Balanced/Unbalanced question

The benefits of a balanced connection are a reduction in common mode noise, that is the noise common to both signal lines. This will ONLY be the case when the source impedance of both lines are equal and the terminating impedances are equal. Any imbalance will convert common mode noise to some differential mode noise. Thus even in the case where a true differential stage is on the receiving end it will amplify this noise or visa versa. So both connections need to be true balanced connections to receive this benefit.

In light of all this, many manufacturers provide convenience balanced connections. These are usually implemented with an OP amp and won't present equal source impedances to the connected device or in the case of an input equal load impedances to the source device.

Like Al said above, you need to read the fine print and know just what you're dealing with. That said, it sounds like from reading the above response that the Parasound units are truly designed as balanced. I wouldn't stake my life on it though until I saw the schematics.

All of the above is true, but the bottom line is if you do have true blanced circuits (seperate + and - and not XLR inputs for cosmetic reasons), then it will sound better. My Ayre equipment sounds better with XLR connections utilized.

"03-06-15: Stringreen
All of the above is true, but the bottom line is if you do have true blanced circuits (seperate + and - and not XLR inputs for cosmetic reasons), then it will sound better. My Ayre equipment sounds better with XLR connections utilized."

Here's something interesting. I have a CJ preamp that I sometimes put into my system. I connect it to one of my Ayre V-5's via an unbalanced IC. You're supposed to flip the switches in the back of the Ayre from balanced to SE operation, of course, for this type of connection. The odd thing is, if I leave the switches on the Ayre set to balanced, it sounds better. The only catch is that I get a hum with all of my cables, except for my Audioquest. Using the AQ IC's, I get away with it, no hum. Not sure why this is. My best guess is that AQ uses better shielding.

ZD, my speculation would be that the center pin of the RCA input connector on each channel of your Ayre amp is electrically connected to pin 2 of the XLR connector (the non-inverted signal pin on the XLR connector), and is processed through the same differential receiver stage as the balanced input. And that setting the balanced/unbalanced switch to unbalanced would connect the other input to that stage, which would be the inverted signal on XLR pin 3 if a balanced connection were used, to the amp's circuit ground.

I'm not sure which version of the V-5 you have, but the specs that are presently shown at the Ayre site for the V-5xe indicate input impedances of 100K unbalanced and 100K per phase balanced, higher than is typical for a solid state design. And the corresponding figure for the VX-5 Twenty is 1 megohm (1 million ohms)!

If my speculation about the design of the input circuit is correct, by using the unbalanced input with the switch set to balanced you are leaving the input to the differential receiver stage that is connected to XLR pin 3 in a state that due to the high impedance approaches what is called "floating." Which means that it is in an undefined and uncontrolled state that would have greatly increased susceptibility to pickup of EMI/RFI, hum, and noise, as well as crosstalk from signals that are physically nearby, all of those effects having little if any predictability.

As to why it subjectively sounds better that way, one possibility that comes to mind is that the addition of small amounts of high frequency noise can, as I understand it, sometimes be subjectively perceived as an increase in "air" and ambience. Another possibility might be that a small amount of crosstalk is occurring from the output of the differential receiver stage to the essentially floating input, in effect creating a feedback loop around that stage, which might be affecting and possibly even improving some forms of distortion.

As far as the cable differences are concerned, differences in shield quality could certainly be a factor, but other differences in cable design can also affect hum, in part due to their effects on ground loops. Including the resistance of the return conductor; whether or not the shield is the return conductor; and the direction of the cable if the shield is not the return conductor and is grounded at just one end. (Re the latter, my understanding is that if such cables are marked with an arrow some manufacturers use the arrow to indicate the direction of signal transmission, while others have the arrow pointed toward the end of the cable at which the shield is grounded, the intention being for that end to be connected to the component which is driving the cable. So if a variety of cables are tried with the arrow always pointed in the same direction that direction may be wrong for some of the cables, and may result in increased hum or noise).

The bottom line would seem to be that with the switch in the balanced position you are probably getting performance which is technically a bit less accurate, but which happens to be subjectively preferable. Not an infrequent occurrence in audio, of course.

Best regards,
-- Al