GoodSoundClub - Romy the Cat's Audio Site - Alternate Grounding Schemes?

11-15-2020

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anthony
Posts 338
Joined on 08-18-2014

Post #:	1741
Post ID:	26001
Reply to:	25997

Alligator clips

Romy the Cat wrote:
Solder 10-15 inch 10Ga wire to you negative grounded terminal. Then begin to tough diligent points of you circuitry with other sides of your wire. You very fast will find how to bridge you ground in order to get rid of you noise. You might hold that wire in hands and just short different pars of grounds, but your hands might act as own antenna. You get the idea….

Yes, I did this just with alligator clips...very quick results...

11-16-2020

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	1742
Post ID:	26003
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Thank you

Thank you very much for all the help/advise. I'm still to investigate the problem. The working hypothesis is that my phono has some GND routing problem. Will examine it with the scope and shortening method to see if that's the case.

PP does damp its filter caps noise to GND, the info I got from PP (hope can publish):

"The charger and the input AC filter circuits both connect to incoming AC and both are connected to ground through their filter caps and therefore feed filtered noise to ground - where in a perfect ground system it would disappear from our life forever as intended."
Indeed, the noise at the output of my phono looks like charging voltage of a cap input filter (5ms base = 100Hz fundamental freq):
Output 5ms PP Online shorted MM.bmp

It is NOT present at the input RCA's and varies in amplitude depending which phono input I select (shorted MM smallest, Decca cart biggest).
Will let you know the results.

Cheers,
Jarek
STACORE

11-16-2020

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Paul S
San Diego, California, USA
Posts 2,658
Joined on 10-12-2006

Post #:	1743
Post ID:	26004
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Shield Unused Phono Jacks

Metal caps over phono stage unused RCA jacks can help with stray EMF/RFI. Cardas and others sell them.

Not saying something is wrong with the PP, just saying it doesn't take much to get noise from a phono stage, including any change in ground potential.

Paul S

11-16-2020

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N-set
Gdansk, Poland
Posts 617
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Post #:	1744
Post ID:	26005
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Have them

The GND noise enters somewhere past the input RCA's. And this GND noise is not the PP RFI/EMF.

RFI/EMF of PP looks like this:
Output 5ms 2mV GND lifted PP Online Decca.bmp

Output 5ms 2mV GND lifted PP Online Decca.bmp

This one is caught by my Decca cart (phono GND lifted) but similar is present in the air, caught just by measuring cables. Time basis is still 5ms (vertical is 25x less than above). You can see the characteristic 'pumping' in regular periods (try to ignore the 50Hz hum).
That's probably the charger.

Cheers,
Jarek
STACORE

11-24-2020

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	1746
Post ID:	26012
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Still fighting

My exorcisms to eliminate 100Hz PP induced noise in the EndOfLife phono gave no results so far.

- I took GND from the PP socket and tried connecting it to various GND points I could access (the signal GND plane, input sockets GND, the case). This only increased the noise.

- I tried connecting different GND points within the circuit. No results.

- The noise seems larger when the PP batteries are not 100% charged, suggesting it comes from the charger working (it disappears when the PP is in the battery mode)

- On the SUT inputs, the noise changes its amplitude with changing the orientation of the signal unit with respect to the power supply but never vanishes completely.

The last makes me suspect it might be emitted by the phono power supply and travel by the air to the signal unit. Perhaps PP excites the supply big chokes? But then why lifting the phono ground from the PurePower eliminates the noise completely?? Cannot understand it. Will get a scope tomorrow and try seeing where the noise enters.

Cheers,
Jarek
STACORE

11-25-2020

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	1747
Post ID:	26013
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Edit

- The noise has two phases - large noise and steady state noise. Large one ocures when the PP is switched offline and then switched on. This noise depends on the input (SUT or MM) and the orientation Signal enclosure vs power supply
- When the battery is fully charged, what remains is the steady state noise - much smaller. It doesn't seem to react to anything.
- Lifting the ground (disconnecting the signal ground from the chassis) has no effect

The only conditions so far to suppress the 100Hz noise are:
- Switching PP to the battery mode
- Disconnecting phono ground from the PP ground

Cheers,
Jarek
STACORE

11-25-2020

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steverino
Posts 367
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Post #:	1748
Post ID:	26014
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All signs point

to the usual suspect.
I can certainly understand your reluctance to send the unit back for repair. I would not do so myself although since I have the older model they don't even support them in theory anymore. I think you have to take it to a local tech repair shop as I do mine. Typically what fails are standard things so I am pretty sure they can find out the part which is malfunctioning. It probably won't cost more than the back and forth shipping anyway.

11-25-2020

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Paul S
San Diego, California, USA
Posts 2,658
Joined on 10-12-2006

Post #:	1749
Post ID:	26015
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"Ground" ?

Jarek, when you say disconnecting the phono ground from the PP ground stops the noise, why is it you don't just do that? Are we confusing "ground" and "neutral again? If the phono stage works quietly when its ground is disconnected, why don't you just lift it? If it's star grounded in the first place, then the ground plane dumps out via the neutral wire, already, and the safety ground would make a loop, in any case. My own phono stage uses only the neutral wire for grounding (the safety ground is lifted). What am I missing here?

Paul S

11-26-2020

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N-set
Gdansk, Poland
Posts 617
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Post #:	1750
Post ID:	26016
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Reasons

Paul, ground is ground, neutral is neutral. Where they are connected I have no idea, for sure not in my equipment. The case of my phono is connected to the safety ground not to the neutral. The reasons why I'm onto this and has not listened to the system for 2 weeks already:

A) check if my phono internal wiring is ok; perhaps I have some GND problem which PP highlighted; this becomes less and less of an option now
B) check if PP is ok or faulty as steverino suggests
C) Phono connection to GND is my only connection to the safety ground and I want to keep it

Cheers,
Jarek
STACORE

11-26-2020

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Paul S
San Diego, California, USA
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Post #:	1751
Post ID:	26017
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ICs

From your descriptions, it sounds like your phono safety ground makes a ground loop, or at least raise resistance for something, when you connect it to your PP. Are any of your ICs connected to ground at any point? The ICs "should" connect your components on the neutral leg, which also makes a safety ground redundant.

Best regards,
Paul

11-26-2020

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drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #:	1752
Post ID:	26018
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Noise on the ground connection

The way it is described, I have to agree about taking the Pure Power to a trusted local repair shop to get it scoped out.
I will just say again that repairing the Pure Power seems to fix the problems, for those who have been able to get their unit back.
If you have a oscilloscope, it would be of interest to see the waveform going across the connection between the Pure Power Ground and the Phono ground. You can also try adding a capacitive filter in the connection to see if this blocks the noise.
This can reveal more about what may be causing the noise, but as I said before it is probably best to get it to a local repair shop before catastrophic failure occurs!
:-)
Adrian

11-27-2020

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Paul S
San Diego, California, USA
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Post #:	1753
Post ID:	26019
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Alternate Grounding Schemes?

I'm trying to remember if you have copper water pipes, and wondering again how these measure for ground resistance. You MIGHT be able to ground your phono stage case to a water pipe as a "bleeder". You could start by "jumping" it, then do something more permanent if it works. This would lift it off the PP, albeit there might be other electrical noise on the pipes, to begin with. I suspect this would only work if your phono stage case is isolated from you neutral in the first, but one never knows, it might work, anyway.

Best regards,
Paul S

11-28-2020

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N-set
Gdansk, Poland
Posts 617
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Post #:	1754
Post ID:	26020
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More

Adrian, I'm not yet convinced the PP is to blame. Also PP Richard is helping a lot to understand the issue (thank you Richard!). Now this f@#$%@%$ 100Hz noise stepped on my male ego - want ot understand where it comes from.

I quickly cheked the signal between the PP ground and my phono. Nothing unusual: some 50Vrms of 50Hz when the PP is online, pretty much the same as between the phono and my wall GND when the phono is connected to the wall.

Interestingly, if I connect the phono and PP GND via amperemeter, it shows an AC current diminishing practically to zero (some 0.4mA). So this 100Hz noise is not from a current loop? Or this 0.4mA rms is enough? Cap coupling GND's I might try for a test, but ultimately I want to have a DC connection for safety. I was thinking of trying this GND blocking scheme, Fig. 4: https://circuitcellar.com/resources/ee-tips/find-and-eliminate-ground-loops/
Another interesting thing I'm strugling to understand is why lifting the phono signal ground from the chassis ground has no effect on the noise. Only lifting the chassis ground from the PP ground kills it. This suggests it gets to the signal either via the air of via the supply lines (B+ and/or heater which biases the 2nd stage). I have to scope theose lines throroughly. But then again, why disconnecting GND kills it?

Pual - I checked my wall GND. First of all it is there (made tests with controlled 30mA shorts to GND - fuses worked). I was looking at the heating too but have no idea if the pipes are all metal or plastic. A bulb test will show.

Cheers,
Jarek
STACORE

11-28-2020

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Paul S
San Diego, California, USA
Posts 2,658
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Post #:	1755
Post ID:	26021
Reply to:	26020

Again With the Star Grounding

Again, there is no need, even for "safety", to have a separate ground wire if everything is star grounded. Since the neutral and the safety ground connect at the service bus, running the "safety ground" back to that bus for your phono stage apparently makes a classic ground loop, at least as far as your phono stage is concerned. Double Hz of service cps is "normal" noise.

Best regards,Paul S

12-04-2020

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	1756
Post ID:	26023
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AC cord sensitivity

Looks like I've found a solution but I don't understand it:

1) Lifting the phono ground from the PP with a cheater plug and connecting the phono case to the SAME PP ground with a separate cable not only does not bring the 100Hz noise back but actually diminishes it! So the phono wants to be grounded to PP but via a separate cable, not through an AC cord.

2) Changing in the above setup an ordinary utility AC cord used for experiments to my DIY braided solidcore and BUM +7dB noise increase

3) Changing to Furutech FP-alpha 3 cord and the noise is lower than with the DIY braid but some 3dB higher than with a cheap utility cable

4) Changing the ground connection wire to an amperemeter shows a negligible AC current of 0.4mA between the phono case and the PP gnd, so this i100Hz noise is most probably not a ground loop but an induced voltage in the AC cord?

I have no idea what is going on. Anyone any clue?
Anyway, I plan to do like Romy said - move PP some 2m away from the rack and bring the power from it via a single powerstrip. Then grounding the phono to the powerstrip or to the PP via a separate cable.

Cheers,
Jarek
STACORE

12-04-2020

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Romy the Cat

Boston, MA
Posts 10,159
Joined on 05-28-2004

Post #:	1757
Post ID:	26024
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Very simple

It sounds that in your phonostage has to good (from electrical perspective between you ground entry from PC to the unit and the main ground terminal (presumably it would be the ground of your RCA). Some people feel that it should be 4-6Ga terminal with a loot of cooper in it (as some people call it the electrons pool) in the way how I did it Milq. I still feel that it is all not good for phonostages and we in phonstages should not use the wall grounds, it is juts to duty. So, in my system you will see power cords and broken off off ground terminal. I connect all my components with 2 pins not 3 pins and that was I advocated with very begging of this conversation. Now about your “solution”. As I said. Get a think wire or 2 or 3, connect them to a single point at ground of your RCA and “touch” different ground locations of you phonostage of your other elements. In my case I have a wire running from ground of my RCA to my TT’s tonearm on the other side of my SUT. As you find your configuration what you have no noise with max up volume juts solder the setting and juts forget about it. You do not need to understand it or to rationalities it. Who cares! Make it silent, move over and do not worry about why it does it. You will find you perfect setting VERY fast if you stop thinking about it and start juts touching your system with grounded wire at different locations. I do not advocate to be brainless typically but in this case, I do not feel that understanding is necessary. You will not have it and only God know why it works in the way how it works. I was taught by the guys who built high frequency transmitters and what they do with ground and antennas is an absolute black magic with deny any understanding. In our case the thing are very simple and our objective is not best termination of the UHF transition lines but juts killing the auditable noise, very simple…

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

12-04-2020

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	1758
Post ID:	26025
Reply to:	26024

Magic

Thanks Romy, this seems the most practical solution. I will connect a wire to the gnd terminal at the phono inputs and see where it wants to go: power strip, PP or wall ground. I have two more questions:
-- the cable you run from your PP to the power strip where the system is connected, is it shielded or bare?
-- does it make sense to install a dedicated power line with a separate fuses for the PP or this brings no difference with respect to the household line?

Cheers,
Jarek
STACORE

12-08-2020

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	1759
Post ID:	26026
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Victory over GND

1) GND NOISE

After more experiments, I can proclaim a victory over the 100Hz noise on my End of life phono. For whatever reason the GND connection does not want to run in a close physical proximity of the line and neutral and demands a separate cable. So this was not a faulty PP. Where I terminate this cable: at the PP output sockets or at the wall it does not matter - the audible noise is gone, only my FFT shows a pronounced 20Khz peak but more on that later. The PP is 2m away from the rack, the power is connected via a normal household strip for a moment, the separate GND wire is 5mm, 13ga cable connected to the phono input ground terminal.

Proximity effects: If I disconnect the GND wire from the ground and start moving it around, the closer it is to the PP output cable (the power strip cable) the more noise is picked and present at the phono output. So there is some coupling, which lead to the noise. I examined the field around the power cables - connected a small 47mH RF choke to one input of the sound card and a pair of loose cables to the other to catch both B and E fields on my laptop scope. Indeed there is quite some trash around the power cables: The closer to the phono power supply the more of it and more spread in the air (phono cable has a gnd drain cable connected to PP gnd on one side only), while the closer to the PP output socket the quieter and more concentrated around the cable. 20kHz is all over in the air, in the radius of 2m around the equipment and is happily picked by my cartridges (esp. the Decca). I speculate most of this noise is electric field and open loop antenna picked much more than a coil.

Given that, PP users, do you use shielded power cables around your PP's to constrain the emission?

Cheers,
Jarek
STACORE

12-08-2020

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	1760
Post ID:	26027
Reply to:	26026

PP output study

2) OUTPUT STUDY

I decided to check what my PP outputs. After some listening my HF is harsher than I would like plus on older equipment (like Sansui TUX1) I can sometimes hear a gentle transformer whistling, suggesting high harmonics. Plus the omnipresent 20KHz noise, I measure everywhere (in the output, around the cables, in space around the phono).

Here is the PP output, ONLINE mode at 180W amplifier load:
PP online amplifier load.bmp

And its FFT (RED TRACE):

PP online amplifier load FFT.bmp

One can clearly see the 20kHz and its harmonics riding over the sine plus some trash around 3kHz.

For comparison, here is the BYPASS mode (so the wall power) same load:
PP bypass amplifier load.bmp

PP BATTERY operation:
PP battery amplifier load.bmp

I also checked switched the PP to 220V. Seems marginally better around 3kHz area (online mode below):
PP 220V online amplifier load.bmp

Romy, I remember seeing such waveforms, HF riding on a sinus, when you studied your PP. What were your conclusions?

Cheers,
Jarek
STACORE

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