Balanced But Not Fully Balanced

If the gear uses transformers for input or output, then it can operate fine in the balanced domain with no tradeoffs. But preamps with input or output transformers are rather unusual.

Balanced operation was originally conceived to eliminate problems with interconnect cables and it does that very well, in fact so well that it does not matter if the equipment is balanced or not if it can drive the cable correctly- the difference is that profound. Its how the record industry was able to hang mics in a concert hall 50 years ago and at the other end of 200 feet it still sounds like music :)

But a lot of companies just install the XLR cable to be trendy. If that is what you have it will probably work no better than the RCA connection.

@almarg and @atmasphere 

I realize I am resurrecting an old thread, but only because the two of you have chimed in on this one do I prefer to do so instead of creating a new one :) Hopefully you will appreciate the question.

How can one determine if their amp is "fully balanced"? 

In my case I have a Musical Fidelity M6si. I do not find this information on the manufacturer or other websites.

Thanks.

There is no good way to know without really understanding circuitry when you see it, so usually the best means is to ask pointed questions of the manufacturer. Quite often though the fact that the circuit is 'fully balanced' will be a selling point, so it should not be hard to sort out.

@gdhal
Hi Hal,

In the case of an integrated amp (or a power amp), if the design is fully balanced there usually will be statements in the manual and/or marked on the rear panel cautioning against connecting the negative speaker-level output terminals to any kind of ground point.   Since in the case of a fully balanced amp that terminal provides a full amplitude signal, having opposite polarity relative to the signal on the positive output terminal, which of course should not be provided with a path that would result in its being shorted to the amp's circuit ground.  And I see no such indication in the manual or in rear panel photos of the M6si.

That same caution, btw, would apply in the case of an amp whose outputs are internally bridged, as well as in the case of some older class D amps whose + and - outputs are offset from ground by a substantial DC voltage.  So while the absence of such a statement is usually a pretty good indication that the amp is not fully balanced, the presence of such a statement does not necessarily indicate that the amp is fully balanced.

Also, as Ralph indicated above I would expect that the manufacturer's description of a fully balanced amp would usually proclaim that fact proudly and prominently.

Best regards,
-- Al

@almarg and @atmasphere

My sincere thanks to both of you. Very informative and rather prompt too I might add.

I have since asked Musical Fidelity. Their response:

"No it isn’t fully balanced. It is converted to single ended to work with the rest of the amplifier."

The aforementioned being the case, could you advise then whether or not it would be preferable to connect the amp to equipment that I believe purports to be fully balanced (specifically Emotiva ERC-3 and Oppo UDP-205) via XLR or RCA? I currently have it connected via XLR. Sounds great either XLR or RCA. Just wanting to know if theoretically better to connect via RCA when connecting a true fully balanced piece of equipment to a non-fully balanced piece.