ef37a wrote: ↑Mon Feb 06, 2023 3:07 pmHugh, do I detect tongue slightly in cheek there? I was suspicious of some of the distortion figures bandied because 0.0003% is I would think very close to the residual in even the best analysers?
Tongue not in cheek on that occasion. Benchmark design some incredible stuff and know how to test it properly. I'm not at all surprised their amp genuinely achieves Mr (Quad) Walker's famous 'straight wire with gain' goal.
I use an APx515 analyser which is the poor-man's Audio Precision model (intended for production compliance testing). With a short loop cable between analogue in/out my residual THD+N is 0.00027% or -111dB (and I get the same figure using the internal loop-back mode, proving my local wiring isn't degrading the measurement performance).
The best AP model (x555) claims a residual THD+N of -120dB or 0.0001% — twice as good!
So my 25m of mis-wired starquad cable adds a teeny-tiny bit of THD+N above the residual of my AP, which is what I'd expect.
I would also be interested to know if the crosstalk of the stereo cables was acceptable?
I measured -96dB at 10kHz, reducing to around -102dB at 1kHz on a 25 metre cable run. So definitely perfectly acceptable. (The x515 residual crosstalk is -136dB at 10kHz, so this is real measured cable crosstalk). I'd expect cat-5 carrying balanced audio to be about the same.
I've used starquad for stereo mics on 3 metre runs from a stereo dead cat on a stick into a shoulder recorder many times without any problems. But I was slightly nervous about a long 25m run — hence the AP tests. I need not have worried!
I have to go to my 'man cave' near town to retrieve my long two-pair multicore cables (with separately screened and insulated pairs) to see how they compare. I'd expect less crosstalk, but probably not that much lower. I'll report back once I've tested it.