My build uses a shielded cable between the PS and preamp box. The shield is connected only at the PS end, and floats at the phono preamp box.
My TT wiring doesn't require the additional ground wire to be connected to the preamp to prevent hum. It's extremely quiet as-is, other than gain-related hum, which is minimal compared to other phono preamps I have.
My TT wiring doesn't require the additional ground wire to be connected to the preamp to prevent hum. It's extremely quiet as-is, other than gain-related hum, which is minimal compared to other phono preamps I have.
I would have thought that the "shield" and related wiring should be separate from the signal (and power) ground until the last possible moment... at the bridge.
Logically, I would think that the shield of the umbilical should connect the shield enclosures at both ends as their separate shield ground. Connection to earth would be on the chassis side of the bridge. The signal ground from the boards would be run in a dedicated wire in the umbilical to the signal side of the bridge.
I'm not sure how the TT ground wire and the ground post figures into this particularly in a dual mono setup. (two ground posts?) (connected to the signal chassis? or not???) Flexibility either way is likely in order.
My logic could be flawed. It wouldn't be the first time.
Logically, I would think that the shield of the umbilical should connect the shield enclosures at both ends as their separate shield ground. Connection to earth would be on the chassis side of the bridge. The signal ground from the boards would be run in a dedicated wire in the umbilical to the signal side of the bridge.
I'm not sure how the TT ground wire and the ground post figures into this particularly in a dual mono setup. (two ground posts?) (connected to the signal chassis? or not???) Flexibility either way is likely in order.
My logic could be flawed. It wouldn't be the first time.
The shield should be connected to earth ground ONLY at one point... usually the upstream ( "head") side. Otherwise you are creating a ground loop with the "ground wire"... The Hot and Ground wires are connected at both ends... the Shield only at one end.
You ever seen directional RCA connectors? That's how they're wired. Except that in that case, the shield and ground are both connected at the "head" end.
Balanced connections are a bit different since, by definition, the noise will be filtered out. But even so, if using a shield ONLY connect it to one end point. The idea is to separate the noised picked up by the shield and shunt it to ground.
For your power supply interconnect, the shield should be grounded at the power supply side... to earth ground. This will ensure a PS DC signal(s) devoid of RF interference.
BTW, this should be the REAL ground, the chassis.
I consulted the P3 building guide. There is a wiring diagram like this:
In the PSU chassis (the green box) is going to chassis. I guess this is via the "bridge" on PSU PCB.
I am using the UDP3. But think I can elaborate from this drawing and make something that will work using the UDP3.
There is also UPD3 documentation I can look into in dedicated UDP3 thread.
But all this assume I can get a kit.....or a least a set of P3 PCB's
In the PSU chassis (the green box) is going to chassis. I guess this is via the "bridge" on PSU PCB.
I am using the UDP3. But think I can elaborate from this drawing and make something that will work using the UDP3.
There is also UPD3 documentation I can look into in dedicated UDP3 thread.
But all this assume I can get a kit.....or a least a set of P3 PCB's
Grounding is a complex subject. I try and maintain isolation between chassis and signal ground all the way back to a single point ground in the power supply. The goal is to A) make sure no current flows through the chassis, B) maintain chassis + enclosure + cable shield integrity as an overall Faraday screen. For some small signal applications this needs to be modified, but that is generally a phenomenological situation.
If you want a good starting point:
https://extapps.ksc.nasa.gov/Reliability/Documents/Preferred_Practices/1214.pdf
If you want a good starting point:
https://extapps.ksc.nasa.gov/Reliability/Documents/Preferred_Practices/1214.pdf
I confirmed, shield should be connected only at one end, usually the power supply enclosure chassis. I wouldn’t expect using a shielded cable between the supply and phono would have such a great impact on noise, on the phono side. The shield protects only from high frequency noise and has marginal effect on the line ac noise. The physical separation of the power supply and the phono is doing the real reduction of ac noise in the phono. That and the actual steel shielding of the enclosure.
The only real location where shielded cable can have a real impact is at the highest gain point, the phono input. Using a small coax cable from the input RCA to the phono input is the way to go…
SB
The only real location where shielded cable can have a real impact is at the highest gain point, the phono input. Using a small coax cable from the input RCA to the phono input is the way to go…
SB
Not every configuration works for everybody and you should try different configurations. My umbilicals have ground on the shield and the inner conductors have V+ and V-. It’s quiet.
Would the shield being only a shield and ground having a discrete wire inside be beneficial? I don't know. It certainly may be, and is worth trying.
Confirmed from whom?
And to reiterate, yes, this might work, but grounding is weird, so try everyting if you have issues.
Would the shield being only a shield and ground having a discrete wire inside be beneficial? I don't know. It certainly may be, and is worth trying.
Confirmed from whom?
And to reiterate, yes, this might work, but grounding is weird, so try everyting if you have issues.
Shield should not carry current, otherwise it can reinject noise into the cable conductor. Fine to connect both end, if there is no ground loop, not so great if there is a ground problem. Look at Neutrik XLR connector, equipment side, most of them have a shell pin, and a lot of XLR cable have a shield connected to the shell, but the shell pin is rarely connected anywhere in equipment, or is an option with a jumper. Balanced and shielded cables are rarely needed in any home application unless there are used in long run, speaking very long run, like in pro application, live show, et . Twisted pair are a lot more effective on the short run to cancel out induced noise. In home environment, audio applications, like we do most of the time, shielded cables are not that useful, except for very low level signal, tonearm cable, turntable cable, phono input cable or high frequency digital signal, as SPDIf for dac. For the rest, interconnect, power cable, shield it is not that important, unless your sound system sits next to an industrial arc welder…
That is what I do, shield iis a shield is the shield, signal ground is an internal wire or possibly a second internal shield layer if using a triaxial connector, but in either case isolated from chassis ground.
It gets dicey when some things, like one very nice digital attenuator, tie chassis to signal, or more correctly in my book do not maintain chassis isolation.
^ @6L6 "...Not every configuration works for everybody and you should try different configurations. My umbilicals have ground on the shield and the inner conductors have V+ and V-. It’s quiet..."
Do you mean that your power supply umbilical has no ground? ( forget the shield )...
Isn't you umbilical a differential wire then? I guess you could derive the "ground" via a resistor bridge between V+ and V-.... In a differential wire, by definition, noise should be common...
I keep wondering though, how important is the shielding in the cable of a power supply if there is some kind of noise filtering at the input... A differential power supply cable is definitely intriguing... as all such differential wires I've ever worked with were for signals so I always had a ground to work with.
Do you mean that your power supply umbilical has no ground? ( forget the shield )...
Isn't you umbilical a differential wire then? I guess you could derive the "ground" via a resistor bridge between V+ and V-.... In a differential wire, by definition, noise should be common...
I keep wondering though, how important is the shielding in the cable of a power supply if there is some kind of noise filtering at the input... A differential power supply cable is definitely intriguing... as all such differential wires I've ever worked with were for signals so I always had a ground to work with.
GND is state of mind.....
Before or after the after dinner drink?
I find myself well balanced and grounded in reality before the drink but I tend to float afterwards.
Given enough drinks I'm really dynamically floating in an atmosphere of single ended free ions.
⚛️⚛️
Hello Randy,
at the moment I have the TT-ground to audioground. But I have a hum. The hum is also there, if i disconnect the TT-ground.
So - it has another reason. Still checking.
In my PEARL 1 and in my PEARL 2 I had the TT-ground to the audioground (on the PEARL-pcb) without problems.
Greets
Dirk
at the moment I have the TT-ground to audioground. But I have a hum. The hum is also there, if i disconnect the TT-ground.
So - it has another reason. Still checking.
In my PEARL 1 and in my PEARL 2 I had the TT-ground to the audioground (on the PEARL-pcb) without problems.
Greets
Dirk