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preenfm2 and preenfm3 / Custom Pfm3 screen development.
« on: May 14, 2023, 01:41:42 PM »
Hello.

We have been dreaming of a custom made screen for PFM3.
There is always issues with the chineese versions. They come in different shapes. Some have completely wrong PCB layout for the SD card. Some have a different PCB diemensions. Some dont work at all due to bad quality or broken screen.
So me as a Preen builder have always struggled witht screens. You never know whats in the box.

Took some time, but finally I found time to make my own pcb for the screen.

Some notes on the process.

* MicroSD card instead of SD.
* no touchscreen pins
* 1.6mm pcb thickness.
* 3.3V for the screen and SD card. Chineese screens are using lower voltages for some reason.
* voltage regulator in bigger package for better heat dissipation. Pcb layout adjusted to support it.
* 3 Separate voltage rails and filtering groups for microSD card, screen logic and screen background light. This will take care of the wandering pulses in power rails.

The screens will be prebuilt in PCB fab except the glassbody, this has to be hand soldered.
We will test all the screens before shipping.

https://vandaal-electronics.com/wp-content/uploads/2020/11/20230509_091927-scaled.jpg

https://vandaal-electronics.com/wp-content/uploads/2020/11/20230509_091920.jpg

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preenfm2 and preenfm3 / Pointing out screen issue on PFM3
« on: December 01, 2020, 11:14:11 AM »
Hello,

I have encountered some issues with the TFT screen in PreenFM3.

When you build it from DIY kit yourself, make sure you isolate the screws and nuts from the pcb where the traces are very close to the mounting holes.
If that PCB lacquer fails to isolate. You are feeding the TFT datalines with noise. And this causes issues.






Insert plastic isolation washer between the nut and pcb.

Pictures are taken from the first patch PCB-s. But the next patch still has them too close and the nut will touch one of the traces.

3
preenfm2 and preenfm3 / PreenFM Eurorack module
« on: January 04, 2019, 03:14:39 PM »
Hello,

I am starting this thread to give more information about the PreenFM Eurorack implementation.

We have now finished the case design.

Beta panel looked like this but had some mounting issues etc. So we had to make a change.



Current and the latest revision.




Unit has total of 5 different PCBs. So its a bit complex build but it can be DIY kitted and assembled with good instructions.





CV1 is routed to GATE and it triggers a note.
Gate input is limited to 3V pulse. So it is only capable to trigger something like Gate but also it can be mapped to the matrix.

CV2 is routed to V/Oct input. It is designed to get 0V to 10V input. 1V is one octave. PreenFM is using only 8 octaves on that input.
CV3 and CV4 are similar -5V to +5V.

All the inputs are buffered and voltage protected. meaning that they can take anything coming from Eurorack system.

CV1-4 inputs can be mapped to matrix parameters.
Options:

None;
Gate;
IM1; IM2; IM3; IM4; IM*
Mix1; Pan1; Mix2; Pan2; Mix3; Pan3; Mix4; Pan4; Mix*; Pan*;
o1Fq; o2Fq; o3Fq; o4Fq; o5Fq; o6Fq; o*Fq; o*Fh
Att1; Att2; Att3; Att4; Att5; Att6; AttC; AttM;
DecC; DecM; RelC; RelM
mx01; mx02; mx03; mx04
l1Fq; l2Fq; l3Fq;
e2si; s1ga; s2ga;
Fltr

PSU section.
Takes a normal Eurorack +/-12V power and +5V. There is an onboard 5V regulator if your eurorack system doesnt have a 5V rail.
You can choose to use that regulator by connecting a jumper to "Reg." position. Or to "Bus" if you have a 5V bus.


On the Audio outputs there is an option to use a stereo cable by having a jumper installed to RIGHT-LEFT link pins.
Then Stereo output is LEFT channel out.

USB power has 5V supply cut to escape various powering issues.

31HP in width.
Total 400mA current draw, using +5V; +12V; -12V; bus.

V/Octave calibration process:
Menu > Tools > Set > to adjust v/oct (first 3 encoders change the parameter, last 4th encoder changes the value)
You need to adjust CV A(33) (midi note 33) and adjust CV A(81) (midi note 81).
This will scale the V/Oct with out the need to adjust each octave one by one.
Example values are: CV A(33) 256 and CV A(81) 735. Each unit has its own values and depend on your voltage generator settings.

I will post some videos in the near future how it performs.

We will start to produce the modules assembled this month.
They will become available here: http://vandaal-electronics.com/product/preenfm-eurorack-module/


Any feedback is welcome and will help with the developement!

4
Hello,

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

In short.

Reason:
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.

Measuring:
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.

Observation1:
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.

5
preenfm2 and preenfm3 / Yamaha Sysex files for DX5
« on: April 26, 2017, 08:14:20 AM »
Hello,

I have seen people asking about the sysex files and PreenFM.
I have an opportunity to work with a Yamaha DX5.

It was broken and not functional.
I have managed to restore most of it. So now its playing and its a gem.
But I have some trouble getting the factory sysex files as the memory was corrupted on this one.

Do you know if there is a patch available of the original DX5 soundbanks?
I can upload them over MIDI. I have no cartridges.
The interface is still a bit confusing to test it out so it would be easy to have the factory sounds available.

Thanks!
Ardi.

6
preenfm2 and preenfm3 / PreenFM assembly (New! with Case assembly)
« on: February 10, 2016, 03:45:13 PM »
Hi.

I made a video of the PreenFM assembly.
Its a first assembly video I ever made.
It does not contain the case assembly.

Audio is produced by PreenFM and ran through Van Daal Filter (LP2,LP4,BP) with some character and I also used transformer Color module in 500 format
Prickwall limiter was added digitally.

https://youtu.be/KQJTWJ9GH_U


Ardi.

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