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In Reply to: RE: Low mass / 47Labs Stratos IC plugs not working with new setup posted by horst on October 02, 2023 at 09:29:04
Required impedance of 75ohms in your (S/PDIF?) interface may be way off, causing the DAC to balk at decoding or to plain just fail to lockup the signal at all. Add in an apparent lack of any useful shielding and you likely have a real mess on your hands either way.
But that's just a guess.
Yes, S/PDIF digital out from the DVD player into the DAC.
I understand the possible issues, but that's not the question; the same contact issues exist with the interconnects between the Topping DAC and Fosi V3 amp.
What does a DMM report as end-to-end resistance at the contact points?
Roughly the same as other cables which work.
Granted, my multimeter is the cheapest POS I could find many years ago - and it's not digital. ;)
So it probably doesn't do anything but suggest that the cable isn't broken.
Well, at least it helps rule out one of the obvious failure modes.
My other thought would be to validate adequate insertion depth for the suspect signal pin(s).
Would that matter?
My assumption is that the sockets are lined with conductive material all the way through.
And thank you for the patience and advice, much appreciated.
It's more likely that insulation, rather than contact material, is omnipresent.
I doubt you can "pull the cover" on the Mac, but where one can I'd do a basic continuity check from the signal lead coming off the back of each S/PDIF socket, to the signal wire on the far end of your cable assembly, while the problematic connectors are in place. Ideally that test would be conducted from both the source and destination devices; but that may not be feasible considering the components involved.
My point is that you have to provide assurance to yourself that a signal is even making it into the DAC. The most apparent symptom, as you have already discovered, is that it probably is not.
Goodness, I feel quite silly now - it was the insertion depth all along...
Turns out the 47labs plugs are too short to reach far enough into the RCA sockets; and those sockets in both the Topping DAC and the Fosi amp have their (main?) contact area fairly far in, further inside than the older amps I have here and have used before with those plugs.
Thanks a bunch, mate, your comment on insertion depth pointed me in the right direction!
Of course I should have figured it out right at the beginning, it's the most stupid mistake one can make, but I just didn't think a plug that was working totally fine for years could have such a basic compatibility issue.
Here's an image of my quick and dirty test cable, using heat shrink tubing; I'll get some teflon tubing and do it properly.
My compliments to you Sir, for staying in pursuit of the problem. This "RCA" socket/plug design unfortunately never matured into an enforceable commercial standard, eliminating such wide variance in implementations.
I guess we can thank Digital to some degree for fixing that headache... As in: HDMI / USB / DisplayPort / etc.
Tip-Toe'ing into low-mass variations of relatively ancient designs can be adventurous and fun, but reliability tends to be the occasional victim.
Good work, and enjoy your experimentation. (But get a decent DMM!)
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