Strange Subwoofer Plate Amp

[Jason Dalton]

I was wondering if anyone could comment on this plate amp on eBay:

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1

It has a low pass xover and level control, but only has one set of speaker level inputs, no line level or speaker level pass thru. I've never seen one like this before, seems kind of odd. Anyone know what the story is with this design?

 

[Aaron Gilbert]

The lack of speaker outputs isn't so unusual, although having only a mono input is somewhat weird. What I find very odd, and in my opinion nearly rendering the amp useless, is the lack of an RCA input. It would seem that this amplifier was meant to be used as a stereo pair run in parallel off your main speaker outputs. Not too bad a price, but not flexible at all, and only gives you about 1/2 the benefit of a subwoofer, because you'd have to set your fronts to large, your LFE to off, not to mention you physically need two subwoofers (or put both plates in one box, I suppose).


Aaron Gilbert

 

[Jason Dalton]

The lack of the RCA input is what really threw me. I was wondering if you could wire a couple of RCA jacks in place of the speaker inputs. I don't know if it would be possible.

Also, what would be the point of running the sub amp off your main amp? Unless you're main amp is very low powered, then you're just throwing away the power output of the amp. Essentially, the sub amp would just be acting as a power boosting crossover. Weird.

 

[Aaron Gilbert]

It's possible that you could replace the speaker inputs with RCA inputs, but of course you would only get one input jack, not left and right. It's hard to say how well it would work, because we don't know the input impedance of the amplifier, but in most cases it should work ok.

When you connect your receiver or amplifier to the speaker level inputs on a powered subwoofer, the amp is really not powering the subwoofer. The input impedance is quite high on the speaker level inputs, so while they do receive the same voltage as if you were powering a speaker directly, the current flow (and thus power usage) is quite small. You're not throwing away any power output.


Aaron Gilbert

 

[Jason Dalton]

I understand the sub amplifier really isn't seeing power from the main amplifier, I just meant that you're wasting a channel on you're amp by using the speaker level connections. Could you hook up a speaker AND that amp to the same channel because of the high input impedance of the amp?

 

[Aaron Gilbert]

Yes, you could hook up a speaker and the sub amplifier to the same terminals on your receiver/amplifier without worry. If it's easier, you could use the 'B' speaker outputs, if you're using a receiver, which would allow you to easily disable the subwoofer without doing any rewiring or unplugging.

Aaron Gilbert