Balanced But Not Fully Balanced

@gdhal
Hi Hal,

As you are aware, the Oppo player is clearly described as featuring "a true differential signal path all the way from the DAC to the 3-pin XLR connector." And as you indicated the Emotiva ERC-3 purports to be similar in that respect. However despite the ERC-3 being referred to as a "Differential Reference (TM) CD Player/Digital Transport," and despite suggestions in its manual that its balanced analog output is "generally preferred," IMO there is enough ambiguity in its descriptive literature to leave me at least a little bit uncertain as to whether its analog signal path is in fact fully balanced. Also, we have no way of knowing "a priori" whether the net result of the tradeoffs I referred to in my post above dated 9-20-2012 would work in favor of the balanced or unbalanced inputs of the M6si integrated amp.

So the only way to be confident of the answer to your question would be to try both players both ways. Which it sounds like you’ve already done, with similar results in each case. But if in fact there is any difference, given that the M6si has only a single XLR input, and given that the Oppo can be said with certainty to have a fully balanced analog signal path, my guess would be that the best odds of obtaining optimal results would be if you were to connect the Oppo via XLR and the Emotiva via RCA.

Best regards,
-- Al

@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

Regardless of whether or not the component has a balanced internal signal path (i.e., is "fully balanced"), a well designed balanced interface will reduce susceptibility to ground loop effects; will to some degree reject noise/RFI/EMI that may be picked up in the cable; and may also reduce sensitivity to cable effects and cable differences.

Having a fully balanced internal signal path provides additional benefits that are essentially unrelated, including reduction of certain forms of distortion.

However, the potential advantages of using a balanced interface between components having unbalanced internal signal paths will in some cases be outweighed by adverse sonic effects of the circuitry required to convert the unbalanced internal signals to the balanced signals that are provided to output connectors, and to convert the balanced signals at input connectors to unbalanced form. Also, I suppose that at least a few highly compromised designs may exist that don't bother to include any conversion circuitry, and instead provide unbalanced signals to XLR connectors, which would negate the potential advantages of a balanced interface.

So if the components provide both choices, and are not fully balanced, the only way to determine which interface will perform best in your particular setup is probably to try both of them.

Regards,
-- Al