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Here’s a few more audio bits and a video from the new Phoenix modules:

This first one includes an appearance by the noise generator, some inter-osc FM, both filters, and the distortion/preamp (on the noise, post-filter):

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The next one is the two Nick W. VCOs into the ring mod/multiplier, processed with the MFOS filter and distortion, also includes feedback via an active mult and a mixer channel:

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Up next, we have the same two VCOs, this time each goes to a VCA (each modulated with an Ian Fritz AD envelope), and from there each gets one of the filters. More feedback in this one, I think you’ll notice when it kicks in:

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And here’s the video- same basic patch as the second audio demo above, but different settings:

As some of you may recall, I had built an AD633-based analog multiplyer (ring mod) module early on in the first Phoenix chassis, then removed it in favor of keeping that box single-supply- with the intention of putting it back in rotation when I broke out the dual supply again. Well, that time has arrived. I’ve used the same chip, but on a new board. I used another Ray Wilson design this time- namely the MFOS Analog Multiplyer from his “Ultimate Expander” project. I will be adding attenuators to the inputs, other than that, no changes.

On the same board, sharing a TL074 with the multiplyer’s input buffers, are a very simple preamp and noise source.

As mentioned in the notes, the noise source is a little quiet, while the preamp can be excessively LOUD. You may want to follow it with an attenuator if not using it somewhere where you can easily patch it into one. With the gain cranked, and a high enough input level, it’s gonna be as close to rail-to-rail as the TL074 will go. Way more gain available than needed, really, but I figure it’s better that than the opposite problem.

Here’s a recording of the Nick W. VCO (pulse wave) and the MFOS VCO (triangle wave) through the multiplyer, which is in turn put through the LDR filter (bandpass mode) with a little overdrive- the filter cutoff and VCO pulse width are modulated with triangle LFOs:

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Loid is growing quickly… after the first two modules, I decided to build another oscillator board. I had been looking at two things I’d come across at the Deathlehem forums: YAVCO and Ryk’s 4023 Pulse Width Oscillator. Ryk’s osc sounded really cool in the description, but that left 4 unused oscs in the 40106- so, I decided to see what happened if I combined the two. It worked great on the breadboard, so onto perfboard it went. I basically built the 4023PWO, then added two more oscs, which are controlled from a dual-ganged 100k pot. For the second of those two oscs, I added a 50k pot in series, so it could be offset from the main pitch. For the 4023, I wired up the unused NAND gate to be used with external signals. I also added a DPDT switch so the oscillators could be switched between standard powered operation, or the YAVCO-type pseudo-CV, with a SPST in series for the 4023 so that it’s power could be cut completely.

Here are two recordings from the post-build test- the first is showing the whole module in use, with the extra NAND gate being fed from the onboard oscs and one of the oscs from the first osc/divider board:

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The second one is just the PWM osc, switching between “normal” power and the CV input here & there:

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Next, I decided I needed some kind of mixer/output stage. I had recently scavanged a 10-way DIP switch, so I decided to build a 10-input unity gain mixer with a dual op amp. It’s very similar to Circuit 2 from this page at all-electric.com, without the capacitors in the feedback paths. I also used 100k resistors.

The mixer, output jack (with signal LED), and power distribution board are mounted on a plastic tuner-face scavanged from an old stereo. The power board is just a bunch of two-pin headers pulled from computer equipment mounted on stripboard, with the power coming in from a 1/4″ jack mounted on the face of Phoenix. The power supply I’m using there is big enough to handle all of these and several more modules.

While testing the mixer on breadboard, I had come to the conclusion that building this synth in the standard modular way, with nice panels & jacks, would be pretty expensive. With just the two oscillator boards, the Melody Generator, and the mixer, I was already looking at 39 jacks! I’ve seen other people just building everything on perfboard with no panels/case at all, using various headers & board-mounted pots, but I don’t really have an area where I could put such a thing and not worry about something happening to it. After a little thought, I decided to go with a method I’ve used before: plastic coffee cans. I just drilled holes in the sides for the input/output wires to hang through, with heat shrink used in places to keep them from going back through. Each coffee can comfortably hold at least two modules.

This photo shows the Lunettoid modules I have finished so far, with a 4051 on the breadboard:

The can on the left holds the two oscillator boards, the one on the right holds the Melody Generator and two pseudo-ring mods, one using a 4011 (see this page for a schematic) and the other using the TS12A Chopmodder I also used in Phoenix.

Here’s a recording made with the patch shown in the photo:

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With the arrival of a couple more LM567′s and some other IC’s, phase 1 of the Phoenix project is complete (that is to say, this rack is full). I do plan to make a final faceplate for it, and do a little rearranging & such, but it’s more or less complete module wise. There will be one last small change, which I will go into in more detail below.

As hinted at in the title, the final two modules both ended up being AM devices, one of which is a simplified version of the LM567 amplitude modulator/oscillator combo from the Modutronic Messmaker. The other is even simpler: one chip, three jacks, power optional (that’s right, though it sounds a bit different, it does work with no power connected). It’s based on a TS12A4514P analog switch chip, and I call it Chopmodder:

Here’s a photo of the breadboard build:

I doubt I’m the first one to think of this, but I haven’t seen it anywhere else yet myself. Please let me know if you have.

Here’s a shot of Phoenix with some of his friends:

You may notice there is one empty hole- I plan to move the white noise output over, and make that a jack connection to an LED, which will be paired with a photoresistor to give me CV control of the osc in the 567- the old homemade vactrol trick. I will also be adding a smaller pot for fine-tuning of said osc, which I’ve already done for the 566 VCO.

Here’s some audio including the latest additions (no external machines or effects, other than the blue lantern filter):

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So, the plan for the 567 changed a little bit. Meet the Modutronic Messmaker- I added a 555 oscillator to make it a synth (with audio input for the AM part). Here’s the schematic:

I actually used 2.2k pots where 5k’s are specified in the schemo (more scavanged parts). Here’s what the final circuit looked like before going into a case:

I recently came across a plastic VHS tape case, so that became the housing.

There are a total of four jacks- from left in the above picture: 555 CV in, 555 output, 567 AM (pseudo-ring mod) in, 567 out. The inputs use switched jacks, so when nothing is plugged into them, they receive input internally. With no inputs, the 567 is fed from the 555 output, and the 555 CV input is fed from the 567′s output. There are controls for the frequency of each osc, voltage starve, 555 CV input level, 567 output level, and a control for the frequency of the 567′s simple filter.

Here’s a video of the Messmaker in action:

Once again, thanks to Beavis Audio Research- this time it’s a tremolo/quasi-ring modulator circuit built from the LM567 tone decoder chip. As an added bonus, the squarewave oscillator also works on its own, without any input.  Click here to view the pdf from the Beavis audio site (includes schematic and breadboard layout). This chip was traditionally used for touch-tone decoding in telephone & other communication systems (I recently harvested two of them from an old modem), and includes an internal oscillator and bandpass filter.  Here’s what the circuit looked like on the breadboard:

And here’s a shot of the final perfboard build:

I made substitutions for the filter and volume pots: instead of a 50k on the filter and 100k on the volume, I used a 22k for the filter, and a 50k for the volume- the original 50k on the filter seemed to have a lot of extra travel (and so does the 22k, but I’ve got a few to use). The volume pot sub was just because I had no 100k audio-taper pots.

Here’s a recording of the circuit being fed with the APC side of Mimsy Modular:

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My original thought was to make this into another module for the Phoenix project, but now I’m leaning towards just making it a stand-alone fx/noise box. Since there is so much extra room on the board, I’m thinking of adding a simple distortion circuit of some type on the output, which could be switched in & out.