Phono stage options - balanced with XLR both input and output...

@dover Thanks!!

Burmester 838 fully symmetrical phono pre-amplifier

@dover Curious. The images I can find don't appear to have a balanced input (only RCA connections), but do have a balanced output. Why do you say it had balanced inputs?

Really - I hooked up a Burmester pre with balanced phono inputs back in 1985.

I'd be interested in knowing more about that. To my understanding Burmester introduced their preamp later.

I agree with lewm that cartridges are not inherently balanced (only 2 terminals)

@hagtech A balanced source will not have a center tap. This is because a center tap will decrease the Common Mode Rejection Ratio (CMRR) on account of the fact that the center tap (even if caused by two matched resistors) can never truly be center. So phono cartridges are indeed a balanced source, as are dynamic microphones (which are similar in that they are simply a moving coil attached to a diaphragm). Tape heads are also a balanced source (whether used that way or not).

One proof of a balanced source is to reverse its connections at the source. This will merely invert phase. If its a single-ended source, the reversal will result in a loud buzz. The ground connection is only used for shielding so no signal currents are passed through the ground. This is another reason why center taps are never used since they will result in some signal current in the otherwise neutral shield.

Almost all tonearms have 5 wires; 4 signal wires and the ground. These are balanced sources; when used single-ended you wind up with that 'ground wire' and a buzz will result if its not connected. A real single-ended source would not need a ground wire. But if you are connecting a balanced source to a single-ended input, you have to sort out what to do with the ground connection and using the ground wire is the best technique.

You're mistaken - ARC was building balanced, differential amplifiers and preamplifiers long before the design became popular. The Reference One preamp goes back to the mid-90s, for example.

@cleeds Atma-Sphere was the first to offer a balanced phono input, back in 1989. The sales manager of ARC contacted me about how that connection was done (mijostyn and lewm did a good job of explaining it above) since he saw us demoing it in a store in LA back about 1992; I sent him a copy of our MP-1 owner's manual that explains the connection and a couple of years later ARC had a balanced input.

To my understanding they didn't keep it on their preamps, likely because dealers didn't like changing tonearm cables in order to audition the preamp in stores so they went back to single-ended. I was too dumb to sort that out and so maintained balanced inputs. After 30 years this sort of thing is a lot more common, but 30 years ago was a different world...