xlr vs rca

I understand it is better to used balance interconnects if possible. Is this always the case?

With good compatible XLR equipment YES - this is always the case. However connecting between low quality consumer RCA to pro-quality XLR is not always straightforward - check this out Ground loops are most often the culprit - this is probably one of the main reasons consumers report so much differences with interconnects - it is just not good to have stray ground voltages flowing through signal wires, as is done with RCA.

If you are connecting a balanced (xlr) output to an unbalanced (rca) input, be careful about using an adapter. Most commercially available xlr-to-rca adapters and adapter cables short pin 3 (the "cold" signal, which on a balanced output is an actual signal, despite its name) to pin 1 (ground). Nearly all pro equipment, and a lot of consumer equipment, can tolerate that, but on some consumer equipment (depending on the design of the output driver stage) the result may be compromised sonics, or degraded long-term reliability, or immediate damage. Check with the manufacturer first.

Using an adapter or adapter cable to connect an unbalanced (rca) output to a balanced (xlr) input is no problem, though. Although of course doing that does not provide most of the noise rejection that is provided by a balanced interface (if done right, it can provide some noise rejection -- see Figure 2.1 of the reference Shadorne linked to).

As Sid indicated, using an rca cable with rca-to-xlr adapters at both ends makes no sense, although it will function (apart from the possible effects that I mentioned of shorting pin 3 to ground). The noise rejection advantages of a balanced interface occur because noise picked up in a balanced cable is presumably picked up equally on both conductors, resulting in cancellation in the differential receiver stage of the equipment the signals are going into, which responds to the difference between the voltages on the two input lines. A balanced cable makes that possible by using two identical conductors, twisted together, within an overall shield. An unbalanced rca-type cable has only one inner conductor, with the shield serving as the other conductor, and so noise will obviously not be picked up equally between the two conductors, due to the physical asymmetry.

As has been alluded to, it is important to distinguish between "fully balanced" equipment (i.e., balanced internally as well as at the interfaces), and equipment which is only balanced at its interface connectors and the corresponding input and output buffer stages.

Fully balanced design, which is normally found on only some very high end equipment (such as Ayre, BAT, and Atmasphere, to name a few examples) provides a separate channel from input to output for both the "hot" (pin 2) signal, and the "cold" (pin 3) signal. (Hot may be pin 3, and cold may be pin 2, on some equipment not made in the USA). That provides cancellation of some forms of internally generated distortion, as well as cancellation of noise picked up in the cabling. Balanced cabling with xlr connectors should obviously be used with that type of equipment.

Designs which are not fully balanced, but have balanced (xlr) interfaces, and which may offer rca interfaces as well, may sound either better or worse when the balanced interface is used. Better if noise may be a problem in the particular setup; worse if that is outweighed by the sonic effects of the additional stage that the equipment introduces into the signal path to perform single-ended to balanced or balanced to single-ended conversion.

The reference linked to by Shadorne is excellent, and well worth taking the time to study.

Regards,
-- Al

Fully balanced design, which is normally found on only some very high end equipment (such as Ayre, BAT, and Atmasphere, to name a few examples) provides a separate channel from input to output for both the "hot" (pin 2) signal, and the "cold" (pin 3) signal.

Don't know about the others but Atmasphere uses differential circuits, which even though balanced are not completely separate.

Modifying an SE cable by putting XLR connectors on it or using RCA to XLR adapters does not turn it into a balanced cable. It is still SE.

I think the salient points are:

1. if it is designed to operate as balanced use it that way
2. XLR connectors are better than RCAs but if you are using SE equipment you are stuck with RCAs unless you DIY.
3. In an electrically noisy studio with a myriad of equipment balanced has distinct advantages and that is why pro gear is balanced, but your house is not a studio.
4. With the large amount of excellent SE gear it is hard to argue that balanced is inherently better in a home environment even though those that make it and use it would disagree. You will hear the argument that I tried my balanced amp both ways and balanced sounded better so balanced is better. If it was designed from the ground up to be balanced it should sound better when operated that way, but it doesn't prove anything about balanced vs. SE.

Hi Herman,
I like your précis, it's about as much to the point as it will get, but let me add one small item I been missing going through the thread.

The 'common mode rejection' also has the effect of favouring odd-order harmonics and cancelling even-order.

This seems to favour a more 'dynamic' presentation for rock and pop compared to SE which in turn would sound just a tad more 'natural' or ‘right’ with classical and acoustic instruments.

I am talking nuances here, but it can be heard, and which one is preferred is a matter of taste as always.

Greetings,
Axel

It's amazing how audio myths and misinformation persist in the minds of audiophiles. I vote with Almarg. He is about the only person who got it all correct. Raul was not wrong, either. His response was just not complete. Others get part credit. Herman, please tell me how the balanced differential circuits of Atma-sphere products are not "completely separate". Atma-sphere should get all credit for pioneering the use of balanced circuits at a time (early 80s) when such topologies were practically unheard of in commercial audio gear.