Balanced vs. Unbalanced Inputs

@cleeds
 So this is the crux of my delima. Since the AR Phono 3SE is a fully differential phono stage, and, since it ONLY has RCA inputs and a ground post then:
      On each of the RCA inputs, do the center pins and the shields carry the hot (+) and cold (-) signals respectively while the grounding wire/grounding post becomes the tone arm/turntable chassis ground connection common to BOTH channels?

This is the only way I can logically assume that the input to the ARC phono stage occurs since there are only 2 connections on an RCA to begin with. Unlike an XLR that has 3 connections.
So then, does Linn's email response:
   
"All Linn arm cables are terminated with a 5 pin DIN connector with the center pin being arm ground, which on an LP12 is also used as the chassis ground.  This is separate from the left and right channel grounds and hots which are on the other 4 pins."

mean that the signal going from the DIN to the phono stage IS balanced? Or, do I have to assume that I would not be able to use a factory Linn tonearm cable and have to arrange for some kind of bespoke wiring in my arm so as to feed the ARC phono stage a balanced signal to begin with???
I can see why there is so much confusion around this topic of balanced/unbalanced signals with the unwillingness of audio companies to follow a strict set of standards.
Thank you for taking the time to respond. I really do appreciate it very much @cleeds 

brskie

... Since the AR Phono 3SE is a fully differential phono stage, and, since it ONLY has RCA inputs and a ground post then:
      On each of the RCA inputs, do the center pins and the shields carry the hot (+) and cold (-) signals respectively ...

Yes.

... while the grounding wire/grounding post becomes the tone arm/turntable chassis ground connection common to BOTH channels?

No. The ground is independent and not common to either channel.

@cleeds 
So I just have to figure out my tonearm wiring to get the balanced signal into the ARC RCAs.
Thank you again for so freely giving your help.

Bruce

RCA connectors can't carry a balanced signal. You need to use cables with XLR connectors to support balanced.

This isn't entirely true. If the sleeve connection is shielded in the interconnect cable independantly of ground, and if the ground connection is in no way allowed to contact the sleeve, then the RCA can transmit a balanced signal, with the only issue being its slightly more capable of hum pickup at the connector itself. In practice this isn't an issue unless you touch it.

Technically a phono cartridge is "floating" which means it's neither balanced or single ended. It can be wired either way but the reason there are so few balanced turntables/phono stages is that there is diminishing return on splitting the signal to make it balanced, particularly when the signal from a cartridge is already so weak. 

This statement is false. A floating inductor like a cartridge is in fact a balanced source. In order to run it single-ended, you have to do something with the grounding system, which is that weird 3rd ground wire that no other single-ended source seems to need. With a balanced source, ground is ignored (the ground wire, which is also the tonearm tube); there's no connection between the source and ground.

You don't have to 'split' the signal. In a balanced system, the floating signal is applied to the inverting and non-inverting inputs of the amplifier or preamplifier. Again, ground is ignored- its only used for shielding and there is no signal current in it.

A 5-pin DIN connector like on the Linn is a balanced connection. Pin 3 of the connectors becomes the shield of both channels and ties to pin 1 of the XLRs at the other end of the tonearm cable.

I can see why there is so much confusion around this topic of balanced/unbalanced signals with the unwillingness of audio companies to follow a strict set of standards.

@brskie  When we made the world's first balanced line preamp (for home use) back in 1989, it didn't occur to us that we should do anything other than meet the standards of balanced line operation, known as AES48. But as balanced line became a thing in high end audio, we found that almost everyone was ignoring or were unaware of the standard. So there is a *ton* of confusion about this topic. 

... while the grounding wire/grounding post becomes the tone arm/turntable chassis ground connection common to BOTH channels?

No. The ground is independent and not common to either channel. 

This is begging for clarification! The ground (shield of both channels of the interconnect cable, pin 3 of the DIN connector) is grounded to the chassis of the phono preamp. In the case of the ARC, it should not contact the sleeve of the RCA connection in any way. But obviously since its tying to chassis, its by definition common to both channels.

@atmasphere 
Hello again. In your response:
"...A 5-pin DIN connector like on the Linn is a balanced connection. Pin 3 of the connectors becomes the shield of both channels and ties to pin 1 of the XLRs at the other end of the tonearm cable..."

However, the Linn arm cable terminates with RCA not XLR.

Then you said:

... while the grounding wire/grounding post becomes the tone arm/turntable chassis ground connection common to BOTH channels?

No. The ground is independent and not common to either channel.

"This is begging for clarification! The ground (shield of both channels of the interconnect cable, pin 3 of the DIN connector) is grounded to the chassis of the phono preamp. In the case of the ARC, it should not contact the sleeve of the RCA connection in any way. But obviously since its tying to chassis, its by definition common to both channels. "

So does this mean that to send a balanced signal to the phono pre I should connect that "weird 3rd ground wire" to the ground post on the ARC, or, should I ignore it and tape over the end so it won't ground to the chassis of some component.

Thanks again Ralph for all you give to everyone in this community.

Bruce