Background electric noise problem

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Graham Hinton
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Re: Background electric noise problem

Post by Graham Hinton » Mon Mar 16, 2020 6:16 am

Clank wrote:
Sun Mar 15, 2020 12:05 pm
the case Is grounded thru it's own brick converter as long as you buy a grounded one.
What else?
Correct grounding can never be achieved using an external brick and a dc barrel jack. That is why if you see a dc jack on the outside it doesn't matter what is on the inside, it's just not going to do the job properly.

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Re: Background electric noise problem

Post by KSS » Mon Mar 16, 2020 10:42 am

Graham Hinton wrote:
Mon Mar 16, 2020 6:16 am
Correct grounding can never be achieved using an external brick and a dc barrel jack. That is why if you see a dc jack on the outside it doesn't matter what is on the inside, it's just not going to do the job properly.
Is a secondary mains plug with only GND wired an effective work-around? (Given that the real solution is a different-better initial design.)

If yes, would this 2nd mains plug -if competently implemented- fail to pass expected or required electrical safety regs and agencies?

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Re: Background electric noise problem

Post by StillNotWorking » Mon Mar 16, 2020 11:12 am

KSS wrote:
Mon Mar 16, 2020 10:42 am
Graham Hinton wrote:
Mon Mar 16, 2020 6:16 am
Correct grounding can never be achieved using an external brick and a dc barrel jack. That is why if you see a dc jack on the outside it doesn't matter what is on the inside, it's just not going to do the job properly.
Is a secondary mains plug with only GND wired an effective work-around? (Given that the real solution is a different-better initial design.)

If yes, would this 2nd mains plug -if competently implemented- fail to pass expected or required electrical safety regs and agencies?
I think problems arise from certification has be be done with an given PSU with secondary guaranteed to be insulated from mains. And with a power brick this can't be done.
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Re: Background electric noise problem

Post by StillNotWorking » Mon Mar 16, 2020 11:22 am

KSS wrote:
Mon Mar 16, 2020 10:42 am
Graham Hinton wrote:
Mon Mar 16, 2020 6:16 am
Correct grounding can never be achieved using an external brick and a dc barrel jack. That is why if you see a dc jack on the outside it doesn't matter what is on the inside, it's just not going to do the job properly.
Is a secondary mains plug with only GND wired an effective work-around? (Given that the real solution is a different-better initial design.)

If yes, would this 2nd mains plug -if competently implemented- fail to pass expected or required electrical safety regs and agencies?
I think problems arise from certification has be be done with an given PSU with secondary guaranteed to be insulated from mains. And with a power brick this can't be done.

Edit: To clarify. With user being able to change power brick such garantie are impossible.
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Re: Background electric noise problem

Post by Graham Hinton » Mon Mar 16, 2020 1:18 pm

KSS wrote:
Mon Mar 16, 2020 10:42 am
Is a secondary mains plug with only GND wired an effective work-around? (Given that the real solution is a different-better initial design.)
Yes. It's a bodge, but it's all you can do if you want it to work. If you can find a place to attach it...
If yes, would this 2nd mains plug -if competently implemented- fail to pass expected or required electrical safety regs and agencies?
Given that the product doesn't meet any anyway?

There are regulations that apply to products being sold, what you do to them afterwards is outside their scope as long as you don't resell them.

There are professional recommended practices that are not regulated. The AES has standards for audio equipment, but they cannot be enforced. Most manufacturers outside the modular synth bubble understand that ignoring them reduces sales.

There are safety requirements within an organisation or country. UL listing is not mandatory, but shops in the US are unlikely to carry a line without it because they want to avoid liability and it might be an insurance requirement. PAT testing is not mandatory in the UK, but you do it if you have any sense.

All these are different and squaring the circle involves meeting all legal regulations for the world regions being sold in as well as accepted practise. No-one said this was easy.

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Re: Background electric noise problem

Post by Graham Hinton » Mon Mar 16, 2020 1:21 pm

StillNotWorking wrote:
Mon Mar 16, 2020 11:12 am
I think problems arise from certification has be be done with an given PSU with secondary guaranteed to be insulated from mains. And with a power brick this can't be done.
Switch mode PSUs still have mains transformers that have to be insulated. They are just not so noticeable because they work at higher frequencies and thus don't need large iron cores necessary at 50/60Hz.

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Re: Background electric noise problem

Post by KSS » Mon Mar 16, 2020 3:24 pm

Thank You Graham.

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Re: Background electric noise problem

Post by StillNotWorking » Tue Mar 17, 2020 7:17 am

Graham Hinton wrote:
Mon Mar 16, 2020 1:21 pm
StillNotWorking wrote:
Mon Mar 16, 2020 11:12 am
I think problems arise from certification has be be done with an given PSU with secondary guaranteed to be insulated from mains. And with a power brick this can't be done.
Switch mode PSUs still have mains transformers that have to be insulated. They are just not so noticeable because they work at higher frequencies and thus don't need large iron cores necessary at 50/60Hz.
I where thinking more like not all switching PSU on markedare are legal missing optocouplers and/or correct PCB spacing. When you can't have control of this certification of any added grounding schemes that potentially could make it even more dangerous seems unlikely.

Rememeber back when we had electrician upgraded our kitchen with grounded Schuko contacts he warned us "Remember now you kids only need one knitting needle to shock them self". Reason being ground pin are open on Schuko's. And yes he where rhetoric, we opted for version with pin protection where botch pins have to be inserted simultaneous.
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Re: Background electric noise problem

Post by snakejaw » Tue Mar 17, 2020 8:22 am

Graham Hinton wrote:
Wed Feb 19, 2020 7:45 am
You should be using a TS to TRS cable going to the mixer, but that won't solve the problem of your case.
Graham, could you please explain what this does?

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Re: Background electric noise problem

Post by Graham Hinton » Tue Mar 17, 2020 9:31 am

snakejaw wrote:
Tue Mar 17, 2020 8:22 am
Graham Hinton wrote:
Wed Feb 19, 2020 7:45 am
You should be using a TS to TRS cable going to the mixer, but that won't solve the problem of your case.
Graham, could you please explain what this does?
It converts an unbalanced TS jack output to a balanced TRS input. The balanced input is looking for the difference between two signals and they should be the signal output and its local 0V, which is connected to the TS screen. So TRS-R to TS-S via screened twisted pair cable. Single core cable should not be used. The TRS screen should also be connected to the TS screen, but sometimes this needs to be disconnected at the TS end. Try it connected first.
ts_trs.png
If you use a TS-TS cable it shorts the ring and screen at the input and so makes the balanced input see the difference between the signal and the input's own local 0V which will be different from the remote 0V.

StillNotWorking wrote:I where thinking more like not all switching PSU on markedare are legal missing optocouplers and/or correct PCB spacing. When you can't have control of this certification of any added grounding schemes that potentially could make it even more dangerous seems unlikely.
If you buy a PSU with certification it only applies to that product as sold, not to anything it is connected to. If somebody sells a synth, case, laptop or whatever with an external bought in PSU that is a new product that requires retesting and certification. You can't inherit the certification of another product, although its certification is required to buy it.
Rememeber back when we had electrician upgraded our kitchen with grounded Schuko contacts he warned us "Remember now you kids only need one knitting needle to shock them self". Reason being ground pin are open on Schuko's.
Schuko sockets also accept 4mm banana plug patch cables. For this reason banana plugs are illegal on audio equipment in EU, but nobody enforces that or seems to notice synths using them. Banana plugs on most test equipment are shrouded.
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Re: Background electric noise problem

Post by StillNotWorking » Tue Mar 17, 2020 10:25 am

Graham Hinton wrote:
Tue Mar 17, 2020 9:31 am
If you buy a PSU with certification it only applies to that product as sold, not to anything it is connected to. If somebody sells a synth, case, laptop or whatever with an external bought in PSU that is a new product that requires retesting and certification. You can't inherit the certification of another product, although its certification is required to buy it.
What I so clumsy tried to say in reply to KSS, but you so elegant complement using your own language :tu:
Graham Hinton wrote:
Tue Mar 17, 2020 9:31 am
Schukos don't have a ground pin, you mean Live is unshuttered.
Schuko sockets also accept 4mm banana plug patch cables. For this reason banana plugs are illegal on audio equipment in EU, but nobody enforces that or seems to notice synths using them. Banana plugs on most test equipment are shrouded.
Yes can confirm banana plugg regulation. Hi-fi guys here have to remove the dummy plug originally inserted to have gear comply with the rules.

Grounded Schuko wall socket have two spring loaded ground pins exposed. Her in Norway using Insulated Terra distribution in home residence you can shock yourself with approx half the main voltage from any phase to ground.
Image
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Re: Background electric noise problem

Post by KSS » Tue Mar 17, 2020 3:57 pm

Note, Below question is OT for Graham:
Graham Hinton wrote:
Tue Mar 17, 2020 9:31 am
and they should be the signal output and its local 0V, which is connected to the TS screen.
Is this still true for a properly designed system with TS jacks? Where I'd thought the screen *should* be connected directly to frame ground. (understood that in many or most synths TS screen is -improperly?- connected to signal 0V instead.)
-----------------
Say I have 6 Bus Bars. Single IEC AC mains input. feeding separate PSUs for Lamp digital and Audio -/+V
1) Frame GND, which is connected to all jack screens and also the metal panels and chassis construction.
2) Lamp-Digital V+
3) Lamp-Digital 0V (GND?) connects to its PSU 0V.

4) 15V+
5) 0V connects to its PSU 0V.
6) -15V

Bus Bar 1 is connected directly to Mains earth with high amperage conductor. (TE-Technical Earth, Safety GND and Screen)

1) 3) 5) connect at TE also. The "star" GND. With the connection and wiring sized for low resistance between TE and BB's 1) 3) 5)
----------------
Is that correct?

Coming back to the thread topic. If the TS jacks are actually wired to Screen instead of local signal 0V, then the TS to TRS unbal to bal you drew would be using the 'lifted' screen at the TS end version of your prior reply?

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Re: Background electric noise problem

Post by Graham Hinton » Tue Mar 17, 2020 6:10 pm

KSS wrote:
Tue Mar 17, 2020 3:57 pm
Is this still true for a properly designed system with TS jacks? Where I'd thought the screen *should* be connected directly to frame ground. (understood that in many or most synths TS screen is -improperly?- connected to signal 0V instead.)
Yes, if it has an unbalanced output, but if you can find a properly designed synth you'll find a balanced output too.
Say I have 6 Bus Bars. Single IEC AC mains input. feeding separate PSUs for Lamp digital and Audio -/+V
1) Frame GND, which is connected to all jack screens and also the metal panels and chassis construction.
2) Lamp-Digital V+
3) Lamp-Digital 0V (GND?) connects to its PSU 0V.

4) 15V+
5) 0V connects to its PSU 0V.
6) -15V

Bus Bar 1 is connected directly to Mains earth with high amperage conductor. (TE-Technical Earth, Safety GND and Screen)

1) 3) 5) connect at TE also. The "star" GND. With the connection and wiring sized for low resistance between TE and BB's 1) 3) 5)
----------------
Is that correct?
To an extent, but you are introducing undefined or vaguely defined terms.

Is this hypothetical or something you have? It would depend on what the "lamp-digital" power is used for and how that needs to be referenced to the analogue supply. Most theory in this area revolves around single pieces of equipment, not large modular systems. You have to examine where currents are flowing because there will always be a voltage drop and the aim is to pull 0Vs in different parts together rather than force them apart.
Coming back to the thread topic. If the TS jacks are actually wired to Screen instead of local signal 0V, then the TS to TRS unbal to bal you drew would be using the 'lifted' screen at the TS end version of your prior reply?
No. The object of a screen is to create a non-current carrying layer over everything. If both the synth and mixer conform to this principle (aka AES48) the screening should be continuous and the differential amplifier needs the remote 0V as a reference. It would be better it the unbalanced jack were converted to a pseudo balanced output using the local 0V on the cold side.

The reason for lifting the screen is that the synth is poorly designed and would use the screen as a signal return path. In this case an isolating transformer would be preferable (if the input doesn't have one). It depends on if the synth stays within the mixer's common mode range.

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Re: Background electric noise problem

Post by snakejaw » Tue Mar 17, 2020 6:35 pm

Thanks for answering my question, Graham, and for all the help you provide on Muffs.
Last edited by snakejaw on Wed Mar 18, 2020 10:39 pm, edited 5 times in total.

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Re: Background electric noise problem

Post by KSS » Tue Mar 17, 2020 7:07 pm

continued OT
Graham Hinton wrote:
Tue Mar 17, 2020 6:10 pm
To an extent, but you are introducing undefined or vaguely defined terms.
Is this hypothetical or something you have?
It's a work in progress. Not hypothetical.
It would depend on what the "lamp-digital" power is used for and how that needs to be referenced to the analogue supply.

Curently the lamp-digital is used for lamp only, and does not present any problems. Using the lamp supply to support future digital modules seems worth trying to get right. Typical dirty-clean power separation.
Most theory in this area revolves around single pieces of equipment, not large modular systems. You have to examine where currents are flowing because there will always be a voltage drop and the aim is to pull 0Vs in different parts together rather than force them apart.
This is the expected answer and confirms the path I've taken. Thank you.
---------------------------
/OT
Graham Hinton wrote: No. The object of a screen is to create a non-current carrying layer over everything. If both the synth and mixer conform to this principle (aka AES48) the screening should be continuous and the differential amplifier needs the remote 0V as a reference. It would be better it the unbalanced jack were converted to a pseudo balanced output using the local 0V on the cold side.
Italicized portion makes sense as solution if-when possible.
The reason for lifting the screen is that the synth is poorly designed and would use the screen as a signal return path. In this case an isolating transformer would be preferable (if the input doesn't have one). It depends on if the synth stays within the mixer's common mode range.
Thank you.

At the top of your reply you suggested that a properly designed synth would have balanced output too. (Bolding mine) For clarity, are you speaking of what might be expected as 'final' output? Or do you mean that a modular synth should employ balanced I/O throughout. i.e., between modules?

Asking because the work in progress synth means to eliminate all 0V signal returns on screen leg of TS jacks. Screen being screen. Seeing that you were pulling -in your drawing- from the more commonly seen use of screen as 0V signal return; instead of true screen is what prompted the initial question. Because there wouldn't be any access to signal 0V at any TS jack. Only signal and screen. Which I'd understood as a preferable situation compared to what's commonly seen in classic and present modular synths. I was considering that any such TS jack 'could' end up being final output in a modular patch, and trying to understand how that would fit into the drawing you shared.

I'm now understanding? that you meant this drawing to be applied to an expected and normal output module or circuit. And that such a module or expected output portion of the circuit should be better designed in the first place to interact with outboard gear.

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Re: Background electric noise problem

Post by Graham Hinton » Wed Mar 18, 2020 8:53 am

KSS wrote:
Tue Mar 17, 2020 7:07 pm
Curently the lamp-digital is used for lamp only, and does not present any problems. Using the lamp supply to support future digital modules seems worth trying to get right. Typical dirty-clean power separation.
You can only keep digital separate if it is totally isolated at every point.
Calling something dirty or clean does not make it so. You need very rigorous design rules and in an open system any third party manufacturer can wreck the scheme.
At the top of your reply you suggested that a properly designed synth would have balanced output too. (Bolding mine) For clarity, are you speaking of what might be expected as 'final' output? Or do you mean that a modular synth should employ balanced I/O throughout. i.e., between modules?
You cannot keep expanding an unbalanced system indefinitely, the more you spend the worse it gets. If a sub-£200 mixer can have balanced I/O on every jack there is no reason why synthesizer modules can't apart from ignorance.

Balanced outputs are not necessarily line drivers too, but a main output should be both.
Because there wouldn't be any access to signal 0V at any TS jack. Only signal and screen. Which I'd understood as a preferable situation compared to what's commonly seen in classic and present modular synths. I was considering that any such TS jack 'could' end up being final output in a modular patch, and trying to understand how that would fit into the drawing you shared.
If you have screened TS jacks they can only be used within that system and if you use it for final output the screen becomes a signal path. If the system is grounded for safety the Earth in the mains lead becomes part of the signal path too. If you have multiple unbalanced devices then a 0V path of much lower resistance than the cable screens and mains leads in parallel is required.
I'm now understanding? that you meant this drawing to be applied to an expected and normal output module or circuit.
Yes, the drawing was to clarify the answer to the question asked. It is the first thing to try before wasting money on mains conditioners and DI boxes.

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Re: Background electric noise problem

Post by BugBrand » Wed Mar 18, 2020 9:27 am

Graham Hinton wrote:
Wed Mar 18, 2020 8:53 am

Balanced outputs are not necessarily line drivers too, but a main output should be both.
Oh, that's an interesting point, not something I'd come across before.
How would you define a line driver?

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Re: Background electric noise problem

Post by KSS » Wed Mar 18, 2020 11:07 am

Thank You Graham. Always appreciate your insight, experience and continued willingness to share.

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Re: Background electric noise problem

Post by Graham Hinton » Wed Mar 18, 2020 12:40 pm

BugBrand wrote:
Wed Mar 18, 2020 9:27 am
How would you define a line driver?
Something with <50 ohms output impedance that can cope with 100m or more of cable. Common or garden op amps are usually good for 20m to 40m, less if they have 1k output resistors.

Again, if you look at the ubiquitous <£200 mixer the main stereo outputs will be beefier than the others. Typical usage would be local FX interfacing and then a long run, e.g. stage to FOH.

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Re: Background electric noise problem

Post by BugBrand » Wed Mar 18, 2020 3:33 pm

Thanks Graham - had come across the term before & figured it must be something along those lines, but I'd not have known it was viewed as a standard part of such designs.

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Re: Background electric noise problem

Post by snakejaw » Wed Mar 18, 2020 11:59 pm

Graham Hinton wrote:
Tue Mar 17, 2020 9:31 am
snakejaw wrote:
Tue Mar 17, 2020 8:22 am
Graham Hinton wrote:
Wed Feb 19, 2020 7:45 am
You should be using a TS to TRS cable going to the mixer, but that won't solve the problem of your case.
Graham, could you please explain what this does?
It converts an unbalanced TS jack output to a balanced TRS input. The balanced input is looking for the difference between two signals and they should be the signal output and its local 0V, which is connected to the TS screen. So TRS-R to TS-S via screened twisted pair cable. Single core cable should not be used. The TRS screen should also be connected to the TS screen, but sometimes this needs to be disconnected at the TS end. Try it connected first.

ts_trs.png

If you use a TS-TS cable it shorts the ring and screen at the input and so makes the balanced input see the difference between the signal and the input's own local 0V which will be different from the remote 0V.
Related, is this correct?

https://www.soundonsound.com/forum/view ... 15&t=66035

"Oh... and bear in mind that pseudo-balanced cables are only of use with synths that have grounded power supplies. If used with synths that have double-insulated supplies (most of those with wall-warts) it will usually make unwanted noises worse!"

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Re: Background electric noise problem

Post by Graham Hinton » Thu Mar 19, 2020 9:25 am

snakejaw wrote:
Wed Mar 18, 2020 11:59 pm
Related, is this correct?

https://www.soundonsound.com/forum/view ... 15&t=66035
Since none of them are defining the cable wiring, who knows what they are talking about?
"Oh... and bear in mind that pseudo-balanced cables are only of use with synths that have grounded power supplies. If used with synths that have double-insulated supplies (most of those with wall-warts) it will usually make unwanted noises worse!"
I would expect a SOS designed cable to make it worse. Take all the filler between adverts with a pinch of salt.

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Re: Background electric noise problem

Post by snakejaw » Thu Mar 19, 2020 11:14 am

Phew! Thanks.

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Re: Background electric noise problem

Post by anre » Thu Mar 19, 2020 11:34 pm

I think our psus does a really great job since is the first time someone experience a noise problem which btw I'm pretty sure, like you said at the end, comes from the modules itself.
The case itself is great. I don't know all the technical details but the new GSM powerbrick does its job and I don't have any ground noises anymore. This was my fault in using the wrong type of power brick. The only noises I still have are 1kHz produced by modules Antumbra Atom in greater extent and less with After Later Audio uBurst, the both are built by same manufacturer After Later Audio and have similar power specs. Saying ''That seems to be the case" I agreed on the fact that the modules are scanning for the knob values and this may cause such noise (this is a case of ambiguousness in English language using the word CASE that I didn't realise when posted my answer, because it is not my native language). I don't agree with the statement that the MODULAR CASE is somehow doen't meet my requirements, in opposite by I'm totally satisfied with it and this is the best what I could have found on the market, especially with all customisations that they offered to me. May be some "true" modular systems are built with conventional linear power, but I don't need it. I needed a compact and light solution that would be convenient for travelling and inspirational for my eyes and I'm happy that I have it now.

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Re: Background electric noise problem

Post by snakejaw » Fri Mar 20, 2020 4:05 pm

Would installing a module like the intellijel Audio I/O (in a case with an external wall wart PSU) and then connecting the inputs and output between the case and the mixer via the Audio I/O's balanced jacks "solve" the problem?
Audio-IO-3U-2018-161x408.jpg
intellijel Audio I/O


Or, would it just be preferable to, as suggest, just use a TS to TRS cable, that was previously referenced, from the case to the mixer, and use a TRS to TS cable, per below, for going from the mixer to the case?
TRS to TS cable.png
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