DoublePlusBass

 Yo, it's the first PCB I designed!

This circuit, the DoublePlusBass, represents the culmination of a LONG journey starting with my first complex point-to-point success (a TR-808 kick drum) and wanting a 909 style kick drum. Couldn't get it. Failure after failure.

Thomas Henry's Bass++ is a miracle of minimalist complexity, wringing a very capable and versatile kick drum voice out of a single LM13900 and a dual op amp. Quick note: there's a .pdf on that website that is AMAZING you HAVE to see it okay fine here's a link my god it's a thing of beauty.

So, I got massive kicks out of Thomas Henry's excellent work, but I wanted more flexibility and less "crosstalk" between settings. Which involved more parts. I wanted a pitch envelope that made the kick pitch more similar to the 808, which sags right at the end vs. the 909, which spiked downward fairly quickly after the attack.

Feature creep crept in, with every problem being solved with more buffers, so my own kick drum diverged significantly from the Bass++ inspiration, so the DoublePlusBass was born.

All my schematics had been hand-drawn up to this point, but the DoublePlusBass was super complicated, so I was struggling fitting all the schematics neatly on one page. Yes, I resorted to cutting and pasting. But then I started investigating electronic design applications, and after much frustration, landed on EasyEDA, which runs in a browser, which kinda rules.

After getting the schematic drawn, my mouse crept up to the "create PCB" menu item so with much trembling and quaking, I clicked it. POW!!!!! All my parts were there, on a blank field, ready to organize and trace. Incredible. Mind-blowing.

I've never had success with any kind of 2 dimensional prototyping. 3D is where my brain lives, where my circuitry took shape and gained life. BUT!!!! The 2 dimensions of a PCB somehow did click, so ...

... to make a long story not any longer, this is my first PCB. The current prints are a lot better in layout and whatnot, but the ELEVEN potentiometers are still laid out like they were, and the functionality is basically the same.

Okay, I'm actually NOT going to list everything that each pot and jack does, I'm in a hurry, but here's the biggest surprise: the 808/909 envelope moves the fundamental pitch up a great deal when turned toward the 808 side. The 909 starts high and drops to the fundamental pitch. The 808 hits its fundamental pitch right away, and sags down from there. So my least solvable problem was this: that knob fades between two theoretical fundamental pitches, but there's only one pitch CV, which ... the user has to turn lower when choosing a more 808-style pitch envelope.

Okay, that's all for now.

PlusSnare, an 808 snare with a twist!

 This little fellow is a basic snare voice module that accepts a trigger, and outputs a snare. It's a modern copy of the Roland 808 snare voice, snappy volume, two different "body" bridged-T circuits that make a "bong" sound, and a knob that fades between the two. It sounds like a reasonably accurate synthesized snare drum, and exactly like some* 808 snares.

*the OG '80s and '90s Roland drum machines are mostly analog, with 5% carbon film resistors and (aging) electrolytic or (high-tolerance) ceramics and maybe even (SCARY) tantalum caps. So, every one of those machines will sound slightly different, sometimes you'd even be able to tell by listening. But they all sound like 808s or 909s or 707s or whatever.

Anyway, this module ALSO has a delay circuit. It uses the ubiquitous PT2399 chip, with the parameters shoved way past where they're supposed to go, we've all heard the runaway delays and the CRONCHY delay times that happen when a designer wrinkles up the datasheet .pdf and drags it into the recycle bin.

Also also, you can inject whatever sound you want for the "snappy". Kinda fun to experiment with a random audio track, say, Carly Rae Jepsen's hit pop anthem Call Me Maybe? The input will be getting the same filtering and VCA'ing that the white noise gets, just so you know.

Okay lemme seeeeeee... hmm, instead of trying to remember what this module can do, and how to get it to do it, allow me to send you to a Youtube video of it:

 

 

Okay there it is! Quick rundown if you don't want to watch a video:

Jacks:

Trig triggers, MixCV controls the wet/dry mix, with high voltages injecting the snare voice into the delay circuit. The delay tails, so a low voltage won't cut off the delays. It's fun to have the 3rd snare per phrase have a dump of delay... this module was inspired by King Tubby's use of this technique. Acc is basically CV control over the amplitude of the snare. The 808 machine has two levels, but this is infinitely variable. Out is out.  Alt is for alternative "snappy" sound inputs.

Knobs:

Tone fades between the two "body" resonant voices. Snap adjusts the volume of the white noise or the alternate signal. Delay controls the length of the delay repeats. Reps controls how much of the repeated signal gets passed back into the delay circuit. These last two controls will crunch and degrade, and repeat into very loud runaway feedback. Mix is the initial wet/dry control of the output between the snare voice and the delay circuit. Vol is output volume obviously, with a twist: the first two thirds or so of the volume are straightforward amplitude, but the last third soft-clips against a pair of diodes, making for a nice saturated snare sound.

Huh, I guess that's a pretty complete rundown, not as quick as I'd thought. Okay enjoy!

POWER to the People

Here's a module that's got +12V, -12V, optional +5V, and a headphone amp. It charges via USB-C, and seems to work pretty well... my multimeter shows confusing numbers when I try to measure millamps, hopefully some actual stats will be forthcoming.

So here's the placeholder for the build document. I'll hurl some

 SAFETY WARNINGS

 here because lithium ion batteries can be hazardous.

• Never short a lithium ion battery. They will die, possibly by bursting, possibly by lighting on fire. They are very difficult to extinguish, since they often have oxidizing chemicals built in, as though they're DESIGNED to be rocket fuel or something.
• If you do have a battery light on fire, put it in a bucket of sand and move the bucket to a well-ventilated area. Wait for the battery to stop being on fire. Wait even longer for it to cool. Then take the goo to a qualified battery disposal site in your area.
• Pay extremely close attention to the polarity of the battery you're plugging in to this module, and the polarity of the pads or connectors you're connecting to. I can't guarantee that your battery will be correctly labeled or built, so please check that stuff. This module has reverse-polarity protection, but try not to test it.
• Avoid shorting the outputs rail-to-ground, or rail-to-rail. The module is built with short-circuit and over-current protection, but again, try not to test it.
• Use boxed-style IDC headers for the Eurorack cable headers. This is important because you don't want to plug your cables in wrong, but even more importantly, they'll provide the physical foundation for the cable ends that the 13650 battery you might be zip-tying to your module. This module will work with any single (1S, in battery lingo) lithium ion battery, but there's holes to make it easy to zip-tie a cylindrical cell there.
• Please secure whatever battery you use in a safe way inside whatever enclosure this module will live in. Lithium ion batteries should never be rattling around inside anything, so seriously, folks, don't goof around with this stuff.

Features of the M4TM POWER to the People

• Rechargeable and portable bipolar power for Eurorack modules
• Optional 5V power rail 
• ? mA of power with ? voltage sag ??
• Overcharge, undercharge, overcurrent, and short-circuit protection
• Headphone amplifier! Stereo, with the top input sending signal to both channels if nothing is plugged in to the bottom input
• The cheapest battery-capable +/-12V power supplies out there will abuse the battery if you charge the battery while using it. This one has a little mosfet that allows for use WHILE charging. Neat.

Okay that's it for now. I'll probably make a build-guide which will hopefully be here, or at least I'll link to it. 

Juanito's Sweat Factory

 Hey everybody, this is basically a placeholder.

I'm developing a CV sequencer module! Four inputs with knobs, for parameters. Eight CV knobs for, like, setting the CV of each step. One button in the middle. Oh yeah, two buttons under the top left and right pots, y'know, like HorseDebt. Eight outputs, one Pure DAC analog, three PWM analog, four digital but there's spots on the PCB to add a capacitor for smoothing if you wanna write firmware that can put out more PWM signals.

EXCITING THING: this is a radically flexible module. At its heart is a AVR128DB64 chip, which can be coded in the approachable Arduino IDE, and there's even gonna be a USB jack right on the PCB so all  you need is this module, a USB cable, and a computer, and you'll set to program this little guy??????

I haven't even started writing code for this, but it's gonna be flashy, it's gonna be flexible, and it's gonna have TWELVE JuanitoPots with addressable LEDs under them. BlinkyFlashyBloopyFun

FZilter featuring a MB87186 chip

 

A mysterious forest wizard shot an arrow into a nearby tree trunk with a message wrapped around the shaft. It said "Wouldst thou deign to design a PCB for an exotic precious gem of a microchyppe which one canst obtaineth not except by exxtraction from a Casio FZ-1 or symilar keyboarde?" so I stuffed a message in a bottle saying "heck yes" and threw it on the water.

I had never heard of this chip or the fact that you can build it into a Eurorack module, but it's quite a unique thing. The chip is a "digitally" controlled filter and amplifier, which garnered some praise back when it was new for sounding analog. Turns out it IS more-or-less analog, with a switched-capacitor filter and hmm, I'm not sure how the audio amplifier is managed.

What is a switched-capacitor filter?????? Glad you asked. A filter is almost always a capacitor-resistor situation. A resistor reduces how much current can flow, and a capacitor can be thought of as a kind of balloon which "fills up" when a current flows into or out of it. Most synthesizers vary the resistance (sort of) to adjust the frequency at which a filter takes effect. You can do this with a potentiometer, which you need to turn with your hand like a cave man (ugh) or you can use a voltage-controlled resistive part like a Vactrol or an OTA which stands for operational transconductance amplifier obviously but just understand that it's MUCH easier to use a voltage to adjust the "resistance" section of a resistor/capacitor filter than adjusting the capacitor.

Acute cholecystitis and biliary pancreatitis also uBraids

 

You heard what I said. Acute cholecystitis and biliary pancreatitis.

Cholycystis is the fancy word for gallbladder, "gall" being bile, or the "coleric" humor in the old Humorism concept of human health. Gotta have those humors in balance, right?

Biliary pancreatitis is where your pancreas gets irritated, inflamed, basically super pissed off. The pancreas is the chemical plant of the body, it makes insulin, pancreatic polypeptide (????) and something called pancreatic juice.

Why "juice"? I don't think of "juice" as a medical term. I guess it is though.

What happened? Well, my gallbladder filled up with stones, and from time to time, one of them got passed through my Main Bile Duct, and when it was a difficult passage, it made me feel gross. My tummy would hurt and my pancreas (I know now) would get upset and hurt as well.

A gall stone got stuck in that main bile duct sometime before Christmas Eve, causing my whole digestive tract to give up, shut down, say "NOPE" as clearly as possible, so anything I ate or drank came back up the way it went down (except much more unpleasantly.)

I got more and more uncomfortable, until my wife drove me to the emergency room and they admitted me to the hospital, calmed my extremely intense pain down with opiates, palpated my abdomen, gave me two IV antibiotics as a preventative (?????), passed my torso through the opening of a CT machine, and declared that I would need my gallbladder yeeted into the biohazard bin.

I asked so many times if I could keep my extracted gallbladder but everybody said no. I wanted to make it into a hacky-sack. Turns out though, the "stones" aren't actually mineral stones, they're made of cholesterol or bilirubin or blood ewwww and I bet it smells bad, so I'm okay with them just throwing it away.

It was big, though. I have a "four inch" (less than three inch real measurement) incision right below my lower right rib cage where they had to pull out the gallbladder.

The pain before and after the surgery was intense. Worst pain of my life before, even worse pain after. Somebody mentioned within my earshot post-surgery that my uncomfortably bloated abdominal cavity was filled with "a straw-colored fluid" which (in my imagination) became pancreatic juices and enzymes eagerly trying to digest my liver, intestines, bladder, kidneys... as though somebody had inflated the muscle/skin balloon surrounding my guts (this happened -- they use carbon dioxide gas) and rubbed Frank's Red Hot all over my entrails. Ow ow ow ow. Plus, the bloating was severe and got worse, making it impossible to take full breaths.

Well anyway, that was two weeks ago. I'm weak, skinny, exhausted, but basically pain-free using OTC pain meds (severe family history of opiate abuse so No Thanks, Prescription Painkillers!) and as of today I'm allowed to lift more than 20 pounds (9.071847 kilograms exactly) so I can get myself back in shape.

Some of you will have donated to my "Fix Juanito's Tum-Tum" fundraiser to help pay medical expenses, and for that, thank you so so much. Mutual aid is a grimly heartwarming bandaid for our extremely broken, abusive system of paying for medical care. Thank you again.

HungryFuzz HEY GUYS, new module!

NEW MODULE TIME! Well, prototype time. The design is done, and there's some germanium transistors that will be going in there, and they need testing. So here's the rundown of the module and circuit, and if you're looking for build tips, those are after the break!

I like distorted kicks. It's part of my identity. Both modules in my Hungry- series work so well with kicks, the HungryRat (Proco Rat clone) is HARSH SHARP, and my HungryThumb is a compressor and does amazing things to kick drums, including soft clipping, compressing, saturation, lots of fun. Well, I don't know how many germanium transistor distortion pedals have been ported to Eurorack, but the number is probably low (germanium transistors aren't common) so here we go!

The original Fuzz Face pedal "remains an enigma". It was released in 1966, consists of a battery, four resistors, three capacitors, two germanium transistors, and two potentiometers. Ludicrously simple!  The page I just linked to talks about how some of the unique sound may have been a happy accident. There's asymmetrical clipping which starts out soft and goes harder with increased signal voltage. I think that's probably the main accident?

The design has been developed exhaustively over the years, with different designers experimenting with different transistors and transistor types (NPN silicon transistors, for instance), and tweaking resistor values, and (my favorite) hurling potentiometers in there wherever they might make a difference in the sound.

For pedals, where the knobs are in the stompbox which is usually on the floor, two knobs may be fine. But we synthesizer guys love to have all the knobs at our fingertips, and the Zvex Fuzz Factory seems to be the most complex design out there, with five whole knobs to play with. So I cribbed from that circuit, added my starve circuit which also allows the distortion core to work with bipolar voltages (so there's no DC swing when adjusting the starve, right?) (although I left the DC blocking capacitors in the signal path) (which are MLCC in the prototype because I don't believe that most capacitors "sound" like anything). There's a stupidly wonderful tone control in there, and of course a proper output buffer with adjustable gain to get the output to be a nice safe 1K impedance at 10V peak to peak.

And that's the circut! I have zero zero zero hands-on experience with a Fuzz Face of any variety, so I'm.... excited to see how the prototype sounds?

But I'm neglecting to talk about germanium transistors! They're nifty! And very obsolete. So check after the break for what to do with these weird parts!