Peter Blasser’s paper circuits are made by printing out a graphic, such as the above, at the right scale to match up with the physical sizes of the actual components, resistors, capacitors, integrated circuits, etc.. The printout is glued to a piece of stiff cardboard, then holes made with a needle, the components inserted and connected by wiring on the back side. Peter’s graphics are laid out in a planar manner, such that most of the wiring can be done without crossing wires.
Some people make printed circuit boards based on paper circuits. I bought one for the Esoterica Spike Ring from Dennis Verschoor that he had assembled The Spike Ring consists of a filter circuit combined with a pulse generator.
It has four pots. Pitch and Resonance apply to the filter, Delay and Chaos to the pulse generator. There is a designated audio output (filter band pass), filter high and low-pass outputs, and a pulses output. There is also a balanced input indicated by a castle symbol, for FM of the filter, that I tried hooking to a piezo disk with some success. The swirly symbol node is an input for affecting chaos. The antenna-like symbol node is an input that seems intended to gate the pulses into the filter. Here’s the full schematic.
The top portion of the schematic shows a state-variable filter topology, with the input ‘P’ coming out of the pulse generator circuit below. The band pass output is AC-coupled, while the high and low pass outputs have 10K series resistors going to nodes. Note that X and Y resistors are 10K and CHAO is 220K. I made one circuit change, to lower the resistor from the Delay pot from 1M to 470K so that the pot would have an effect. The castle symbol indicates a dual input that is clearly intended for FM, but we’re not sure what the intended use of it is.
I don’t understand the chaos pulse generator very well. A scope shows high frequency small oscillations on pins 2 and 3 of the TL074 chip. These produce a continuous and noisy pulse on pin 1, but this signal doesn’t get through to the filter until a finger (or some other signal) is placed on the node with the antenna symbol. Then, the pulses are passed to the filter and also to the star symbol pulses out node.
We made a video of me fooling around with it. Thanks, Diana, for the video processing!
love it
Cooooool, thanks for sharing that! Amazing response and sounds. I’m going to try building this, really curious what problem you had to fix. Grateful for any insight you have regarding the range of those X, Y, and CHAO resistors to try. And about those two caps above the 064 chip? I was wondering if any value between 102 and 103 was implied by their symbol?? Many thanks!
The problem was just a mistake in wiring. I have more investigation to do concerning the capacitor values and the X, Y, and CHAO resistors. I will be posting a schematic diagram, too, once I figure these out.
Cool, looking forward to your findings. Im a big fan of Peters instruments and enjoy building his paper circuits, but I’m quite the novice to DIY electronics. Really appreciate all the knowledge you’ve shared here. All the best.
Great work Richard!
I got another batch of pcbs in 1.5 week!
Awesome! I’d like to get one of these PCBs.
Got a PCB from Dennis as well. This article is very helpful in finding my way into Peters instruments.
Thank you, Richard ☺️
Hello Richard, i think there is an error in your schematic, the 103 caps near the BP an LP out are in fact 472 polys. The symbol look similar to classic 103s but the middle bar is not complete, you can find one on the PCB near Resonance pot 😉
I just found out while building mine today (didn’t try to swap with 103 to check the difference for now).
Thank you for your amazing documentation on CL paper circuits!
Simon, that is a very good catch! Those caps are the integrators, meaning that the frequency of the filter is much higher than it should be. I’ll try the 472s. Thanks!
I think I’ve more or less figured out the chaos portion of the circuit. Those two sets of NPNs and PNPs are called PUJT oscillators, and they’re the same thing used in lil sidrassi. Their base frequencies are controlled by the Vcc resistor and ground caps that the PNP emitter is connected to. Notice that they have different resistor values, so they’re at different frequencies. Another property of these oscillators is that their amplitude is inversely proportional to their frequency. Because of these factors, the output of the comparator is already pretty complex (I imagine…) But then we have the output of the comparator modulating the frequency of one oscillator, creating a nonlinearity in the system. The chaos knob changes the frequency of the modulated oscillator, and the capacitor placed in the pulse’s feedback loop makes it bipolar, thereby adding and subtracting from that base voltage. I’m not sure whether or not this system is chaotic in the truest sense of the word, but it’s certainly a decent imitation at the very least. I hope this analysis all made sense.
I am curious about the PLL aspect of the Esoterica circuit or… dual circuits? Was it implemented to use in conjunction with these chaotic fluctuations for pitching lower frequency pulses up above 20hz? I’m curious for a couple of reasons on the one hand it sounds like the opposite of the ultrasound which with those high frequencies you’re describing here Id immediately try this through but on the other I’m very curious about the potential of using this in conjunction with the rollz circuit topologies so I can produce pitch and rhythm from 1 source simultaneously. It would be a way to sort of improv with the early concerts Stockhausen described for realizing his piece Gesang. Honestly I’m convinced Peter has a deep knowledge of all the mid-century modern composers because when I look at the Plumbutter alone I see Pulse arrays as already mentioned, the ultrasound like Madame Butterfly by Oliveros but in a decidedly more post-modern form and even Trautonium esque concepts. I would love to more broadly realize the PB with PLL’s, and a few other tricks I think would help. Have you tried the Chainlock in such a way? Perhaps used some of the Serge modules with his instruments? Thanks!
Hi Shea. Have you listened to Peter B’s own music? I’m not ready to speculate on his influences, except to say some Japanese concepts, too.
I haven’t built a Chainlock. As for using PB circuits and instruments with Serge or other modular, check out the ciat-lonbarde tag here.
I’m glad you commented on this post, because Spike Ring has been gathering dust in a drawer, awaiting a proper panel and power supply. This nudges me to get back to that project.
Thanks,
Richard
Hey! Thanks for this awesome documentations! I’m curious as to if you can mod Peters paper circuit for jacks that go directly into the filter in , and a switch to turn on/off the pulses going into the filter. Do you know where on peters paper circ the input for the filter is?
Hi sadnoise,
Sure, those mods can be done. The letter ‘P’ on the schematic I drew shows the point where the oscillator goes into the filter. You could put jacks at both of those points.