Fully balanced, Transformer balanced, Active balanced, Impedance balanced

[Dzoing]

OK first what are the technical difference between these?

I know Xformer balanced uses Xformer, which eliminates ground loop issues. Active do not, instead they use some active circuitry with caps etc, and are supposed to be cheaper. But...
Is "Impedance balanced" the same as "Active balanced"?
What is exactly the so called "Truly/fully balanced"? as "Xformer OR Active" but as opposed to "Impedance"?

Secondly... what'd be the incidence on the sound? "Xformer balanced" more colored, "Active balanced" clearer, "Impedance balanced" just crappy, etc?

Thx for sharing your theoretical knowledge and/or empirical experience !

[brianroth]

None of those terms mean much beyond what the flaks in the marketing department concoct! You have to actually look at the schemtic to see what is "under the hood".

Bri

[Sam Lord]

Originally Posted by Dzoing

OK first what are the technical difference between these?

I know Xformer balanced uses Xformer, which eliminates ground loop issues. Active do not, instead they use some active circuitry with caps etc, and are supposed to be cheaper. But...
Is "Impedance balanced" the same as "Active balanced"?
What is exactly the so called "Truly/fully balanced"? as "Xformer OR Active" but as opposed to "Impedance"?

Secondly... what'd be the incidence on the sound? "Xformer balanced" more colored, "Active balanced" clearer, "Impedance balanced" just crappy, etc?

Thx for sharing your theoretical knowledge and/or empirical experience !

As an aside to Brian's remarks of timeless wisdom thumbsup , 1) circuit connections need to virtually eliminate DC, which Xformers or caps do completely and DC servos can do well enough; 2) Xformer coupling may or may not solve ground loop; 3) same as above for active circuitry with cap coupling, ; 4) DC servo circuitry can tailor LF response with various slopes; 5) Ground loop problem-solving greatly improves with electronics knowledge, especially in finding thorough and lasting solutions. Experience here is priceless.

"Impedance-balanced" *should* mean that inverting and non-inverting conductors have the same output and input impedance to minimize common-mode noise picked up by cables. This is mostly done with series resistors to match impedance of one leg (usually the "cold" or inverting leg) with the active circuitry of the other, and can work very well. Some circuits ("Xformer OR Active") can switch between Xformers in series with the output and alternate components. This can be either A) the caps in series with output or B) DC servo circuits parallel to the output of the unit. Xformers at inputs are less-often switchable. "Active balanced" should mean balanced circuits like this circuit: http://www.forsselltech.com/JFETMP1.PDF (thanks to Peter Andersson for link). Balanced circuits are costlier for a given part quality, but ultimate sound quality depends on many factors besides balanced vs unbalanced topology.
Regards, Sam

[Bob Ross]

As you should infer from Brian & Samuel's posts, there is no strict universally-accepted definition for "impedance balanced." For that matter, most of the quote-unquote "strict" definitions for any of those terms are not universally accepted, and vice-versa.

Note that the strict definition of "balanced" makes no mention of the symmetry of the signal on the + and - conductors, it only stipulates that the impedance of those conductors with respect to ground (or to one another) is identical.

This definition seems really bizarre to folks who grew up around audio but didn't study electronics in depth. Like me. And, perhaps fortuitously, like the guys in the marketing departments of audio companies who proudly tout their stuff as featuring "impedance balanced" i/o.

While the IEC insists that *any* balanced circuit be "impedance balanced", the marketing guys use this term to differentiate gear which does *not* have symmetrical signals on its + and - conductors from gear which does

...I think.

[brianroth]

A so-called "balanced input" stage is relatively easy to provide...balanced outs, sans transformers, are another story.

Bri