With reference to signal cables running inside amplifier/preamps such as from RCAs to boards, volume pots to boards etc. In the past I've used twisted pairs of single strand copper that I've extracted from Cat5/6 cables. I've been careful with wire routing and physical separation of supplies etc. and so far it seems to have worked fine. However, I have so far also avoided putting big linear supplies in the same box.
So, in the context of an amplifier using a big transformer in the same case and using a ground loop breaker / ground lift thingy using shielded cables for small signals seems like a better idea:
It appears that in general people use single core coax cable for their small signal routing on and off boards. They connect the core to the signal and the shield to the return which typically is the `signal/pcb' ground. There is an effective faraday cage around the inner wire, but the signal return/ground (the other half of the circuit), is `exposed' so doesn't this negate the value of using a shield? - I appreciate that the far end of the `signal return'/pcb ground is connected to ground via a ground loop breaking resistor/diode bridge arrangement, but in an ideal world I'd assume you'd want to avoid adding noise anywhere in the signal/return circuit.
Follow up question: Does it make sense to use cable that is two core + shield with the Signal and `return/pcb ground' connected to the two inner cores and the shield connected to the Permanent earth/safety ground/case at one end (...one end only Vasily).
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So, in the context of an amplifier using a big transformer in the same case and using a ground loop breaker / ground lift thingy using shielded cables for small signals seems like a better idea:
It appears that in general people use single core coax cable for their small signal routing on and off boards. They connect the core to the signal and the shield to the return which typically is the `signal/pcb' ground. There is an effective faraday cage around the inner wire, but the signal return/ground (the other half of the circuit), is `exposed' so doesn't this negate the value of using a shield? - I appreciate that the far end of the `signal return'/pcb ground is connected to ground via a ground loop breaking resistor/diode bridge arrangement, but in an ideal world I'd assume you'd want to avoid adding noise anywhere in the signal/return circuit.
Follow up question: Does it make sense to use cable that is two core + shield with the Signal and `return/pcb ground' connected to the two inner cores and the shield connected to the Permanent earth/safety ground/case at one end (...one end only Vasily).
?
Does make sense to me.
However, I have to say that I have never had any noise issues with unshielded twisted pairs for audio signals even in amps with big power supplies.
Also, the cable shielding would only help against electric fields, not shielding from magnetic fields from a transformer. To shield against magnetic fields, you would have to use magnetically highly permeable materials (i.e., Mu-metal, permalloy, or "magnetic steel").
I usually use twisted pairs of 30 gauge Kynar wire (got pointed to that years ago by Zen Mod) - I suppose that's similar to the twisted pairs in CAT 6 cable ...
Regards, Claas
I usually use twisted pairs of 30 gauge Kynar wire (got pointed to that years ago by Zen Mod) - I suppose that's similar to the twisted pairs in CAT 6 cable ...
Regards, Claas
A better cable to use is shielded twisted pair rather than coax.
Ground the shield to chassis ground, ideally at both ends of the shield.
I use twisted pairs with no shield and have not encountered any problems.
Layout of components, routing of wires, minimizing loop areas, are all factors affecting the quietness of audio equipment.
Ground the shield to chassis ground, ideally at both ends of the shield.
I use twisted pairs with no shield and have not encountered any problems.
Layout of components, routing of wires, minimizing loop areas, are all factors affecting the quietness of audio equipment.
Running signal wires inside of a chassis drives crazy. Yes, it is wise to route them where they are out of the way of magnetic interference, and yes, I think that a shielded cable is a good idea too. OTOH, I like the idea of twisting wires because they seems to be easier to deal with on the final end that you solder. Shielded cables hardly ever work out for me with length that looks good and dressed when you are done.
In the case of transformers, I just go ahead and get a cover for them. This solves most of the trouble with the magnetic field, but be careful, even the gap at the bottom of the cover may be letting some get out, so pointing that gap where it is less of a problem also helps.
In short, the best bet is to try and limit the length and area of the affected cable whenever possible.
In the case of transformers, I just go ahead and get a cover for them. This solves most of the trouble with the magnetic field, but be careful, even the gap at the bottom of the cover may be letting some get out, so pointing that gap where it is less of a problem also helps.
In short, the best bet is to try and limit the length and area of the affected cable whenever possible.
For me, when all the obvious stuff had been dealt with, it always came down to minimizing loop area ...