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DIY Interconnect advice pelase

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Dan K

pfm Member
I'm getting myself in a mess with some DIY RCA interconnects. I've some frankly stunning ex MIL cable that I was given and when soldered up with Cardas quad to Eichmann bullets it sounds amazing. The thing is it's not shielded, or rather it is but the shiled is not earthed. So.... I decided to earth the shiled to the source end and I've made everything more 'Naimy' ie more PRaT but less real/3D. Why is this? (I suspect that it's because I've now doubled the capacitance)

How do I get more PRaT AND more 3Dness?

Any ideas?
 
Really I would be looking at the systems coupling capacitors as a more dramatic way of changing the sound signature, or even feedback capacitors. IMO this is your area for bangs per buck.

Interested in what aspects of the MIL spec cable are stunning, normally they are just industrial control cables that the manufacturers jumped through a few more hoops and submitted samples for certification.
 
Bemused is spot on re. changing the voicing of the overall system, if that's your ultimate aim. Cables can help but they can't improve on what is already inside the cases, only subtract from it to a lesser degree (subtracting some less desirable things can improve things sometimes of course).

What's the cable spec exactly Dan? Got a link to it? I've seen lots of ex-mil stuff on ebay, most of it is silver-plated multistrand with maybe 2 PTFE insulation layers and a braided shield, usually in quite a compact bundle. Nothing super-special but probably better than cheapo cable. What's the cable capacitance and inductance? Like i've mentioned to you before, cable capacitance can be an issue sometimes, especially if the cores are close together like other mil-spec cable i've seen (cores closer together = higher capacitance)
 
The cable is apparently 1980s American. It's orange in colour and looks to me like a flight test data cable (which TBH it could well be). The outer looks like teflon and it's twin core, there is an outer aluminised shield and then two cores that look to be made up of very thin silver or perhaps silver plated copper conductors each with a teflon dielectric, when you strip off the inner teflon a gold coloured enamel is revealed that covers the inner wires. They are the most 3D and natural sounding cables that I've ever heard (not that that's saying too much).
 
Nothing super-special but probably better than cheapo cable. What's the cable capacitance and inductance? Like i've mentioned to you before, cable capacitance can be an issue sometimes, especially if the cores are close together like other mil-spec cable i've seen (cores closer together = higher capacitance)
Click to expand...

Yes we use mil 4 core screen at work, its dirt cheap, small od and hence does not fill our trunkings. Its a tightly packed cable.
I actualy have some 6 meter interconnects from it as it was so cheap but I had to adjust the cable somewhat to reduce capacitance which involved totally stripping and rebuilding the cable, far too much faffing really.
No RCAs in my system for years though.
Its currently running my HackerNAPs directly from my Buffalo thing and about to be replaced with Gotham quad onto nCores.
Shortly to be replaced
 
Right thats not just run of the mill defence spec cable then, some sort of flight certified cable, beware of aluminum though as its needs special treatment when jointed to copper.
 
S_J it was (I am told) 20pF at nearly 3m including connectors. I assume that would have doubled this when I earthed the shield, which is why it sounded different... not necessarily worse, but more PRaT and less 3D/air.
 
I assume the cable connects a source item to your preamp? If so try turning the cable around so that that the screen picks up its grounding connection from the preamp instead.
 
20pf will make absolutely the square root of bugger all difference, it wouldn't even have an effect in a tonearm cable.
 
In the recording studios you will not find any cables shorter than 3m, most microphone cables are 10-20m long ...
My favourite diy cable is Belden 1694, 1505f and Mogami 2549. IMHO Mogami is probably the best choice for Naim.
 
Try grounding the shield to the load end as well, through a 220pF capacitor (ceramic is best). This will complete the shielding at RF, while breaking the ground loop at audio
 
Thanks chaps, I'll try to post a pic of this cable.

David, your 220pF Cap suggestion sounds very interesting - not something I've tried before.
 
Chops, I've got 2 pairs of these cables. 1 between my Lightspeed Attenuator and my NCC200/Cap6 amps and the other between the Lightspeed and my Metrum Octave. The Lightspeed is battery powered.
 
Dan K said:
Chops, I've got 2 pairs of these cables. 1 between my Lightspeed Attenuator and my NCC200/Cap6 amps and the other between the Lightspeed and my Metrum Octave. The Lightspeed is battery powered.
Click to expand...

You've nothing to lose trying them back to front have you? The first cable with its screen grounded via the NCC200 and the other grounded via the Lightspeed. FWIW all my pseudo balanced cables have the screen grounded at the load end as I prefer them that way.
What's a Metrum Octave when it's at home?
 
tomek said:
My favourite diy cable is Belden 1694, 1505f and Mogami 2549. IMHO Mogami is probably the best choice for Naim.
Click to expand...

The Mogami 2549 is great. Cheap, rugged, easy to work with, sounds excellent... what more do you need? :)
 
Chops54 said:
You've nothing to lose trying them back to front have you? The first cable with its screen grounded via the NCC200 and the other grounded via the Lightspeed. FWIW all my pseudo balanced cables have the screen grounded at the load end as I prefer them that way.
What's a Metrum Octave when it's at home?
Click to expand...
If the outer shield is only grounded at one end, it makes sense for this to be the equipment that is actually earthed. Usually that means the amplifier
 
If I had several cables next to each other, as you have on the back of your amplifier, I would like to see all of the shields at the same reference.
Just try it, it won't do any harm.
 
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