Balanced in phono stages preamp?

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.

When you get away from purely technical considerations, and you have the average buyers desire for best bang for the buck in both sound quality and reliability, you wonder which approach outweighs the other at a fixed cost of manufacture?