synthgeek's blog

First, two Phoenix vs. Mimsy videos:

One of just Phoenix:

…and one of just Mimsy:

This one started from a basic schematic in the 566 datasheet:

For my build, I substituted a 1.2k resistor in place of the 1.5k (because that’s what I had on hand), used a 500k pot for R1, and a 1µF cap for C1. Here’s a shot of the breadboard:

You may notice the second jack in the above photo being routed to pin 5 of the 566, which is the CV input.

The next step was to build it on perfboard. I also wanted to add a saw wave output to the 566′s “built-in” square and triangle waves, and once again, the Experamentalists Anonymous schematic archives came to the rescue, in the form of this schematic, an op-amp and about a dozen components. This is an early shot of the perfboard build, some tweaks were done later:

I’m not getting a very good saw wave with it, which could be due to my having to sub some components. The schemo specified 330nF caps for the square-to-saw converter, and the closest I had were 220nF. Also, there were no specs for the diodes or trim pot, so better results may be possible with different components there- again, I was just using what I had on hand.

After testing, I decided to replace the trim pot with a panel-mounted control, just for added odd sound capability. Here’s what it sounds like through the Blue Lantern filter, with some tweaking of the shape knob and a CV input later on:

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Another 386-based lo-fi bass amp build, again inspired by ideas from Beavis Audio Research and Runoffgroove. This one is a bit more complicated, incorporating power supply filtering (via 220uF capacitor), buffered input (via 2N5951 transistor), and a tone control (from the Beavis Audio article on the Big Muff Pi tone stack, inserted between volume control and 386 input pin).

The input section (including buffer) is like the one from the Beavis Audio Noisy Cricket design, but with the BMP tone stack instead of the one from the Cricket. Also, I used a single 100nF cap in place of the 47nF specified in the Cricket schematic, and omitted the second input cap. The rest of the design is inspired very much by the Grace Overdrive design from Runoffgroove, with a larger output cap.

Perhaps you’re wondering where the name came from… well, like the Candy Land Combo, the Dirty Cow gets its name from its enclosure:

The jack with the red plug in it is the input, output is on the back. There is a power switch and LED, and the knobs (from left) are: gain, tone, and volume. Their placement is a bit misleading, since I went with a “non-master” volume setup (the volume is on the input, not the output). That also means the volume and gain knobs are interactive, allowing for a more adjustable response. Compared to the Candy Land amp, this one is a little louder, but is also capable of more sounds approaching “clean” territory.  Here’s some audio (kinda sloppy playing, sorry)- first up, a cleanish tone (same active Ibanez bass as last time) volume just over 3/4, gain lowish):

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and here’s a more distorted one (volume and gain around 3/4):

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…and some even sloppier guitar playing, gain and volume cranked (passive-pickup cheap Strat copy):

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Another project based on a schematic from the Experimentalists Anonymous archives, with a tone control added to the return path.

The tone control follows the schematic in the Beavis Audio Research article on potentiometers. It’s a very simple passive resistor/capacitor network that works like a guitar’s tone knob.

Since I’ve been putting together the material for the upcoming SC show (see the website for details), I decided it’s as good a time as any to post about the setup I’ll be using. Here’s my ugly but informative diagram:

The centerpiece of the rig is a Tapco Mix 260FX mixer, which I probably spend more time “playing” than any actual instrument in the rig, unless you count the Nocturn. The “brain” of the rig is the K2000S, which handles most of the sequencing duties and serves as a source of synth sounds. The laptop serves as a sort of virtual rack, hosting several synths and effects in a modular host (namely energyXT). I’m generally not doing anything very complex sequence-wise in a live setting, though the K2000 could certainly handle it if I wanted to.

The K2000S can play multiple sounds at once, but only has two assignable outputs (there are 3 pairs of stereo outs, but one is the “mix” out), so in most cases I only use two sounds from it at any given time. That may not be a lot, but with the laptop it works out fine in practice.

The laptop (on loan from Kris) is not exactly a powerhouse (2.8GHz P4 w/512MB), but it can handle a couple of synths with effects. It usually handles the drums and one or two other sounds. I also have the output from the SoundBite loop sampler routed into its inputs, set up so I can sample whatever’s playing through the mixer’s control room routing and mess with it via software. This is one of the nice touches on the Tapco mixer I’m using- unlike many budget mixers, it has a ton of routing options- including the ability to choose which sources go to the control room/headphone outs (the choices are main mix, submix, and CD/tape input, and all 3 can be engaged at once).

Speaking of routings, I have some unorthodox stuff going on there too (nothing extremely crazy, but not quite “right”). You may have heard of the old dub trick of routing a signal out through an aux send, through a delay, and back into a mixer channel, which can then access the same aux send for feedback purposes. I have an old ADA digital delay setup that way, coming back into a mono channel- the mono channels have sweepable mids, which is very handy in this application. I also have the submix outs routed to a Kaoss pad, and back into a mixer channel, stereo in this case. I didn’t do that one so much for the feedback possibility, but to have a sort of freely-patchable insert effect. Since it comes back through a channel, it can also be used with the other effects.

Although it’s rather simple, I find this rig quite flexible, and lots of fun. All in all, it may be better suited to noise than anything resembling music, but it can be tamed. Something I would like to point out is that my use of hardware does not imply any lack of faith in a software-based setup, it only reflects the fact that I don’t have that much power available in software here. I do enjoy sequencing on the K2000, but I’m much more comfortable in a more visual environment. Also, the dub-feedback thing is easier to pull off in hardware.

My friend Kris has given me a bunch of interesting materials for use in my electronics experiments, so I figure the least I can do is build him something. His main instrument is drums, but he also plays bass, so I’ve decided to build him an LM386-based portable bass amp. I have a small Candy Land lunchbox that will make a perfect enclosure:

The circuit is cobbled together from ideas snagged from three other designs: the Little Gem and Ruby designs from Runoffgroove, and the  Noisy Cricket design by Beavis Audio Research. Ultimately they all lead back to the Smokey Amp by a guy named Dave Stork.

The controls are pretty simple- on/off switch (with LED), and volume & gain knobs. The silver jack is the input, the black one is the output. I used a switching jack for the output so the internal speaker turns off when you plug it in to a seperate cab.

Here’s an example of how it sounds- for this recording, I had the output going to a 12″ speaker, close miked. Bass is an Ibanez active 5 string with its volume set low, volume on the amp is cranked, gain about half (I think you’ll recognize the tune):

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Here are a couple of longish (8+ minutes) recordings made with the Phoenix/Mimsy combo. Not to be confused with music.

The first one is the raw dog: no effects, just a single output into a mixer channel. There are some bits in this one that do a fine job of demonstrating the fun that can be had using Mimsy’s 555 osc as a modulation source, while modulating it with the Phoenix LFO. With the voltage starve in the mix, some interesting semi-randomness is possible.

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The next one gets the Kaoss pad and rack effects in on the fun:

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This module was made in the true spirit of the synth’s name, in that it is based on two 2N3904 transistors salvaged from the ESQ motherboard. The schematic was again found at the Experimentalists Anonymous archives: see it here. Here’s the board:

Another very simple build, 6 components plus connections. Didn’t bother with a panel photo this time, since it’s just one jack.

Here’s a recording of the noise source being fed into the Blue Lantern filter, with modulation via the Phoenix LFO and some audio-rate modulation via SAM being fed with the new 555 osc in Mimsy Modular and the Phoenix APC osc (just for a little extra edge).

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I decided to try something different, this time with a 555 timer chip. I removed the second side’s synth (the non-APC one), and replaced it with a super-simple 555 osc, very similar to this one from the Get Lofi site.

The controls are now arranged thusly: on/off switch at the top, second switch for choosing triangle or square wave, red knob for voltage starve, upper silver knob controls frequency, lower one controls CV input level.

This osc has a very wide frequency range, from sub-audio LFO freqs to very high. Here’s some audio which shows this range using this osc to modulate the APC side. The very first bit demonstrates the LFO sweeping from low frequencies into the audio range.

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