Inter Connects - What I know and don't know

Maybe I was being presumptuous by assuming that the signals pins == "signal circuitry" in the diagram.

@nquery You were. the lines from the bottom of the 'signal circuitry' box are ground connections. The signal passes from left to right in the diagram.

This document relates to how EMI circuitry should be used in balanced connections to deal with high frequency issues that may result in noise. So it shows a variety of hookups and shows how a number of them can be problematic.

In any even while the signal circuit does use ground as a reference, the signal current does not enter or use ground. For example in our preamps, which have a patented direct-coupled balanced tube output, if you ground one side or not, the signal level remains constant; IOW is the same amplitude.

I'd be very interested to see a circuit where signal currents are not present in the ground, yet when operated balanced you get double the output you do single-ended!

@nquery I don't see any figures in the document at the link which have the signal pins tied to 'REF'. If they were tied in such a fashion, I imagine they would be shorted. Perhaps you can list the page number on which the figure is found?

@nquery this might be easier to understand:

Balanced line connections

Its from the Rane website- they are a manufacturer of studio equipment. 

The reason ground is ignored (whereas in a single-ended connection the ground is part of the signal) is because ground loops are endemic. So rather than trying to prevent them, the balanced line system simply doesn't use ground. In a recording studio where you might have an enormous amount of equipment, this makes it easy to hook things up with confidence; hunting down errant buzzes is much more rare.

An advantage of not using the ground is that the cable itself becomes more neutral. So much of what we hear as differences in cables has to do with how the shielding is constructed since a signal (at ground potential) is being passed through it. When that issue is removed the cable becomes more neutral. 

@nquery My guess is that it isn't.

If you think about a simple audio transformer that has an input and output, and the output is connected to the XLR connection, that transformer only has a winding driving the output and so there are only 2 wires for each end of the winding. One of them is tied to pin 2 and the other to pin3. You can see that grounding pin 3 to pin 1 would not change the output level, and you can see that the output of pin 2 is produced with respect to its opposite, pin 3.

There is no connection to ground- its only used for shielding. So its perplexing to me how the output voltage would double if both pin 2 and pin 3 are used as opposed to the RCA connection. Clearly an output transformer isn't used (although a lot of solid state pro audio gear does use transformers).

So my surmise is that in order for the RCA connection to work, the XLR connection that corresponds to it (IOW, if both are the non-inverting outputs) will be the same as the RCA. A digital voltmeter will reveal what that is about- there will be zero Ohms between the signal pin of the RCA and pin 2 or pin 3 of the XLR...

There's an easy way to know. If you run it single-ended into our amps and it plays at a certain volume, does it play louder when running balanced?

If yes= does not support the standard

if no, volume is the same = supports the standard.

This is because the balanced standard ignores ground- the output signal is generated with respect to its opposite rather than being generated with respect to ground. If its generated with respect to ground, its really just two single-ended outputs, one of which is out of phase with the other. While that is balanced, it doesn't support the standard.

@69zoso69 If stop gap is the measure then why bother with expensive interconnects till you have everything sorted? I think you will find the Mogami cable to actually be quite good.

@jerryg123 @69zoso69 

Our amps support the balanced standard (AES48). To that end, if your preamp does too, then inexpensive studio balanced line cables will work quite well with very little to be said for exotic cables costing quite a lot more! I use Mogami Neglex at home. If your preamp does not support the standard then you may find that you have some auditioning ahead of you trying to sort out what works with your source.

Heavier gauge is useful for speaker cables- the lower the impedance of the load, the more important this becomes (this being an advantage of higher impedance speakers BTW). But for interconnect cables its not needed and might be a hindrance since it might cause capacitive issues which some preamps or sources might not like.