Ground Loop Issue/Question

[Speedskater]

If a wall jack has enough amperes to my opinion a power conditioner is not neccessary

If a wall AC power receptacle doesn't have enough amperes, it will trip the circuit breaker!
That's the only way it can limit current.

 

[AnalogSteph]

The phono preamp is a Jolida JD9, here is a link to the manual: https://www.manualslib.com/manual/1015268/Jolida-Jd-9.html#manual
It does mention that it must be connected via a 3prong plug to a "wall" receptacle or similar heavy-duty source, and to avoid extension cords (guilty on all charges initially but did just try the receptacle as well).

That's common for equipment with "vacuum bulbs" (as shango066 calls them). If in doubt, electrical safety > audio concerns. It still means it's an IEC Class I device, which as you have found can wreak all sorts of havoc with unbalanced audio connections if multiple of those are involved. I would prefer one that gets by with a modest transformer plug pack.

I do have to mention that my turntable is a VPI Player (hey, I had to save money somewhere)

Well, "save money" is all relative. That thing costs the better part of 2 grand if I'm not mistaken - some people don't spend that much on a car, and entire perfectly decent audio systems have been built for less. Manufacturing quality seems solid, but it's very barren on the feature side, the tonearm doesn't even have antiskating (?! - I can only imagine what our @restorer-john would have to say on that). Other manufacturers also seem to have figured out how to run tonearm wiring through the base decades ago. If you didn't actually need the headphone amp functionality or preamp, you could have bought a superb Technics (like the SL-1200GR) for that kind of money!

that has a built-in phone preamp section which I disabled (following VPI's youtube video). I read that someone had noise issues as doing so renders the ground screw useless (VPI's answer when he contacted them), so he somehow wired it where the ground screw could be used again. Maybe that's all I need to lower the noise from the phono preamp, I suppose those ground screws on turntables and next to the phono inputs on amps/preamps must be there for a reason .

Here's the video, and the comment in question:

I did this to run it through a Shiit Mani and was getting pretty significant hum. After troubleshooting I narrowed it to something in the turntable. After I contacted VPI, I was told that the tonearm isn't grounded if you bypass the phone stage, but what it really seemed to be had to do with the power going to the board for the pre-amp. I thought about this because even with everything bypassed, turning the volume knob up made the noise worse. I disengaged the one harness labelled pre-amp and it's working great now with no noise.

I suspect the fact that the turntable is an IEC Class I device may have something to do with that. A turntable with no extra circuitry can just route the tonearm wiring through no matter what the motor drive circuitry is doing, but with a preamp installed things are a bit more complicated. Unplugging preamp power may be what's needed to resolve the ground loop. (Or maybe it's just capacitive coupling via the mains transformer?) Having a ground loop running over your phono audio cable obviously is about the worst thing possible, given how low signal levels are on there.

The extra ground connection in a standard turntable connects to the tonearm tube to provide electrostatic shielding for the wiring running inside. (If this is not working, the hum should react to your hand getting close and such.) The idea is to have separate grounds for left, right and shield that are only coming together at the preamp (star grounding), so as to avoid any internal ground loops. A bit of tracing with a multimeter may be needed to determine what is happening inside the VPI.

BTW, you'll probably want some pseudo-balanced cables like these for your problematic AVR to amp connection. Well, actually, they may help out the phono preamp to amp connection as well. You spent enough money on an integrated amp with balanced inputs, so you might as well use them as intended.

 

[ftv]

That's common for equipment with "vacuum bulbs" (as shango066 calls them). If in doubt, electrical safety > audio concerns. It still means it's an IEC Class I device, which as you have found can wreak all sorts of havoc with unbalanced audio connections if multiple of those are involved. I would prefer one that gets by with a modest transformer plug pack.

Well, "save money" is all relative. That thing costs the better part of 2 grand if I'm not mistaken - some people don't spend that much on a car, and entire perfectly decent audio systems have been built for less.

Don't tell that to my wife!

Manufacturing quality seems solid, but it's very barren on the feature side, the tonearm doesn't even have antiskating (?! - I can only imagine what our @restorer-john would have to say on that). Other manufacturers also seem to have figured out how to run tonearm wiring through the base decades ago. If you didn't actually need the headphone amp functionality or preamp, you could have bought a superb Technics (like the SL-1200GR) for that kind of money!

The headphone amp and preamp sections were a nice bonus but not the main considerations, just happened to get a great deal at a show on it. Figured good enough to see if I'd be serious about vinyl before spending more $s on one. Still have my original Revox B-790 as well but needs a connector re-soldered before I can use that (which requires some disassembly).

Here's the video, and the comment in question:

I suspect the fact that the turntable is an IEC Class I device may have something to do with that. A turntable with no extra circuitry can just route the tonearm wiring through no matter what the motor drive circuitry is doing, but with a preamp installed things are a bit more complicated. Unplugging preamp power may be what's needed to resolve the ground loop. (Or maybe it's just capacitive coupling via the mains transformer?) Having a ground loop running over your phono audio cable obviously is about the worst thing possible, given how low signal levels are on there.

I have already disconnected the power to the preamp section, and since the hum is there even w/o the turntable connected I suspect it's the ICs or the phono preamp itself.

The extra ground connection in a standard turntable connects to the tonearm tube to provide electrostatic shielding for the wiring running inside. (If this is not working, the hum should react to your hand getting close and such.) The idea is to have separate grounds for left, right and shield that are only coming together at the preamp (star grounding), so as to avoid any internal ground loops. A bit of tracing with a multimeter may be needed to determine what is happening inside the VPI.

BTW, you'll probably want some pseudo-balanced cables like these for your problematic AVR to amp connection. Well, actually, they may help out the phono preamp to amp connection as well. You spent enough money on an integrated amp with balanced inputs, so you might as well use them as intended.

Will those prevent ground loop issues over those connections? Ordered some from amazon (cheaper and faster for me) to try, should get here on Wed.

At the end of the day, I still need to use some kind of power strip/conditioner as I only have a single plug in that location. Hopefully those XLR-to-RCA connectors will help with the Panamax, if not maybe a simple power strip will have to do.

 

[AnalogSteph]

I have already disconnected the power to the preamp section, and since the hum is there even w/o the turntable connected I suspect it's the ICs or the phono preamp itself.

As I said, if in doubt some more investigation would be needed.

Will those prevent ground loop issues over those connections?

That is exactly the point.

Ordered some from amazon (cheaper and faster for me) to try, should get here on Wed.

As long as they are wired like the ones I linked (i.e. with shield branching off at the RCA side), those should be OK. The main issue I have with starquad in an application like this is that parasitic capacitance is higher than regular 2-conductor twisted pair at the 18' length you need. It should be roughly (150 + 185) pF/m * 6 m ~= 2 nF. Doing the math with the Arcam's 560 ohm specified output impedance gives us a -3 dB corner frequency of 141 kHz (and -1 dB at roughly half that), so we should still be well in the green there. I just wouldn't exactly recommend it for an FM tuner with a 3 kOhm output impedance.

 

[ftv]

Got the RCA-to-XLR cables today and the hum from the AVR input is gone!

Also used RCA-to-XLR between phone preamp and amp but no improvement. With the amp on the input from the phono preamp, turntable OFF and phono preamp ON, I can touch the tonearm and get a buzz from the speakers but there is no constant hum! If I then turn the turntable ON, I get a noise at startup and the hum is there as well with increasing volume, so possibly two issues (hum when turntable is on at higher volume levels and buzz when you touch the tonearm).

I reconnected the preamp section in the turntable just in case that is needed to ground the unit, and I also had a ground wire from turntable to phono preamp, but not between phono preamp and amp (which does not have a ground screw).

Both phono preamp and turntable are plugged into the Panamax power conditioner, as are the Rega DAC and the amp, and all are sitting on the same rack. I can try moving the turntable and phono preamp a few feet away and put them on a separate outlet. Don't know if a ground wire from phono preamp to the amp's chassis would help but may be worth a try as well.

 

[AnalogSteph]

Got the RCA-to-XLR cables today and the hum from the AVR input is gone!

Yay!

Also used RCA-to-XLR between phone preamp and amp but no improvement. With the amp on the input from the phono preamp, turntable OFF and phono preamp ON, I can touch the tonearm and get a buzz from the speakers but there is no constant hum!

That still shouldn't be happening though. Looks like the tonearm isn't grounded.

If I then turn the turntable ON, I get a noise at startup and the hum is there as well with increasing volume, so possibly two issues (hum when turntable is on at higher volume levels and buzz when you touch the tonearm).

Either this is electrostatic coupling or the synchronous motor is getting into a ground loop inductively. Which is quite possible if the tonearm wiring is never truly floating but still connected to earth via the preamp and preamp power supply. This would only work out with zero other earth connections in the entire system, where yours is blessed with plenty (starting from the phonopre).

Honestly, I would just return or sell the turntable and get a bog-standard one that doesn't give you this much grief just hooking it up. The entry-level Technics my dad bought 30 years ago would have worked just fine out of the box.