Balanced in phono stages preamp?

That is simply not true. It is not required. A cartridge connected to a single ended input sometimes will hum with the ground connected and sometimes without. Sometimes the ground connection makes no difference.

This is consistent with balanced operation: you may not always get hum when converting to SE. However there is a reason why nearly every turntable manufacturer has a 5 wire system rather than 4, to prevent ground loops (IOW the ground is not mixed with the signal- this implies that the minus output of the cartridge is actually the inverting output, and in balanced systems the inverting signal is often denoted by a minus sign).

Even BSRs and Garrards from the 60s and 70s are set up that way. As a result they can all be run balanced since the ground is not ground looped with the signal.

While it may be true that balanced equipment might have been used in the recording process, the groove in the disc is not balanced.

By that measure, neither is it single-ended! Once the sound is mechanically encoded, you have the same conundrum that you have with actual sound- it is neither SE or balanced- it simply is. It is the way we handle the sound, once it exists as an electrical signal, that makes all the difference (no pun intended :)

Ashly pro audio equipment uses what some would call "pseudo balanced" outputs. (Inputs are true differential balanced circuits).

In the "pseudo" configuration, the wire that would normally (in a single ended interface) be ground is isolated from ground by a resistor of the same value as the output impedance of the active circuit, in my case 100 ohms. This wire is carried to the (-) differential input of the following electronics, along with the signal wire (+), and a ground wire. This scheme will give the same imunity to noise pickup as a "true" balanced output. This approach could be used with a phono signal if the preamp had a true differential input.

it is neither SE or balanced- it simply is

You lost me there. I'll have to think about that one, but I would argue that the record groove as well as sound itself is single ended. I don't think something is balanced unless you have a pair of signals of opposite polarities.

Since nothing in the home stereo meets this requirement unless we create the opposite signal, it is single ended. I'll have to ponder the situation of a cartridge hooked up to the inputs of a diff amp as noise rejection at this low level makes sense. I may try that myself, but I see no compelling reason to go balanced after that.

>>Everyone here is getting the terms differential and balanced mixed<<

That would be me! Perhaps we are all in agreement technically, just not semantically.

For me, "balance" is like a scale (in the original sense). Or akin to a see-saw. Two ends, and a solid pivot point in the middle. Remove the pivot and ... well ... you have a cartridge.

http://en.wikipedia.org/wiki/Balanced_line

Calling the turntable ground as the "third wire" is disengenuous. As was pointed out above, it is not part of the signalling.

jh

OK, now my brain hurts. Here's an interesting read.

http://www.ultracad.com/articles/differentialrules.pdf

It would seem to support Ralph's assertion that a cartridge is balanced IF you accept that differential signals are the same as balanced. If you go with Hagtech's definition that a 3rd ground leg is required to meet the definition of balanced then a cartridge is not.

However, I can't find any definitions or discussions (other than this one) that require this ground. The ones I have found discuss currents in the 2 legs as equal but in opposite directions, which a cartridge would fufill. It also seems to me that if you want to get a ground refernce involved, as soon as you hook up the leads to a differential amplifier that they could be referenced to that circuit's ground.

Then again, I suppose Ralph's assertion that what really matters is the circuit and how it sounds and it doesn't matter what you call it might be the best approach.