PreenFM Forum

PreenFM => PreenFM2 => Topic started by: Xavier on April 03, 2016, 02:05:52 PM

Title: Yellow OLED : high frequency solution
Post by: Xavier on April 03, 2016, 02:05:52 PM
Situation : Yellow OLED display have a big inductor that sends a 13.5Khz sin wave in the preenfm2 audio path.

Yellow OLED solution

I spent some time trying to find a solution to this problem, and i have somthing really efficient.
Look at the After and Before screenshot.

If you have a PCB R5d (or +) : solder a 22ohm at the "oled" position and go to step 4 directly... DON't do step 1,2,3.

If you have a PCB R5c (or -) : step 1,2 and 3 is for you.

The idea is to put a resistor 22 (ohm) between the LCD and the preenfm2 5V.
As there's no direct possibility, we'll use the Led+ pins (pin 15 of the LCD) that is not used with OLED display and where we can insert a resistor.

Step 1 : put a 22 ohm in the 68 ohm slot... this resistor is between the 5v and the pin 15 of the display.
Step 2 : cut the pin 2 of the OLED so that it's disconnected from the preenfm2 5V.
Step 3 : Link the pin 2 and 15 on the Display. Now the Oled is powered throught the 22 ohm resistor and get around 4v.
Step 1 to 3 makes the parasit frequency much more sensitive to shield. I think it removes almost totally the electronic noise but the magnetic noise is still there.

Step 4 : build a shield with many alumnium sheets that you use for food. you may have that in your kitchen.
The more you put the more efficient it is.
Take a 22cm x 22cm, fold 1 time then 2 times horizontaly, same thing vertically. You get 16 layers.
Do that with 4 sheets to get at least 64 layers.
Put that in a plastic bag (antistatic may not hurt) and add some tape. Be sure no aluminium will touch the contact.

Step 5 : put your shield under the screen.

Step 6 : Let me know :)

Xavier
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on April 03, 2016, 02:06:39 PM
Details screenshots....
Title: Re: Yellow OLED : high frequency solution
Post by: clément on April 03, 2016, 03:02:53 PM
Oh nice Xavier! Gotta try it out soon thanks for taking your time looking into this :)
Title: Re: Yellow OLED : high frequency solution
Post by: jarilo on April 04, 2016, 11:15:18 PM
Done and done, 64 layers of alu foil, wrapped in antistatic bag twice and then sticky tape (not sure if antistatic bag can damage something, just to be sure).

High pitch noise is drastically reduced just by adding this shield. (sadly, I didn't try to make a shield as proposed by clément, I suppose I was too lazy to cut and solder perfboards :) )

I didn't hear any difference with or without 22 ohm resistor, but I was only using my ears for testing, as I don't have oscilloscope... After soldering, I used soundcard oscilloscope (didn't come to my mind earlier), and peak is much lower with shield.

I am thinking about making (some day) shield out of thin steel sheet, like on RF tuners, this could maybe lower magnetic noise...

Thanks very much,
Djordje
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on April 04, 2016, 11:35:14 PM
The 22 ohms resistor alone does not change anything.

You have to cut the pin 2 of the OLED header then link pins 2 and 15... See the red wire on the picture above and the missing pin between the OLED and the preenfm PCB.
I remove the whole pin but simply cutting it on the OLED side will work.

Then yes it's really worth it...

Title: Re: Yellow OLED : high frequency solution
Post by: jarilo on April 05, 2016, 02:26:05 AM
Yes, I did cut the pin from oled. I forgot to say most important thing, that I did all modifications :D

I was comparing (by naked ear) first only with shield, and after that shield+resistor+modified oled pcb. It was silly to compare it, because it is impossible for me to determine volume of sound of such high frequency by ear...
What I wanted to say is that I was pleased with results even when using only shield. (but did all of the modifications nonetheless)

Anyway, after playing with it for a few hours, I can confirm that I can no longer hear high pitched sine through my speakers, but I can hear it from preenfm2 box (I have moved box 3 meters away from speakers to be sure).
This is what clement mentioned in other thread, probably coil oscillating.

As high-pitched noise is practically eliminated in signal, I am no longer motivated to try a steel shield. :)

Thanks,
Djordje
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on April 05, 2016, 09:28:52 AM
From my experience, with the shield only I could decrease the parasite by 10dB at best.
With the full modification i achieved a 35dB improvement.

You can check easily check with voxengo SPAN (http://www.voxengo.com/product/span/).
You should place your shield with SPAN active because a 3mm position move can easily lead to a difference of 6dB or more.

Xavier
Title: Re: Yellow OLED : high frequency solution
Post by: clément on April 21, 2016, 11:55:49 AM
I gave it a shot and the results seem to be great indeed, thanks Xavier! :)
Title: Re: Yellow OLED : high frequency solution
Post by: jarilo on May 15, 2016, 03:40:45 PM
Tested in rehearsal studio situation (finally), works perfectly, no high-pitched noise here. I've turned the mixer volume as high as it goes, to the point where I hear (relatively) loud white noise, and there is no ~15kHz peak.

I haven't yet come to measuring it with real tools, but I am perfectly satisfied with this, as it can be used in live situation, as far as me and my people are concerned.

Thanks again,
Djordje
Title: Re: Yellow OLED : high frequency solution
Post by: alien_brain on May 17, 2016, 04:46:13 PM
could it be that i dont have the same issue for some reason?  i have the yellow OLED too
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on May 17, 2016, 08:37:01 PM
could it be that i dont have the same issue for some reason?  i have the yellow OLED too

It's more likely that you don't hear it.
Most people don't hear a low level 15Khz sin (I don't hear it at all).
Title: Re: Yellow OLED : high frequency solution
Post by: lokki on July 08, 2016, 04:52:36 PM
hi xavier,

i put a 68ohm instead of 22ohm in there, is it also ok? everything seems to work, so i thought i ask why exactly you choose the 22ohm value? (brightness maybe?)

also note that this "mod" cures my problem with power feeding from the macbook air (if you remember). so it seems the display was the current hungry thing that made the macbook air struggle.

cheers
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on July 08, 2016, 11:04:56 PM

Hi,

With a 68 ohm resistor, the OLED is darker, and it is powered by around 2.5V although the OLED requires between 3.3 and 5.0V.
If it works for you and if you like dark OLED, that's fine  ;)

With this resistor, it's possible that the overall current requires by your preenfm2 is smaller. So it's now small enough to be powered by your macbook air.

Xavier
Title: Re: Yellow OLED : high frequency solution
Post by: lokki on July 08, 2016, 11:31:30 PM
ok, thanks for the clarification. strange, it does not look darker at all! surely perfectly useable for my purposes.

the aluminium shield / resistor mod combo works wonders, thanks for this simple fix! i put 128 layers of aluminium between the display and the pcb and i cannot see (or hear) any spike in voxengo span. this is with the internal input (gain maxed out) on a macbook pro. with 64 layers i could still see a small spike.
Title: Re: Yellow OLED : high frequency solution
Post by: tubeohm on September 13, 2016, 02:53:26 PM
Details screenshots....

 Hi Xavier - i noticed this peak on - 70 dB . This you normally can't hear . Have you set the Slope on the FFT to zero ( linear )
Specially this FFT had a slope function that enhances   the high frequencies  up to 6 dB  and its is on - on default .
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on September 13, 2016, 11:13:33 PM
Without the modification described in this thread., some people hear this peak.
As you use PCB R5d you already have step 1,2,3 done by just soldering the 22ohm OLED resistor, so the peak is smaller that it was on PCB R5c.
If you make a shield as described it will be even smaller.
Title: Re: Yellow OLED : high frequency solution
Post by: kylelandstra on January 31, 2017, 05:09:18 AM
Just a quick question on the aluminum shield mod:  Do you just stuff the bag between the OLED screen and the PCB?  Do you secure it all?  Is it okay if the bag is touching the board?
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on February 01, 2017, 10:06:57 AM
Just a quick question on the aluminum shield mod:  Do you just stuff the bag between the OLED screen and the PCB?  Do you secure it all?  Is it okay if the bag is touching the board?

As far as only plastic touch the board it's totally OK.
Title: Re: Yellow OLED : high frequency solution
Post by: mmontag on February 13, 2017, 11:05:04 PM
I definitely noticed the squeak after upgrading to OLED, but the shield fix was easy and effective. No extra soldering needed with the recent board revisions. Thanks Xavier.

 :D
Title: Re: Yellow OLED : high frequency solution
Post by: served on May 24, 2017, 12:38:39 PM
Hi.

We have now had some time to test the noise issues.

Some remarks:
We have tested various inductors, to look for a low-noise unit that may have some better characteristics. No success in practice.

We have stopped producing and adding the metal sheet behind the screen. It shields the noise from the audio, but produces a new issue. Physical noise in the unit.

So the new Rev2 solution is a Aliuminium tape + coppertape with soldered cable and grounded + Plastic tape for isolation.
A Grounding cable will give you better shielding properties.

We are now basically following Xavier solution except added a GND cable.
Title: Re: Yellow OLED : high frequency solution
Post by: sixbyseven on November 01, 2017, 02:21:05 PM
Sorry, (I am new to this conversation), if these questions don't seem relevant.

1) Does this same signal (around 14Khz) appear when the OLED is in sleep mode (blank).
2) Has anyone tried a different colour OLED (example:Blue) from the same manufacturer?

Thank you,

Todd
Title: Re: Yellow OLED : high frequency solution
Post by: Godric on November 27, 2017, 01:06:12 PM
I made a shield as described, which seems to be working (at least I'm not aware of any noise). I was then sent a shield by Ardi at Vandaal, as it (and a volume knob) had been missing from the kit when it was posted out.

I notice Ardi's shield has a wire soldered to it and I assume that the other end needs to go to Ground or 0V. Any suggestions about the best place to solder this shield to?

Godric
Title: Re: Yellow OLED : high frequency solution
Post by: Godric on November 27, 2017, 07:08:11 PM
I'm assuming the power connector ground would be a good place?
Title: Re: Yellow OLED : high frequency solution
Post by: lokki on November 27, 2017, 09:00:00 PM
yes, that would be ok.
Title: Re: Yellow OLED : high frequency solution
Post by: molpho on February 11, 2018, 10:12:02 PM
Hi! I bought a Preenfm2 from Van Daal. I'm really loving it, but I hear the "OLED noise" and since I don't know anything about soldering and DIY I was wondering if there is a way to delete that freq without affecting the timbre of my patches... may I use an eq? could be enough?
Title: Re: Yellow OLED : high frequency solution
Post by: clément on February 12, 2018, 05:10:09 PM
If you are monitoring through a DAW you may use an EQ around 15.5 kHz with a really narrow bandwidth, that will work and should be quite discreet.
Title: Re: Yellow OLED : high frequency solution
Post by: molpho on February 15, 2018, 09:56:26 AM
Thank you clément, I'll try to follow your advice!
Althought maybe I'll look for someone in my region capable to accomplish Xavier's trick.
thanks again
Title: Re: Yellow OLED : high frequency solution
Post by: ladyday on December 11, 2018, 10:11:58 PM
Hello to all!
I am a newbie here.
I bought an assembled blue preenfm2 and I can hear the high noise that you are talking about.
It seems that if I use earphones it disappear.
Now, my problem is very big: I can't solder and I have no one that can help me.
The noise is a big problem to use the preen in the studio.
And now I have to use it in Conservatory too for my studies.

PLEASE: CAN YOU HELP ME?!

THANKS A LOT
Title: Re: Yellow OLED : high frequency solution
Post by: Xavier on December 12, 2018, 08:35:14 AM
EDITED : i thought it was a blue OLED. Seems like it's a yellow OLED in a blue metal box ;)

Hello,

I have a blue OLED and it makes lots of noise (not the 13.5Khz noise though), unfortunately i don't have a solution for the blue OLED.
The only solution you have if you cannot modify the hardware is to have a look at the noise with a spectrum analyser and set an EQ to remove it.

Xavier
Title: Re: Yellow OLED : high frequency solution
Post by: served on December 13, 2018, 06:17:01 AM
We will solve it. Its a yellow OLED screen.

Hello to all!
I am a newbie here.
I bought an assembled blue preenfm2 and I can hear the high noise that you are talking about.
It seems that if I use earphones it disappear.
Now, my problem is very big: I can't solder and I have no one that can help me.
The noise is a big problem to use the preen in the studio.
And now I have to use it in Conservatory too for my studies.

PLEASE: CAN YOU HELP ME?!


THANKS A LOT

Title: Re: Yellow OLED : high frequency solution
Post by: kreeper_6 on December 14, 2018, 06:22:08 AM
I just built one with a Newhaven Blue OLED and have no noise from what I can hear and see. Is there something that needs to be done for it to manifest?

Last I looked into general OLED issues the Newhaven, Vishay and Raystars were all the same boards, correct?
Title: Re: Yellow OLED : high frequency solution
Post by: served on December 14, 2018, 07:38:42 AM
I just built one with a Newhaven Blue OLED and have no noise from what I can hear and see. Is there something that needs to be done for it to manifest?

Last I looked into general OLED issues the Newhaven, Vishay and Raystars were all the same boards, correct?

Its very high pitch noise. So it depends on your hearing. Best would be if you look at it by running Preen into your soundcard and looking at the spectrum graph. It should present a peak in 15-16kHz region.
The loudness varies on different things. So you might be lucky or you might not hear it. The boards seem to be the same, but components on the boards vari.
Title: Re: Yellow OLED : high frequency solution
Post by: kreeper_6 on December 15, 2018, 04:47:28 AM
Its very high pitch noise. So it depends on your hearing. Best would be if you look at it by running Preen into your soundcard and looking at the spectrum graph. It should present a peak in 15-16kHz region.
The loudness varies on different things. So you might be lucky or you might not hear it. The boards seem to be the same, but components on the boards vari.

I think it would help if those with issues referenced the part number of the OLED installed. I will be trying out various OLEDs available to me (Newhaven/Vishay) and post my results.

Newhaven Blue NHD-0420DZW-AB5

(https://i.imgur.com/mzdiXY3l.jpg)

(https://i.imgur.com/QLNgIbJl.jpg)
Title: Re: Yellow OLED : high frequency solution
Post by: clément on December 15, 2018, 10:03:22 AM
I posted mine somewhere in the forum, other members did.
But I'm so glad to see your results! You are not using any shielding like it's mentioned in this topic?
Title: Re: Yellow OLED : high frequency solution
Post by: kreeper_6 on December 15, 2018, 07:12:29 PM
I posted mine somewhere in the forum, other members did.
But I'm so glad to see your results! You are not using any shielding like it's mentioned in this topic?

No shielding and using the latest PCB. I didn't even know there were issues with OLED as it seemed to be the standard choice for the preenfm.
Title: Re: Yellow OLED : high frequency solution
Post by: served on December 18, 2018, 06:55:02 AM
I can confirm that Blue OLED screen from Newheaven does work. No whining noise.
But it has issues with the pixcels brightness and it sometimes skips as the signal level is probably on the low limit.
Title: Re: Yellow OLED : high frequency solution
Post by: maximee on December 18, 2018, 05:57:47 PM
Hi all, thanks for sharing your recent discoveries about the different OLED types.

I'm eager to try a different display myself, because I couldn't sufficiently tame the noise issue.
I was going to try to replace the inductor with a shielded one, but from what I see the results on the spectrum posted above look much nicer.

Too bad those OLEDs aren't exactly cheap. Would love to keep my PreenFM yellow – will post back when/if I try it with the NHD-0420DZW-AY5.

Title: Re: Yellow OLED : high frequency solution
Post by: served on January 05, 2019, 08:06:50 PM
Hello,

I can confirm that the whining noise that you can hear from the screen or in the audio path is due to the Inductor type.
I have swapped the Bluse screen inductor to a different type and it started to make loud audiable noise.
Same test in the Yellow screen. And the symptoms are the same.

Keep your eye on the heat when using different colours. Blue screen for example draws a lot more current than the Yellow one. So your voltage regulators will go a lot hotter.
Title: Re: Yellow OLED : high frequency solution
Post by: kreeper_6 on January 11, 2019, 03:17:52 AM
I can confirm that Blue OLED screen from Newheaven does work. No whining noise.
But it has issues with the pixcels brightness and it sometimes skips as the signal level is probably on the low limit.

Do you have a resistor in the OLED position? At first I had some pixel brightness differences across the display until I pulled the resistor and put in a wire jumper.

Hello,

I can confirm that the whining noise that you can hear from the screen or in the audio path is due to the Inductor type.
I have swapped the Bluse screen inductor to a different type and it started to make loud audiable noise.
Same test in the Yellow screen. And the symptoms are the same.

Keep your eye on the heat when using different colours. Blue screen for example draws a lot more current than the Yellow one. So your voltage regulators will go a lot hotter.

I have marked down some shielded inductors for order to test on a Newhaven Green NHD-0420DZW-AG5 that has the noise problem @ 13.8k; It has a different component configuration to the Blue display. I had ordered a blue Vishay Blue O020N004ABPP5N0000 but the display has some character line issue, the board is exactly the same as the newhaven including the components so I'm not sure if it could be the controller or possibly just defect. I may order a different color Vishay to test again; It does not suffer from the noise issue as it has what I assume is a shielded inductor that is the same as on the newhaven Blue.

I'll take note on the heat of the regulator and maybe swap it out for a switching regulator.

Newhaven Green NHD-0420DZW-AG5

(https://i.imgur.com/oooOERul.jpg)

(https://i.imgur.com/fxsZDLel.jpg)


Vishay Blue O020N004ABPP5N0000

(https://i.imgur.com/RLkMLwEl.jpg)

(https://i.imgur.com/7zfsOmSl.jpg)

(https://i.imgur.com/sSG1ZS5l.jpg)

Title: Re: Yellow OLED : high frequency solution
Post by: served on January 11, 2019, 07:04:04 AM
Good points! I will check that resistor!

Butw it would be interesting to know what inductor is on the Blue screen.
I could not find it anywhere. Not even similar one.

If you need inductor for the other colours read this thread:
http://ixox.fr/forum/index.php?topic=69470.0
Title: Re: Yellow OLED : high frequency solution
Post by: kreeper_6 on February 02, 2019, 05:59:25 AM
I swapped out the inductor with a few others to no avail. One did manage to shave off the peak from the noise spike but all 3 had introduced audible noise emanating from the inductor itself.

It is possibly the power converter that needs to be replaced. I'm not sure of the difference between the two power sections on the Green vs the Blue as they both look to output 5v. The blue uses a TPS61040DBVR from what I can tell from the chip marking and the datasheet suggests a Sumida CDRH3D16-100 inductor that looks similar to what is on board. I haven't been able to track down the Green converter part number or spec but I might just swap it blind. The converter on the blue boasts a switching frequency of up to 1mhz and I'd guess that the converter on the green/Yellow and Red vishay has a switching frequency in the audible range.

I may have to contact newhaven to get the scoop on what is going on.

Coilcraft LPS4018-334MRC

(https://i.imgur.com/sI2Girol.jpg)

Bourns SRR4528A-331M

(https://i.imgur.com/3fAqUcTl.jpg)

Bourns SRR4028-331Y

(https://i.imgur.com/PACYOtAl.jpg)
Title: Re: Yellow OLED : high frequency solution
Post by: served on February 04, 2019, 07:23:42 PM
I have contacted newheaven and Raystar.
They are extremely secretive about the design and they dont acknowledge the noise issue.
After tens of emails I got only one fact that I could use. It was about the inductor specs that are used. And they didnt want to comment anything else.

We decided to take a more simple and easier path.
I have re-designed PreenFM PCB to make this issue disappear. PCB Drawings will be released in nearfuture. (a month or so)
Still need to test and measure and maybe make some corrections.
Title: Re: Yellow OLED : high frequency solution
Post by: kreeper_6 on April 01, 2019, 05:22:07 PM
I have contacted newheaven and Raystar.
They are extremely secretive about the design and they dont acknowledge the noise issue.
After tens of emails I got only one fact that I could use. It was about the inductor specs that are used. And they didnt want to comment anything else.

We decided to take a more simple and easier path.
I have re-designed PreenFM PCB to make this issue disappear. PCB Drawings will be released in nearfuture. (a month or so)
Still need to test and measure and maybe make some corrections.

Newhaven never got back to me as expected. How is that new PCB coming?
Title: Re: Yellow OLED : high frequency solution
Post by: served on April 02, 2019, 07:35:58 AM
Done and working.
I am currently a bit struggling with semimodular part of the project design.
But in few weeks I should have that ready.