you move those knobs, so be careful with your headphones.
 
Oct 28, 2009 at 6:15 AM Post #3 of 7

eddiewalker

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I think your notion that "professional" equipment is automatically superior is a little misguided. Apologies, but that amp is pretty low-end, however, some of the "consumer" amps discussed here could easily hold their own against the headphone outputs on very high end professional equipment.

I mix audio for network television. I operate audio consoles costing $100,000+ every day, but even their headphone outputs probably don't get the most attention in the design stages. It's just not the equipment's primary function.
 
Oct 28, 2009 at 3:45 PM Post #4 of 7

Moontan13

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Quote:

Originally Posted by eddiewalker /img/forum/go_quote.gif
I think your notion that "professional" equipment is automatically superior is a little misguided.


No, not superior, but worth examining.
 
Oct 28, 2009 at 3:51 PM Post #5 of 7

Moontan13

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Quote:

Originally Posted by eddiewalker /img/forum/go_quote.gif
Just fyi, Optimus is a Radioshack brand. Those "volume" controls are actually meant to function as somewhat permanent gain settings, and actual volume is to be controlled by a mixer. I wouldn't be surprised if the amp also popped when you move those knobs, so be careful with your headphones.


The amp is built by Pyramid for Optimus/RS. The volume controls do work with the line-outs from a CDP and DAP, but the usable range is only 15% of dial motion, even with speakers. No popping and I was careful to use cheap phones 1st. would an ordinary pre-amp work with this, or do I need a unit built for it?
 
Oct 28, 2009 at 4:07 PM Post #6 of 7

Paul J.

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It might not "spin the meter" much. Depending on how it is biased (given its PA nature I'd assume close to class B), it probably idles fairly cool. Does it warm up much when you run it? Power has to go somewhere, so if it is not putting out much heat, and it isn't driving anything, it isn't consuming much power. Have you opened it up? I haven't seen one, but the headphone amp might be on it's own PCB. You could power it with batteries, a SMPS, or whatever else you choose. FWIW, its also awfully easy to take anything with a stereo volume control and convert it to two single gang pots or a dual concentric (which could actually fit in the same hole).

More to the topic though: Low power, not traditional audio, if size and weight aren't a concern, how about old reel-to-reel amplifiers? (They actually were home audio back in the day, but we'll ignore that fact). They can range from real junk to pretty nice stuff. There are some old tube models that have great amplifiers (Sony, Akai), and some later solid state that would be fun to play with. Given their age, tinkering if often in order. Sometimes sellers want a premium for 'em, but a good day on craigslist will net you something neat for under $50.

Paul
 
Oct 28, 2009 at 6:03 PM Post #7 of 7

Moontan13

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I'm more into yard sales than Craigs, but old RtRs are fairly common. I had not considered them as amps, though I have played with cassette deck amps. Thanks for the tip!
/makes note to self...

I could easily plunk down several k$ for a really nice set-up, but seeing what can be accomplished with mix and match of ordinary stuff is so much fun.
 

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