Balanced vs RCA between amp/preamp

The way to solve a ground loop is to purchase properly or fix improperly designed equipment. Adding a transformer is a bandaid. Bandaids fall off.

My company wired recording and film studios in Los Angeles and New York in the 1980s & 1990s. We had transformer and electronic balanced and unbalanced equipment to interface. Hundreds of connections that could be reconfigured into literally millions of combinations. Correctly done, there is no ground loop.

If you detail out your equipment and connections, perhaps we can solve your issue. By detail, I mean brand, connection, electrical power etc. Since we can now post images, draw a sketch.

" The problem with this approach" Do you mean Transformer coupled approach?

@runwell No. If you are dealing with a ground loop, the transformer can fix that, but take @ieales' post seriously.

My Ayre electronics sound better using the differentially balanced outputs/inputs than the RCA's

@atmasphere 

 You suggest to use transformer isolation and you deny the way to use it. 

What is your opinion?

Audio Research reply directly that I should use transformer coupled  to connect RCA pre with their XLR only power amplifier.

 You suggest to use transformer isolation and you deny the way to use it. 

What is your opinion?

Audio Research reply directly that I should use transformer coupled  to connect RCA pre with their XLR only power amplifier.

@runwell If you are using a single-ended preamp, using a transformer might be the only way to drive certain power amps with a balanced input. ARC is often one of them. I'm not familiar with their current lineup, but it was only 5-6 years ago that some of their gear was only offered with a balanced input, but that input had a poor CMRR (Common Mode Rejection Ratio) according to a personal friend of mine who used to work there (Kalvin Dahl). Apparently it was only about 20dB. This meant that if you tried to drive it with a single-ended source, the distortion of the amp was very high and the output power was much lower. So a transformer was the only game in town if you had a single-ended preamp with that amp (which otherwise got good reviews).

If you have an ARC amp and a single-ended preamp, from what I've seen of their circuits I would advise the use of a transformer like the Jensen to do the conversion from single-ended to balanced, so I agree with ARC's advice above.

I don't like using transformers in the signal path which is why I designed a direct-coupled circuit that supports AES48. But transformers have their place; most of the classical LPs or CDs of recordings from the Golden Age of stereo (1958 to 1963) have several transformers in the recording signal path. Jensen and Lundahl arguably make some of the best transformers for this purpose.

Based on what you've told me so far, I would use the transformers!