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Messages - Xavier

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PreenFM2 / Re: STM32F4 - serial (which is good/best, wich is bad?)
« on: September 20, 2019, 05:45:44 PM »

The parts of the preenF405 board are listed here :
So it's a STM32F405RGT6.

If you buy another stm32f4 model you'll have to modify the firmware and that can be a lot of work.



Difficult to say anything from the mp3.

Try the following :
Set the number of voice of I1 to 1. The other I2, I3, I4 to 0.

Instrument 1 :
Set velocity to 0.
Use Algo 2. And make Sure mix1 is 1.0.
Is it better ?
There's good chance what you hear is the limit of the preenfm2 DAC when the oscillator have no enough bits.

You may want to verify the resistors 115K and 1.8K they're used to link the 12 bits DAC with 6 bits of the other one to make a good sounding 18bits DAC.
If those resistors are wrong, the resolution is only 12 bits.

PreenFM2 / Re: Arturia Keystep sequencer problem
« on: September 19, 2019, 10:14:20 AM »
That's weird.
I have a beatstep (must be the same internal as a keystep) and never saw this problem.
Is midi thru turned off ?
The additional voices comes from other instrument or only instrument 1 ?

PreenFM2 / Re: Big Problem..
« on: September 19, 2019, 10:12:33 AM »

Your 7805 maybe dead.
Plug a USB cable that provides directly 5V and check voltage as descibed message #6 here :

If the leds blinks it means the preenF405 is still allive. Does it still make sound ?
If yes he problem can be the only the screen.

PreenFM2 / Re: Cannot read or write to USB storage
« on: September 04, 2019, 03:13:12 PM »
Hi Nick,

That really sounds like a problem with your USB stick.

Try to format it again in fat32.
Then unzip this file.
on it.
You should have everything in a /pfm2/ folder.

Optional : add in the /pfm2/ folder the 2.10 binary for Eurorack :
So that you can easily flash it if needed.


PreenFM2 / Re: New filters
« on: August 24, 2019, 12:14:10 PM »
Could someone provide steps to upgrade this for me?  I have upgraded my PreenFM2 to 2.10 o but do not know how to adjust the source code to add these new filters.  Is anyone able to "dumb down" the steps for someone like me?  I would appreciate it!  :) 

You don't have to compile the firmware.
Download the latest firmware attached to Toltekradiation's message just above.
Easiest way to upgrade is is to put in on your USB key and to flash from it. Step 1&2 here :

PreenFM2 / Re: New filters
« on: August 22, 2019, 09:49:20 PM »
@kaosbeat : If you flash this firmware on a eurorack you'll lose the eurorack specific features.

@Toltekradiation : FYI the eurorack version is in the "adcIn" git branch :

@megalomidiac : maybe the name is too long if you flash from the the USB key.
Rename it to 8 charaters + ".bin" and try again.

I'll eventually merge this modification into the main branch, add the filters in the editor and release both main and Eurorack version. I just cannot say when  because i have no idea ;)

PreenFM2 / Re: Change MIDI parameters
« on: August 18, 2019, 10:20:55 PM »
Hi! how can I change the MIDI parameters to associate it to another values?


You have to re-compile the firmware.
Then it's easy, change the value in the following enum :


PreenFM2 / Re: New filters
« on: August 17, 2019, 08:49:58 AM »

I haven't tried it yet, but thanks a lot for sharing this.  :)

PreenFM2 / Re: Bug when using editor
« on: August 17, 2019, 08:48:37 AM »


No it's not a known issue.
Pressing INST+MENU should reinit the engine without the need to reboot.

Do you use the plugin or the standalone version ?
Can you try without plugin your keyboard directly in the preenfm2 midi in but in another midi that you redirect to the plugin (that's the config i use) ?

PreenFM2 / Re: Basic waveforms with FM
« on: August 17, 2019, 08:40:23 AM »
Hi Xavier,
when I read this for the first time (in an older thread), I assumed it was a typo, but as you repeatedly say it's a low-pass filter, I am curious now... because for all what I recall, it is a high-pass filter which is required to get rid of the DC-component of the resulting spectrum in case of FM (PM does get rid of the DC-component inherently)...

Yes, sorry. It was a typo, it's a high pass filter, as you said to get rid of the DC-component.

PreenFM2 / Re: Latest firmware : 2.10 (2019 june 13th)
« on: August 04, 2019, 10:53:57 AM »

Thanks a lot for these interesting links.

I doubt any of them would fit the required low CPU usage.
Once the preenfm plays 8 voices of 6 ops algos, the CPU left i very small.

It would also takes time (i don't currenly have) to implement them.

If anyone wants to give a try, i can guide you through the code files.


That's a nice idea, but I don't think i will ever implemented this in the preenfm2.

You can use a keyboard that does that for you.
My old Novation SL49 compact has zones that do that very well.
I imagine many other keyboard can do that.

PreenFM2 / Re: modulating the frequency of an OP/OSC in octaves?
« on: August 04, 2019, 10:45:23 AM »

Not sure i fully understand but I don't think you can do that.

You can try to use step sequencer in the LFO. You will get jump in frequency.

PreenFM2 / Re: Basic waveforms with FM
« on: August 04, 2019, 10:42:18 AM »

BTW: just curious, but what was the reason for not using phasemodulation but real FM?

The reason is that the preenfm started as a simple FM attemp and turned into a synthetiser over time.
I was even not aware at that time that other synths used Phase modulation.
Phase modulation avoid a pitch shifting when cascading 3 operators or more without any CPU impact. And i think that the reason why 80s synth used it.
FM needs a low pass (EDITED :!!!!TYPO <= It's a HIGH PASS) (few HZ) after operators to avoid this pitch shifting.

I don't remember the maths, but PM/FM spectral diferrences should be obvious when cascading at least 3 operators.

Thanks for the nice words...
but i don't have any plan to PM to the preenfm2 ;)


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