Ginsly
Well-known member
Ah! Ok didn’t consider that.
Shielded Wire Advice?
- Thread starter Ginsly
- Start date
There's is a thought process of isolating the ground of the output of audio devices and and forcing the inputs to do all the grounding. This works because you only need to ground a shield once.
It creates a better star ground because all individual grounds meet back at the power source and only the power source. Think of an upside down tree. On the tips of the twigs are the 3pdt then the PCB then the jacks. Adjacent are the jacks and cable(only "touches" one jack), then DC connector, then PSU. There's a bunch of branches(pedals) all like that. And they all never touch until the PSU.
The down side is if something breaks...
Shield is compromised at one end of the cable, jack gets dirty, etc. Then you could loose your shielding and pick up noise.
Ground loops on pedal boards are more of a myth, IMO. For ground loops, you need distance and usually things operating on different circuits.
That's why you see them on DIs a lot.
FOH is operating on a different circuit than the stage. That means if you connect grounds of the pedal board and the mic cable to fog, you've completed a loop that goes AAALLLLLLL the way from the pedal to the wall to the main breaker through the mains backplane to the FOH breaker to the FOH mains power plug and through its power supply. And, as we discussed, you only need one end of a shield grounded. Hence, the ground lift.
It creates a better star ground because all individual grounds meet back at the power source and only the power source. Think of an upside down tree. On the tips of the twigs are the 3pdt then the PCB then the jacks. Adjacent are the jacks and cable(only "touches" one jack), then DC connector, then PSU. There's a bunch of branches(pedals) all like that. And they all never touch until the PSU.
The down side is if something breaks...
Shield is compromised at one end of the cable, jack gets dirty, etc. Then you could loose your shielding and pick up noise.
Ground loops on pedal boards are more of a myth, IMO. For ground loops, you need distance and usually things operating on different circuits.
That's why you see them on DIs a lot.
FOH is operating on a different circuit than the stage. That means if you connect grounds of the pedal board and the mic cable to fog, you've completed a loop that goes AAALLLLLLL the way from the pedal to the wall to the main breaker through the mains backplane to the FOH breaker to the FOH mains power plug and through its power supply. And, as we discussed, you only need one end of a shield grounded. Hence, the ground lift.
If you have a ground loop on a pedal board, it's probably not the board.
1)make sure it's on the same circuit as what it is feeding(amp, PC, etc)
2)if all else fails, lift the ground on the output of the board. The other end *should* be grounded, if by nothing else a chassis earth ground.
Getting way off topic but I feel it's all (semi) relevant.
1)make sure it's on the same circuit as what it is feeding(amp, PC, etc)
2)if all else fails, lift the ground on the output of the board. The other end *should* be grounded, if by nothing else a chassis earth ground.
Getting way off topic but I feel it's all (semi) relevant.
I've heard of people sticking hampsters up their butt too
But I wouldn't do it.
If you really wanted to recycle something I suppose you could find some old RG coax cable
DailyDovetails
Well-known member
I have been thinking about this whole shielding/ground loop thing a fair amount recently. It at first seemed a little abstract but I think the noise comes down to the following areas.
Antenna. Although possible none of our equipment other than say a cable which is improperly wired makes a very good antenna. I think the best practice for minimizing this type of noise is to keep the unshielded lengths of wire as short as possible.
Capacitive noise. This is the noise that happens when you have paths with dissimilar voltage close to one another. Like when your input and output wires are close or you have a wire close to your board. This can be minimized by either increasing the distance between points or shielding.
Ground loops. This is when there are multiple paths to ground and current is able to flow between the different paths creating noise. This one was the most abstract to me. I try to think of it like the different ground areas are ponds of water and I am trying to drain them using single streams to one location. So this would be having a grounding plan and avoiding excess paths.
The pedals I have been building recently have been really quiet. I often turn up the gain and volume up all the way even to hear what the noise floor might be. I shield the input and output jacks, make sure all the pots, switches ect have continuity to the case, and make sure the top and bottom of the case have continuity. I sometimes wire the shield to the jack, the footswitch board or both, for me it hasn’t made much of a difference.
The one additional thing I want to try is to print a plastic washer to isolate the output jacks from the case.
What I wonder sometimes about ground loops is if the power supplies we use and the guitar cable create a ground loop. I wonder if the best practice would actually be to wire all the pedals and amp to a single ground and terminate the cable shield to that point.
Antenna. Although possible none of our equipment other than say a cable which is improperly wired makes a very good antenna. I think the best practice for minimizing this type of noise is to keep the unshielded lengths of wire as short as possible.
Capacitive noise. This is the noise that happens when you have paths with dissimilar voltage close to one another. Like when your input and output wires are close or you have a wire close to your board. This can be minimized by either increasing the distance between points or shielding.
Ground loops. This is when there are multiple paths to ground and current is able to flow between the different paths creating noise. This one was the most abstract to me. I try to think of it like the different ground areas are ponds of water and I am trying to drain them using single streams to one location. So this would be having a grounding plan and avoiding excess paths.
The pedals I have been building recently have been really quiet. I often turn up the gain and volume up all the way even to hear what the noise floor might be. I shield the input and output jacks, make sure all the pots, switches ect have continuity to the case, and make sure the top and bottom of the case have continuity. I sometimes wire the shield to the jack, the footswitch board or both, for me it hasn’t made much of a difference.
The one additional thing I want to try is to print a plastic washer to isolate the output jacks from the case.
What I wonder sometimes about ground loops is if the power supplies we use and the guitar cable create a ground loop. I wonder if the best practice would actually be to wire all the pedals and amp to a single ground and terminate the cable shield to that point.
Ginsly
Well-known member
Huh - so even when you grounded both sides of the Input and Output wires it didn't make a difference one way or the other? In that case, why would you need to look into plastic washers to isolate the Output jack from the case?
Since you've tried it in different permutations, which one do you typically go with?
Ginsly
Well-known member
That's a helpful analogy, thanks!
DailyDovetails
Well-known member
I had been doing the separate shield and ground but now I am mostly grounding the shield at the jacks just because it’s neater. The isolating washer is just a best practice type thing that I was considering messing with.
Some of the other things I have run across that are grounded this way is a mixer I recently rebuild which is pretty quiet after rebuilding.
Also EMG pickups are grounded that way. They look like they aren’t but if you pull back the heat shrink the black wires go to the shield.
