Balanced vs. Unbalanced Inputs

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

"...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.

@brskie
Yes. Linn chose to use RCAs and bring out pin 3 as a separate connection (the ground wire). But if you run balanced, there is no ground wire because it is ground, which is pin 1 of the XLRs, which are tied to pin 3 of the DIN connector. IOW, you merely change out the interconnect cable.

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.

Since ARC chose to use a non-standard connection (an RCA instead of XLR; this was done so you could just plug in a regular single-ended connection and it would still work) the cable you need is a bit confusing.


At the tonearm end its a DIN connection. The cable for one channel needs to have a shield around a twisted pair. The twisted pair will carry the signal. They will tie to the RCA connector at the output. The shield ties to pin 3 of the DIN connector and will have to have a wire attached to it at the other end of the cable with a little bit of length, so it can be tied to the chassis ground post of the preamp. The other channel should be the same thing (so this makes the pin 3 connection of the DIN a bit tricky). The two wires at the output end are then tied together and a lug installed. The lug is then attached to the ground post. Care must be taken in the construction of this cable so that the shield is not able to come in contact with the sleeve of the RCA connectors and also does not tie to anything but pin 3 at the DIN end of the cable. If you have a cable made up like this it will be plug and play with no buzz issues, as long as nothing is touching the RCA connectors when they are plugged in.


We put XLR connections at the input of our phono section so that the end user would be forced to set up the cable correctly. There is no need for an RCA connection if your phono section is balanced; the only reason ARC did this was to make dealers happy so they wouldn't have to change their interconnect cable for the tonearm. The downside of this is that the most important place in the entire system to get the cable right is arguably the tonearm cable- anything that goes wrong at that point can't be made up for downstream!


The whole point of balanced cable operation is to avoid interconnect cable interaction with the sound of the system and if the tenants of the balanced system are followed, it does this very well. This means that to sound right, the cable does not have to be expensive, it simply has to be correct!

WOW
Thank you Ralph for the detail here. Now I Understand the mechanics, and I believe, the theory too. This is the clearest explanation I have found in a week of searching.
Be well, stay safe and Better New Year everyone !

Bruce

Good ol' Ralph,
Always the best information in clear understandable English.
B