I realised when I looked back at this that the codes for the components (R1, R2 etc) on the BOM and schematic did not match the stripboard layout. I have corrected them now. Following the advice of @K.ostas and @analogoutput I have also increased the resistors on the clock input and output to 10K. I’ve tested that modification and it works.
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I built the Prioritron 3 designed by @Micraster and gave it a front panel that allows me to mount it in my eurorack.
To get rid of the DC offset of the PWM based DA conversion circuit I added an 22uF capacitor to the output.
I glued a 3D-printed raster to the neopixel matrix to compartmentalise the leds so that they will not bleed any light and glued a piece of the diffuser sheet taken from a broken LCD-tv cut to size on top of that, thus resulting in a nice evenly lit display. The picture does not do it justice (the camera is too sensitive and thus maxes out).
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Hi, I’m trying to look for some advice on the MFOS 2 pole, 12db State Variable Filter with VC resonance. I works like a charm but my resonance knob isn’t fully closing which means that when this knob is fully CCW, there is still a small spike of the resonance visible on my oscilloscope. Which resistors do I need to change to get zero resonance? thanks in advance for your help. I will post the correct schematic later today.
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I wanted to add the possibility of a hardware reset so that I can start the Prioritron 3 (described by @Micraster in a known state. So I looked at the pins used and found that I could use pin D4 and the PCINT mechanism for this.
For this to work I added this library to my platformio.ini (VSC project) file
neu-rah/PCINT r-site.net@^4.0.8
And these few lines to the original code:
// define a pin for the external reset signal
#define RESET_PIN 4 // D4 = PCINT20
// include the library header file
#include <pcint.h>
// Define a software interrupt service routine.
// This will reset the sequencers to their 1st step
// and initiate the 1st step.
void reset_interrupt_service_routine(void) {
step = startStep;
noteDelay.start(tempo);
if (drumBool) {
playDrums();
} else {
playNote();
}
pulseCheck = 1;
digitalWrite(CLOCK_OUT, HIGH);
timeSinceLastClock = millis();
}
Near the end of the setup()-function these 2 lines need to be added:
pinMode(RESET_PIN, INPUT);
PCattachInterrupt<RESET_PIN>(reset_interrupt_service_routine, RISING);
The original code almost completely uses the available storage on the nano, so adding this code and the library made it an even more tight fit. At a rising signal on D4 the device will now reset either its note sequencer or drum sequencer and initiate the 1st step.
As the Prioritron does not have a spare input jack, I connected D4 via a resistor to pin 8 and 16 of a 16-pin flatcable connector (the 2nd resistor is a pull down resistor). In my rack I’ve designated pin 8 and 16 to be used as a ‘bus’ for a general purpose reset signal (see Reset-O-Matic), so this works nicely for me.
6 Likes
Hello,
I made this to power my breadboard (and maybe a standalone synth) and think it can be usefull for someone else. It use a ICL7660 DC/DC charge pump and deliver +9V/-9V with a single battery. The ICL7660 can work from +3,5V/-3,5V to +12V/-12V but I don’t have test it with another voltage than 9V.
I don’t know how many mA it can deliver (because I don’t understand the data sheet), but at that time I have an oscillator, a VCF, a LFO and a noise generator on my breadboard and it works fine.
Here is the link to the data sheet:
https://www.renesas.com/en/document/dst/icl7660s-icl7660a-datasheet
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ICL7660 can typically supply 20mA in the negative rail which should be generally enough for testing a module.
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Does anyone have schematics for Snare/Tom by “Unauthorized Service”?
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I made it here 
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Thanks Dud! Very helpful. I was trying to understand pot directions, especially tom vol and noise vol where pin 1 and 3 are on the opposite side.
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When you turn the pot to the left, it’s cut the signal to the GND, so in front of the pot (1_2_3) you put the GND at left (1) to increase to the rigth.
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Given your comment, when I compare the stripboard layout with your schematic, it looks like direction of the noise vol pot on the stripboard layout is wrong.
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To draw a schem it’s more pratical and usual to put the GND to down , but imagine to open and close the pot, or follow the number here.
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Note that a drawing like the one shown is an abstract representation of the real thing. The actual orientation of the components often is not drawn when a component is symmetrical (like a pot or a resistor). Anyway, I guess you will be using wires to connect the pot to the board, so you can always swap the outer two if the direction of change does not correspond to what you would like it to be.
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Unfortunately…
I decided to first finish the main board and test the pot directions before soldering the stripboard for the front plate
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yes sorry i’m just a DIY guy , i ve mad this to help, but the orientation of the pot are good.
even it’s already solder, you can cut the line on the board and add some little wire.
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Thank you Dud, your schematics really help a lot, as well as your feedback does. I am also just a DIY guy and all the support I received was great
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last but not least: Are there any changes required if powering the opamp with +12V/-12V instead of +12V/0V like in the video?
I would imagine so as you are biasing the opamps to run on a single rail, when on dual rail you need 0v for the + pin 5 for the output opamp at least. Not sure about the other + pin 3 but I guess that also need changing.
3 Likes