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impedance mismatched ?

Audio Aero Capitol Mark 2 running directly into amplifiers via balanced outputs has a output impedance of 100 ohms.
My VTL 750 REFERENCE amplifiers balanced input impedance is 137 ohms. Is this a impedance mismatch which could possibly cause a audible [20 feet away] hum to result when using 1 meter balanced Interconnects? when using the RCA outputs and RCA inputs with same components as above [same impedance specifications for RCA also] their is absolutely zero hum. And yes the XLR pin configuration has been confirmed as being correct on my balanced Interconnects for these components. was suggested could be a ground loop causing the hum but when plugged all 3 components into a power strip the hum still remains, even if floating all the grounds with cheater plugs.
mejames

Showing 1 response by gs5556

gs5556
1,241 posts
 
The XLR introduces one more ground plane, so now you have the grounds from two or more outlets (the amps) and the grounds in the XLR cables creating a grid with loops.

The RCA's ground the signal to chassis only while the XLR's bond to equipment, so the RCA's break the grid (even though they're more prone to picking up common mode noise, their main advantage is not creating a ground plane).

XLR's reject common mode noise and can create ground loops, especially if the equipment they're connected to are on dedicated circuits.
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