Are You Happy With Your Phono Preamp?

@cleeds 

Thank you.

But I still cannot see how it can be fully balanced if it has only phonos for inputs.  If phonos can be balanced, why does it need XLRs for outputs?  And why do ARC included XLRs in and out on the Ref pre-amps?  And on earlier phono amps like the PH2 that I used with pleasure for 20 years.

All fully balanced phono amps offer XLRs for both inputs and outputs.  And, as you say, the ARC Ref preamps (I use a Ref 6 and have favoured ARC preamps in the past) include XLRs for input and output that I use as I want to run fully balanced throughout.

But I still cannot see how it can be fully balanced if it has only phonos for inputs. If phonos can be balanced, why does it need XLRs for outputs? And why do ARC included XLRs in and out on the Ref pre-amps? And on earlier phono amps like the PH2 that I used with pleasure for 20 years.

@clearthinker  The tonearm cable from turntable has a separate grounding wire. Instead of duplicating the ground wire per L+R channels (dual 3-pin XLRs), here it’s common for both channels. That’s what the grounding lug next to the input RCAs is for. So IF they wired the tonearm RCAs with "+" and "-" balanced signals on pin and barrel, with ground on the separate grounding wire, and with the ARC taking it in this way (isolating the barrel signal carrying "-" from the chassis), it could be fully balanced over RCAs. There are enough separate conductors. BUT I have no idea if this is how it’s actually setup; it depends on your tonearm cable’s wiring, and I’m not sure this is even a good idea - exposing the "-" signal on an exposed RCA barrel kind of defeats the purpose of common mode noise rejection.

Even if it’s NOT a balanced signal coming in, there can still be benefit from using a differential input stage and running everything downstream fully balanced, IMO (like Stax headphone amps).

@mulveling 

Thank you for these elaborations.

I understand what you are saying, but that is exactly how tonearms were wired to amp inputs before there were balanced domestic set-ups e.g. my first stereo system in the mid 1960s (balanced started in studios where they had long inter-connect runs).  So what has changed to make that connection pattern balanced now?  Note in this set-up the earth is common to both channels, no separate earth for each.

So with that historic pre-balanced pattern I am inclined to think the ARC Ref 3 is not fully balanced..  I was involved a while back here in a thread where a piece was specced as 'fully balanced' but posts were saying it was not 'fully balanced'.  Some while back I had some leads made up with XLRs on one end to suit my tonearm output and phonos on the other to input to a phono only phono amp.  Since then I have decided not to go that way.

I don't pretend to know the answer, but in an environment where some say so -called fully balanced amps are not, I prefer to see XLRs on both sides.

By eliminating the XLRs they once put on their top phono amps ARC may have lost a sale here as I decided not to dem it.

I used the top Stax headphones and dedicated amp when I lived in an apartment from the mid 1990s.  They were awesome. Even if single ended - I have no idea with that five-way single connector.   I ought to get them out again and have a listen.

@cleeds 

I think we shall agree to differ.