XLR waste of time ?

Jimjoyce25, that's really a tough call. The problem is that you have to find a preamp that is single-ended, built to a certain built quality, and then have a differential preamp that is otherwise the same topology and build quality. There are no such products out there, so winnowing out the differences purely on if it is differential or not is nearly impossible.

So your plan B is to listen to the

best that balanced has to offer

and compare it to the best the single-ended has to offer.

Here are the actual (as opposed to theoretical) benefits of differential operation:
*up to 6 db less noise per stage of gain.
*distortion cancellation with each stage of gain.
*rejection of noise common to both inverting and non-inverting inputs
*superior rejection of power supply noise

Here are the disadvantages:
*50% more parts in circuit path
*requirement of a minus power supply
*less gain than single-ended

Here are the myths:
*signal path is more complex
fact: its the same with equal number of gain stages
*you need more gain stages
fact: not if you don't make as much noise- 2 stages of gain might be 12db less noise than SE
*equalization errors are magnified
fact: anyone who says that has not tried it :)
*'phase splitter argument' the idea that the signal gets messed up due to the differential amplifier splitting the phase. This comes from a fundamental misunderstanding of how differential amplifiers work.

I know you see it as some sort of marketing plan on my part but I simply practice what I preach. BAT was an early customer of ours before going into business for themselves, we influenced ARC, Sonic Frontiers and host of others as we were the first to have a balanced high end product which was the MP-1 preamp. The fact that it is balanced has been the single **biggest** marketing problem that we have had with it! So in a nutshell balanced differential has been out anti-marketing plan :) ... anyway in recent years balanced has finally caught on so the MP-1 has become one of the top contenders in that field, due in part to our experience and also we control a patent in the area as well.

Ralph, thanks for the comprehensive and excellent summary.

In your list of "actual as opposed to theoretical" advantages of balanced operation, my feeling is that reduced likelihood of ground-loop issues is another advantage that merits explicit mention, although it is perhaps somewhat implicit in your mention of noise rejection.

As can be seen from some of the posts earlier in this thread, it is not uncommon for audiophiles to discount the importance of noise rejection in a home environment, due to the short cable lengths and simpler setups relative to a pro or studio environment. But as we've seen in many other threads here at Audiogon, home systems with single-ended interfaces often encounter ground-loop issues involving low frequency hum and/or high frequency buzz, that would most likely not occur if the signal interfaces between components were balanced (due to the separation in balanced interconnections of signal return currents from ac-related currents that flow through the cable shields).

That advantage would seem to be particularly pertinent to setups that have MULTIPLE dedicated ac lines powering the different components in the system.

Best regards,
-- Al

I second Al, thanks Ralph! Your contributions a lot of weight. Although I have not built an amplifier for 25 years - I am glad to see that the tried and true electrical engineering principles remain on solid ground. There are plenty of textbooks that would support your statements - so no need to apologise for "tooting your horn" about your own rigorous design choices.

What I will say is this....there are several reasons for the consumer audio industry to promote RCA single ended over fully balanced:

It is hard to convince most consumers of the benefits of fully balanced and it is much cheaper to go the RCA approach. So RCA means a lower price point and/or more profit. The lower cost approach is so important that as you correctly point out...most equipment with XLR connections is not actually fully balanced (at the circuit level)

Jimjoyce, Your dream of comparing single-ended to balanced under any sort of controlled situation is just a dream. What you could take from this thread are the tips about when you would want to use an XLR connector (in or out) and when it is a waste of time and/or possibly even a detriment. You probably would be best advised to take that information and use it if you are mixing true balanced and SE components in the same system. Otherwise, find what you like and listen to it, single-ended or balanced notwithstanding.

Ralph's remark about the anti-market effect of balanced design reminded me of the time about 10 years or more ago when I was standing in a friend's listening room, which contained many megabuck pieces, and talking with some guys who were in the high-end interconnect business. When they found out I had a balanced preamp (the MP1) they looked at me with nothing short of pity. Didn't I know that a balanced circuit could not possibly sound as good as an SE one, because it had too many parts? I had to walk away to keep from laughing, but there was no reasoning with them.