Wally gets a little brother for Christmas

Looks like I'm getting an Arturia Microbrute for Christmas!

I know it seems like it's not much of a surprise, but I like to think of it as a surprise I know about early! My wife is getting it for me with some support from other relatives.

The thing I like about the Microbrute so much is that it has a patch bay and "speaks" the same voltage languages that Wally does. So this means that I'll be able to use Wally's modules to supplement the MB's features. Which is handy, since the MB only has one oscillator. Wally's VCO will mix in nicely, though I imagine I'll have to spend some time with the o-scope and tuner re-scaling the VCO to match the MB's range. (And tuning the MB's keyboard too - it should be pretty well in tune from the factory, but like with guitar action, I've heard that many MB's need a little adjustment to be perfect. No biggie, that's one thing I do know how to do.)

This does make some of Wally's new modules less urgent, thought I really need to get his scratchy pots cleaned up.

Fortunately, I have a few weeks of vacation coming up soon, and at least half of my time isn't already committed to being places other than where my toys are. Expect some pictures and maybe sounds in the next few weeks.

Ther perils of "almost there"

I've found that now that Wally is 90% usable, I find I'm more interested in playing ON it than WITH it. I've been experimenting with different wave shapes, feeding the VCO's sine wave back into the FM modulation jack, etc.

My current favorite setting is a PWM square wave with the pulse width lightly modulated by a random noise source. I've set the filter to very slowly come down over time so that if I play legato or sustain for a quarter note or two (assume 120-140bpm or so for my noodling around) the sounds mutes some. The random PWM makes the sound seem noisy, but not out of tune like it does if I feed that same signal into the Frequency Modulation. Hardly a revelation, but there you have it.

I still need to get that DeOxIt though, since a number of my pots are still pretty scratchy.

Also, I'm becoming increasingly interested in getting that step sequencer project (or the similar touch keyboard project) going. I'm going to have a little time off next week, so hopefully I'll have pictures of some new projects to post.

I haven't forgotten about you...

I just didn't have the chance to work on Wally last weekend.

Through a little experimentation, I've discovered that I DO need to ground the sleeves of all those new 3.5mm jacks I added. So that, and the new power cables are the next things on my list.

I'll keep you posted.

Frak, Jack and Roll

I promise I'll try to make better titles in the future.

Bolstered by my success with the ARF VCO and Fry's actually having some parts I want for a change, I decided to "finish the job" of re-jacking all the banana plug connections.

This is a view of the half and half stage, with the Noise module completed, but the LFO still rockin' the banana plugs. I started off with the noise module because it's the one I could most afford to mess up. As a side note, it, like most of my modules, is based off of the simple reverse biased transistor noise source, amplified and filtered to get "pink" noise and a random wobble. The "Volts" knob is just a 0v-5v constant source, which is sometimes useful for biasing a CV parameter or testing something out.

That reminds me - I did some tests with my oscilloscope to make sure I had a good understanding of what voltage levels Wally uses internally. My tests show that I do recall correctly - Most of my signals are in the +/- 5v range, with the envelope generator at maximum output swinging from +/- 10v.

Just so you can get an idea what my late-90's DIY work looked like on the inside, here's a shot of the rear of the LFO module. The orange caps are power supply bypass caps, and as you can see, this is a picture from before the banana plugectomy.

Finally, here is a close-up of the finished DIY part of the FracRack, now completely 3.5mm connected. The "Output" panel is not really a separate module. It's connected to the VCA's output jack. With the Vol knob at 12 o'clock, Wally's signals come out about line level, so he won't blow away my mixer's input bus.

I had a brief scare with the VCA. It stopped working during the middle of some testing. It seems that one of the ICs had a faulty solder joint. Hopefully, I won't have any more trouble with it.

Here's a kind of blurry (sorry) picture of Wally, sporting his new chrome-colored connectors. I still have the "1/4 to banana" adaptor panel (right above the ARF VCO) because I found that with cross-patching the banana plugs, I can use it as a 3-way multiple, and feed pitch CV into both VCO and VCF. I'll have to make a real multi at some point, but for now, this hack will work.

So right now, Wally has 7 rack spaces of usable modules, and a total of 9 individual functional units, if you count the dual A/R generator as two functions. Power distribution takes up 3 spaces, and there's a double blank in the FracRack and a single space blank right above the PSU.

With his current configuration, he can make some musically useful sounds, some cool wind effects, and some cat-destroyingly horrible screeches. When I get some time, I'll try putting together a video or something.

My next project will be to rework my power distribution scheme. Fry's had the molex connectors I need for the project, but I have some thinking to do before embarking on that project. Largely because the FracRack also has a PSU in it, and the MIDI->CV converter runs from a separate wall wart. Ideally, everything should run from the same "on" switch.

One other consideration - Ikea makes a nightstand that is exactly the right size to use for an 6 rack-space high enclosure. It can go to 8 spaces if you mount the bottom shelf lower. That would be a lot nicer than the open frame metal thing I'm using now, and for about $30 total, I can add some protection to Wally, as well as hopefully a place to mount the PSU that doesn't take up front panel space.

ARF VCO - No Bananas

Last night, I went ahead and performed the "bananaectomy/phonejackoplasty" operation on my ARF VCO. Sorry for the quality of the pictures. I'm not sure how to insert proper links to the larger images. Blogger seems to just want to use the thumbnail version.

The original panel was hand-drilled, hand-labeled, and fitted with banana jacks. Since this is a "free rack" module (that is, a 19" rack unit, not a FracRack or other sub-rackspace format), it's destined to get 1/4" jacks.

The conversion was both harder and easier than I was expecting - the banana plug mounting nuts were a bear to get loose until I remembered I had an appropriately sized nut driver in the garage. The wires however, were pretty easy to get loose. I wound up labeling them with masking tape so I wouldn't get confused about which wire went where.

I also performed the conversion one column at a time. Here's the view after the first column was replaced.

Grounding is always a problem with 1/4" jacks. Though they were mounted to a metal face plate, and that provides a common solid grounding point, I also decided to go ahead and wire each ground lug together. I "snaked" the ground through all the lugs, and attached a fly wire from the last one back to the PCB's ground area, approximating a star grounding configuration. I suspect this step was unnecessary, and my multimeter's continuity tester showed that the panel was already electrically connected to the module's ground line, but since my other ARF module wired all the ground lugs together, it seemed appropriate.

Here's the final back panel. After hooking everything back together, I returned the module to its home, and everything is working fine! I really do like the feel of phone jacks over bananas. It's so easy to repatch things that nothing gets in the way of sonic exploration.

The whole project took around two hours, including time for trying to find hookup wire and nut drivers. Not too bad, though now I'm out of 1/4" jacks, and future work will require actually spending some money. Alas, can't be a cheapskate forever. ;)

Here's the VCO patched up for a simple "play me a square wave mixed with a triangle wave, with vibrato added from an LFO" voice.

The one down side to this scheme is that I lose the color coding for the SYNC plugs, which are not V/Oct control voltages.

Stop Jackin' Around and Give Me Some Power

So my conundrum about how to reconcile the fact that Wally uses pretty much every different connection standard ever gained another twist.

I asked my wife (who is way more practical-minded about, well, everything than I am) for some advice. I'd been trolling the PAiA and Blacet websites, ogling FracRac format modules I can't afford (don't judge), when it occurred to me that most of my modules are actually 3.5mm jacks, and so are the jacks on some of the other gear that I've been lusting after (Arturia MicroBrute, Korg Volca series). Well, that's not strictly true, most of my jacks are Banana Jacks, but I'm almost positive that I want to move away from those.

"So," says my wife, "why not just use 3.5mm jacks for everything that's Frac format, and 1/4" jacks for everything else?"

Why not, indeed?

So that means I can convert the LFO, VCA and Noise modules in-place by swapping out their jacks. The ARF VCO will still get 1/4" jacks to match the ARF VCF and A/D Generator.

I'll need to get more 3.5mm -> 1/4" cables. I already have 3, and they work fine. I'll also need a fist full of 3.5mm patch cables. Blacet makes a cable kit I could use to get both, but I should shop around some. I also just discovered Stackcables, which makes banana jacks even less desirable. Though at over $8 a pop, I won't be getting a ton of these. :)

This leaves the question of power distribution. At the moment, the FracRack itself has a simple but effective +/-15v supply in it. Power from that is distributed by basically the same sorts of connections we used to use to power disk drives in computers. It turns out that that's a TERRIBLE way to distribute power to analog equipment. But what can I say, I was young and needed the milliamps.

My "big boy" power supply uses three screw terminal blocks (+V, Gnd, -V), and expects each module to have a 3 wire connection that can clamp down. Electrically, it's sound enough, but it's relatively hard to attach and remove things.

My old MOTM stuff had this great block sort of like this one, and lucky me, I found the extra one I had! So, clearly, it's time to retrofit my system to use the more stable and convenient connectors. Blacet sells a kit of headers and wire which I can use. I might be able to get equivalent parts from Mouser or Jameco, so I'll be doing some shopping.

So there you have it - 3.5mm jacks for my FracRack stuff, 1/4" jacks for my "free range" modules, and MOTM-style power blocks for everyone!

Time to start saving my pennies.

Touch Keyboards and Step Sequencers

Aside from module renovations, I'm also planning on creating some "modular synth" style controllers. I do have a MIDI interface which works well enough, but I've always been intrigued by step sequencers and "Serge Touch Keyboard" type controllers.

I'm still very much in the brainstorming phase, but essentially, I have two projects planned - a simple 8 stage step sequencer and a capacitive touch keyboard controller (TKB). I'll have a lot more to say about these in the near future, but for now, consider this a sort of "statement of intent".

I've also started a YouTube channel to put up some video reference for these projects. So far, it's just me running my finger over the pins of a touch sensor chip and a few linked videos of devices like I'm considering. I plan to shoot a similar 10 second video of the 4-stage prototype sequencer I breadboarded over the weekend. It's also just some flashing lights at this point, with a rate controlled by a knob, but it's progress.

My sequencer is based off of a 4017 decade counter and a 555 timer. Hardly a creative and unique design, but I need something simple for my first time. I'm planning to base it off of the version in Barry Klein's book, which in addition contains some logic to support external and manual stepping controls. I'm going for a single CV output, portability and the ability to run off of a 9v supply.

The TKB is similar - this first version is 8 stages with touch-capacitive plates to activate each stage. The stages will be individually tuneable, so the keys won't correspond to piano keys, unless you tune them that way of course. So it's a very small keyboard at the moment, but I'd like to save the expense of a larger keyboard for after I've discovered what's horrible about my design.

The TKB is going to be controlled by an Arduino, since I'm better with software than hardware. The sensor I'm using is an AdaFruit CAP1189. I'd like to build some sequencing features in as well, so you can either play it like a keyboard, set it running, or both. The Korg Volcabeats is an inspiration, as is of course the Serge TKB.

A side note about the CAP1189 - it seems from the datasheet that I could use the built in LED driver hardware to trigger the key stages, as the chip can be set up to output whatever values you want from those ports instead of echoing the touch plate sensors. I had originally planned to use 74HC595 shift registers, driven by the Arduino using data pulled from the CAP1189. But if I can use the CAP1189 for both duties, then I can save some board real estate and part counts.

Sounds like a good next step for the software part of that project.