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Parasound A21 question - can I use both balanced and unbalanced input on the amp?

In my second system, I would like to double the duties for both HT and music. For preamp, I'm using a Cambridge Audio 851D, which unfortunately doesn't have any HT bypass or even analog inputs.

Originally, I was thinking that I might be able to connect the pre-outs from my AVR to the 851D. And then from 851D to Parasound A21 via balanced/XLR connection. But the problem is that my AVR has only RCA pre-outs and the Cambridge has only digital inputs.

Another option that comes to mind is something like this:
1. Cambridge 851D --> Parasound A21 via balanced/XLR -- for music listening
2. AVR --> Parasound A21 via unbalanced/RCA -- for movies

Is this even possible? Assuming it is, can this cause any potential harm to the amplifier if both balanced and unbalanced inputs are connected to different sources? What should I set the switch (Balanced/Unbalaned) to on the A21?
arafiq

Showing 1 response by dhl93449

dhl93449
455 posts
 
The answer to the OP original question is NO, unless the AVR is completely disconnected from the A21 when using the balanced inputs.

I have a schematic of the A21, and the #2 pin of the balanced XLR is directly connected to the single end RCA "hot" input. This means any active amplifier connected to the single ended RCA will be directly connected to the (+) output of the amplifier connected to the balanced input.

You should NEVER connect the outputs or two active amplifiers together as they will fight each other. The signal that actually gets to the A21 will be a sum of the two different amplifiers, modified by the source (or output resistance) of each amplifier.


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