Digital coax

[rikardo1979]

I thought I can make some digital cable for CDP, DVD, BD, DAC etc...
Would this cable (http://goo.gl/Eo2u7E) be any good?

http://uk.farnell.com/productimages/large/en_GB/142330807-40.jpg

And than I would need to find some decent connectors which fits this thin cable

[CageyH]

RG316?

Just look fora connector with good strain relief. I used some Neutrik Reans. Cheap but good enough.

[rikardo1979]

Neutrik Reans
looks good to me, thank for this ;)

and what you think about that cable?crazy? or should work?

[CageyH]

It's a coax. It will work.

I use a 5m one between my PC and DAC.

[Barry]

It's RG179 and has a characteristic impedance of 75Ohms so will be fine. In fact any coaxial cable with a characteristic impedance of 75Ohm will do. However if I were making a digital cable, I would use RG59 as I find cables with an outer insulation of FEP are too 'springy' and difficult to lay/dress neatly.

[Audio Advent]

To a degree, any old cable with two wires will work too - I've often used cheap dual core phono wires for digital with no problems. Not saying it will sound the best and certainly may have issues over longer lengths.

[Barry]

To a degree, any old cable with two wires will work too - I've often used cheap dual core phono wires for digital with no problems. Not saying it will sound the best and certainly may have issues over longer lengths.

"To a degree" yes - but it won't necessarily sound as good as it should As an experiment I tried some 50 Ohm cable (probably RG58) and it wasn't as good as 75 Ohm cable: flatter soundstage with a 'grey' sound (reduced dynamics?), but even worse was the 'freebie' analogue interconnects that come with some CD players. So yes, almost any bit of wet string will convey a signal but not optimally. Given the rise time of the sampling, the digital interconnect needs to be regarded as a transmission line with a well defined characteristic impedance. S/PDIF is defined to be 75 Ohm.

[walpurgis]

You'd not expect cable selection to be critical for digital signal use. But strangely, there can be very noticeable difference in the effect they have on sound quality.

[NRG]

"To a degree" yes - but it won't necessarily sound as good as it should As an experiment I tried some 50 Ohm cable (probably RG58) and it wasn't as good as 75 Ohm cable: flatter soundstage with a 'grey' sound (reduced dynamics?), but even worse was the 'freebie' analogue interconnects that come with some CD players. So yes, almost any bit of wet string will convey a signal but not optimally. Given the rise time of the sampling, the digital interconnect needs to be regarded as a transmission line with a well defined characteristic impedance. S/PDIF is defined to be 75 Ohm.

And yet it's complete twaddle as the RCA connectors used are no where near 75ohm impedance....

[Barry]

And yet it's complete twaddle as the RCA connectors used are no where near 75ohm impedance....

Agree about the RCA connectors; they should have specified 75 Ohm BNC connectors. However since the length over which the mismatch occurs is short, the overall total mismatch is not as large as it could be.

[rikardo1979]

http://www.wbt.de/english/products/a/Detailansicht/Artikel/nextgenTM-rca-connector-topline.html

OP2

[NRG]

AFAIR somebody measured those on DIY audio and found they didn't measure 75ohm, anyhow, what about the socket they plug into ;) length does matter btw due to reflections caused by the impedance mismatch.

[Barry]

http://www.wbt.de/english/products/a/Detailansicht/Artikel/nextgenTM-rca-connector-topline.html

OP2

If they are designed to have a characteristic impedance of 75 Ohm, this impedance will only be maintained if the plugs are mated with WBT's own non-standard RCA sockets. The great majority of CD players use a standard RCA socket for the coaxial digital output.

[NRG]

Yup, apparently they claim 75ohm characteristic impedance with their matching RCA socket, so if you have to use a special socket (probably an expensive one at that) you may as well use a BNC connector that was designed for the purpose from the outset, not some over priced bling. Just sayin......

[Barry]

AFAIR somebody measured those on DIY audio and found they didn't measure 75ohm, anyhow, what about the socket they plug into ;) length does matter btw due to reflections caused by the impedance mismatch.

I was referring to the length of the plug. The impedance mismatch is 75 Ohm to ~ 35 Ohm at one end of the plug, and ~ 35 Ohm to 75 Ohm on the other side of the connector. Since these two mismatches are in the opposite sense (the reflection coefficients are equal but have opposite signs), they will partially cancel.

Sometime ago I posted the actual calculation; despite the near 2:1 impedance mismatch at the plug and at socket, the overall total mismatch is lower.

Experimenting with cables having a characteristic impedance of 75 Ohm, 50 Ohm and cables having an unspecified impedance, I found the 75 Ohm cables sounded better.
.