Disservice: XLR interconnects

Audiogon Discussion Forum

The posts by @atmasphere on this subject are the most informative, maybe also the most controversial since he does not see the need to spend a lot of money on XLRs for AES48 compliant gear.

I agree with that assessment based on my own listening tests. There are some differences in the cables but nothing that is making a big sound difference. On my gear that is not AES48 compliant I use my more expensive XLR's (Audience).

A balanced component like the HiFi Rose will output double the voltage on XLR, usually while keeping noise floor the same.

@mulveling 

If this is the case then the equipment isn't AES48 compliant.

In a balanced line, ground is ignored. sSe the explanation below. If the XLR doubles the voltage at the input, this means ground is being referenced by the XLR; hence it is not compliant.

@navyachts 

AES48 is the balanced line standard and the idea has been around a long time. It was Robert Fulton who founded the high end audio cable industry back in the late 1970s, but his cables were single-ended. Balanced inputs didn't exist on home amps and preamps until Atma-Sphere introduced the MA-1 in 1987, followed by the world's first balanced line preamp, the MP-1, in 1989.

The simple fact of the matter is there was an exotic cable technology prior to Robert Fulton and that is the balanced line system. We know this system works because there are classic recordings made in the 1950s that to this day sound better and better as you improve your system. Some of these recordings had microphone signals traveling as much as 200 feet before arriving at the microphone preamp! Obviously this system is very successful at its task. The exotic part of it is the transmitting and receiving technology, not the cable itself.

In order to take advantage of what balanced operation offers, you have to support the standard. Here is most of it:

1) pin 1 ground, pin 2 non-inverting signal, pin 3 inverted signal

2) neither pin 2 or 3 reference ground; instead they reference each other. Put another way the voltage of pin 2 is made with respect to pin 3 and vice versa. The usual implementation of this if an output is the secondary of a matching transformer, with one end of the winding tied to pin 2 and the other to pin 3. Pin 1 is thus chassis, with no part of the transformer winding connected thereof.

This means there is no signal return current in the shield of the cable. It literally is for shielding only. When there is signal current there, all of a sudden the construction of the cable affects the sound.

3) a third aspect is that a balanced line system will be low impedance. This is not part of AES48 however. But any studio equipment uses fairly low impedances so that if any noise is impinged on the cable it will be swamped, dwarfed by the impedance, which in the old days was 600 Ohms; these days more like 1000-2000 Ohms. We didn't have any idea to not support this aspect in our products as well so our preamps, which are all-tube, drive 600 Ohms no worries.

Anyway, if your equipment supports just the AES48 aspect I think you'll find that the system is far less sensitive to differences in interconnect cables.

As always, Ralph-@atmasphere, gives the best advice.

FWIW, I bought a 25 foot run of his Mogami cable when I got his amps and preamp.

My dealer suggested moving to AQ, so I did, (as I respect his opinion).

Long story short, I noticed very little difference between the two cables- except the price. 

So, the takeaway is that if the equipment supports the AES standard, cables will not result in changes in sound reproduction.

Bob

@atmasphere - Thank you for your detailed response Ralph. Just an FYI while I've got you here: I've always wanted to own one of your amplifiers but with retirement just around the corner I think I may have to wait for my next life! 

@ditusa  - thank you Mike for your article as well.

I did find through this information that my XLR interconnects are AES48 compliant.