Troubleshooting channel differences

[One and a half]

The music room is adjacent to the office, when the ifi neo stream arrived, I could listen in the main system or the office, feed the neostream from one to the other or from the main system to the office.

Gouged a hole in the wall, installed keystone RCA and RJ45 jacks and with excess RCA cables connected the systems together using the REC out on the office amp and Line 3 in on the main system.

It was here that there was a perceived channel imbalance where the right channel would dominate. Adjust the Pre-amp in the main system to Left a little and the symmetry came back. Hmm. where could the trouble be. From either amp, there are three RCA cables or the keystone jacks at fault somewhere. Could have been a fault in the amps, but each one is fine on its own.

 

Removed the cables from the office amp, and injected 24Vdc into the office cable and measured (with Fluke 289) in the music room with a lab SMPS. There the volts measured 24.533V L, 24.536V R at the wall. 3mV, that could be it. At 100mV signal, a drop is then 3%., This value is in the 'audibly noticeable' region.

The last cable in the chain, an Audioquest green forest, was added  at the wall and the measured results were 24.545V L 24.546V R. Hmm. Since the plugs were inserted several times to verify measurements, perhaps there was just a build up of goop on the connectors. To jump from 3mV to 1mV difference is showing something. 

 

It is possible to measure resistance, but the cable has to stretch from oner oom to the other, or make short circuit at the cable, but the resistances are very small, and I don't have a resistance meter that stretches' to 6 decimals.

 

Sprayed the AQ Forest and the Line 3 in connectors with Deoxit D5 and measured again. The difference of 1mV was still there, couldn't push the power supply any higher that would be of benefit, not going to push 120V let alone 230V down a wire that isn't intended for such voltage to obtain a better difference reading. The measurements depended on how much pressure I placed on the shell of the connector with the meter's probe, so a bit of leeway there. OK, let's put the system back together.

 

After listening for some time, the channel balance was restored with the Balance control back to the centre in the usual position.  Deoxit D5 to the rescue!