Is there advantage to balanced phono-preamp

There seems to be some confusion here.

A phono cartridge is inherently balanced. That is, it has separate hot and neutrals for left and right, and one shield.

There are no better places to run balanced connections than from your phono cartridge into your phono preamp, and then from your phono preamp to your line stage. If those are truly balanced (differential) amplifiers, then balanced connections should yield the highest gain and the lowest noise.

If the "balanced" amplifiers aren't really differential amplifiers - but use op-amps on the inputs and outputs to process balanced connections - then you may lose some of the benefits of a truly balanced set of connections. But with phono connections, it's still likely to result in the lowest noise.

lewm
" ... You get a bit more gain in balanced mode ..."

If you’re using truly balanced, differential amplifiers, you can pick up 6 dB of gain going with balanced connections. That’s a lot of "free gain" when we’re talking about a phono-level signal.
 
" ... usually you won’t want an XLR to XLR phono cable. Usually you will want a DIN to XLR cable, to connect your cartridge to a balanced phono input."

Not necessarily. You’ll want to use the connectors appropriate for your system. For example, some balanced phono preamps use RCA connectors on the inputs and a ground wire separate from the signal’s neutral. ARC phono preamps work this way and as long as you keep the shield electrically separate from the neutral, you’ve maintained the integrity of the balanced connection.

Some users prefer that the phono cable go straight from the pickup arm to the phono preamp, but that isn’t always possible. VPI arms, for example, won’t allow that - you’ll need to go from the arm’s breakout box to the phono section. I’m pretty sure that VPI uses RCA connectors on that box, but I think they may offer one using XLRs. But either way, as long as the shield is electrically isolated from the signal neutral, you’ve kept your balanced connection.

Some audiophiles object to phono cable breakout boxes, believing that the extra connectors compromise signal quality. I like to use a breakout box, but you’ll want to choose one that uses only the best wire and connectors if you go that route.

czarivey "The signal from phono cartridge actually comes BALANCED.
Each channel has +, - and ground.
all you need to do is separate ground between 2 XLR connectors."

There's nothing magical about XLR connectors. You can maintain balanced operation by using RCA connectors, but you must keep the ground separate from the neutral or - as others have also pointed out - more correctly the opposite phase signal.

lewm

 "CLeeds, Please note that I used the word "usually" when describing the cable needed.  You've pointed out the cases where one would do other than the usual."

Oh yes, duly noted. Fair enough.

" The user should beware of using an RCA-terminated IC for balanced phono, since in that case it is possible that one half of the signal, which for convenience we can call the negative phase, is being carried on the cable shield.  (There is no "neutral" in the balanced mode.) That is a compromise I would not care to make. "

Agreed!

" Are you sure that ARC phono stages that purport to be truly balanced use RCA input jacks?"

Yes, absolutely.