The 8450 looks really attractive. Easier to work with solid core if I need to put the cable ends into PCB holes. Will see if someone will sell me a reasonable length at a reasonable price. Thanks.
One end: yes. Should I connect to the chassis or to the PSU ground point between the capacitor banks?
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In the context of this shield grounding discussion, here's one interesting page I found:
Cable Shield Grounded At One End Only - EMC Standards
Cable Shield Grounded At One End Only - EMC Standards
If the signals are at low impedance you won't need any shielding at audio frequencies unless you are obsessive (or running very long cables around, or have very high bandwidth amps) - though it definitely looks more professional to use shielded cables, the electrons may not care!
If at high impedance you will need to take tha shielded cable's capacitance into account in case its affecting the frequency response (usually not an issue with solid state, the impedances are too low)
If you want pluggable connections I'd suggest using RF patch leads with SMA connectors, they are reliable (gold plated) and easily sourced.
If soldering very stiff coax (such as teflon/silver), you will need strain-relief as the stuffness of the sheath is enough to break the centre conductor if it can move around.
If at high impedance you will need to take tha shielded cable's capacitance into account in case its affecting the frequency response (usually not an issue with solid state, the impedances are too low)
If you want pluggable connections I'd suggest using RF patch leads with SMA connectors, they are reliable (gold plated) and easily sourced.
If soldering very stiff coax (such as teflon/silver), you will need strain-relief as the stuffness of the sheath is enough to break the centre conductor if it can move around.
You know what? I never subscribed to those audiophile beliefs, but coming from where I am coming from, even I thought of one scenario where a cable might, just might, deliver slightly different "sound" when flipped on its end, all else being equal.
This applies to my basic belief that one will get much better noise shielding even with unbalanced connections if one uses a 2-core+shield cable. If one constructs such cable, one will connect the shield to the signal-ground conductor of only one RCA plug, i.e. only at one end. Otherwise one will get a ground loop.
So, you now actually get an asymmetric cable; a cable where the earthing of the noise depends on which end's RCA plug is connected to the appliance which has better earthing. So, in theory, I think it's possible that such a cable may give you (some) audible difference in the sound when flipped on its end, when connecting a specific pair of appliances. The difference will be in the difference in the quality of noise earthing.
This applies to my basic belief that one will get much better noise shielding even with unbalanced connections if one uses a 2-core+shield cable. If one constructs such cable, one will connect the shield to the signal-ground conductor of only one RCA plug, i.e. only at one end. Otherwise one will get a ground loop.
So, you now actually get an asymmetric cable; a cable where the earthing of the noise depends on which end's RCA plug is connected to the appliance which has better earthing. So, in theory, I think it's possible that such a cable may give you (some) audible difference in the sound when flipped on its end, when connecting a specific pair of appliances. The difference will be in the difference in the quality of noise earthing.
I use Mogami W2697 and/or W2901 microphone cable. It's very very small diameter ("lavalier") microphone cable, not the big fat rope that vocalists nervously fiddle with while they sing. I bought both types of Mogami from a US website called "Redco Audio".
Both of them have two signal conductors plus a ground shield, see attached diagram.
I use one signal conductor for "signal hot", connected at both ends. I use the stranded copper shield for "signal cold" a/k/a "ground", connected at both ends. I also connect the other (the second) signal conductor to ground, at the source end but not at the destination end. What I mean by source and destination is:
RCA input jacks ---> amplifier PCB: Source = RCA jack, Destination = PCB
PCB --> volume control potentiometer: Source = PCB, Desgination = Pot
I prefer to use the copper shield for "ground" at both ends, because it is bigger and heftier (more massive) than the second signal conductor. So it provides better mechanical support at each end of the cable, thus the weight of the cable is not pulling on a tiny and fragile stranded wire signal conductor. That's what I tell myself anyway.
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Both of them have two signal conductors plus a ground shield, see attached diagram.
I use one signal conductor for "signal hot", connected at both ends. I use the stranded copper shield for "signal cold" a/k/a "ground", connected at both ends. I also connect the other (the second) signal conductor to ground, at the source end but not at the destination end. What I mean by source and destination is:
RCA input jacks ---> amplifier PCB: Source = RCA jack, Destination = PCB
PCB --> volume control potentiometer: Source = PCB, Desgination = Pot
I prefer to use the copper shield for "ground" at both ends, because it is bigger and heftier (more massive) than the second signal conductor. So it provides better mechanical support at each end of the cable, thus the weight of the cable is not pulling on a tiny and fragile stranded wire signal conductor. That's what I tell myself anyway.
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Now that's a good question!
A better question might be:
Why use any Shielded Twisted Pair (STP) for an unbalanced RCA interconnect? When a coax with a heavy braided shield would be a better choice.
Not sure about "better". I think STP is better because the signal "live" and signal "ground" are both protected from EMI by the shield. Even if your circuit is unbalanced, you can get better protection of your signal if you keep the two signal wires unconnected with the shield.
Ideally even unbalanced circuits have their signal "ground" floating, so the pair of conductors can in effect give you some of the EMI immunity of a balanced connection.
If your source is floating and small (e.g. phono cartridge) then you may get some advantage from running a pseudo-balanced cable to an unbalanced input i.e. shielded twisted pair.
If the source is not floating (and most sources are not floating) then you need a low impedance ground connection, best delivered by a shield grounded at both ends. Given that, there is no point whatsoever in having two wires within the shield.
If the source is floating but large then you gain little from shielding the connection as the source itself will pick up noise.
Hence the only place where an interconnect can usefully be unbalanced twisted pair within a shield is a cartridge (or similar e.g. microphone - although these often use a proper balanced connection). The same applies within an enclosure if there are noise/hum sources within it - which there often are.
If the source is not floating (and most sources are not floating) then you need a low impedance ground connection, best delivered by a shield grounded at both ends. Given that, there is no point whatsoever in having two wires within the shield.
If the source is floating but large then you gain little from shielding the connection as the source itself will pick up noise.
Hence the only place where an interconnect can usefully be unbalanced twisted pair within a shield is a cartridge (or similar e.g. microphone - although these often use a proper balanced connection). The same applies within an enclosure if there are noise/hum sources within it - which there often are.
chill man.
i use mogami neglex 2539 quad, you can also use use mogami 2549 dual.
Belden or Canare also make similar cable
if you want to try unshielded you can also use twisted cat 5 or cat 6 cable. it's cheap and maybe you can get it for free (just ask nicely yr office network guy). Use cable sleeve if you want to make it look cleaner.
i use mogami neglex 2539 quad, you can also use use mogami 2549 dual.
Belden or Canare also make similar cable
if you want to try unshielded you can also use twisted cat 5 or cat 6 cable. it's cheap and maybe you can get it for free (just ask nicely yr office network guy). Use cable sleeve if you want to make it look cleaner.
I've been tempted to consider Cat 5/6 actually, when I need to run a whole bunch of signals from one point to another. Not common in a typical preamp or amp, but sometimes I wonder whether these cables will be better than the typical flat cable when connecting an off-board volume pot to a board. I think a flat cable is used there for convenience, not audio quality. STP Cat 5 seems the ideal choice for such use-cases. IMHO, that is.
Did you see the last sentence of post 36?Mark Johnson said:
A high proportion of internal signals are merely continuations of external wiring. For those that are not, the same principles apply.
For connecting a volume pot to a PCB I would normally use shielded cable. If possible, the ground should follow the signal path.
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