Digital Interconnect Cables - What's Your Experience?

OleBoot

I have never owned any systems that were above mid-fi, and have found that different S/PDIF cables can make a more than subtle difference. I have no experience with USB connected DACs . However, I would expect that cables would make far less difference for an an asynchronous USB connected DAC (which applies to most high and medium end DACs nowadays) as the DAC is in charge of the clock and jitter is vastly reduced. S/PDIF is a flawed interface from the start, as nobody back then even considered word clock jitter when it was designed, let alone the effects cable differences (particularly capacitance) or cable induced noise could have on it.

tonyb

I don't think there is any one connection that doesn't have some sort of flaw attached, or possibility of one.

Music, from that first pluck of a guitar string to the first breath into those horns is by nature analog. Anything done after degrades the sound to some degree I would imagine. Nuthin' like sitting 10 feet away from a sax in a smoke filled bourbon smelling room in my book.

Master analog tapes...R2R....Vinyl.....is about as good as it gets portraying that musical environment. Anyone who grew up with it, knows the difference between digital. The closest we've yet to come is SACD or DSD files now, but then we still rely on cables and circuits to carry everything to the speakers, which by itself is another animal.

That's why the purist in audio will tell you do no harm....keep it simple stupid, less is more. The longer a signal stays in the digital domain, the more harm is done.

BUT.....we live in a world of convenience and that ideology of the purists doesn't fit well into modern lifestyles. So we compensate by adding personal flavor enhancers, tube buffers, different cables,dacs, speakers, rolling tubes, etc. In essence, we try to replace what has been taken out of the music, tone/flesh/air/weight, breath of dimension and so forth.

If a cable helps me get there, so be it. If a pre amp helps me get there, or some other piece of gear....so be it. The very first thought that should enter ones mind in any of these cable debates is....how does it sound to you. How it manages to do it is irrelevant to me, regardless of known scientific faults. Nothing else matters except the sound to your ears.

heiney9

Digital coax - yes, subtle but noticeable with proper listening. About on par with hearing the differences between a switching power supply vs. linear power supply on my Squeeze Touch. Once you hear the differences, you can't go back.

USB - no, I haven't been able to discern any differences. But to be fair I haven't gone as high up the chain.

H9

DarqueKnight

Further Study: USB Cables And System Master Clock

I was getting ready for another round of USB cable trials, but the arrival of the Revelation Audio Labs Prophecy Cryo-Silver Reference DualConduit USB cables caused a "slight" change of plans. I have both the dual-A plug and single-A plug versions of the RAL USB cable. Both versions have the signal and power wires in a separate cable. The dual-A plug version allows the disconnection of the power leg after the DAC has set up the USB connection. Removing the power leg is claimed to improve performance by lowering the noise floor. That claim was immediately confirmed.

I wasn't going to do another USB cable shootout until my dCS Debussy DAC arrived. My current DAC, the DAC section of a Cary Audio CD 306 Pro Version SACD player, does not have a USB input. With the assistance of dCS's North American general manager, I recently found a good deal on a used recertified current version dCS Puccini U-Clock master clock that came with full three year warranty.

The U-Clock acts as both a system master clock, for up to four digital components, and as a USB-to-SPDIF converter. The USB-to-SPDIF converter is particularly useful to me since the USB output of the BDP-2 is the lowest in sound quality among its output types (SPDIF is best, then AES)

I had never used an external master clock before, but I had modified a Sony CD player (CDP-XA7ES) and a Denon CD player (DCD-1650AR) with upgrade master clock kits. There were substantial performance improvements in both cases.

I can't currently get the full benefit (significant jitter reduction) of the U-Clock because all digital components in my system would have to be connected to it. The CD 306 does not have a word clock input. Out of curiosity, I wanted to see if the U-Clock alone would facilitate sonic differentiation in USB cables. It did.

The U-Clock conforms to the "Grade 1" AES11-2003 standard for master clocks and has a frequency deviation of no more than +/- 1 part per million. Grade 2 clocks have a frequency deviation of no more than 10 parts per million. The class of master clocks above AES Grade 1 are "atomic frequency standard" clocks, such as the Esoteric G-01 ($22,900). The G-01 has a frequency deviation of +/- 0.05 parts per billion. In cost comparison, the U-Clock's MSRP is $5,500.


Figure 1. RAL USB cables: single-A plug version in foreground, dual-A plug version in rear.

Prior to this test, I had tried the following USB cables with a Cary Audio DMC-600SE DAC:

1. Generic computer grade USB cable #1 (free).
2. Generic computer grade USB cable #2 (free).
3. AudioQuest Coffee ($279).
4. AudioQuest Carbon ($129).
5. AudioQuest Forest ($35).
6. Pangea USB-PC ($35).

I didn't hear a difference among any of the above in the previous test.


Figure 2. Center bottom to top: PS Audio PowerBase isolation platform, dCS Puccini U-Clock, Bryston BDP-2, granite slab for vibration damping, Dell M1330 laptop computer running JRiver Media Center.

The current test included the following USB cables:

1. Generic computer grade USB cable #1 (free).
2. Generic computer grade USB cable #2 (free).
3. Pangea USB-PC cable ($35).
4. RAL USB single-A plug cable.
5. RAL USB dual-A plugs cable.

Digital sources were a Dell M1330 laptop computer running JRiver Media Center and a Bryston BDP-2 digital file player. Either the BDP-2 or the M1330 were connected to the U-Clock's USB input. One of the U-Clock's two coaxial outputs was connected to the coaxial input of the CD 306's DAC section.

The most surprising result was the tremendous improvement in sound quality of files played from the laptop, which were previously "unlistenable" compared to files played from the BDP-2. I could also discern a moderate improvement in clarity, detail, and image weight when I went from the generic USB cables to the Pangea. The RAL cables were an order of magnitude better than the Pangea and generic cables. In addition to sounding clearer and more detailed than the Pangea and generic USB cables, the RAL USB cables also sounded apparently louder.

The RAL single-A plug cable sounded identical to the RAL dual-A plug cable, until I pulled out the power leg (the leg with the name label). Pulling out the power leg resulted in a further apparent increase in sound level, and a further increase in overall clarity, detail, and image weight. I had planned on ordering a few more USB cables to evaluate, but they were all single-A plug designs, and I am not going back to that.


Figure 3. dCS Puccini U-Clock front. The curved fascia is styled to match the Puccini SACD player.


Figure 4. dCS Puccini U-Clock rear.


Figure 5. dCS Puccini U-Clock inside. Like an atom, the interior of a U-Clock consists of mostly empty space.

I hope that the most expensive component of the U-Clock isn't its sculpted and milled aluminum case. The U-Clock uses an oven controlled crystal oscillator (OCXO) to help maintain frequency stability. The crystal is isolated from thermal effects in an electrically heated enclosure or "oven" . OCXOs range in cost from a few hundred to a few thousand dollars. The OCXO in figure 5 is the orange and white box.

Assuming things work out with the dCS Debussy DAC, the U-Clock and Debussy will be stacked and located in the location currently occupied by the Cary CD 306 Pro version SACD player. The Cary will be retired and retained for research/testing/other unspecified purposes. I went into some detail with dCS explaining the difficulties I had with two other DACs. I was assured that I would not encounter such problems with the Debussy and that there weren't other interface issues lurking.

For one micro-nanosecond I thought about replacing the Cary with a dCS Puccini SACD player, but I realized that would have been a waste of money. I don't currently use the Cary, not even to audition newly purchased CDs and SACDs. New disc purchases are ripped and copied to the BDP-2's solid state drive, then auditioned. I definitely can't imagine ever going back to spinning digital discs one-by-one in my two channel system-not as long as I can sit in my listening chair and pull up high quality rips of any and every CD and SACD that I own-not as long as my rips sound equivalent to, and in most cases much better than, the physical media they were ripped from.

References

1. Word Clock Synchronization - When and Why You Need It (PDF Download Link)

2. Does Your Studio Need A Digital Master Clock?

3. Oven Controlled Crystal Oscillator

4. AES Standard AES11-2003 (PDF Download Link)

BlueFox

Interesting DK. I've never dealt with external clocks before, but having a common clock for all the digital gear does make sense. Also, from what I have read, the Berkeley USB to SPDIF converter is supposed to be excellent for that purpose, and it is relatively inexpensive, if I remember right.

I should contact RAL and find out what a custom umbilical would cost for my Lumin power supply. The stock umbilical is much better than the stock Pass umbilical, but my gut says the RAL would sound better.

[Deleted User]

Awesome! Thanks.

DarqueKnight

Clock Cables

"Interface-induced Jitter
Regardless of how good your clock source, the cable you use to connect clocks and digital audio signals can affect the clocking accuracy quite dramatically. Word clock signals are conveyed as a simple square wave running at the sample rate, and are always conveyed using a matched‑impedance interface designed specifically to convey high‑frequency signals. In fact, it's the same basic interface as is used for conveying video signals, with 75Ω terminations at each end and cables with a characteristic impedance of 75Ω."
Reference: Does Your Studio Need A Digital Master Clock?

My U-Clock came with three Pro-Signal brand 2 meter BNC-BNC coaxial cables, model number PSG00542. The retail price is $5.00. I also have a Revelation Audio Labs CryoSilver coaxial cable which has pure silver conductors, a vibration abatement jacket design, and Oyaide SLSB BNC connectors. The retail price of the Oyaide SLSB BNC connectors is $108 per pair. The retail price of a 1meter RAL CryoSilver coaxial cable is $449.


Figure 1. Pro-Signal 75 ohm coaxial cable with BNC connectors.


Figure 2. Revelation Audio Labs 75 ohm coaxial cable with Oyaide BNC connectors.

There was a difference in rise and fall times of the U-Clock's square wave pulses between the Pro-Signal and RAL cables. The output from the RAL cable was closer in shape, rise time, and fall time to the U-Clock's output.


Figure 3. Rising edge of U-Clock's square wave pulse at U-Clock output.


Figure 4. Rising edge of U-Clock's square wave pulse through Pro-Signal cable.


Figure 5. Rising edge of U-Clock's square wave pulse through RAL cable.


Figure 6. Falling edge of U-Clock's square wave pulse at U-Clock output.


Figure 7. Falling edge of U-Clock's square wave pulse through Pro-Signal cable.


Figure 8. Falling edge of U-Clock's square wave pulse through RAL cable.

The halving of rise and fall times with the Pro-Signal cable gives me some concern:

"For applications outside the realm of high speed electronics, long (compared to the attainable state of the art) rise times are sometimes desirable: examples are the dimming of a light, where a longer rise-time results, amongst other things, in a longer life for the bulb, or digital signals apt to the control of analog ones, where a longer rise time means lower capacitive feedthrough, and thus lower coupling noise."
Reference: Rise Time - Wikipedia

I assume that the U-Clock's supplied coaxial cables, like the supplied power cord and USB cable, are the "throwaway type and dCS expects the owner to use their favorite brand of aftermarket cables. However, it will be nice if it turns out that there is no performance difference between the $449 RAL and the $5 Pro-Signal cables.

tonyb

[quote="DarqueKnight;2128334 However, it will be nice if it turns out that there is no performance difference between the $449 RAL and the $5 Pro-Signal cables. [/quote]


....and that's the ticket to it all anyway. Doesn't matter if all the graphs in the world show a difference, only matters if it's audible or not.

BlueFox

Unfortunately, that sentence will get taken out of context, and then used by the weak minded as proof cables make no difference, regardless of the situation.