This is the Rollz-5+ PC Board by Meng Qi. The circuits follow fairly closely the original paper circuits, designed by Peter Blasser. I am building it with modifications of my own to make it more modular. Here’s the back side of the board.
I’ve drawn schematic diagrams for all of the circuits and added my own modifications to the drawings. The Rollz-5 circuits are early, non-voltage-controlled versions of the ones that ended up in the Plumbutter. While Plumbutter schematics are available (see previous link), I haven’t been able to find normal schematic diagrams for the Rollz-5. Peter B. provided the paper circuits only, which are pictorial graphics of the circuit layouts. I drew my schematics referencing those graphics and checking against the Meng Qi board shown here and against the Plumbutter schematics. (There may be mistakes on my diagrams, so be warned.)
AVDog
AVDog is made up of three internal ‘modules’. An envelope generator, made from a filter set to a very low frequency, drives a transistor VCA that gates a simple audio oscillator. ‘Inpulse’ triggers the envelope. I’ve added four features. A dual-ganged pot replaces the ‘x’ resistors, so you can control the period of the envelope. The oscillator has a separate output jack, plus a switch into the VCA so you can cut it off. Finally I added an auxiliary input to the VCA.
Also show is one of the 3-Roll Rollz circuits (which is unrelated to the AVDog).
2-Roll
I bread-boarded up the Roll circuit and played around with it. I made 2-, 3-, 4-, and 5-roll versions. I found that the odd number ones oscillated at ultrasonic frequencies (~100 KHz), and I didn’t want those. I found that a 2-roll produced a nice LFO. I added a positive pulse output (like Plumbutter) and an LED driver by Ken Stone. The two ‘nodes’ still have jacks. I’m building all eight Rollz identically, but with different value capacitors. These are the rhythm generators.
Gong
Gong is a low-pass filter, combined with a circuit to ring it. Interestingly, this gong circuit is different from both the paper gong and the gong in Plumbutter. The PC board has places for two 2M trim pots, but I will use a ganged panel pot, so that you can adjust the filter frequency. I’ve also added an auxiliary input, so you can patch any of the other modules through it.
Ultrasound
Ultrasound is a switch-capacitor filter with an internal high frequency oscillator. If you build this PC board, you should add the missing 22K resistor to ground to each circuit. I’ve added an output jack with 10K series resistor for the H.F. output (this is the yellow banana jack on Plumbutter).
Output Mixer and Voltage Regulator
Plumbutter has an output mixer with pots for Gong, AVDog, and Ultrasound that mix each one of the pair to left and right outputs. Rollz-5+ has 12 audio modules (4 each of those just mentioned), so I designed this output mixer to be similar to Plumbutter. There are six ganged pots. Each pot sends a pair of the same type of module to both right and left. The connections to the mixer aren’t shown on the individual schematics above, but they will tap off just ahead of the series resistor going to the corresponding output jack on the panel.
I’m including a 7809 voltage regulator. This takes a 12V wall wart supply input. I am not building the Vactrol voltage starvation circuit that’s on the PC board.
Construction
I’m planning to build this behind a clear acrylic panel, so that the PC board will show. The pots will all be panel-mounted. More details to follow.
Hey there! Awesome that you’ve documented all this, thank you for that!
Just one question. Why are there still those “node”-jacks in the rollz schematic, and what happens if you put some voltage in it?
The node jacks on the rollz are the brown jack patch points. Located at the base of transistors, they can act as both output (from previous transistor) or input. Since connected directly to the transistor, patching here could result in damage, but there will be no harm if patching from other outputs on the Rollz-5, because of the 10k resistors on those.
Thank you for the reply! So would there be any way to secure these inputs/outputs so that you could supply voltages in there from eurorack clock sources? 10K resistor before the jack?
If you want to patch into these from Eurorack, yes, a 10K resistor in series would be a good idea. But I don’t know if patching from Eurorack into these nodes would be very useful for anything. I suggest you go to the Ciat-Lonbarde discussion on MuffWiggler and ask this question.
https://www.muffwiggler.com/forum/viewforum.php?f=65
Hi Richard!
I’ve replaced gong trimmers with 1M dual gang pots (with 22k resistors in series – one for each trimpot). When compared to the gongs with trimpots the dual-ganged gongs do not get as low and has lesser decay. There’s also some volume loss. Could this be cause I’m not using 2M’s, or could I have wired the resistors all wrong (resistor goes between pcb and lug 1(A & B)..?
Any help is greatly appreciated.
all the best
Jesper, I just double checked my build. I used dual gang A1M (audio taper) pots with 47K series resistors to replace the trimpots on the gongs. The series resistor value limits the upper and lower frequencies of the gong. See what I said about frequency ranges here.
http://pugix.com/synth/rollz-5-completed/
Mine went down to 95 Hz (1M + 47k) and up to 2.1 Khz (47k). With 22k series resistors, you would see higher values for both of these, which is what you reported. If you want lower frequencies, change the 22K for 47K or even 100K.
Okay! Yes, the gong freq spectrum is definitely higher. I’ll try out some different resistors and compare with the trimpots.
I’ve been using linear pots.. Do you think they could be the cause of decay loss?
Anyway I’ll change these and let you know the results. Thanks a lot!
In the Plumbutter schematics for AVDog, there are some weird components that look like two circles intertwined with each other. Any idea what components are those supposed to be?
http://ciat-lonbarde.net/plumbutter/labrolzpapersz.pdf
The two entwined circles is Peter’s shorthand for (I think) a two-transistor current circuit. I remember seeing a catalog of all such idiomatic symbols he uses, but I can’t find it right now. His Wesleyan Thesis contains many of them.
Hi Richard,
I have an almost-complete Rollz-5 (revision 3 board) that is giving me some trouble. I’ve built a few of them before successfully but this one is baffling me.
First of all there seems to be a weird power issue. Using a decent 9V supply, the av dogs won’t trigger unless there is something fed into the ultrasounds. If I remove the 4066 ICs the av dogs work OK. Further to this, if I reduce the power input (down to, say, 7V) then the av dogs work. I’ve done the 22K to ground mod (without this the ultrasounds don’t work at all).
Second, the ‘envelopes’ on the gongs are ridiculously short. I’ve looked at your schematics but I can’t see what part of the circuit forms the envelope. I’ve built it with ‘standard’ components, no modifications.
What is strange is, if it were just one or two of the av dogs (and gongs) that were misbehaving I’d put it down to an error on my part (bad solder, short, mistake etc.) but it’s ALL of the av dogs and ALL of the gongs.
I’m very baffled!
Thanks
It may be either a bad IC, or a problem with the etch on the board.
Unplug all the ICs. With power off, check the VCC (ground) pin of each IC for connection to ground.
Then check power up with 9V battery and check that the mido voltages are 50% of the power supply, i.e. 4.5 volts with a 9 volt battery. AVDogs and Gongs have separate mido voltages.
Also check that the power pins of all ICs are at +9 volts.
Adding back one chip at a time, power up and check the power pin on the chip for +9V.
Finding something wrong during this procedure should point you in the right direction. Try a different chip if one doesn’t work.
Thanks, Richard I’ll give that a try.
Hi Richard,
I tested the ground on all the IC sockets – all good.
I tested the VCC on all IC sockets – all good.
I tested the mido voltages on the av dogs: from your schematics I determined this should be present at pins 3, 5 and 9 of the av dog TL084s? The voltages here were all around the 8.5V mark. 4.17V was present at pin 10
I tested the mido voltages on the gongs: from your schematics I determined this should be present at pins 3, 5 and 10. These were all correct (about 3.9V anyway – the voltage from the power supply is about 8.7V)
Quick update – once I’d installed the ICs back into the av dogs the mido voltages were all around the 4V mark. I guess the TL802s are part of the circuit that scales down the 9V?
Anyway, I put the ICs back in and all voltages remain as they were with the ICs removed.
One other thing I forgot to mention: with the power supply set at 9V, triggering the av dogs produces no audio unless I patch a signal into the ultrasound on the same half of the board. If I drop the power input to 7V triggering the av dogs produces audio as normal without the need to patch anything into the ultrasounds. There’s something very odd going on!
If power looks OK, then I suggest looking for some board fault or construction error. Double check values of all resistors and capacitors. It’s probably not a board fault, because of the global behaviors being the same. Did you use CMOS ICs from the same batch as those that worked on the other boards? Some CMOS chips just don’t behave correctly in low frequency circuits.
Hello Richard,
As a first thank you very much for your great and informative site.
I have a few questions regarding a project.
I got a board from Rollz and I want to modify it according to your model.
But I have probably got a newer board with Tl 074 and tl 072 ics, which looks a bit different from the design ago than the Rev 3.
On the pictures of your Rollz I can not recognize where you go with the VCA Aux input on the board. (I’m new in Synth diy, have a bit of trouble with scematics)
I could determine the switch.
Is it possible to send me a detail picture of your Rollz with a bit better resolution?
Thanks and keep it up
TL072 and TL074 are equivalent to the TL082 and TL084. You are looking for pin 1 of a TL072 that is the square wave oscillator. It has a 100K resistor going to the base of a transistor. I just added another 100K resistor to that base to inject an external signal. And I added a switch to the resistor from the oscillator, so I can turn it off.
Hei Richard,
Thank you for your answering.
I will still use Switch potis for the Hairy Caps to switch between the different values.
Hey Richard,
Thanks for this. I think i`m going to use them schematics to build one of my own.
Peters were kinda hard to read and i`m reeeellly lazy :))
Thanks.
Hey Richard,
In your diagram of the voltage regulation circuit there is a capacitor labelled “104” in parallel with the 10uf cap, could you tell me what that means? Is that a value or a reference?
Thanks!
Hi Forrest,
The 104 is 100000 picofarad (10 + 4 zeros), which is 100 nanofarad or 0.1 microfarad, a standard bypass capacitor value.
Hi Richard –
On the Output Mixer schematic – below the 6 pots and into 5,6, and 7 of the TL082 – what goes before the Cap where you have “Similar Ganged With Right Pots”? Is it another series of 6 pots?
I am building my own version based on paper circuits and would like to add the output mixer –
I will only be using 2 gong, 2 AVDog, and 2 USF – so the top section showing the outs from those modules to the ins of the mixer makes tons of sense – but what goes to the other section that I mentioned?
Hi Joshua.
On the other (Left) output section, there are six pots just like the above. But since they are ganged, there are twelve output channels on six ganged pots. Two pairs of Gong, two of AVDog, and two Ultrasound PER CHANNEL. If you don’t understand this, look up ganged pot. It’s just two pots on one shaft, commonly used for stereo volume control, etc.
The Rollz-5 board has four of each circuit, so there are twelve outputs total. I used six ganged pots, like on the Plumbutter, with two of each (left and right) Gong, AVDog, and Ultrasound. If you are building half of this, then you have only six outputs.
You have a choice: You can use six pots, one for each output, with three of them going to the left and three to the right outputs. Then you don’t need ganged pots. Or you can use three ganged pots, which is like the Plumbutter.
Richard,
Thank you kindly for the response!
I have actually never used a dual ganged pot, most of the analog stuff I build just utilizes regular alpha pots 🙂
Thanks for the tip on 3 to Right and 3 to Left! That makes a lot more sense now!!
It is awesome to have someone as knowledgeable as you, that is willing to respond to inquiries!
Thanks again!
Josh
Hey Richard,
Sorry to bother you on this one again –
I am curious about the Mixer again – would this not produce inverted phases?
I started working on my version of it and posted it in the LMNC forum when I was curious about the dual ganged pot wiring
https://lookmumnocomputer.discourse.group/t/potentiometer-wiring-question/1745/5
Could you possibly help me understand this?
Thank you kindly!
Hi Joshua,
First, phase inversion isn’t going to matter here. We’re just mixing all the audio outputs together. It would matter more if mixing control voltages.
Second, I’m afraid that ‘Jos’ doesn’t know as much as he thinks he does. There’s a virtual ground at the summing node of the op amp (the negative input). The three inputs don’t affect each other at all. It is also convenient to put a decoupling capacitor here. If you listen to Jos, you’ll need three capacitors. It’s equivalent, so why add unnecessary caps?
As for the + input of the op amp, it’s connected to a middle voltage (+4.5V), because the op amp is powered by +9V and ground (instead of +/- 9V). We want the mix centered in the middle of the supply rails. That is also why there is a capacitor on the output: to re-center the output around ground (0V) from the perspective of the external amplifier.
My circuit works just fine, despite Jos’s lack of understanding.
Richard,
Thank you so kindly for the response!!
I will use the circuit as is then 😀
I look up to you in regards to your designs and your work that you share here!
Thanks so much again!!
Just want to say, this discussion on the mixer is very helpful Josh and Richard.
I have one more question, on the 1uF polar cap that is connected to gnd and the virtual ground on the + pins of the op-amps. My guess is that it slews the voltage change to 4.5 when power is turned on (and back to 0 when turned off) so you don’t get a click in the audio output.
Hi John. No, the purpose of that capacitor is simply to bypass any oscillations that might develop at that voltage divider. Just a precaution. Everything would work without it. A 0.1uf cap would likely work just as well.
Hey Richard,
I was curious, what are the characteristics of the pulses generated by the rolz circuits? More specifically what’s their amplitude, rise/fall time, and general shape?
The reason I ask is I am building a little board to ping my deerhorn organ; basically a piezo into a comparator into a pulse shaper. The pulse shaper will be designed to emulate the pulses generated by rolz circuit and be fed into the orange input of the deerhorn. This will allow me to play the deerhorn in a slightly more precusive manner, akin to what hainbach does here with the plumbutter rollzer: https://youtu.be/FGYkUpCLdBs?t=836
I’de measure the pulses myself and design to that, except I do not have a plumbutter (yet)
Hi Reid,
I just went and measured these and put them on the scope. I compared the Brown to the Orange on both my Rollz5 and Plumbutter.
Browns, unpatched, emit from -6.2V to +0.7V, with a sharp negative going spike followed by a linear, slow rise. Yes, a negative voltage, despite the single +9V power supply. Due to AC coupling.
Orange, unpatched, emit from +0.05V to +7.3V on the Rollz5 and +8.9V on the PB. The Oranges exhibit a logarithmic rise (similar to a classic envelope generator attack), followed by a sharp fall.
Thank you for posting these. I am working on a version of my own and using alot of the “upgrades” you posted. I fell in love with the stereo voices from listening to your samples posted on later posts.
I am doing it with a combination of Paper circuits and some available from reverb ( i believe you got a few PCB’s from this seller recently).
Thank you for sharing these and all your CL circuit discussions, they are quite a valuable resource for the sonic renegades lurking around.
I am building a Rollz 5 in a similar way with stereo outputs and double the modules.
I have a question on the auxiliary inputs. I do not have any other banana jacked gear so I thought it might be handy to use 1/8 in jacks for the aux inputs. Do you have any advice on what I should connect the sleeve/gnd to in these circuits? would it just be the 0v / negative power terminal, or would it make more sense to tie it to the mido voltage, or maybe nothing?
Thank you!
Lars, the aux inputs can be used with the additional outputs on the Rollz. For example, you can patch a Gong output into an AVDog aux input (which is why I have a switch to disconnect the AVDog’s oscillator from its input). That was the idea.
If you want to use 3.5mm (1/8″) jacks for the aux inputs to patch from other gear, do the following. First have a way to connect the ground (power supply commons) between your external gear and the Rollz. I have a banana jack for that purpose. Then, put a 0.01uf (102) capacitor in series with the 100K resistor for the aux input and connect the jack sleeve to the internal ground.
Then if you want, you can make up a few patch cables with a banana plug on one end and a 3.5mm plug on the other (just connecting the tip), for patching within the Rollz itself.
Hi Richard,
Thanks so much for all this info! I am got the PCB’s for this project and want to build the output mixer circuit as well, and I had a couple of questions.
First, could I use just one TL082 chip for the mixer because it is a dual op amp? Also I saw on the original Rollz-5 instructions to use the TL082CN IC but neither it or the TL072CN are in stock on Mouser or Tayda these days, is there is another equivalent IC that would work?
Thanks so much!
Joe
Hi Joe,
You can use any flavor of TL082. Mouser has TL082ACP in stock, which are better than TL082CN.
Hi Richard,
Are the resistor values before 3.3uF NP caps 33 ohm or 330 ohm?
Thank you!
Sorry to not clarify – on the mixer section outputs
Hi Paolo. Sorry my drawings are so hard to read. Those are 330 ohm. But they could be any value from zero (omitted) to 1K. I probably chose 330 ohm as being 1/100 of the negative feedback resistor.
Thanks so much! So, i built it with the 330 resisters on a strip board, but unfortunately it’s not really working 🙁 The pots seem to ever so slightly attenuate with full turn, but the difference is barely discernible. Any idea what could be up / things to check? i have a multimeter and signal tracer. Thanks!
Hi Richard! Thank you. I built the mixer on a strip board with 330 resistors. Unfortunately it doesn’t seem to be working properly. Signal gets through, but the pots just barely seem to attenuate with a full turn. Any ideas? I’m using the mix with original paper circuits. Thank you!!
Hi Paolo,
Sorry for the delay in reply. I didn’t get notified.
If the attenuator doesn’t work, it must be a wiring error. Are the pots grounded? Did you ground the mixer ground to the paper circuits ground?
Thanks so much, Richard! I did forget to ground the pots. It’s working wonderfully now 🙂
Hi Richard! I built the stereo mix and my left channel is quite a bit quieter than the right. Any thoughts on what to check? Thanks so much
Hi Paolo,
Was it working OK back in May? Is the left channel quieter on all three, AVDog, Ultrasound, and Gong?
Thanks for the speedy reply!
I have been slow at this assembly. When i was experiencing the low volume on left side it was just the ultrasound filters. Today, i just finished and tested the gongs and for some reason, that particular volume issue is not presenting. It seems to have a low output in general – having to really crank my little speakers and still have more playing to do, but it seems good. The Ufilters are louder than the gongs, which is fine because they have these great volume knobs – Thanks!! The circuit is finicky in other ways that it doesn’t behave as expected (different voices receiving same pulse change when connected, some voices cancel others?, etc). Getting used to it though. Thanks again for the mixer. All best.