Ideal DC Power Cable

The Trichord phono stages are supplied by a separate PSU, of which there are a few types, but the better models (above the useless wall wart) are pretty serious affairs, providing +22v DC and -22v DC to the phono stage itself via a four core cable.

Trichord offer a £140 upgraded power interconnect for the interconnection, which has received a good review and looking at the standard lead, it's no wonder there are improvements to be had from using something proper.

It's obviously an easy DIY make... but I was wondering if anyone has any thoughts on the ideal characteristics for a DC power cable, especially bearing in mind the positive and negative DC provided.

I have already tried a four core cryo'd belden cable, which had larger conductors than they use for the trichord big money lead, teflon throughout, but this was your usual belden style tightly bound cores with their double screening... and it doesn't sound very good (worse than the standard wet-string lead!), which got me thinking that the screen (which I have connected to a mains earth via a flying lead and not connected to any of the DC cores at any point) may be increasing the capacitance of the cable - great for AC mains, but presumably doing nothing helpful in a DC context.

If anyone has any thoughts about this I'd be intregued to hear... I was considering an arrangement of conductors spaced apart (to minimise strange field interactions which may be causing the Belden to sound so bad due to close conductor layout), but was wondering if there's any existing wisdom on the subject.

 

shall i tell him or does somebody else want tell him who makes the sited power connect upgrade?

 

Thanks loads.

 

Having tried about 20 or so different ones I believe Graham (trichord) settled on one by Omiga Audio.
I also believe It can be enhanced even on that one

 

I'm really after the electrical properties of the theoretical ideal DC cable, but thanks for all the help so far.

 

The ideal cable is no cable.....! so someone famous once said.

As for DIY cables.....I'm getting people asking me would silver make a good power cable to be honest I've not tried. But a twisted three core of a minimum 1mm dia per core properly insulated should work. But I feel its more the topology of the cable not the materials in power cables that make the difference.

Suggestions then ...2 x ptfe ag/cu equipment wire twisted tightly together in a suitable jacket should work. Pay attention to the quality of the connectors, like everything else these should make difference to the performance.

 

Any thoughts on capacitance, inductance, conductor spacing? Which of the four conductors should be twisted together? Does it matter if the cable is stranded or solid core? Would some kind of litz arrangement prove worthwhile?

What effect would all of these factors have on the fields in a quiescent stage, the further effects when more power is suddenly drawn, and how would changes in these electrical properties limit the unhindered supply of DC power?

Low resistance is obviously important, and the use of pure silver may be closer to the ideal due to better conductivity over copper, but I find cryo'd OCC copper to be a better conductor than non-OCC 99.99% pure silver across the board. Better purity OCC silver is now widely available, which may be worthwhile once (as you've identified) the optimum design has been achieved.

As I've already tried - tightly wound conductors provide a negative effect sonically, and I'm thinking a pair of twisted pairs (one pair carrying +22v and the other carrying -22v), separated from each other (prevent inverse fields from interacting?) would be a better approach to start. I'm unsure about the optimum capacitance (in a high/low sense) for this application, which is my main quandry... so if anyone has any knowledge on this it'd be appreciated.

 

Personally I would be inclined to try solid core and in the configuration you mention - one twisted pair carrying the +ve and one the -ve. You can get suitable solid core, ptfe insulation hook up wire from places like RS and Farnell.

 

From a theoretical standpoint, for a DC power cable surely the "ideal" set of properties is 0 DC resistance, 0 series capacitance and high series inductance? Capacitance to ground would be desirable.

I would also think that for a DC power cable you want to shield it well to prevent RFI (although a high series inductance will lessen RFI effects significantly).

 

Thanks so much Isaac, that answers my question perfectly.

Do you think the use of ferrites would be a route to increasing inductance in this case? I have tried them widely before and found them to have a negative effect on all power cables - both AC and DC, which I attributed to an increased inductance.

 

For something shielded an interesting proposition would be to try a DC version of the Synergistics Research approach to mains cable - ie a co-ax geometry. Could use some high quality miniature co-ax probably for this app to maintain flexibility.