Aesthetix IO Eclipse

Lewm - to be more precise, the Io is fully balanced after the input stage. Using RCA or XLR gets the same output, the rest of the amplification is fully balanced. The one advantage of a balanced input would be common mode noise rejection, assuming a fully differential input. My system does not have such noise problems with the Io phono stage. I found that using a well shielded phono cable eliminated any hum or coupled noise.

Lewm -- follow up; direct quote from the Aesthetix Io manual (from the Aesthetix web site):
The phono stage contains three main amplification sections and an output buffer section. The first section is a high gain, low noise, zero feedback single ended amplifier composed of two low-noise 12AX7 vacuum tubes. This then feeds a high gain, low noise differential amplifier (two 12AX7 vacuum tubes) which amplifies the signal and produces a complementary minus phase signal. Thus, the unit is balanced from the second amplification section through the output.
So, from this description, there is no advantage to using XLR or a balanced input from the cartridge.

It is my understanding that the first gain stage of the IO is single ended. Hence the reason it does not matter if the input is single ended or balanced. It could matter if an opamp was used on the balanced input but one leg is simply sent to ground, making it for all practical purposes identical to the single ended input. I do use the XLR input on my Eclipse but only because I think it is a better physical connection. There also may be an advantage in cable geometry with a balanced cable.

The original BAT phono stage also had a single ended input (the next two stages, like the IO, were balanced). Viktor K stated bringing in a balanced phono signal was not all positives. You could cancel differential noise but since you are using two wires for the signal (plus and minus) you are also bringing in twice as much inherent noise. At the time (15 years ago??) there might have been only one or two phono stages that were balanced end to end. I think the technology to use such a low voltage balanced signal properly was not easily available at the time.

Later (10 years ago??) BAT did implement a true balanced input, so Viktor did have a change of heart and was able to technically accomplish what he could not earlier. Apparently Jim White is still of the "old school" on a balanced input.

Got it. I was wrong. The Io's first gain stage is NOT balanced. Ergo, there is no particular advantage to using the XLR inputs. I knew this was true of their less expensive phono stage, but I obviously thought differently (not to say "differentially") as regards the Io. I learned something. Thanks.