Balanced or Not

I answered most of your question here. Concerning why manufacturers would do this, cost is certainly a major factor.

Regards,
-- Al

You still get benefit of common mode noise rejection using balanced cables even if amplifier is not fully differential. You also get benefit of better, safer locking connectors. Balanced cables are better, IMHO, but it is matter of your environment (amount of electrical interference) and design of an amp. If amp is designed such way that extra output and input stage can compromise the signal, as Almarg explained recently, then you might get better results with single ended (RCA) cables. Balanced/differential input is often converted to single ended signal (ground referenced) by input transformer. This transformer does not improve sound and is known to produce harmonic distortion at low frequencies. Small distortions at low frequency are not very audible (many great amps have transformers at the input) but still it is a compromise.

Fully balanced design is better but costs more. Common mode noise rejection improves a bit, even harmonics produced by an amp are canceled, power supply gets balanced load (no big ground return current in power amp), each half requires half of gain and the same output power can be obtained from twice smaller supply voltage (bridged output). There might be some issues of gain or phase shift matching so it would be interesting to hear from the amp designers.

Almarg:

Thanks for responding again. I started this thread in the Tech Talk group because I thought it was the more appropriate category for it and I wasn't generating any responses under the Amp/Preamp section. I tried to have the Amp/Preamp thread moved to the Tech Talk category but Audiogon said they could not do that. Wasn't trying to be redundant.

As to cost for fully balanced. I had thought that was the issue but recently have seen some pretty reasonably priced units that are fully balanced. In my case, I do get way better sound by using the XLR inputs and outputs. Was just interested in what I am missing out on. If the incremental improvement in sound in not substantial enough, I can stop obsessing over this!

Well I'm a manufacturer so you have to take my comments with a grain of salt on this one: once you've heard a fully balanced setup there is no going back to single-ended. I've said that a lot over the last 20 years and it continues to be true.

Well I'm not a manufacturer, but you can still take my comments with a grain of salt. I have heard AND owned fully balanced setups. I am now back using single-ended, so obviously, there IS going back. The main reason for going back to single-ended designs was economic reasons.

That being said, my current system is still very quiet and revealing. I will admit that the noise floor using a fully balanced system was lower, but once you factor in all the other noises in a real world listening enviornment, I can't say that I'm suffering.

My current system is about 20% of the cost of my old big rig days, and to be honest, I'm embarassed by how close it is sonically. To think....all those years of what I was sure were "upgrades"... Sure makes me wonder what I spent so much time and money obsessing over.

Tube/SS, Vinyl/Digital, Balanced/SE, just relax, have fun and enjoy the music.