Atom 'Lytic Triple Barrel Lo-Fi Electret Distortion
(with 3-band EQ)This one is dedicated to fans of open air recording. I hope I've succeeded in going completely in the opposite direction of the other entrants...
As with my previous builds, my goal was to build something I've never seen in a stompbox, make it as far removed from anything commercially available and make it a complete piece of artwork both inside and out.
This is one of those ideas I came up with late at night hanging with friends, told em about it and was then dared to do it. As usual, they thought I was joking.
I used an LM386 to drive a combination of three speakers (IN the stompbox) and mic them with an electret microphone.
The Process:The first step was to find three small speakers with completely different tones and ones that encompassed bass, mids & treble, like a lo-fi 3-band equalizer. I went through about fifteen or twenty of all types, sizes and ages. The 1.5" one was pulled from a vintage transistor radio and the other two from kiddie toys from my circuit bending days. Here's the toy that housed the 1" speaker.
Purple freak w/ heart removedOnce I had the speakers, the first problem was finding a decent looking enclosure that was large enough and deep enough to handle all three. A big rectangular box would've been simpler, but I chose a sloped LMB "modular desktop console" that I picked up at a ham/electronics fest. Though not sold as a pedal enclosure, you'll see DIYers use 'em for TB MKI builds. It's 6" X 4" X 2.5", so deep enough to handle a mounted speaker.
To pick up the sound, I used an electret mic that came with an old computer when video conferencing was first becoming popular.
Electret Mic:
If you're not familiar with an electret, it's basically a small condenser mic that's used in a ton of stuff today:
Electret Mic WikiThe next part was easily the toughest...positioning the speakers in such a way that all the sound is picked up relatively evenly, doesn't feed back and of course doesn't interfere with the other components. After much experimenting, I determined that the most feedback was caused when the mic was pointing directly at a speaker. So, the configuration I wound up with has all three speakers facing the sides of the mic. To do that and fit them in the enclosure, one speaker had to be facing up and the other two on each side. That way there is no feedback at all.
I built three mounts for those speakers with a combination of plywood and balsa.
Speakers in Mounts:
A long time went into figuring out the best way to mount the mic to make it simple and flexible for adjusting. I originally was going to have it attached to the lid, facing straight down, but that wasn't flexible for tweaking since you can't actually see it at the same time as the speakers. The next idea was to make a boom with thin music wire that could be bent into position with pliers. I almost did that when I realized I still had the original mic stand. I carved it down to a thin strip so it wouldn't interfere with the speakers and mounted it on a hardwood block. This way, I could loosen the screw, rotate it any way I wanted at the mount, then re-tighten. I also can rotate the mic where it's attached at the end of the boom, so I have loads of control for tweaking.
Mic mount:
I initially was going to use a 3-way switch to choose one single speaker at a time; either high, medium or low...but mid-way through the project I realized I could have multiple on at the same time with no problems, so I added a switch for each individual speaker. This way, I had seven possibilities instead of three (!), and I could get ANY combination of high, medium & low (1, 2, 3, 1/2, 1/3, 2/3, 1/2/3)…a lo-fi 3-band EQ!
During breadboarding, I also noticed that altering the resistor on the mic actually acts as kind of a tone control, with lower voltages (10K) giving more of a bassier tone and (30K) producing more treble. Below 10K is very hissy and above 30K, the volume drops way off. So, I went with a 10K limiter with a 20K pot.
I had a couple weeks left, couldn't help myself, so decided to build this point to point using mostly vintage components, including some crazy monster caps, since those types were actually used in old amps...hence, the "triple barrel" (three large caps & three speakers). I always have a blast, and find it a challenge to fit large components into unlikely places. Between the switches worked perfectly for the caps, with the added benefit of the common switch lug wired to "cage" them in.
I "sacrificed" two of my favorite-named Sprague caps, an "Atom 'Lytic" and a "Vitamin Q". I'm not sure of the brand of the third, but like the Atom 'Lytic, it has a cardboard casing.
Comically, each of those caps can cost nearly as much or more than the enclosure....some people are nuts:
Atom 'Lytic FSVitamin Q FSIn addition to the caps, I also used a couple vintage 1960's 1% military glass resistors, one vintage 60's speaker (as mentioned earlier, from a transistor radio that was used for germanium harvesting), a jewel from a vintage amp, a couple vintage (late 70's - early 80's) 1/4" jacks, a few 60's terminal strips and lastly, a couple vintage metal knobs from an "autonomic nerve-point finder".
Nerve-Point Finder missing twoLastly, the main part of the box is painted with a textured paint and the sides are black hammered. The interior is navy blue with black speaker and electret mounts and mic.
Possible mods: There are so many things that can be done with the speakers, mic and enclosure. Of course, everything makes a difference. The angle of the mic, the proximity of the mic and even the size of the enclosure. I experimented by putting different "lids" over the speakers when miked and each one produced different tones and volume levels. The coolest thing I did was slash a speaker to get a more fuzzy distortion, but I opted out since I didn't know how long the speaker would actually last.
The half with the components:
The half with speakers before the mic was added:
Fully wired with mic and third set of terminal strips for the mic (note that the mic boom was adjusted towards the "high" speaker to make up for it's lower volume):
Schematic:
Layout:
The outside:
In Camouflage:
Controls on bottom:
I only had access to a camera video which has time and memory limits (thus the separation and brevity) and doesn't pick up the full bass range, but hopefully I was able to clearly show the variety of tones:
First, each of the three speakers one at a time, then mic setting full CCW (bass), then full CW (treble):0:00 Clean
0:09 Speaker 1 (low)
0:30 Speaker 2 (mid)
0:54 Speaker 3 (high)
1:16 Mic CCW (bass)
1:41 Mic CW (treble)
Different combinations of the low-mid-high (left to right) speakers. 0:00 Speaker 1
0:11 Speaker 1-2
0:19 Speaker 1-3
0:28 Speaker 2-3
0:38 Speaker 1-2-3
In retrospect, I probably should've gone with chords, so I recorded a second video with another camera with better mic, but much lower quality video. Enjoy the lo-fi grain. But in the end, I probably would've needed a better mic (external) so you could easily hear the high, mid & low separation. Those switches work like a primitive 3-band EQ.
For this I started with all three speakers on, then removed highs & mids, then added them back in a different order:0:00 Speaker 1-2-3
0:08 Speaker 1-2
0:16 Speaker 1
0:24 Speaker 1-3
0:33 Speaker 1-2-3
I didn't include a gain control since rolling back on the volume cleans up good enough.0:00 Volume Rolled Back
0:11 Full Volume
For the fun, with a wah & lo-fi camera. Surprisingly, It actually works very good before or after the wah. Appropriately, I busted a string right at the end:If you go for it, this will most likely not sound like any distortion you have. You’ll have control of low, medium and high ranges, coupled with a tone control for any of the seven combinations. It has a completely different nature and sound than any of my numerous distortions. That hollow, lo-fi, miked sound would be tough to duplicate any other way.
