Another Ciat-Lonbarde PC board from crucFX, a.k.a. Josh Rodriquez, with circuit design by Peter Blasser. Dubernator is a dual bandpass filter, highly resonant. It features two identical, independent filters, each with cutoff and resonance pots and normal and inverting CV inputs for cutoff frequency. A third input mixes with the other inputs to both channels. A third output is a mix of the two outputs. The outputs are orange banana jacks, the inputs gray, CV inputs blue.
I made a case from 1/8 inch thick plexiglass for the top and bottom panels, just as I’ve done for the large Tetrazzi and the DIY Quantussy. A local glass business cuts these to my specification for a very reasonable price. Holes must be drilled at a low speed to avoid melting.
More Construction Photos
The only modification I made was to add 10K resistors in series on the two individual outputs. Peter always does this, so it must have been a mistaken omission when he drew the schematic that Josh worked from.
The bypass capacitor on the input to the 9 volt regulator was specified at 2200uf by Peter. I found a 1000uf 25 volt cap only 3/4 inch high that I knew would clear the one inch spacing I put between the board and the panel with nylon standoffs. Luckily it cleared the input banana jacks. I laid out the panel without taking it into consideration!
I ordered polystyrene capacitors for the filter integrators, Mouser 23PS210. These are axial packages. You can see them standing on end in the photos.
Peter B’s Dubernator Schematic
Test setup and demo recordings
A very simple patch: one Tetrazzi ramp wave output to the “both” filter input. Filter outputs go to left and right recording inputs. For the first test I demonstrate self-oscillation of the filters. They can get raunchy sounding and go to pretty low pitches. To oscillate, the resonance is turned all the way up. I then manually twiddled the frequency knobs.
To demonstrate filtering, I started with low resonance for the first minute. Then I turned up the resonance, and then again, twiddling the oscillator and the filters. A couple of times I also patched one of the other Tetrazzi oscillators into a CV input.
Gonna hafta order myself some of those 104’s.
Xicon and Nichicon always seem to have great performance!
Awesome Build as always Richard!!
Thank you, Josh, for the board. The white box 104s? Those are Kemet. Mouser 80-R82DC3100AA50J.
Hi, thank you for the documentation. I am also building a Dubernator. What values do the bypass caps have and what are they for? Cheers Florian
Hi Florian,
Well, the bypass capacitor on the input to the 9 volt regulator was specified at 2200uf by Peter. I put a 1000uf in there, but I think there might have been an extra zero added by mistake. A 220uf would surely work just as well. I also left off D3 and D5, which are overkill. If you will not be using a 9 volt battery, you can also leave off D2 and D4. The fuse F1 is also overkill. Just replace it with a wire.
I always add 0.1uf (100nf, 104, etc) bypass capacitors across the power pins of each IC socket, soldering on the bottom of the board. Although not strictly necessary, bypass caps can prevent some unwanted circuit behavior. I suggest you research it.
Thank you Richard for the answer.
I will read up on the IC bypass caps.
Can the P6KE24A diode also be omitted? I am having trouble finding one that fits. The one that was in my order has way too thick legs and doesn’t fit in the board.
As for the 2200uf, I saw pictures of an original board from Peter on the /////-forum. The capacitor was quite large. That seems to be correct.
I meant the P6KE10A
Neither of those P6KE voltage suppressors are needed. As for the big bypass capacitor, you can compare against other, almost identical power circuits around the 7809 type regulators on other of Peter B’s designs. They use anywhere from 220uf to 2200uf. All that these do is to smooth the input voltage coming from a wall wart 12 volt supply. A lot depends on the quality of the wall wart. Whether you use a 220uf or a 2200uf, there will be no noticeable difference. Just be sure to check that you have a clean 9V output from the regulator.
Did you get a 2200uf capacitor? It ought to be 25 Working Volts, 16 at minimum. The 1000uf I happened to buy is already very large.
Thank you! My 2200 has 16V, so I’m probably on the safe side.
Heyo, Mike again… where do you source those good looking spacers for your panels?
Hi Mike,
The spacer parts are from Mouser.
Nylon hex spacer 1/4″ 534-4800
Nylon hex spacer 3/8″ 534-4802
Nylon hex spacer 1″ 534-4806
Nylon pan head screw 4-40 1/4″ 534-9327
Nylon hex nut 4-40 534-9605
The nylon is nice to work with plastic and PC boards.
Hi Richard. I appreciate the wealth of info you share here. It’s kind of priceless. Im putting together the dubernator now. I was wondering about the mod for the 10k resistors in series on the outputs. Are they just soldered straight in between the board and the output jacks? I’m still pretty new to this. Sorry if this doesn’t make much sense.
Hi Sebastien,
Yes, the 10K resistors go from the individual outputs to the banana jacks.