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PreenFM2 / PreenFM Noise issue; whining, tone, high pitch
« Last post by served on July 23, 2018, 08:04:17 AM »

Just writing for the community about the last discovery about The noise.

In short.

The noise in the audio path is coming from the OLED screen inductor.
The whole issue is happening because the inductor that is used on the OLED screen is unshielded and radiates EMF (electromagnetic field). One can google more info about the inductor EMF if needed.
Also what doesnt help is that inductor is located exactly on the other side of the Opamp gainstage and its components. This all together equals an audioble noise.
Gainstage picks up inductor EMF vibration. Frequency is the same.

This is a spectrometer screenshot. The conditions for dB measurements are relative. Signal has been run through a MIC preamp with full gain.
Condtions are exactly the same for all the measurements, so you can compare.

PreenFM 2 with Yellow OLED screen. This is what the peak looks like when the noise is present in the audio signal.
dB scale measurement is only for comparsion. Its peak is around 13650 Hz = 13,650 kHz

Test 1:
Aluminium shield between the OLED screen and main board. 0,75mm thickness, no ground.

Test 2:
Shielded SMD inductor instead of the original open inductor. Observe the shift in the frequency.

Test 3:
Shielded SMD inductor plus Aluminium shield. Building instructions in next post.
PreenFM2 / Re: High frequency tone coming from hardware itself!
« Last post by served on July 23, 2018, 07:44:32 AM »
Hello from Van Daal,

Its caused by the Screen inductor making the Noise shield vibrate.
Initially we used steel noise shields. Steel is affected by magnetic field.

Steel provides the best protection against magnetic field.
So your unit has a very low signal noise, but it suffers from physical noise.

You could remove the shield to remove the physical noise.
Use aluminium plate instead. Its not that efficient, but its a compromise.
PreenFM2 / High frequency tone coming from hardware itself!
« Last post by stelpa on July 23, 2018, 05:35:20 AM »
Hi! I've seen plenty of people in this forum complain about a high frequency tone coming from the audio out of their preenfm2, but I couldn't find any thread related to this issue, being that there is a high pitched tone coming from the hardware itself! The tone isn't very loud, but it's definitely audible as soon as it's powered on, even if the audio out isn't plugged into anything.

Is there anything I can do about this? It's my only complaint I have about the preenfm, and if I could solve this it would be perfect.

If it helps, I have a preenfm2 with an OLED screen from Van Daal Electronics.

Thanks a bunch :)
PreenFM2 / Re: preenfm2 editor 2.08.4 (November 25th 2017)
« Last post by lloydcole on July 18, 2018, 10:37:45 PM »
The latest Logic 10.41 won't seem to load the AU plug in, I'm afraid. The mac OS didn't want to let me use the editor and said it needs updating to work with the mac, but that doesn't seem to be the case. The editor seems fine.
PreenFM2 / Re: Preen 2 Parameter Sheet
« Last post by Xavier on July 17, 2018, 10:02:08 AM »

Nice to read you enjoy your preenfm2  :)
There a patch structure schema here :
(3rd image of the page : "Workflow of the PreenFM2 sound generation").

But it seems like you look for something more detailed than this.

Don't forget to share if you make one yourself,

PreenFM2 / Preen 2 Parameter Sheet
« Last post by lloydcole on July 16, 2018, 07:21:09 PM »
Hello, this is my first post here. I'm new to Preen2, but not to FM synthesis.
I'm enjoying the sound and flexibility of my Preen 2, and the editing architecture is incredibly well thought out, but my brain struggles envisaging patch structure, I even struggle with 2 pages per envelope... (I am getting quite old and my memory is clearly not what it was.)
I wonder, before I set about making one, myself, if there is a printable parameter sheet(or sheets) in circulation? If so could somebody point me towards it? I think if I can write the values of the various parameters out, as I go along, I'd find it easier to edit and patches.

Yes, I am aware of the editor software. But I am trying to stay away from my computer...
PreenFM2 / Re: output hiss and cloud
« Last post by Xavier on July 12, 2018, 05:13:06 PM »
The audio path goes through the solder points "circled" in orange.
PreenFM2 / output hiss and cloud
« Last post by smrm on July 11, 2018, 01:47:42 PM »
When using the preen i occasionally get some hiss and distortion from the outputs and it seems to go mono even when connected in stereo. which points must i resolder? thanks
PreenFM2 / Re: Two longform pieces made entirely with PreenFM
« Last post by widdly on July 11, 2018, 05:31:38 AM »
Nice work.  I'm a fan of Laurie Spiegel and John Chowning so I'll have to check out Jaap Vink
PreenFM2 / Re: 30 years of Digital FM Preservation Video festuring the Preen FM2
« Last post by widdly on July 11, 2018, 05:27:25 AM »
Your CX5m sounded super clean.  Were you running it in an emulator?  Mine is pretty noisy.  I keep it around as a dedicated DX7 editor.
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