Author Topic: PreenFM2 new build, audio is mostly noise  (Read 38 times)

Glomerule

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PreenFM2 new build, audio is mostly noise
« on: May 17, 2021, 04:45:06 PM »
Hello fellow PreenFM enthusiasts,

I'll start by saying that I am more than impress the whole initiative and that this really is the kind of project the world needs more of (in every domain).

Biggest shout-out to Xavier.

So here is my story.
A few weeks ago, I saw a mention of the PreenFM2 on reddit r/synthesizer and was intrigued. One or two youtube videos later I was hooked and ready for a sleep deprivation fueled impulse buy.  8)
The Vandaal website was all out of assembled PreenFM2 R6 so I went to the second link, TubeOhm and bought what I thought was an already assembled synth.

Spoiler alert: it was not.

Yesterday I decided to give it a go. I have no soldering skills (a few jacks and midi cables is all that I have soldered before that, and not even very well...).
It almost went smoothly and the most complex thing ended up being the software part as I thought it was pre-flashed when in fact it was not.

Anyway, cutting short, I have a fully assembled PreenFM2 with the latest firmware (not the latest bootloader though, I did not find a version above the 1.11) that responds to midi (the channel number is blinking on note input).

The sound it produces though is not what it should be for sure.
It is constantly there even without input note. It is mostly noise with the FM patch behind. It reacts to preset loading or algorithm change etc but there is this constant noise that I cannot shake off.

There is no instruction on how to install the DAC on the new R6 but the very clear picture on the PCB makes it quite obvious so I think I did it the right way.

Sound example: https://www.dropbox.com/s/23efcyzytpwjm8h/postassembly_noise.mp3?dl=0

I have no idea where it comes from and I'd be really much obliged if someone from the community could help me a bit.

I can post photos or other sounds or even videos if needed of course.

Thank you for your help!



lokki

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Re: PreenFM2 new build, audio is mostly noise
« Reply #1 on: Today at 08:04:41 AM »
Some hires photos of the front and back of the PCB will be very helpful. Does the noise disappear/diminish when you turn down the volume on the preenfm2

served

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Re: PreenFM2 new build, audio is mostly noise
« Reply #2 on: Today at 08:12:10 AM »
It kindof works. So You must have the most of the circuit done correctly.
So its now the question of the analog part and there is few parts only that can be involved. So Send us the pictures!

Glomerule

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Re: PreenFM2 new build, audio is mostly noise
« Reply #3 on: Today at 09:45:35 AM »
Thank you fellas !

here are front and back shots:




I couldn't remove the screen this morning but I'll do it if you think it matters.

Another clue might be this:
When I plug it for power, be it usb or DC, if I use my little Bose speaker that has a metal case, there is a strong noise appearing whenever I touch the metal... I don't have that if plugging in my mixer.
 It seems relevant but what do I know !

Thanks again.
 

served

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Re: PreenFM2 new build, audio is mostly noise
« Reply #4 on: Today at 12:06:14 PM »
Resolder the small green DAC pcb. It looks bad solder there.