Isolating Digital Noise, need help.

Thanks Jim. As with the CD2 only the digital outputs are transformer coupled. And I don’t see any issues with the unbalanced analog outputs Lowrider is using, or with using a Jensen transformer between those outputs and the preamp (assuming cable capacitance at the output of the transformer is kept low, which I believe he is doing).

Best regards,
-- Al

Al and jea48,
I really appreciate the time you've devoted to my situation.
I was out all day, but was able to take some measurements:

- continuity of RCA outer sleeve to metal chassis... reads OL
- continuity of each RCA center pin and pin 2 of XLR... OL
- continuity of RCA outer sleeve and pin 1 of XLR... 000.0

Al, I looked at the 20a dedicated AC line and it appears to be a 12/2 generic cable. I looked at the electrician's invoice from years ago and it is itemized as a Refrigerator line, dedicated 20a circuit.
If you recall, I had a thread where I asked for advise on the proper installation of a dedicated line. That's when I discovered that the electrician placed this wiring near the top of the circuit box and close to the furnace and appliances. So, when I add another line, I will need to have the box reconfigured.

And jea, thanks for the pic of the Cardas jumpers. I found them online and will order them.

Jim (Jea48), you provided an excerpt and a link to Mr. Hansen’s statement in the last post on this page. However, I would not interpret his statement to mean that signal ground should be connected **directly** to the chassis, as that can be conducive to ground loop issues. Preferably signal ground should be connected to the chassis through a low value resistor (e.g., 10 to 100 ohms). As you’ve probably seen, for example, a lot of ARC designs use 10 ohms.

My VAC amp, btw, has a three position switch controlling that connection. One position connects signal ground and chassis directly; one position is described as connecting them at audio and higher frequencies but not at DC (presumably via a high value capacitor, perhaps in combination with a resistor); and one position is described as connecting them only at RF frequencies (presumably via a low value capacitor, perhaps in combination with a resistor). The AF and RF positions seem to sound slightly better in my system than the DC position, and I’ve settled on the AF position (which the manual recommends as the one to start with).

In any event, it is strange indeed that the Sunfire amp connects signal ground and safety ground together but not to chassis. If it happens to be connecting the grounds to chassis via a capacitor, though, it would explain why the meter reads OL between the grounds and chassis. But it still would not explain the safety issue that would presumably result from the lack of a direct connection between safety ground and chassis.

continuity of each RCA center pin and pin 2 of XLR... OL

Check for continuity between the RCA center pin and pin 3 of the XLR connector. If that measures near zero ohms, you would want to put the jumper between pins 1 and 2 of the XLR connector.

If that also reads OL, however, it would probably mean that the XLR and RCA inputs are received by separate receiver stages, in which case it would be ideal (although perhaps neither necessary nor practical) to jumper both pins 2 and 3 to pin 1. Or, in that situation (both pin 2 and pin 3 read OL relative to the RCA center pin) you could try jumpering each possible combination of two pins together (1 to 2; 1 to 3; 2 to 3), assessing the three possibilities one at a time.

Best regards,
-- Al