How will XLR cables vs RCA effect a phono pre

Undertow: Ralph Karsten has talked about this in detail on another thread here:

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1171733027&openusid&zzAtmasphere&4&5#Atmasphere

I'm not particularly technically minded so much of it is beyond me, but after using a fully balanced phono stage I would never use anything but.

Noise is always an issue in phono reproduction. Anything you can do to reduce it is helpful, as long as those techniques do not introduce other problems.

Balanced operation is on of those techniques that works. You get reduced noise in 2 ways:
1) reduced noise from the cable and its routing
2) reduced noise from the phono section.

Differential gain stages have theoretically 6db less noise than the equivalent circuit operated single-ended, after you have accounted for gain differences. The noise of any phono section is compounded from gain stage to gain stage; so if the phono section is fully differential from input to output the reduced amount of noise can be substantial- perhaps 12 or 18 db in theory.

In fact in practice the actual reduction in noise is less, but only by a db or so if you have good design. This phenomena is so pronounced that in our phono section we are able to get sufficient gain with only 2 gain stages- despite the fact that our EQ is passive. With less gain stages there is less places for things to go wrong.

The fact of the matter is that going balanced, fully balanced, offers a very nice upgrade to phono performance. If the preamp is not balanced then IMO there is only marginal advantage to using a balanced cable.

Atmasphere"If the preamp is not balanced then IMO there is only marginal advantage to using a balanced cable. "

I agree.. SO the big question is.... Are we talking about a BALANCED design so to speak which seems to me to be the same on the end of the turntable anyway being its RCA Jacked, or XLR Jacked... Or are we confusing that everyone must Modify their turntable to Wire it VIA XLR?

I mean it kinda seems to me that from the Cartridge to Phono amp there is not really any wiring difference to do here in order to go XLR, and most tables will have to be modified connecting that extra wire, but to what inside the arm? Or simply just shorting pins 1 & 3 to simply interface the input circuit on a "Balanced" phono stage.. Which simply to me would mean you can still have a standard wired RCA style turntable, and just short RCA ground via an XLR adaptor or something to your existing RCA JACK in order to keep everybody from running out and re-wiring (somewhat expensively) their arm and adding XLR jacks to the back of a turntable.

Anyway due to the subject matter I am simply trying to establish a ground point here that its possible you don't need an XLR equipt and wired turntable to acheive the connection at a (Fully balanced) Phono stage.

Hi Undertow, you do **not** have to modify the tone arm. Most arms are already set up as balanced sources, even the lowly BSRs, Garrards and Duals of yesteryear.

You do have to jump through some hurdles with the air-bearing straight tracking arms, as they have so many lateral tracking mass problems that the designers usually eliminate the 5th wire that is common to all other arms.

The 5th wire is the ground, and is why the arm needs no mods.

The cartridge outputs are the twisted pair that runs inside the balanced line. The 5th wire, ground, is the shield of the cable, and ties to pin 1 of the XLR. So the shields of the cables are both tied to the same point at the arm end of the cable (ground).

Note that in this hookup scenario, there is no signal on the shield. So the arm itself shields the signal from the cartridge, and once through the bearing system, the interconnect cable takes over the shielding from there.

If the cable passes through a noise source, the noise will be impinged on both plus and minus signals in the same way, and rejected once arriving at the preamp input. In this way noise is reduced. In a single-ended system this noise would be amplified by the phono preamp.

Thanks for clearing up the gain issue. I was mistaken. Anyway, one of the pre-requisites for any phono stage I buy in the future is that it have balanced ins and outs. Currently, I like the flexibility of the EAR 324 which is similar to my GCPH but it lacks balanced inputs. Hopefully if Ayre releases a PX-R it will have the flexibility of external gain and loading adjustments.