Unbalanced RCA Cables as Digital Coax Cables

[keith_correa]

Analog interconnects do not pay attention to controlling / maintaining an (RF) or characteristic impedance.

(20 KHz is hardly RF... RF is generally referred to for frequencies Above 3 MHz.)

Analog signal cables pay no attention to even maintaining Concentricity between the centre conductor and the shield .... That is why RCA connectors are used.

Analog Signal cables are simply shielded cables and not 'proper' coaxial cables refering to coaxial as referred to for RF frequencies.

Yes, I know. Can I take it that the answer to my question is "No"?

 

[IndianEars]

I believe your question was:
"What was the characteristic impedance of the VDH IC? "

The answer is that analog Interconnects Do Not have a well defined or specified impedance...

 

[IndianEars]

UNDERSTANDING RF IMPEDANCE

Though MUCH is said and referred to about the system impedance, my belief is that the topic is poorly appreciated / understood, by most (even some electrical engineers)

Let me try and explain the concept of system impedance (eg 50 or 75 ohms) in simple terms. The explanation is unconventional but technically correct, and I believe gives a "feel' of the issue.

By Ohms Law,
Current = Voltage / Impedance

(Resistance is applied only for DC current. AC and electrical signals are all AC, so the term Impedance is used).

When a system (such as the SPDIF Digital output) is specified as 75 Ohms, with a 1 volt output, it simply means that 1/75 amperes of current ( ie 13.33 milli amperes or mA) is carried in the system.

The cable is required to carry 1 Volt and 13.33 mA of current.

The cable geometry and dielectric must therefore have a certain ratio... ie which yield a cable impedance of 75 Ohms.

If the cable dimensions and or dielectric are different, it will not be able to maintain 1 Volt when transmitting 13.33 mA of current.
The excess voltage will be Reflected back to the sending point!

That Bounced Back voltage can interfere with the signal and cause problems.

DACs may get confused when they receive 2 signals - the actual Music (as a digital signal) and the reflected / Bounced Back signal.

This can add to jitter.

Loosely speaking, jitter in digital audio is similar to a "Ghost' in TV transmission. The Ghost on the TV screen was a signal reflected from other buildings. The reflection arrived late, and appeared as a second outline on the entire picture, smearing the picture.

Similarly, Jitter Smears the music signal, reducing perceived resolution and masking finer detail.

Also, if the Cable is 1.5 meters or longer, the reflected signal will come back after a long enough delay, so as not to confuse the DAC.
The DAC will clearly recognize the music signal and reject the reflected signal.
That is why 1.5m+ length of cables are recommended, cause even if their impedance is not 75 ohms and they reflect back voltage, that voltage is less likely to add to jitter

 

[keith_correa]

I believe your question was:
"What was the characteristic impedance of the VDH IC? "

The answer is that analog Interconnects Do Not have a well defined or specified impedance...

They do have a defined impedance. You are right in that they are often not specified.

The question/s:

What was the characteristic impedance of the VDH IC? Do you know?

I asked this because it probably was close to 75 Ohms hence worked well. We will never know.

 

[Nikhil]

Incidentally, I personally do not like the sound of Most Van den Hul cables and in jest refer to them as Bland N Dul

I had borrowed a Van den Hul "DIGI-COUPLER 75 Ohm" digital coax cable a few months ago.
Somehow it seemed to "slow down" the music - not sure what was going on there.

Brought a grin when I saw your remark!


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[IndianEars]

Nikhil, the system where the VDH cable worked was Horn Based .... VERY sensitive to tonal variations in the Mid range.

The aim was to 'tame' the mid range just a tad without loosing its Superb realism

 

[Nikhil]

Well my "honeymoon" with the Belden 8402 seems to have come to an end.

While all observations regarding the sound remain as they were observed earlier I made the switch back to my Lifatec optical cable and I could immediately notice the difference. The Belden 8402 seems to have a noticeable grunge in the sound that is completely removed in the Lifatec optical cable. I also noticed that there is a "screech" for a second or so before playback starts. All of this I am assuming is due to the non-standard specs of the Belden I am using.

So it's clear that RCAs will work as Digital Coax and in my case the Belden 8402 has a fantastic sound.
But I think I need to make one keeping the 1.5 m length in mind (to avoid reflection)

Regards



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[kartick]

Hi Nikhil, FWIW, I have been sensing this “grunge” even with the rca application of the 8402. I love the sound of this cable and this grunge seems more apparent post listening to a cable which is cleaner in this regard, in my case, it was the Deulund 20 gauge cable.

 

[IndianEars]

Hi Nikhil, FWIW, I have been sensing this “grunge” even with the rca application of the 8402. I love the sound of this cable and this grunge seems more apparent post listening to a cable which is cleaner in this regard, in my case, it was the Deulund 20 gauge cable.

Have heard praise for the Duelund Cable.

Sadly never experienced it.

 

[kartick]

Have heard praise for the Duelund Cable.

Sadly never experienced it.

Hey, so as per my experience with Deulund cables, I would say these are an interesting bunch of cables and are not for every system. So at present I have these ones to experiment with : DCA16GA, Dual DCA20GA and the Dual DCA12GA models.

I find the 20GA to be the most versatile of the bunch. It is a good gauge to make interconnects and right now I am also experimenting using these as hook-up wires for re-wiring my DAC circuit's output stage. In both these use cases, I have common observations. The mids and highs are its strong suit but it profusely suffers in the bass department. I sense an entire lower octave disappearing. I am currently trying to use these in parallel to some other solid-core and other non-tinned multi-strand copper wires to see how the overall effect turns out to be and first impressions are positive.

The 16GA is a thicker one and not as suitable as an interconnect. It is not bad but again this falls short in the bass region. Here the bass presence (quantity) is more than the 20ga, as expected, but the bass is bloated and not well defined. I had made one more 16ga interconnect which I found best placed between my phono pre and line preamp. It is still there and continues to give a good sound. So two lessons for me here: these cables are extremely system dependent and need quite long break-in periods. I don't personally like this part where one has to wait for hundreds of hours just to see how a cable actually sounds.

Now, coming to the 12ga speaker cables. Sadly, I was the most disappointed with this cable. I put in my tube system. I believed this was a replica of the coveted WE cables from an era where tube amps reigned supreme, but the moment I put the cables between my power amps and speakers, I sensed a huge shift in the tonality and frequency spectrum. The sound was metallic, tinny and not as organic. The Euroclear cables I use as my main cables, are much more relaxed and balanced sounding. I could barely listen to 2 full songs with the Deulunds in and got those out. I think my tube amps don't like tinned plated copper cables - specially such speaker cables. But who knows about the other tinned plated speaker cables out there such as the Belden 9497 or something. Maybe something clicks as well.

Again, as I said, these observations are not gonna be universally true so others might have had or will have different experiences with these cables. I report here what I hear in my system.

Bottomline for me are that Deulunds are champions of giving out great details/information in the mids-highs areas. Textures in voices and strings sound very rich (20ga mainly). I guess using the 20ga as internal speaker wiring for connecting your mids driver and specially with the tweeters/super-tweeters could prove most ideal. Deulunds should be tried before one decides to buy 'em.

 

[Nikhil]

Great feedback Kartick!
I have the Duelund DCA16 GA which I used as speaker cables.

For me the biggest issue with the Duelund DCA cables is the brutal break in period. The sound swings from great in the beginning to really bad in the middle before stablizing after 150 - 200 hrs which is a really long time. Most people will not even bother to listen to the cables that long. Really not sure what the reason is for the break in period.



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[kartick]

Yeah Nikhil, it is really an issue with these cables. So the thing is that when using the 20ga with my dac as the output stage wires, i have the convenience of leaving the DAC on 24*7 and letting it play a song/album on repeat. I have seen the changes come about in the dac's sound after 7-8 days, equivalent to around 200 hours. I still could not just use this wire alone for the sonic reasons mentioned elaborately in my previous post. I would again say, it is not as good an all-round cable as it is touted to be on the media. Oil impregnation is just a gimmick!! Neither do I find its price justified. Like i dont get as much performance or satisfaction out of it for as much as it costs. Again, it is a subjective thing.

 

[Nikhil]

** Have updated the Thread Subject to make it more general

A forum member contacted me about my experience with the Belden 8402 which prompted me to try out a good well made unbalanced IC cable as a digital coax. So last night I added the WSS GoldLine KS1 RCA into my setup and the results were once again fantastic! WSS is a well regarded cable company that makes some really good cables in my experience. This really was about using a cable that was made well over my DIY Belden experiment. Definitely noticeable in the sound.

Will keep the cable playing in my setup over the weekend and observe the sound for a little more time. All I can say is that this has been an experiment well worth the time.



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[Nikhil]

Have been listening to the WSS GoldLine KS1 RCA for the past week. And I have to say I was pretty impressed with the sound. Another one of those moments where you wonder why you hadn't thought of using this cable before.

Sound impressions aside there are some issues like drop outs that happened on one of my listening sessions. There is also a short burst of hash sometimes when you hit play and then things settle down. So while sounding very good, there are these minor niggles that exist presumably due to the deviations from the digital specs. These aren't really a big deal but they are there.

Chalk one more down in the list. Back to my Lifatec optical cable for now.



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[IndianEars]

Good info, Nikhil.

Were the Hiccups while handling a 16/44 SPDIF signal ?

 

[Nikhil]

Were the Hiccups while handling a 16/44 SPDIF signal ?

It was while playing a stream from Spotify so probably not even that.


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[IndianEars]

OK.

That's Bad News

 

[Doomster69]

Prolly someone has already answered this on the post..I'm planning to pair my denafrips dac with Digione over spdif. The connection will be through the BNC port on the back as coaxial one is connected to another dac.

Wondering whether to go with a 75ohms sub cable from bluerigger or purchase new mogami gold W2964 ? How much difference can be expected in SQ? My system isn't most revealing.

Also would it matter/be better if I get a BNC to RCA spdif cable or get a RCA to RCA spdif and use a RCA to BNC adapter? Would that degrade SQ?

Anyone having a spare spdif cable to sell may please dm as well.

Thanks..

 

[IndianEars]

RCA to RCA Digital Cable with a BNC adapter will have no audible penalty in your setup

 

[manek]

RCA to RCA Digital Cable with a BNC adapter will have no audible penalty in your setup

Agree !