Here’s a demo video of the Z5524 card. Very happy with how this turned out: dual VCO with VCF and lots of features. The demo really flies through the feature list. If you’re interested there are other vids on the youtube with some other details.
The Z5524, like all the other Zoxnoxious cards, is open source and perpetually 6-months out from getting something the public can play with.
[edit: changed video link after redo-ing the digital FM section]
Anyone remember the Spy Hunter arcade game? One of my faves, even if I haven’t played it in the arcade in 20+ years. I’m toying around with doing a full version of this where the Spy Hunter van delivers all the Zoxnoxious synthesizer modules.
Work in progress: tech deep dive videos on the Zoxnoxious synth. First vid will cover the Rack frontend; the next video towards the hardware / Raspberry Pi side of things. Presented without explanation here; the finished vid will have my boring monotone voice to provide explanation (or confusion) along the way.
Does anyone have points they’d be interested in seeing on how the sausage is made?
would like to know how you made all the DAC control things!
Coming soon: I’ve redone my original Z3340 VCO card; I just got the PCB back from JLCPCB. After doing a few other designs it was useful to go back and revisit my original Zoxnoxious card. Or maybe embarrassing to revisit the design: many “oh why did I do that?” moments.
Possibly the coolest new feature of the redesign is it allows all the sync modes that the 3340 VCO offers. The datasheet describes four different sync modes; my previous build offered two of them. The new board should do all four. I’m not aware of any build that does this. Are the sync modes actually different? Eh, enough so to call it a feature. I’ll put a demo together once it’s all working. Until I improve my UI skills, it’ll have a boring interface like this:
In the meantime, here’s the sound of a space alien crop duster flying over its home world (and using the “old” version of the Z3340 VCO).
@Luca-Feelgood - I started with one of your patches for the above, with the intent of porting it to Zoxnoxious modules. Porting isn’t quite the right word, maybe mutated, and rather poorly at that compared to what you had. Still, it was fun to play with and give that a shot!
It would be interesting to know which patch you have used here.
I went a bit over the top with this (what should be final!) revision of the Z3340 VCO board. I can’t think of any more features to add to this board. It’s got every sync mode the CEM 3340 datasheet mentions (four of them). The sync modes can be combined if you’re into getting some effects. I added VCAs for all the VCO waveforms, so everything is mixable on the primary output, and AC coupled. It’s got a second output with fixed level waveforms that’s unipolar. Having both available can be useful in this weird architecture of a synth.
Started development on the next Zoxnoxious plugin card which will be an analog filter. And not just any filter, but a modern version of the SSM2040. Sound Semiconductor’s SSI2140 is a modern equivalent, with the same engineer at the helm who did the original. It’s been out for a few years.
To put an interesting twist on it I’m adding in Sound Semiconductor’s SSI2190 which is a 6-channel analog mixer. The mixer will allow pole mixing from the '2140. One should be able to run it as a lowpass, highpass, bandpass, notch filter etc. How effective that is in practice I’m not sure, still building it. I do think it’ll be pretty good. And with cpu control of a DAC controlled mixer that should allow for some fine-tuned calibration versus designs like Oberheim’s Xpander, where the various pole weightings were fixed.
Oh, and here’s the really cool part. Since it’s a mixer to control filter weights (versus switching like the Oberheim Xpander), one should be able to crossfade/morph between filter modes. That’d be pretty slick. For the Rack interface, I’m thinking of having the core filter as Rack module, and have the filter “definition” be a separate module. Instantiate however many definitions you want, then use standard VCV Rack modules to link the definitions with the filter. Use a crossfader, sequential switch, put a slew limiter between filter modes. Get creative. In other words, the user is in control of how the morph works, it’s not an algorithm of the filter module. That’d give it some pretty big functionality.
With all that, here’s the hardware block diagram of what’s to be the Zoxnoxious Pole Dancer filter. Pole Dancer. LOL, I’d develop it for the name alone.
The Zoxnoxious Pole Dancer filter is starting to dance. Very first impression: this thing screams. I’ve a long way to go in developing software for this, and the hardware just gets by, but it’s just a “wow, I can configure this filter any way I want”. By first impression, I mean I’ve only got things soldered up and the software configured a few hours back. What is the Pole Dancer? It’s a filter based around an SSI2140. This is the same SSM filter that was used on the rev1 Prophet 5. Then for pole mixing add in an SSI2190, which is basically a voltage controlled mixer. The pole mixing is all configurable through the SSI2190 to however one sees fit. Based on the mixing one should be able to get various low pass, high pass, band pass, notch, and all pass configurations. Here is a very early demo video here that shows filter sweeps via while tweaking the filter pole mixing.
This has a lot of potential with VCV Rack. Beyond the filter itself, I intend to put together a module with filter definitions (high pass, low pass, etc etc). Wire those up with crossfaders, switches, or whatevz to the filter module and you’ve got analog filter morphing. Pretty cool stuff.
I’ve only started to explore this and it’s sounding pretty cool. The filter pole mixing is entirely voltage controlled, so here’s an example patch of what one can do. I started off by defining some presets on Raiju for various filter modes, a dozen various modes. It’s just various voltage levels for the mix, so that’s easy enough. Get a couple of those Raiju modules going to an LFO-controlled crossfader. Split the output so only one filter pole goes through a Slew Limiter, merge the signals back together and have the Pole Dancer do its thing.
I thought the 2040 was developed by Ron Dow, and I thought he is dead? I guess one of those things (at least!) is not correct?
I found this on the interwebs - it has to be true (JL is Jay Lee in Polyphony Magazine November/December 1981. DR is Dave Rossum):
JL: You were involved in the design of the first electronic music chips (SSM). To what extent were you involved in this?
DR: The story goes something like this. Back in 1975, Ron Dow dropped by E-mu and had this idea for a VCA design on a custom chip. He wanted us to kick in the $1000 or so it took to integrate it, because he didn’t have the money. It sounded interesting, but then he said the power supplies couldn’t be any higher than +12V. Since the E-mu system was based on +15 and I didn’t want to change the whole system standards for one IC, the idea no longer made sense to me. So we turned Ron down and he then got connected with SSM, and they were the ones to integrate and start selling the SSM2000.
About a year later I ran into Ron again, and he mentioned an improved VCA they were working on with+15V supplies. With my major objection gone, I became interested again. I contributed some ideas to the SSM2010 (low distortion VCA), then Ron started frequenting E-mu and used our lab to develop the chips - first the 2020 voltage controlled amplifier, then the 2030 voltage controlled oscillator (which was a very hard project and took about a year), the 2040 voltage controlled filter which went pretty quickly as did the 2050 transient generator, and we’ve kept up the collaboration since then. My involvement varies from chip to chip; with the 2020 I helped Ron design the control stage, while he did the VGA cell entirely by himself. The oscillator was definitely a joint -effort, while the 2040 and 2050 were largely my designs. All of the SSM chips vary like that. We’ve pretty well decided that we’re codesigners on what we do, because you just can’t separate where an idea came from. Ron might suggest something to me for a filter design, but I’ll end up using the idea with something like a transient generator instead.
Wayback Machine archive of the interview.
@Jens.Peter.Nielsen gets it right, Dave Rossum. He re-did it for Sound Semiconductor as the SSI2140 that includes a couple upgrades and the same filter character. Not dead yet!
I must be mis-reading his post. It seems that DR is saying that Ron Dow designed these chips. Isn’t that what it says? I think it says DR gave some help, too? Oh, I see, he says he did most of the design on that chip. ok.
nice! I’m pretty sure I subscribed to Polyphony then. I knew Row Dow, only spoke to DR on the phone 
Nice! I don’t know the details on the designs, I’d guess both were involved. A modwiggler thread says Dave did circuit design while Ron did layout. Maybe a fair bit entwined between them. Sound Semiconductor is Dave Rossum’s thing, and it’s great to have access to modern versions of the SSM chips from those involved in the original designs. Sound Semiconductor has a library of a half dozen chips which all pack a punch in analog synth design. I used their 2130 VCO on a previous project which does through-zero FM. And SSI’s new chip, the SSI2190, is a really cool OTA based 6-channel mixer. The confluence of the mixer & the filter chips are the engine behind the pole mixing filter I just put together.
Here’s an example of the Pole Dancer filter morphing between filter modes along with some filter cutoff modulation. Expedition Electronics has a great website to toy around with what’s going on from a technical standpoint, so I demo that a bit. Then setup a Pole Dancer “Personality” for a double notch filter. De-construct the mixing with a Split, modify one of the mix levels, then Merge that back together to patch the Personality to the Pole Dancer.
I re-worked the previous video and did an in-depth demo of the Pole Dancer voice card. Demo shows the VCV Rack module for the Pole Dancer along with it’s companion Personality module. I’m not aware of any analog filter like this. Lots of analog filters can switch modes; Oberheim was always good with that. The Xpander had 15 filter modes, or the SEM could morph between two filter modes. The Pole Dancer gives an unprecedented amount of control over a pole mixing analog filter. And it uses the SSI2140 under the hood, a great sounding filter. I’m hoping to pivot soon to getting the voice cards and overall synth in a more usable form factor. I was going to do that a few months back then this Pole Dancer idea caught my attention. A couple months of dev here and wow, that’s a cool filter!
Pretty basic looping arpeggio here: goal was to show the Zoxnoxious synth not as just a monophonic synth. So 4 VCOs and 3 VCFs; one of the VCFs has a white noise source. Managed to get a couple voices and some percussive elements out in a single take. No effects, just the raw synth for demo.
Visuals: just a bunch of the schematics & layouts to keep it geeky.
From the Stairway manual:
In 1978, Bernie Hutchins published an article in his Electronotes (issue 85) entitled “Additional Ideas For Voltage-Controlled Filters”. In the article he outlined how a lowpass ladder could easily be modified to produce many filter responses other than the normal lowpass.
This idea was (we believe) first commercialized in 1984 by the Oberheim Matrix-12 analog polyphonic synthesizer.
This idea was also commercialized in the Mutable Instrument 4 Pole Mission filter board for the Struthi synthesizer. This was released in 2011 or 2012, and designed by the legendary Émilie Gillet.
We imagine that there are many digital filters that use this technique. In VCV the Blamsoft FXF-35 in transistor ladder mode seems to.
In Stairway we use the Mutable Instruments method of adding the extra filter types, which give somewhat different responses than the Matrix-12 method.
