Author Topic: Hiss with AC-DC buck supply: how shielding ?  (Read 6580 times)

0 Members and 1 Guest are viewing this topic.

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #75 on: December 16, 2017, 03:40:08 am »
You can simply make a cable where the shielding is soldered to the connector only one side, you know  ;)
Probably easier than messing with your pedals.
What you need is that any wire going between two devices  has the shield connected only on one side (doesn't matter which one).


I did the test only with the two critical pedals, ie the Zoom / Arduino + Wah Wah + a single cable, with shielding connected only on one side, to connect the Zoom output to the input of wah wah but unfortunately the TAP TAP did not go away and it was added even the noise of an airliner parked during taxiing

https://youtu.be/zWUQr6lTicM?t=108
 

Offline janoc

  • Super Contributor
  • ***
  • Posts: 2813
  • Country: fr
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #76 on: December 16, 2017, 07:56:30 am »
You can simply make a cable where the shielding is soldered to the connector only one side, you know  ;)
Probably easier than messing with your pedals.
What you need is that any wire going between two devices  has the shield connected only on one side (doesn't matter which one).


I did the test only with the two critical pedals, ie the Zoom / Arduino + Wah Wah + a single cable, with shielding connected only on one side, to connect the Zoom output to the input of wah wah but unfortunately the TAP TAP did not go away and it was added even the noise of an airliner parked during taxiing

https://youtu.be/zWUQr6lTicM?t=108

How did you connect the power? Did you use the star grounding? If you only remove the ground and don't fix the rest, it will not work! In fact, it will be worse because now the ground return path for the signal is even worse than before.
 

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #77 on: December 16, 2017, 09:24:18 am »
How did you connect the power? Did you use the star grounding?

I used two terminal strips, on one I set the positive of the power and on the other the negative of the power. In the first I then connected the positive of the two pedals and on the other terminal I connected the two negatives.

If you only remove the ground and don't fix the rest, it will not work!

"fix the rest"... what do you mean?

Edit:

I mean that I seem to have done as you said or I missed something ?
« Last Edit: December 16, 2017, 10:08:28 am by mauros »
 

Offline janoc

  • Super Contributor
  • ***
  • Posts: 2813
  • Country: fr
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #78 on: December 17, 2017, 12:07:44 am »
How did you connect the power? Did you use the star grounding?

I used two terminal strips, on one I set the positive of the power and on the other the negative of the power. In the first I then connected the positive of the two pedals and on the other terminal I connected the two negatives.

If you only remove the ground and don't fix the rest, it will not work!

"fix the rest"... what do you mean?

Edit:

I mean that I seem to have done as you said or I missed something ?

By "rest" I meant implementing the star grounding.

How is the arduino connected? Also by its own pair of wires to the two terminal strips? It would help if you could draw a diagram again how did you connect everything together.

Now for debugging it - if you remove the Arduino and leave only the pedals setup like this - is it still noisy? (power the Zoom from 9V directly, not through USB).

 

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #79 on: December 17, 2017, 01:30:00 am »
Now for debugging it - if you remove the Arduino and leave only the pedals setup like this - is it still noisy? (power the Zoom from 9V directly, not through USB).

I do not remember if I wrote it but I think it has already said in some of my message that without Arduino I have no kind of noise, connecting it directly to 9V ( NO USB ) and even in daisy chain. It is its presence in the pedal board the cause of all the strange noises, from the ticking with the PSU switching to the humming at 50 Hz with linear power supply with transformer.
 

Offline janoc

  • Super Contributor
  • ***
  • Posts: 2813
  • Country: fr
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #80 on: December 17, 2017, 06:30:12 am »
Now for debugging it - if you remove the Arduino and leave only the pedals setup like this - is it still noisy? (power the Zoom from 9V directly, not through USB).

I do not remember if I wrote it but I think it has already said in some of my message that without Arduino I have no kind of noise, connecting it directly to 9V ( NO USB ) and even in daisy chain. It is its presence in the pedal board the cause of all the strange noises, from the ticking with the PSU switching to the humming at 50 Hz with linear power supply with transformer.

That's a bit of a red herring.

In your original setup (with the bad ground system), the Arduino has been in the ground return path of *every single signal* on that pedal board. So no wonder you had problems. Any noise it generated or picked up got added to your signals.

I suggest the following to make sure we are able to get rid of the tap tap noise first (that one is added by the digital MIDI signal).

Connect only the Arduino and your Zoom. Remove any other pedals from the signal chain - you can leave them powered, just remove any signal wires. (don't forget to connect the shielding of the cable to your amplifier and from your guitar to the ground of the Zoom/pedal board!)

Is it noisy like this? Do you hear the tapping noise or any other unusual noise? Is the noise still there if you short the input of the Zoom to ground?

If it is still noisy (tapping noise), then the problem is definitely with the Arduino/USB shield noise getting into the Zoom and the Zoom not having it properly filtered internally. That could be a really difficult issue to solve without modifying the device. In such case try to power the Zoom from a separate power supply (not just over USB). If it doesn't help even like that, then we are pretty much screwed.

If it isn't noisy like this, unplug power, take your multimeter and measure resistance between the ground of the input plug and the negative power supply wire. It should be very low (ideally dead short). If it isn't, then the Zoom has separate grounds for the digital and analog parts and you may need to add a grounding connection between the input connector and the star grounding point.

Once you have things working and noise free, continue connecting the other hardware one by one. If the setup suddenly gets noisy, you will know why and can investigate right away.

« Last Edit: December 17, 2017, 06:34:29 am by janoc »
 
The following users thanked this post: ez24

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #81 on: December 17, 2017, 11:56:10 am »

If it isn't noisy like this, unplug power, take your multimeter and measure resistance between the ground of the input plug and the negative power supply wire. It should be very low (ideally dead short).
Between the negative of the Power Supply and the input ground i measure about 17 Ohms .

If it isn't, then the Zoom has separate grounds for the digital and analog parts and you may need to add a grounding connection between the input connector and the star grounding point. 
Signal input connector ?
 

Offline janoc

  • Super Contributor
  • ***
  • Posts: 2813
  • Country: fr
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #82 on: December 18, 2017, 02:43:14 am »

If it isn't noisy like this, unplug power, take your multimeter and measure resistance between the ground of the input plug and the negative power supply wire. It should be very low (ideally dead short).
Between the negative of the Power Supply and the input ground i measure about 17 Ohms .


Yikes. OK that's not good but not totally unexpected neither (separated signal and digital grounds are common to reduce noise). In that case connect one grounding wire between the input ground of the Zoom and your star grounding point. That should solve that particular issue.

If it isn't, then the Zoom has separate grounds for the digital and analog parts and you may need to add a grounding connection between the input connector and the star grounding point. 
Signal input connector ?

Your Zoom is a guitar effect processor, no? So it has one (or more) jack where the guitar signal comes in and one (or more) jack where the processed signal comes out, doesn't it? That's what I mean by "input connector". In order to eliminate hums and other noises you have to have a low impedance path to ground for the signal. Since you have measured 17 ohms between the input jack and the power connector, we can't rely just on the path through the power supply (17 ohms is not really "low impedance" by any measure).  That's why the added grounding wire is needed.

If you don't want to mess with the wires, try first to connect the signal cables with the shielding connected on both sides (the usual way). That will add that signal ground where needed. It is not ideal (you could get ground loops and hum) but at least if the power wiring is fixed (i.e. separate power/ground wire pair for each device), it is less likely to cause issues than before. Only if this doesn't work then some more drastic measures will be needed.
« Last Edit: December 18, 2017, 02:48:54 am by janoc »
 

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #83 on: December 18, 2017, 04:07:38 am »
...connect one grounding wire between the input ground of the Zoom and your star grounding point. That should solve that particular issue.

I understood what you say, to reset the ddp between the two points but connecting the ground of the Zoom input with star ground ( 23 Ohm) i hear a bump from the amp speaker and the Zoom goes off. I immediately terminated the connection for fear of some failure.
 

Offline janoc

  • Super Contributor
  • ***
  • Posts: 2813
  • Country: fr
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #84 on: December 18, 2017, 08:40:04 am »
...connect one grounding wire between the input ground of the Zoom and your star grounding point. That should solve that particular issue.

I understood what you say, to reset the ddp between the two points but connecting the ground of the Zoom input with star ground ( 23 Ohm) i hear a bump from the amp speaker and the Zoom goes off. I immediately terminated the connection for fear of some failure.

 Oops. Take your multimeter and measure whether the Zoom doesn't have a voltage between the input signal ground and power ground. That sounds like you have managed to make a short circuit somewhere.

And what is the "ddp"? I don't know that term.
 

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #85 on: December 18, 2017, 10:48:02 am »
Oops. Take your multimeter and measure whether the Zoom doesn't have a voltage between the input signal ground and power ground. That sounds like you have managed to make a short circuit somewhere.

And what is the "ddp"? I don't know that term.

Ops, I wrote the acronym in Italian --> ddp = voltage (difference of potential)

Anyway, i tried to put two separate power supplies and while I remembered that it did not make noise, instead the noise exists, no tapping but high frequency noise, but only when the wahwah is pressed down (all sounds sharp). At this point, the only solution without noise is a pair of power bank or my dual power supply in which the hum would eliminate it with the mumetal (but uncomfortable).
In my opinion, as you said, i should find a drastic solution. What do you mean by drastic?
 

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #86 on: December 19, 2017, 05:34:58 am »
Since next week I have to play live, today i tried all the possible power supply combinations that i own :D and for now i found this quite silent solution: the Truetone for the 4 analog pedals, including the wah wah, and the stock power supply for Zoom G3, placing both in a power strip under the pedalboard, as in this photo http://www.johnhendow.com/wp-content/uploads/2012/04/underside-2.jpg
 

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #87 on: December 19, 2017, 08:42:45 am »
Given the cable Truetone is quite long and fat I tried to replace it with another Zoom AD16E
https://tinyurl.com/yafgllf5
but I noticed that a noise is generated that I never heard, like the roar of a lion :D I removed one of the two Zoom AD16E and the I connected it to the wall socket and at that point the lion ran away, instead I would rather keep both in the same power strip
 

Offline janoc

  • Super Contributor
  • ***
  • Posts: 2813
  • Country: fr
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #88 on: December 19, 2017, 09:35:33 am »
Oops. Take your multimeter and measure whether the Zoom doesn't have a voltage between the input signal ground and power ground. That sounds like you have managed to make a short circuit somewhere.

And what is the "ddp"? I don't know that term.

Ops, I wrote the acronym in Italian --> ddp = voltage (difference of potential)


Ah OK. That sounds like the Zoom is a rather particular gadget, with separate grounds and what not.

Anyway, i tried to put two separate power supplies and while I remembered that it did not make noise, instead the noise exists, no tapping but high frequency noise, but only when the wahwah is pressed down (all sounds sharp). At this point, the only solution without noise is a pair of power bank or my dual power supply in which the hum would eliminate it with the mumetal (but uncomfortable).

Hmm, that seems that the pedals are picking up switching noise from the switching power supply. That supply needs more output filtering, then.

Two power supplies will certainly eliminate the tap-tap because now the Arduino is not sharing the power rails with anything else, so any noise cannot propagate further.

In my opinion, as you said, i should find a drastic solution. What do you mean by drastic?

Well, drastic as in modifying some of the hardware or inserting transformers and such but you seem to have found a combination that works for you in the meantime.

Since next week I have to play live, today i tried all the possible power supply combinations that i own :D and for now i found this quite silent solution: the Truetone for the 4 analog pedals, including the wah wah, and the stock power supply for Zoom G3, placing both in a power strip under the pedalboard, as in this photo http://www.johnhendow.com/wp-content/uploads/2012/04/underside-2.jpg

Why not? If it works, good enough!  :-+


Given the cable Truetone is quite long and fat I tried to replace it with another Zoom AD16E
https://tinyurl.com/yafgllf5
but I noticed that a noise is generated that I never heard, like the roar of a lion :D I removed one of the two Zoom AD16E and the I connected it to the wall socket and at that point the lion ran away, instead I would rather keep both in the same power strip


LOL! That sounds like a missing signal ground connection somewhere. Or a feedback. The fact that it goes away when the supplies are not on the same power strip points to the missing ground - in such case the signal will "find its way" elsewhere (such as through the supplies on the same power strip), with all sorts of nasty consequences. Check that all your pedals and the Zoom have actually a common ground connection - if you are using 2 power supplies, the grounds need to be connected together at the star grounding point.

 

Offline mauros

  • Regular Contributor
  • *
  • Posts: 72
Re: Hiss with AC-DC buck supply: how shielding ?
« Reply #89 on: December 20, 2017, 07:59:48 am »
For now I leave everything as it is and I will try this assembly when I go to play for two/three hours continued. Instead I would like to solve another problem for which I will open a new thread. I own two Zoom, one is the one I use with the problems of hiss and noise already treated in this thread and the other Zoom identical to the first one where I have to replace the LCD display that the parent company does not release as spare and I have to arrange myself but I would like to understand how to find what is right for me
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf