Saturday, 14 December 2019

DAFM synth - DIY build notes

My unofficial build notes for the DAFM synth.


I am in no way associated with the developer. These are just my personal build notes to help me trouble shoot, should I have any problems.
The 


The DAFM uses the YM2612(OPN2) and it's CMOS variant the YM3438.
The 2612 was used in arcade machines, the Sega Mega Drive/Genesis home game console (1988), and the Fujitsu FM Towns (1989)
It's a FM/PCM hybrid chip
The chip can have either 5 or 6 FM channels.
 (5 FM channels with 1 PCM or 6 channels without PCM)
   The YM2612 has six channels with four operators per channel.




tHE build is super easy. All parts are supplied and well labelled. If you can follow a recipe and know how to hold a soldering iron, you can build this.



 There are  8 algorithms. The envelopes, frequencies and LFOs can be changed to get a good range of FM sounds.

The midi section is on the top left. A standard DIN connector.
 Thats a MPR121 breakout pcb on the lower right.
It's a capacitive touch sensor controller driven by an I2C interface... probably what controls the cube keyboard.
Presets can be saved in the RAM memory or in a SD card as DMP files that can be opened with VGM trackers like Deflemask.


The top right section... LD33V power regulator & USB - type B, female.
The USB connector is  the power supply of the DAFM synth
The  LD33V powers the touch sensor


Also added the two lower encoders.
These are used to move through the DAFM Synth menus.

That pink board is the audio preamp.


The 8 MHz Crystal oscillator ... for the timing.
keep the dot on the bottom left.

This second pink PCB is a multiplexer.
It lies between the SD card & the DIN socket.

This TCA9548 I2C Multiplexer connects to the four OLED displays.
The four OLED displays share the same I2C address.


Next solder the four 0.96 I2C Monochrome OLED displays.


Now its time for the  STM32F103C8T6.
It's an arduino micro-controller of course






iT'S A wonderful thing when you see the synth power up on the first attempt.



Links
+ buy on tindie
+ Youtube - menu
+ Build instructions 
+ Wikipedia - YM2612 
+ Yamaha FM chips
+ Microcontroller Index Page
+ User guide
+ github - Genesynth   
+ Genesynth - blog
+ Genesynth - pjrc
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FM Index
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Friday, 13 December 2019

bEASTEK - pIXEL dRUM 1.3

sOME pics of the building of a Pixel Drum.
This is a Eurorack module I've bought as a kit.


It's a 12bit drum voice. I'm hoping it can also double as a  compact synth voice.
There are 32 different algorithms.




All parts supplied. :-)




I am not associated with Beastek. These pics are unofficial.
The official website with The BOM and official build notes can be found here:
http://www.beast-tek.com/pixel-drum.html

The two PCBs are connected via headers

 I like to solder these early in the build phase.



jACKS, ETC ... getting ready for attaching the front plate.


sTART soldering the pots and jacks once the plate is attached.

pcb 2

DIODES (ZIENER) & inductor

getting there ...

more diodes & ferric beads.





dsPIC33f128FJ128GP802 - the microcontroller





Notes:
+ All about inductors
+ Microcontroller Index Page

 

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For more Euro DIY builds click here:
http://djjondent.blogspot.com.au/2017/12/diy-index.html
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Potentiometers - convert Linear to Log

Converting the linear potentiometers to log pots.

This may come in handy if you don't have the appropriate Audio/Log pot at hand (because of an odd form factor or dual pot configurations), or if you wish to tailor the log curve.

Usually the three lugs or terminals are numbered:
1. input
2. Wiper
3. Ground

The usual solution is to add a resistor between the pot wiper & ground. If you can pick the right size, the result will be
close to a logarithmic response. This is usually OK for most audio applications. You don't have to stop there. Fixed resistors can be added to both ends. .... ie between the input & wiper, and ground & wiper.

The results can be wonderful ... or crazy.
It's all about taper.
1. Reverse Log / Reverse Audio (A)
2. Linear Taper (B)
3. Logarithmic Audio Taper (A)
4. Straight line "pseudo-audio" taper

Usually a resistor value of 10% to 20% of the pot resistance gives a good approximation of an audio-taper pot.
Smaller values will give less change in volume at the lower portion of pot rotation, higher values will give more change.

This is a dual gang pot.

This is a 1M reverse log pot.
It's marked C1M

Wednesday, 4 December 2019

102

Some pics of the LA67 102.... Dual Stereo Locator
It's not a Buchla Module.
It follows the same size, format & the circuits used are I understand based on Don's schematics.
I hope one day, Buchla will release an official 102.

I've only seen one real Buchla 102 in the flesh. These are as rare as hen's teeth.
The LA67 version is a pretty easy build, though trying to match the JFETS is tricky.
 (I'm still trying to get it perfect at the time of writing).
I'm not affiliated with the manufacturer in any way. I'm building this to learn how it works
and these notes are just my personal doodles to help trouble shoot any issues I may encounter during the build.

 If you are unfamiliar with JFETS check this link out.
 https://djjondent.blogspot.com/2019/05/transistor-families.html

Metro Modular also make a module inspired by the 102 which is worth exploring if this module interests you. (I would also love to see a Buchla USA version).

 Anyway, back to the LA67 module.




The virgin PCBs, etc.


This module has a 0v & +15 power supply. The original used an additional +24V rail.
The original op-amp was most likely a LM301 (which has a +V rating of +18V)
This module's BOM calls for a TL071.



The BOM calls for J201's
Mouser No 106-J201
My sources tell me that the original used  2N4339 JFETs







tHE Rotary switches are these