What a difference a good (digital) cable makes

Posted by: charlesphoto on 13 March 2015

So I've been using my Qute 1 as a digital source only (upnp and radio) and connected to a Dac V1 via a Chord Prodac BNC>BNC cable. The sound was good and engaging but I thought somehow missing something (soundstage esp), and not really all that much better than the UQ on it's own. As all of my other cabling seemed up to snuff, I figured it had to be the Prodac. So I did flurry of research and found an Atlas Opus 1.5mm cable for half price (new old stock as it's been discontinued and in it's place the Mavros at almost 3X the price I paid for the Opus). 

 

Absolutely jaw-dropping difference! I now know what the V1 is truly capable of. Huge soundstage with lots of detail (hearing things for the first time maybe you weren't meant to!) and separation of instruments but without losing any of that Naim PRAT. Sometimes a bit lean for rock, though I was looking for a cable that didn't bloat or increase the bass (I have LS50's near a wall). It did the trick and intact was able to remove the half bungs I had in. 

 

Not all is perfect: in my flurry of considering a half dozen cables I failed to notice that the Atlas was RCA and not BNC. Fine on the DAC end but I need to use an adapter on the UQ out. I do have one of their proprietary made adapters coming to me so will see how that sounds vs the generic one supplied with the Qute. I did email Atlas and got back a nice note saying they would re-terminate if I wanted for the price of postage. But apparently it's a non-compression/non-solder rca fitting they use that helps maintain 75 ohm. So we'll see if I can live without for a few weeks to send it back to Scotland (I'm in Seattle).  

 

My take away from this is that the UQ is a great 'source only' if coupled with the right cable into the right dac. No idea if it's NDX or NDS level but it sounds superb (and shows that I may need to up my amp at some point unfortunately). I think an interesting and unique product for Naim would be a source only half box streamer that had more than one digital out (say two BNC and two RCA). That way you could connect different cables for different purposes and leave them be and change the sound by switching outputs on the streamer and the input on the dac. A cable roller's dream and a great match for the V1. What do you think? 

Posted on: 13 March 2015 by Jan-Erik Nordoen

I concur that a good digital cable can make a world of difference. I had a light-bulb moment when I installed the DC1 between my UnitiServe and Naim DAC ; it finally sounded like the two components were performing as a fully integrated unit.

 

The half-box (DAC-less) streamer has been requested many times here... one can dream. I'm not sure how dual S/PDIF outputs would affect (compromise?) sound quality though. That said, I have run the UnitiServe using both the optical out and the S/PDIF at the same time into different DACs. I didn't  noticed a drop in performance.

 

Jan

cryo-treated cable roller 

Posted on: 13 March 2015 by Simon-in-Suffolk

Hi, a compliant SPDIF cable should have a CI of 75 ohms. However not all cables will sound the same... There is capacitive coupling between shield and core, and also varying dielectric type and designs. Because of the encoding of SPDIF, a more capacitive cable will induce a difference to the rising or sinking edge of the tranport waveform based on the Manchester encoded digital frame carried.

So ultimately, as with all things, trial and error is probably required for critical tuning.

Simon

Posted on: 13 March 2015 by charlesphoto

Yeah, whatever you said it sounds right!

Posted on: 13 March 2015 by charlesphoto

Well, it probably wouldn't be that much of a stretch to have two digital outs, one RCA and one BNC. Must be a way to switch cleanly between the two. Of course that might mean more $. Maybe not such a good idea (for me at least). 

Posted on: 13 March 2015 by Jan-Erik Nordoen

To expand a bit on Simon's post :

 

Capacitance in cable is usually measured as picofarads per foot (pf/ft). It indicates how much charge the cable can store within itself. If a voltage signal is being transmitted by a twisted pair or coaxial cable, the insulation on the individual wires becomes charged by the voltage within the circuit. Since it takes a certain amount of time for the cable to reach its charged level, this slows down and interferes with the signal being transmitted. Digital data pulses are a string of voltage variations that can be represented by square waves with near-vertical rise and fall transitions. A cable with a high capacitance slows down these voltage transitions so that they come out of the cable looking more like "saw-teeth", rather than square waves, and the circuitry may not recognize the pulse. The lower the capacitance of the cable, the better it performs at higher frequencies.  

 

Source : http://www.quabbin.com/page764.html

Posted on: 13 March 2015 by charlesphoto

Here was the reply from Atlas about their cables.

 

Hi Charles,
     Normally you would be absolutely correct in that a BNC plug should
be better as it defines the 75ohm characteristic impedance required to
minimise reflections. Most RCA plugs on coaxial cables attach to the
screen via a collate or grub screw which compresses the cable often
shifting the impedance towards 50ohms which gives rise to lots of cable
reflections (and hence jitter). The Atlas non soldered non compression
plugs grip the outer sheath without compressing the cable so maintain
the 75ohm impedance more regularly.

 

Out of curiosity, does anyone know what sort of sq degradation I should be looking/listening for with an RCA>BNC adapter? 

Posted on: 13 March 2015 by Simon-in-Suffolk

Jan, thanks, far more eloquent than my ramblings.. I would say typically because of the time constants involved with the capacitance with respect to  the SPDIF signal  that the  value of the mid level state  varies with  the encoding bit stream, and therefore slew in the rise or fall time has more a marked effect. (And creates mancheater encoding jitter)

Simon

Posted on: 13 March 2015 by Jan-Erik Nordoen
Originally Posted by charlesphoto:

Out of curiosity, does anyone know what sort of sq degradation I should be looking/listening for with an RCA>BNC adapter? 

It's subtle, but the soundstage tends to be less open, and instruments / voices are less well defined in the soundstage ; kind of a blurring effect. I ran a DC1 RCA-RCA with a BNC adapter for a while, and there is a performance hit as I described, although engagement with the music did not seem to suffer.

Posted on: 13 March 2015 by charlesphoto

Thanks Jan. Good to know. I think I've got very little to worry about then. I'm gob smacked by how the musician's can be heard practically floating in space now, as if they are playing right there in the room. Esp great with jazz and percussion. It's actually taken a bit to get used to all of the new detail. I'd say it's a 100% upgrade over the Prodac (which are bad vfm in the States I've figured out) so even if I'm losing 10-25% in performance I'm still way up there. Will be interesting to see how the Atlas 80% copper adapter works, or if I even notice a difference. Otherwise the cable goes back for new plugs - over my summer holiday!