Which shielded cable would you use for signals inside your amp or preamp chassis? Do you have a specific brand and model?
I'm looking for cables which are easy to work with for a semi-competent DIYer (me) and have excellent shielding.
I know that the Sound Of Cables is a big, hot topic, and I don't want to get into that debate. I will read all your opinions, and I hope you'll forgive me if I will quietly accept those which I can understand, given my (limited) knowledge. Therefore, for instance, I will select pure copper conductors over silver, in cables. I will ignore skin effect claims, and will happily work with solid-core or stranded conductors, depending on which are more easy to work with, break less easily, get soldered and desoldered more easily, etc. I will avoid cables which have capacitance or inductance which are too high for audio (do these things matter in the lengths of inches we need inside a chassis?) To give you an idea of my preferences: I blindly and happily buy cables made by Blue Jeans Cables and look no further.
I'm looking for two-core+shield type of cables, I guess. The better the shielding, the more I'd like it. Why two-core+shield and not coax? It is because I prefer to run signal ground separate from shield. I feel that shield is often more noisy than the signal ground, if I keep them separate. I have had remarkable success with long runs of unamplified mic output running through 2-core+shield cables, because I kept the signal ground separate from the shield.
Blue Jeans happily tells you which 2-core+shield cable they think are great for audio, for their XLR cables. But then, I would think those would be for external use, with thick outer jackets and mechanical protection. What version of those are available for internal wiring?
I searched for cable choices discussions on this site, and read those which I could find, but nothing is addressing the issue I'm asking. They're either asking about how to connect the shield, or getting into areas which I cannot understand.
Which cables do you use?
When I look at the Digikey catalog, I am seeing some 2-conductor cables which specify "1 pair twisted" and others which don't. I'd always pick the twisted over the untwisted -- is there any reason to do otherwise? I know twisting increases capacitance, but will it matter for lengths of a foot with circuits which are not at the hairy edge of unstable? Are the ones which don't specify "twisted" really untwisted? These are some of my doubts.
I'm looking for cables which are easy to work with for a semi-competent DIYer (me) and have excellent shielding.
I know that the Sound Of Cables is a big, hot topic, and I don't want to get into that debate. I will read all your opinions, and I hope you'll forgive me if I will quietly accept those which I can understand, given my (limited) knowledge. Therefore, for instance, I will select pure copper conductors over silver, in cables. I will ignore skin effect claims, and will happily work with solid-core or stranded conductors, depending on which are more easy to work with, break less easily, get soldered and desoldered more easily, etc. I will avoid cables which have capacitance or inductance which are too high for audio (do these things matter in the lengths of inches we need inside a chassis?) To give you an idea of my preferences: I blindly and happily buy cables made by Blue Jeans Cables and look no further.
I'm looking for two-core+shield type of cables, I guess. The better the shielding, the more I'd like it. Why two-core+shield and not coax? It is because I prefer to run signal ground separate from shield. I feel that shield is often more noisy than the signal ground, if I keep them separate. I have had remarkable success with long runs of unamplified mic output running through 2-core+shield cables, because I kept the signal ground separate from the shield.
Blue Jeans happily tells you which 2-core+shield cable they think are great for audio, for their XLR cables. But then, I would think those would be for external use, with thick outer jackets and mechanical protection. What version of those are available for internal wiring?
I searched for cable choices discussions on this site, and read those which I could find, but nothing is addressing the issue I'm asking. They're either asking about how to connect the shield, or getting into areas which I cannot understand.
Which cables do you use?
When I look at the Digikey catalog, I am seeing some 2-conductor cables which specify "1 pair twisted" and others which don't. I'd always pick the twisted over the untwisted -- is there any reason to do otherwise? I know twisting increases capacitance, but will it matter for lengths of a foot with circuits which are not at the hairy edge of unstable? Are the ones which don't specify "twisted" really untwisted? These are some of my doubts.
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I use a flexible shielded cable for internal chassis runs.
Nothing special - ordinary cable like the type used for phono connections - and cut the RCA plugs off.
If preference of a 2 conductor plus shield, then the "balanced" microphone cable is good.
Internal chassis wiring is short enough to not be bothered with all that "capacitance" stuff.
As for anchoring the shields, I basically connect the one end towards a star ground near the power supply.
Nothing special - ordinary cable like the type used for phono connections - and cut the RCA plugs off.
If preference of a 2 conductor plus shield, then the "balanced" microphone cable is good.
Internal chassis wiring is short enough to not be bothered with all that "capacitance" stuff.
As for anchoring the shields, I basically connect the one end towards a star ground near the power supply.
Yes, everything you've said makes sense. I was just hoping to know if there are cable models which are everything you said, plus lighter and thinner insulation in the outermost jacket, so that they are easier to bend and work with. For instance, the Belden 1800F has a bending radius of 2.5", which is a pain for internal-chassis wiring.
This too seems to be an excellent star-quad cable, like the Canare 4E6S which Blue Jeans recommends. But won't it too be thick and stiff for internal wiring and tight bends?
I'm looking at unbalanced signals, actually. I agree that it's more "normal" to use simple coax for such wiring; I'm just trying to be more careful.
I must admit, I'm trying to be more ambitious than what most DIY amp builders here seem to be doing: I'm trying to build an integrated amp. So I'll have the mess of wiring which an integrated amp contains, and I'll also have the high current rectifiers and power supply lines of 150W/ch power amps. So I'm more nervous about shielding than I'd be for a preamp.
Someday, I also want to add a DAC to my amp, and have just one input selector to select from a few analog and a few digital inputs. Even more fear at that time, about HF polluting my analog signals.
I must admit, I'm trying to be more ambitious than what most DIY amp builders here seem to be doing: I'm trying to build an integrated amp. So I'll have the mess of wiring which an integrated amp contains, and I'll also have the high current rectifiers and power supply lines of 150W/ch power amps. So I'm more nervous about shielding than I'd be for a preamp.
Someday, I also want to add a DAC to my amp, and have just one input selector to select from a few analog and a few digital inputs. Even more fear at that time, about HF polluting my analog signals.
"Cable dressing" gets important in such designs.
Which means guide the low level cables away from the high voltage/current circuits / cables.
Going for paired signal cables with grounded shield is what you normally see in industrial installations with control and power wires in the same cabinet.
Search the internet for interior pictures of modern integrated amps to get an idea how the "professional designers" do such arrangements.
For example see this revieuw on 6moons.com:
RSA-777EX
Here you get a top quality integratd amp with power cables all the way to one side of the chassis, line-level at the other side (mounted high) and speaker cable mounted low to extend the space between the different levels as much as possible.
Which means guide the low level cables away from the high voltage/current circuits / cables.
Going for paired signal cables with grounded shield is what you normally see in industrial installations with control and power wires in the same cabinet.
Search the internet for interior pictures of modern integrated amps to get an idea how the "professional designers" do such arrangements.
For example see this revieuw on 6moons.com:
RSA-777EX
Here you get a top quality integratd amp with power cables all the way to one side of the chassis, line-level at the other side (mounted high) and speaker cable mounted low to extend the space between the different levels as much as possible.
Yes, this is the kind of stuff I'm forcing myself to note. I am familiar with cable dressing; we used to use the term often in the context of structured Ethernet cabling back in the day when companies had on-premise data centres with core switches and edge switches and what-not. I'm now aware that with audio, all those rules may be the difference between mid-fi and real excellence. Thanks for pointing out the example.
Yes it'll be a steel-and-aluminium chassis and the signal ground will probably need to be connected to it at some point. This last bit is a question I'm not sure about, and it involves me diving into the can of worms called grounding.
When I think of an audio circuit conceptually, I find that the entire circuit is finally tethered to the transformer secondaries, and there is no need for any current flow between the circuit and mains or chassis earth, therefore there is no need to connect any part of the audio signal related circuit to chassis earth. Shields of XLR connectors may be connected to chassis earth, but that's only because XLR has separate conductors for shield and signal ground. Otherwise, probably there's no need to connect signal ground to chassis earth.
What do you advise?
When I think of an audio circuit conceptually, I find that the entire circuit is finally tethered to the transformer secondaries, and there is no need for any current flow between the circuit and mains or chassis earth, therefore there is no need to connect any part of the audio signal related circuit to chassis earth. Shields of XLR connectors may be connected to chassis earth, but that's only because XLR has separate conductors for shield and signal ground. Otherwise, probably there's no need to connect signal ground to chassis earth.
What do you advise?
You would think so, have a look at this thread and see what you think was happening problem with earth gnd Bonsai is the author of the presentation on grounding I linked to
I don't know what was happening in the OP's initial case. Left to myself, I'd do exactly what you've asked him to do: connect audio ground to the point between the two filter cap banks of the PSU. And I'd connect the earth pin of my IEC power socket to the chassis. Whether I'd then connect this midpoint of my capacitor bank to the chassis earth, I don't know. I'll look for advice.
Yes, that's what it appeared to me, and I am surprised that this was what was observed. It does not match my (mostly theoretical) knowledge.
This is the first time I'm hearing this.
I have had the same experience, hum disappearing when signal ground connected to chassis. Screened cable inside a chassis isn't necessary unless there is RF ingress or generation internally.
Well that depends on a lot of things.
For a Shielded Twisted Pair inside a chassis, I use Belden 8450 solid conductor.
Belden 8451 & 9451 stranded conductor would also be OK.
Only connect the shield to the chassis at one end.
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