[Sweetmeat]

If you've never looked for it, you may not know it's nearly impossible to find a data cable with an RCA plug on one end and a mini phono plug on the other end. I was shopping for that exact cable for the headphone system I use at work. The cable would go from the digital output of my iBasso DX90 player to the digital input of my Burson Conductor SL 9018.
 
In the meantime I was using the adapter supplied with the DX90 along with a standard audio patch cord. I needed to use a 1-foot patch cord because if I used anything longer than that, there was no sound at all. Even with the shorter patch cord, I was getting a lot of dropouts. After a little research I determined the dropouts coincided with operation of one of the many electrical devices in my office, which I share with several other engineers.
 
So I set out to find a shielded SPDIF cable, with the connectors I needed, that will operate at standard lengths. Eventually I found that WyWires builds custom cables, and I made contact with Alex Sventitsky who is Presedent & CEO. He was an extremely gracious fellow, and personally took my order for a 4-ft "Blue" SPDIF cable. I received the cable two weeks later.
 
The cable is extremely well-built. The RCA jack is an adjustable Furutech and the mini phone plug is the sturdiest I have ever seen. The cable cover is very rugged although the cable is not as flexible as I would like. It turns out that Alex uses thick copper shielding for these applications, so his cables are stiffer than others. I can live with it.
 

 
I took the cable to work and plugged it in, and I was relieved that my Sabre DAC would operate with the 4-ft cable. Unfortunately the dropouts continued. I tried everything it seemed like - a Cardas filtered power cable, Furman power conditioner, aluminum foil wrap - nothing worked. I tested the AC plug for polarity and ground, and it was OK. Throughout these tests, I remained in contact with Alex who offered concern and helpful suggestions.
 
Either Alex feels a great responsibility to provide customer satisfaction or he got tired of my emails, but he offered to re-build my "Blue" cable with the same wire used in his newest USB cable. He said the old USB had troubles with sync when the length exceeded 7 feet or so, some of the new USB are 10-12 foot with no issues at all. So I accepted his generous offer to re-build.
 
I've been using the rebuilt cable for a week now with no dropouts. Well, it did have one short dropout but that could have been an under clock event between the DX90 and the Sabre. However the new cable is not completely impervious to RF, it will still drop out when I turn my own desk light off, but I don't do that while I'm on the cans. Overall I am very, very satisfied, and plan on using WyWires again in the future.

 

[Lurker0]

  If you've never looked for it, you may not know it's nearly impossible to find a data cable with an RCA plug on one end and a mini phono plug on the other end.

Such a cable of very good quality can be built yourself for cheap (under $10). No soldering required!
 
The cable shall be 75 Ohm coaxial cable, like is used for TV/CATV/SAT. RG-6 or similar is a 100% working choice, though a thinner cable can be more handy. Then, you need F-connectors on both sides (internally threaded, diameter to match the cable chosen!), and RCA-to-F and minijack-to-F connectors. It would take a couple of minutes for an experienced person, or less that an hour for the first time.
 
The connectors can be straight or right angle - for your convenience. You can even change them in a second!
 
Though the instruction linked from Wikipedia on how to install F-connector requires some tools, in real life all you need is a sharp knife, probably also a tool to cut wires (any suitable).
 
No gold, filters or any other gimmicks are required!
 
Examples of connectors: Male RCA to Female F, Male 3.5 mm Mono to Female F. Also Female RCA to Female F, if you want an extension to iBasso cable.

 

[Lurker0]

And I repeat that I told you in another thread.

S/PDIF cable must be 75 Ohm coaxial cable. USB cable is made from twisted pairs, of different impedance. So, it is wrong to make an S/PDIF cable from USB wires, and don't expect good results from it, regardless of how much it cost.

OK, it can be done e.g. using impedance transformers (aka balun), like used to connect a flat 300 Ohm cable from an aerial TV antenna to 75 Ohm coaxial TV antenna socket, but why anybody should bother if there is a simple solution?

 

[Sweetmeat]

S/PDIF cable must be 75 Ohm coaxial cable. USB cable is made from twisted pairs, of different impedance. So, it is wrong to make an S/PDIF cable from USB wires, and don't expect good results from it, regardless of how much it cost.

I forgot to mention the first cable he built me was true 75 ohm, and that was the one that had all the dropouts. And it was the USB cable that operated without the dropouts. So don't you think the DX90 output may not be true 75 ohms?
 
That was great advice on building my own cable, I am very handy with a soldering iron and I should have tried that. But I couldn't have built anything this nice by myself.
 
And I couldn't have purchased connectors and wire this nice for 10 bucks, that's for sure.

 

[Lurker0]

I don't know what he built, but I use 3 meters coaxial extension cable and no problems.

With unmatched impedance and long (compared to the wave length) cables there are reflections of the signal that may cause problems. Reflections may be caused not only by the cable itself, but also by connectors. Those connectors for F are good matched for sure.

 

[Sweetmeat]

I don't know what he built, but I use 3 meters coaxial extension cable and no problems.

With unmatched impedance and long (compared to the wave length) cables there are reflections of the signal that may cause problems. Reflections may be caused not only by the cable itself, but also by connectors. Those connectors for F are good matched for sure.

Well neither the DX90 nor the Conductor use those F connectors unfortunately.
 
I believe that Alex noticed a similarity between the SPDIF signal and the USB signal which does not require 75-ohm connections. Hey I'm an EE myself, and am familiar with the benefits of impedance matching, but when I look inside my PC I see lots of ribbon cables. I believe you might call this an "out of the box" solution.

 

[Lurker0]

Having a spare time, just try to build a cable like I suggested

 

[Sweetmeat]

Having a spare time, just try to build a cable like I suggested

Well, I really don't need another cable, but I will go forward with your suggestion anyway. I am intensely curious to know how your cable stacks up against the WyWires custom SPDIF. I will post the results in a couple of weeks. If you keep an open mind, so will I.
 
In the meantime, I received an email from Alex that may clear up the coax vs. twisted pair controversy. He wrote:
 
"Regarding the impedance of digital cables, 75 ohms refers to the characteristic impedance defined as the square root of (inductance/capacitance) not the measured resistance of a length of wire. This is where many people are confused. [Lurker and I were already aware of this] Also, S/PDIF cables being referred to as "coaxial" refers to the connectors, RCA, BNC, etc and not necessarily the cable itself. Your cable is twisted pair with a shield that drains interference to ground at the RCA. We've been making these cables for years and they work quite well. Many S/PDIF cables are twisted pair and many are true coaxial. There's no rule about this".