Ground loop suggestions

[John Gallup]

I've had a hissing sound on my turntable/preamp for some months now. It's only audible when the volume above 75% of max (well above my usual listening level) or in quieter passages. I've made shields for the (Rega) tonearm cables and (Kimber silver) interconnects from the preamp to the amp, and grounded the shields to the ground screw on the phono preamp. I've rearranged the gear in the rack so as to minimize interaction between the pieces.  I've also hauled various parts of the system into the dealer for their help, but of course it doesn't happen there.  All the equipment is on the same dedicated circuit, with the amps and subwoofers going direct to the wall, and all the other gear (including a dCS Bartok streaming DAC and Vivaldi clock) to an Audioquest Niagara 3000 power conditioner.

So yesterday I was advised the source was probably a ground loop somewhere in the system, and that "cheater" plugs on various power cords might fix it. I'd be interested in any suggestions on some systematic way proceed with this. Do I want to put cheater plugs on everything at once, or piece by piece? Any thoughts or experiences would be appreciated.

[stratocaster]

@John Gallup I had similar problems with a hum from the 2CE Sig II's when my 2wq's were connected. The hum was consistent but magically disappeared one day. I don't have an elaborate power setup as yours however, the only thing I remember was playing around with the powering up sequence of different components. Additionally, I plugged the subs straight to the wall outlet as opposed to the conditioner. It was a ditch attempt but it worked.

Alternatively, I also discovered that if you load up on tequila, that also seems to eliminate hisses and hums. It's a different story that you begin to hear other things in music that was probably never recorded...🤣

[BKDad]

Oh boy, a mystery!

There’s only 10^8 possibilities.  So, probably a good place to start is to turn off nearby equipment one piece at a time.  Hiss like that often is the result of some EMI/RFI source getting into your phono preamp. 

If that doesn’t yield anything, then ground loop possibilities would be on the list.

What kind of phono preamp is this?

Also, I’ve read that Rega tonearms have kind of a unique grounding system.  That isn’t always compatible with some cartridges and some phono stages.  Cables, too.  Have you looked into that aspect of things?

[Richard Vandersteen]

5 hours ago, John Gallup said:

I've had a hissing sound on my turntable/preamp for some months now. It's only audible when the volume above 75% of max (well above my usual listening level) or in quieter passages. I've made shields for the (Rega) tonearm cables and (Kimber silver) interconnects from the preamp to the amp, and grounded the shields to the ground screw on the phono preamp. I've rearranged the gear in the rack so as to minimize interaction between the pieces.  I've also hauled various parts of the system into the dealer for their help, but of course it doesn't happen there.  All the equipment is on the same dedicated circuit, with the amps and subwoofers going direct to the wall, and all the other gear (including a dCS Bartok streaming DAC and Vivaldi clock) to an Audioquest Niagara 3000 power conditioner.

So yesterday I was advised the source was probably a ground loop somewhere in the system, and that "cheater" plugs on various power cords might fix it. I'd be interested in any suggestions on some systematic way proceed with this. Do I want to put cheater plugs on everything at once, or piece by piece? Any thoughts or experiences would be appreciated.

I would not use "cheater" plugs because of hiss as ground loops are almost always 60 or 120 Hz hum.  Do you have the hiss on any other source?  What do you use for phono as there is no picture of your system?  This forum costs Vandersteen Audio money and all I ask is a photo of each members system.  I guess that is asking too much.  If this forum disappears all will know why.  RV

[John Gallup]

1 hour ago, Richard Vandersteen said:

 Do you have the hiss on any other source?  What do you use for phono as there is no picture of your system?  

Happy to post photos, and sorry that I hadn't.  The sound doesn't occur on other sources.

Current system is:

• Rega Planar 10 turntable and power supply
• Sutherland Engineering TZ Direct phono preamp
• Rogue Audio RP-9 preamp
• dCS Bartók streaming DAC
• dCS Vivaldi clock
• Audioquest Niagara 3000 power conditioner
• Vandersteen M5-HPA amps
• Vandersteen Quatro speakers

Cables are mostly Audioquest.

Edited October 29, 2023 by John Gallup

[Holmz]

7 hours ago, Richard Vandersteen said:

I would not use "cheater" plugs because of hiss as ground loops are almost always 60 or 120 Hz hum.  
…

^This^
Hiss /= hum

 

13 hours ago, John Gallup said:

…

So yesterday I was advised the source was probably a ground loop somewhere in the system, and that "cheater" plugs on various power cords might fix it. I'd be interested in any suggestions on some systematic way proceed with this. Do I want to put cheater plugs on everything at once, or piece by piece? Any thoughts or experiences would be appreciated.

I would be using earphones, starting directly out of the phono preamp. (or if it is a preamp with a phono stage built in, then the earphones onto its main output.)
If there is no hiss on other things, then that sort of points to the phono stage, or phono stage of the preamp..

if you were to try a cheater anywhere, it should be on the TT and the phono pre.
But if they are both plugged into the conditioner, then they would have the same voltage potential.

I suppose it could be possible to have some oscillation happening that could maybe sound like a hiss…but it seems unlikely.
Noise is often something like a radio station on the TT, or other interference coupling in. Any antenna like behaviour of the phono to pre cables should also carry the hiss to the earphone.
Are those phone to preamp cables shielded?
I guess not if you made shields for them… do you have a picture of that?

Do you have an LED lights that are correlated with the noise being present?
And any switching power supplies that can be shut off?

[Richard Vandersteen]

8 hours ago, John Gallup said:

Happy to post photos, and sorry that I hadn't.  The sound doesn't occur on other sources.

Current system is:

• Rega Planar 10 turntable and power supply
• Sutherland Engineering TZ Direct phono preamp
• Rogue Audio RP-9 preamp
• dCS Bartók streaming DAC
• dCS Vivaldi clock
• Audioquest Niagara 3000 power conditioner
• Vandersteen M5-HPA amps
• Vandersteen Quatro speakers

Cables are mostly Audioquest.

Try a shorting plug in the input of your phono and do the same test.  Never use a shorting plug on any output because it could damage the component, but it is a useful test for phono tests.  If the hiss is gone focus on the cabling between the cartridge and the phono stage.  Yours is known to be very quiet.  RV

[John Gallup]

4 hours ago, Holmz said:

Hiss /= hum

True. Been experimenting with cheater plugs this morning to no effect. Also tried unplugging the DAC & clock, no joy.

 

4 hours ago, Holmz said:

Are those phone to preamp cables shielded?

Rega TTs have continuous cart-to-RCA cables and, as Richard said, are thought to be well shielded. They use one of them as the TT ground, I've read. I shielded them with copper mesh stuff from Amazon and ran a ground from the shield to the phono pre ground screw anyway. Did the same for the Kimber silver interconnects which, for the price they charge, are probably pretty well-shielded already. I also tried a pair of AQ interconnects w/their DBS system, to no avail.

Here's the Rega cable. The small gray wire is tied to the shield.

4 hours ago, Holmz said:

Do you have an LED lights that are correlated with the noise being present?
And any switching power supplies that can be shut off?

No LEDs or switch-mode stuff in the vicinity. There's a Leviton wifi-controlled wall switch nearby, but cutting power to it has no effect.

Oddly enough one thing that works is hold each of the RCA jacks in my fingers where they enter the phono pre. Not sure what that signifies.

Edited October 29, 2023 by John Gallup

[Richard Vandersteen]

7 minutes ago, John Gallup said:

True. Been experimenting with cheater plugs this morning to no effect. Also tried unplugging the DAC & clock, no joy.

 

Rega TTs have continuous cart-to-RCA cables and, as Richard said, are thought to be well shielded. They use one of them as the TT ground, I've read. I shielded them with copper mesh stuff from Amazon and ran a ground from the shield to the phono pre ground screw anyway. Did the same for the Kimber silver interconnects which, for the price they charge, are probably pretty well-shielded already. I also tried a pair of AQ interconnects w/their DBS system, to no avail.

Here's the Rega cable. The small gray wire is tied to the shield.

No LEDs or switch-mode stuff in the vicinity. There's a Leviton wifi-controlled wall switch nearby, but cutting power to it has no effect.

Oddly enough one thing that works is hold each of the RCA jacks in my fingers where they enter the phono pre. Not sure what that signifies.

John, does it go away when you put shorting plugs into the phono inputs?  Your body is a very effective antenna for RF but may be out of phase and cancel some noise.  RV

[TomicTime]

AQ and others make shorting  plugs , guessing Bruce and Ray stock

[John Gallup]

Just now, Richard Vandersteen said:

John, does it go away when you put shorting plugs into the phono inputs? 

If you mean ground "cheater" plugs on the phono preamp or turntable power-supply cords, no, that had no effect. Thanks for your attention to this, Richard.

[TomicTime]

no cheater lift the neutral on a 3 prong AC plug and should be used w great caution. input shorting plugs for RCA  are what RV reference 

[John Gallup]

9 minutes ago, TomicTime said:

no cheater lift the neutral on a 3 prong AC plug and should be used w great caution. input shorting plugs for RCA  are what RV reference 

Like this, I presume....

And these would go on unused RCA inputs on the preamp? And maybe the XLRs as well? This makes more sense, particularly since I'm not getting any 60-hz hum.

And yes, the ground cheater plugs scare me too.

[TomicTime]

yep

[Richard Vandersteen]

1 hour ago, John Gallup said:

Like this, I presume....

And these would go on unused RCA inputs on the preamp? And maybe the XLRs as well? This makes more sense, particularly since I'm not getting any 60-hz hum.

And yes, the ground cheater plugs scare me too.

Yes, do those inserted into the phono inputs make the hiss go away?  RV

[John Gallup]

1 hour ago, Richard Vandersteen said:

Yes, do those inserted into the phono inputs make the hiss go away?  RV

Gonna get some and find out.

[John Gallup]

Thanks to all for the helpful suggestions. Here's the sound, if anyone's interested. I captured it on a cell phone and used a (newly downloaded) app called Dolby On, moved to PC desktop, converted to .ogg format to upload here. It plays for me in a browser window.

[Holmz]

If the hiss is still there on the TT input, when the TT shorting plugs are in the phon inputs, then it is the phono stage in the preamp.

But as you said it works fine elsewhere, it is not likely help… but is certainly worth a trouble shooting try.
Shorting the unused inputs is never a bad idea, and some preamps  have relays to do that.

[BKDad]

That doesn’t sound like white noise, aka hiss.  It sounds more to me like rectified RF or an instability in the phono stage.

i’d suggest just removing the input cables to the phono stage and having a listen.  It might get truly hissy, but at least you don’t have to order an open circuit from a dealer.

[Holmz]

1 hour ago, BKDad said:

That doesn’t sound like white noise, aka hiss.  It sounds more to me like rectified RF or an instability in the phono stage.

….

I suppose a clip of the sound would be handy, and running that through an FFT would be the next step.

[BKDad]

14 hours ago, Holmz said:

I suppose a clip of the sound would be handy, and running that through an FFT would be the next step.

OK, but I'm not exactly sure what this tells you:

 

 

[DC-93]

Here’s the original plugs on my 1967 McIntosh MAC1500 tube receiver. Nothing fancy. 

[John Gallup]

I can't find it now* but some years back Fremer wrote  about dismantling an old audio system for a widow who was moving out of her house; the husband had had speakers built into the walls and the system hadn't been used in years. When he went in behind the speakers, Fremer found McIntosh amps with the tubes still glowing beneath a coating of rat droppings and dust.

___________________________________

*A web search on "Fremer rat droppings tubes McIntosh" produced interesting but not relevant results.

[GdnrBob]

53 minutes ago, John Gallup said:

Fremer found McIntosh amps with the tubes still glowing beneath a coating of rat droppings and dust.

Ugh!

More surprising is that it didn't cause a fire.

B

[Holmz]

4 hours ago, BKDad said:

OK, but I'm not exactly sure what this tells you:

 

 

The time domain graph certainly looks like a lot more than noise and hiss.
The 3 peaks at the front look like the drummer doing 3 strikes to get the song started.
it looks more like a song coupled in, rather than hiss.