Update regarding Benchmark custom RCA(preamp)->XLR(amp) interconnect cables (
see previous post here).
I can confirm these cables have the recommended Hypex pinout (via visual inspection and continuity checks):
1) RCA tip to XLR pin 2 (using twisted pair wire)
2) RCA sleeve to XLR pin 3
3) RCA sleeve to XLR pin 1 via cable shield
4) XLR pins 1 & 3 not physically bridged at the XLR (reference potential only from source)
5) XLR case is floating and not tied to XLR pins 1 or 3 (avoids potential ground loop issues with load device)
And imo nice build overall (quality connectors, nice soldering etc.). Satisfied wth the purchase so far, now waiting on the Buckeye delivery

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UPDATE 8.5.2025:
Amp received, installed, and initial testing sounds awesome. Had a look under the hood, clean build and found no loose hardware, cables, etc. Benchmark cables working fine (no hiss, no hum etc. so far).
Thanks Buckeye !!!