Transformer Balanced Pedal Board Input: Impedance?

[RNIII]

I'm currently putting together a transformer balanced input for my pedal board for connecting my rack mounted wireless. I've had all sorts of intermittent noise issues with this and so far my breadboard testing shows the galvanic isolation plus a balanced line fixes this.

Part of me is thinking: "if it sounds good it works!" Leave it alone. But the other part of me has realised my knowledge of impedance here basically comes down to output impedance should be an order of magnitude lower than input impedance. And I have no idea how that applies to transformers... I'm using a 600:600 transformer currently. The other one that seems common is 10k:10k. What differences if any would I expect to see switching to a high-Z transformer? I can't find a published output impedance on my wireless (EW-D) but I think its safe to assume its low. Pedal board input impedance is 1M-ohm. I should also add I've got the wireless configured for unity gain.

Better yet could someone point me at a good resource to better understand audio transformers?

And a related question I've seen a lot of schematics that replace an open circuit ground lift with a resistor and capacitor in series. What's the logic here?

 

[SpringReverbFan1234]

And a related question I've seen a lot of schematics that replace an open circuit ground lift with a resistor and capacitor in series. What's the logic here?

It breaks possible ground loops without removing the path in the event of a major fault. It's mentioned at the bottom of this power supply project:

Power Supply for Power Amplifiers

ESP Project Pages - Audio Amplifier Power Supply.

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As for the transformers, my opinion is that higher impedance = more noise, but also that 600 ohms could be hard to drive. Some opamps like the TL072 are said to expect at least a few kohms. Others like the NE5532 can drive 600 ohms. Your wireless system should be fine, especially if you're already using it with 600 ohms and not noticing any issues. There's a lot about transformers on the ESP website too although it goes very in depth.

Transformers for Audio

Driving audio signal transformers seems to be a straightforward process, but there are some interesting and quite fascinating issues that are poised to cause the user much grief.

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Transformers Part 1

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