Breaking into the McIntosh 21-pin DIN cable

[cpitts]

Hey guys, I know we've been down this road a few times, and I'm just trying to get through my last lot of options before I start looking at fascia plates, etc.

We've all been advised that the outputs on the DIN cable are balanced signals, and I was wondering how that really works. From a schematic I have of the component side of the amps PCB, I can see that the sheild pins are all tied together and presumably then sent to a common earth. (Pins 21, 3, 6 & 11 are all soldered to the same track, hence have to be sent to a common earth point, certainly not used as part of individual channel noise calculations)



So this begs the question, can you determine balanced/unbalanced signal given that there'll be no separate noise reference to subtract from??

Ric, I'd imagine this'd be of interest to you. Anyone else wanting to offer up some good opinions here?

[Ric]

I'm not sure what you mean by "noise reference". The shields are just that, shields. They are not (and should not) be used as any sort of reference for the audio signals.
The correct way to convert from balanced to unbalanced is to subtract the "-" signal from the "+" signal, producing an output which IS referenced to an analog ground point.
This can be done "passively" (using coupling transformers), or actively (using opamps).

The passive approach would be simplest, using five transformers (or four if you don't want the subwoofer output from the head unit).
The active approach could be useful if you need to amplify the signal at all.

[cpitts]

http://www.yamaha.com/yamahavgn/CDA/ContentDetail/WrappedTextDetail.html?CNTID=48542&CTID=227500

Ah, sorry, looks like I was thinking of a balanced setup with a ground reference line as well (like in typical XLR type connector cables). So looks like our output signal is balanced with floating lines (ie: no ground reference).

Well, kinda makes it easier to convert to RCA now!!!

[Ric]

It's not fully floating, if you connected one of the audio outputs to the shield, you'd blow an output transistor.
However if you tried to use just one of the audio wires with that shield as a reference, you'd have a very noisy signal.

[MRGT]

Northfield moorooka crack this for me about when i bought my o7 gt and now running a full Alpine rig of the macintosh.

Cost a fortune but sounds awesome