maybe add a 100K resistor on each side of your mix pot
For the “freeeeezz buttons” i just put a momentary push switch on the pin of the Time pot and the same on the Feedback pot
For the time connect it on the 2 pins who decrease the time (very short time = zzzzzz)
For the Feedback connect it on the pins who increase the feedback (infinity repetitions when you push push push push push …)
Hey Dud,
thanks for the welcome and your speedy reply - and sorry for my slow reply!
Yes, it’s definitely pin 14 - I’m just not sure what components I need to have between it and my output jack.
The schematic you posted looks to me like they are grabbing the signal at the same place as I mentioned (I think the 10uF cap in the schematic is the same as C17 on the module). I assume the rest of the circuitry with the opamp is to then amplify the signal (as it is very quiet). Does anyone know more?
I just ordered myself some opamps and will have a play soon! I did implement your Feedback button, and it’s working great, many thanks for that!
I also found a super interesting tutorial on how to MIDI-sync the PT2399, so I had a go adapting it to the module. It only requires an additional capacitor and resistor and an Arduino and works really well!
To get to pin 5 I simply soldered a wire to the bottom of the PCB. Otherwise I just followed the schematic in the tutorial.
The first capacitor with the unspecified resistor form a low pass filter. The 10 µF cap and 1 M resistor form a high pass filter with an extremely low cutoff frequency, 0.02 Hz, for AC coupling (removing the DC component — though very slowly, RC time = 10 seconds! I’d use a smaller resistor, maybe 10k or 100k , a few hertz for the cutoff should be fine.)
The op amp and 100k resistors form a non inverting amplifier with a gain of 2.
The 1k resistor is a current limiter, to avoid stressing the op amp when the output gets briefly grounded while plugging into it (or gets shorted to ground or ±12 V if you plug it into the wrong thing).
Thanks so much - that is super helpful for making this stuff accessible for a complete novice like myself! Looking forward to adding and tweaking the circuit!
Hi there! I hope it’s not too late to get an answer in this thread xD
I’m using Sam’s simple pt2399 circuit for a synth I’m building, but I’m not sure about the powering of the pt. This synth does not use an eurorack power supply, but uses 9v instead. So for the opamps I’m using +9v as Vcc+, 0v as Vcc-, and for the parts of the circuit that go to gnd, I use a virtual ground (+4.5v).
So here comes my doubt, what should I use as the gnd in the shematics? my virtual ground or the supply’s 0v? I guess that depending on that answer would change what I should use as the pt2399’s Vcc (+5v if using 0v as gnd, o +9v if using the virtual gnd).
I hope my answer isn’t too confusing, since english is not my native language xD
Use 0 V and +5 V. No reason not to. The input and output are AC coupled, that’ll make the input and output signals zero centered. You’ll need to add your 4.5 V bias to the signal at both the input and output op amps.
I turned the cap around because you’re going to a 4.5 V DC component, not sure if that’s right or not. Better probably would be to use an NP cap, or two 20 µF caps back to back.
Also the original design presumably was for 10 Vpp signals whereas with a 0, 9V supply you can only do maybe 7 or 8 Vpp, so some adjustments to gain may be required.
Maybe? It depends on whether the input is coming from a low impedance circuit or not (it would be in a modular synth but I’m not clear on what you have.) If not you would want to buffer it with another op amp. And if you want a low impedance output (as you would in a modular synth but…) you would need to buffer the signal after the pot.
ohh now I got it I’ll try to get np caps if I can find them, it’s hard to find unpolarized caps bigger than 1uf here, at least caps that aren´t too big in size (I already have a few, and they take A LOT of space). But I’ll figure it out.
yes, I thought about it, but also, if I’m removing R8, I’m not summing the dry signal to the output, so it may work. Anyways, if I see it’s distorting, I could just change the resistors, thanks for noting it.
the input is comming from within the same synth, since it’s not modular hence I know it’s centered at 4.5v. Regarding the impedance, don’t really know, it’s comming from a pot that mixes the output frorm a filter and a diode soft clip distortion (both Moritz Klein’s designs). Here’s that part of the circuit
CLEAN_OUT is coming from after a capacitor so might need to be buffered. Also might need a 100k or 1M resistor to ground before the op amps. DIST_OUT is coming direct from an op amp so would not need the buffer.
) I’d rather have full dry/wet mix, so I tried to figure it out here, would it work and do what I want?
