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Balanced vs. Unbalanced Inputs

I am trying to upgrade to a differentially balanced phono stage to compliment my Pass XP-22 pre and Pass X250.8 amp so as to minimize long cable artifacts and benefit from CMR. I do understand the it is the circuitry and not the input connection that determines wether a signal is balanced or not. I am looking at both a Pass XP-27 and AR Phono 3SE as possible options. Both have RCA inputs plus a ground post only. No XLR inputs. 

As far as my understanding goes, a balanced cable must have 2 signal conductors, a hot (+) and a cold (-) PLUS a ground for EACH channel. So, I sent an email to Pass Labs as follows:  

 ".... I want to confirm that there are TWO signal conductors PLUS a ground for each channel. Specifically, 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 was the response:
     "No. RCA shield and ground lug are contiguous connections."

But on the pass website is the following:
     "In order to minimize ground loop issues Pass Labs never manufactures equipment with signal ground and chassis ground contiguous."

When I email Linn about their pseudo balanced  LP12 T cable they responded with:
     "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."

Again, there is no (+) signal to be superimposed with an inverted (-) signal separate from ground for CMR. I Do have a technical background but I am not well versed on circuit design so please forgive my ignorance. I did get some very helpful advice from a member here, however, the further I inquired with the manufacturers the more confusing it became. As of now I am wary about emailing AR for fear of even more confusion. If anyone has any advice on how to proceed I would really appreciate it. Thank you all so much.

Bruce
brskie

Showing 3 responses by cleeds

cleeds
6,107 posts
 
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
6,107 posts
 
rmdmoore
Technically a phono cartridge is "floating" which means it’s neither balanced or single ended. It can be wired either way ...
I am surprised that there remains so much confusion on this. A phono cartridge is inherently balanced. That it can be wired unbalanced doesn’t negate that. (Of course, if you connect it to a single-ended phono stage, then you're giving up the potential benefits of the cartridge's balanced construction.)
... 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.
No, I think manufacturing cost explains why we don’t see more balanced phono stages. Keeping a phono cartridge balanced offers multiple advantages, not the least of which is CMR, which is of particular value given the low signal level of the phono cartridge output.

There is no such thing as a "balanced" or "unbalanced" turntable unless, arguably, you’re referring to a turntable with a built-in phono stage.
cleeds
6,107 posts
 
lowrider57
... the Pass phonostage and it is designed for an unbalanced connection from the turntable ...
No, this is mistaken. You’re confused - its use of RCA connectors doesn’t mean the inputs are unbalanced.
Your LP12 is single-ended.
Again, you’re confused. A turntable by itself is neither balanced nor unbalanced.
I checked the AR and it is the same unbalanced design. Outputs are SE and balanced.
No, the ARC Ref Phono is a fully balanced, differential design.

A phono cartridge is inherently balanced; that is, it has separate positive and negative for each channel. If these are fed to a fully differential phono preamp such as the ARC, then you are balanced from phono cartridge to the phono preamp’s balanced outputs. The turntable really has nothing to do with it.
Again, the LP12 is not balanced, it is single-ended like 90% of turntables.
Completely mistaken.
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