-jkeny: What is your name ?
John Kenny
Anyway, you bring up some essential, investigative insights into cable design/signal transmission. All of which leads to (hopefully) better (sounding) products/cable.
Yet, when you state that: " ... Many years ago, I decided the best way to investigate whether USB cables made a difference (after buying & trying a number of recommended ones with no audible difference) ...."
This surprises me. As I began messing around with computer audio/streaming, SBC's (single board computers) were put to work. Using a Desktop PC, I had to run Ethernet cable (20-25 feet) to the stereo and 'Streamer/SBC'. And from there, various USB cables to the/a USB-equipped DAC.
The first "listen" (first hook-up/connection) was a 'musically' very disappointing experience. I laughed at how bad it was. Yeh right. Simply changing/experimenting with various (cheap/& laying around) Ethernet cable revealed profound SQ differences. Hmmm. Yet SQ remained uninspiring.
Then I connected an Audioquest (Carbon) USB cable, and OMG: It went from AM radio "goodness" (lol) to 'Hi-Rez'. It was startling. And it sounded good. Really good. Further messing around with cables, spdif converters/i2s cable continues to enlighten -and inspire. And oh man, it can/does sound excellent -sometimes spectacular.
Back to my point, it surprises me that you found no (clear, very easy-to-identify) audible distinctions when you did the same (tried various USB cables/found no difference) ? No to put a too-fine point on it, but is your (reference) system/set-up 'resolving' enough ?
This is the point I was making before about the number of variables at play in any setup. I used at that time my battery powered DAC with I2S reclocking, connected directly to battery powered laptop & directly driving headphones from the DAC - no amplifier or speakers or ethernet or SBC - no ground loop issues & nowhere for RFI to flow, no shield connected at DAC, no VBUS power. I didn't try too many or very expensive cables as I felt it was too much like pot luck & I wasn't willing to waste the money
I don't know the variables at play in your setup so it's difficult to compare apples with apples?
Remember, I don't know anything about you -so don 't beat me up. (lol)
pj
Don't worry, I agree that audible differences are dependent on the reproduction quality of the system (& its perfectly reasonable to wonder if this is the case) - I have heard small changes in the past that I felt were not worth the implementation effort only to find that when I improved my system they became more worthwhile.
I don't subscribe to the 'audio perfection' stage as defined by measurements only types - seldom do we see a measurement of the full playback chain - measurements are usually shown for components/devices in isolation & it's the unknowns (because they are not measured, not because they are immeasurable) in the interactions that are often of more importance to our perception of audio playback
Hi John: Thank you or identifying yourself. Nice to meet you.
I'm not certain the scope/intention of your work (and/or product offerings -target audience/consumer), but if your work revolves around battery-powered 'digital' gear -there is little in the way of offering meaningful results/ discoveries for the 99% of audiophiles who power from the 'grid' -and likely a majority that have/use a full-chassis system/ loudspeakers .
When I asked about your reference system, it included its power source -as you've clarified.
Although you correctly state that (sound) systems vary markedly (component selection) from one to the next, the 'systems' power source, along with the gears resolving capability are vital contributor's. I currently have three Balanced/Symmetrical 120V AC power 'supply's'; one for amplification, the others for sources/digital.
Upon installation of each successive Balanced Power Supply (BPS) -and components connected, enormous gains in resolution resulted; far greater mid-band and LF resolution/definition/articulation was revealed.
I believe AC Regeneration to be even better -for 'digital' specifically -and for the same reasons, with the added benefit of enhanced/ exposed 'liquidity' (to the sound); a smooth, natural, flowing presentation while retaining and further enhancing (signal) resolution.
I note some reticence when someone asked you about 'silver'wire/cable ?
I'm currently in the process of evaluating Audioquest "Coffee" USB cable; also having AQ 'Carbon' USB cable (also have DH Labs USB -very good sound/value, Wireworld 'Starlight 7' and quickly parted with Shunyata USB (Venom).
Awaiting an AQ 'Diamond' USB).
Anyway, regarding the AQ 'Coffee', it took the 150-hour mark to finally (
start to) 'expose' itself -and expose it did; a very, very nice (open/transparent, definition/speed, articulation, 'Clarity' revealed. I'm very aware of cable break-in issues (particularly silver, plated and pure), but time can vary markedly.
Surprisingly, disappointingly, AQ feel it not necessary/important to offer up useful information within its (cheap/poor) packaging. I mean c'mon, a simple business-card In the box), stating:
"...Thank you for purchasing .... Break-in/Settling time, DBS system. = ?" Instead, nothing. Too bad.
Also of interest to me (and all others who have AQ's DBs cables), I noticed that the physical positioning of the DBS module (it's moveable by 2"/5-cm or so) has a considerable impact on SQ. Crazy stuff. But that's what can/is revealed after inserting/disconnecting several times (a procedure recommended for early/quicker break-in for cables). Sometimes it sounded really nice, other times WTF -slow, hazy, bland. Incredible. Particularly since it's unclear whether it's AC line conditions, source -or something else causing these observations.
But make no mistake, this cable (AQ 'Coffee' USB), is an excellent USB cable; there's an expansion (holographic-like), height, depth, width upon which instruments fill the space before you -even way up high (triangle taps, etc.), and even the perception of sound from behind (the listener). It's a revealing, engaging, enjoyable, worthy cable. And so far, I believe the best I've had -so far. I'll reserve final judgment until the 300-hour mark.
And, here's the thing: such enhanced resolution (signal tracking) results in far better sound with ANY recording/song, regardless of recording quality. A qualification thus emerges; a song/track/album should have distinctive ( if not wildly varying) sonic signatures including "full-bodied, bright, dull, clear, vivid, hazy, compressed, full-bandwidth etc., etc.).
If your cable/ system follows the song/signal -you are 'hearing' what you should ! And you know something, there is real value, communication -and yes, even complete enjoyment to whatever (SQ) is on offer.
Moving on, system-to-system distinctions are further complicated by equipment positioning; rack type/style. This should not be considered a trivial afterthought; what you position your prized gear upon is highly significant.
For those messing with computer desk-top/mini systems/headphones, try this: place/position your DAC -on a different surface, shelf etc. Then, carefully (do not scratch! lol) place a "weight" on the device/ DAC/ Streamer). And listen. Particularly to low-frequency/vocal articulation/ resolution. If as I, anything (mass/weight) positioned on top of device sucks the life out of it. Try it. Or, position the audio component on a 'stack of CD's -or similar. And listen again.
And other distinctions exist from one component/system to the next, contributing and confounding issues further (with regards to what's doing what to what).
And so the search, and enjoyment continues ...
pj