Forbidden Planet is a movie from 1956. It featured a sound track and sound effects entirely created by electronic circuits. I say circuits because this was 8 years before Robert Moog would produce the first synthesizer. The sound track was produced by Bebe & Louis Barron using circuitas invented for the purpose and test equipment.
I thought I should try my hand at recreating the music of the Krell with circuits I had made!
A good starting recipe is an oscillator, delay, and reverb. The Ugly Face (right) is an oscillator drive by a guitar input. When the threshold is turned up it will self oscillate. The out put is as square wave.
The Barron’s used ring modulation copiously in the Forbidden Planet sound track. I thought I’d get out yhe Zvex Ringtone. The Ringtone is sequencer and ring modulator. The Barron’s didn’t have access to a sequencer since it hadn’t been invented yet.
A ring modulator produces a signal that is the sum and difference of an input frequency and another frequency which is usually produced internally. The sequencer allows us to program the internal frequency in 8 steps. The input frequency comes from your instrument, in this case it’s the Ugly Face.
This demo uses the Commonsound.org Triwave Picogenerator as the sound source. This is a legend in the DIY realm. It’s has two oscillators, and three LFOs. You can mix the amount of LFO that influences the pitch of each of the oscillators. The LFOs also have a rate and shape control.
This is the classic foot switch found in wah pedals and older effects. In the old days this was the switch, 3PDT switches were not available or were very expensive and hard to get. These days these switches are about $10 each! And they don’t have the extra pole for an easy LED indicator and true bypass.
This switch feels solid and industrial. The data sheet says it has a stiff activation of 6 to 8 lbs. and Electrical Life: 25,000 cycles, and Mechanical Life: 100,000 cycles. I’m guessing that 25,000 cycles is important to pedal builders. How long would this last in a pedal? If you stepped on this once per second for 7 hours that would be 25,200 stomps. Probably not going to happen. What if, somehow, you managed to use it on the chorus of every song in a 10 song set you might step on it 60 times, unlikely but possible. You could play 416 such gigs before reaching 24,960 stomps. If you did this gig once a week it would last 8 years.
I’d say it sounds pretty pretty reliable. But not military grade. The construction is a little loose, the lugs are not epoxied in place and wiggle a little. This means it can probably stand higher heat when soldering but also reaches an intermittent functionality sooner than it’s life expectancy would be my guess.
The threaded shaft is tall with lots of threads. It comes with two knurled nuts. Which look nifty but are hard to tighten and seem a little light weight. There are aren’t a lot of tools for tightening these and it seems easy to scratch your enclosure trying to get them tight with a pair of pliers.
Overall the switch is pretty tall. You could use it on an enclosure with a thick wall like wood. The button can sit up higher than the knobs on the top of a box which might help prevent accidentally hitting the knobs with your foot while stepping on the switch.
Overall rating: 5/10 – not bad if, you have one in your parts bin use it. If you’re buying something new get one of the more modern switches for 1/4 the price and the extra pole. Best used for specialty situations like fixing an old wah, something vintage, or you need an extra long shaft.
Harvesting parts from these old PCBs. I had this need for a A100K pot and Christmas 🎄 has holding up the deliver from Tayda Electronics. So I started digging through my bin of old projects that never made it into a box 📦.
I didn’t my ideal A100K pot, it would have been 16mm with legs, but I did find a couple 12mm pots which might sub. These have a D shaped shaft which makes them harder to fit for knobs.
While not finding what I was looking for was disappointing, I think I may have raided this bin at an earlier date, I did find some surprises. I found at least a half dozen J201 Fets, and a 4049UBE hex inverters. The J201s are great for stomp boxes and hard to get these days.
There was also a few 3PDT switches and a bunch of 1/4” jacks along with a handful of other things. Switches and jacks can always find some use. Personally I prefer the open frame Switchcraft jacks but these plastic ones are a good second choice.
I was trying to up the quality of my builds and thought about shielding and noise. Did a little research on the interwebs and came up with a few tips.
First a little background. High gain circuits often run series of gain stages in series. If you have an input stage of x10 followed by an adjustable stage of x10 to x100 you have a minimal gain of x100 to a max gain of x1000. That’s a lot of gain. Anything that gets into your circuit at the input will also be boosted by x100 to x1000! Think of cable crackles, switch pops, scratchy volume pots on your guitar, and more.
Then there’s the noise in the air from electromagnetic interference. It’s not uncommon for pedals to pick up radio transmissions, remember that scene from Spinal Tap? Or the hum of electronic devices like fluorescent lights.
In many ways the enclosure acts as an antenna picking up electromagnetic noise. But it can also be used as a Faraday cage which can be used to protect the circuit inside from electromagnetic interference from the outside. To do this the enclosure must be connected to ground.
if you have open frame jacks like the Switchcraft jacks the sleeve will make contact with the enclosure. This grounds the enclosure for free. If you’re using those jacks with the plastic body you’ll need to run a wire to the enclosure somewhere.
Is it enough to ground the box? Yeah but in the case of painted boxes or boxes with a powder coat the bottom cover may not make an electrical connection to the main body of the enclosure. I used a drill bit to remove the paint from one of the counter sunk screw recesses. This allows the screw to make contact with back cover and main body of the enclosure.
While you were able to get enough parts to make a couple stompbox projects at RadioShack in the past, these you can’t really get more than a cell phone’s there. Sadly there are no brick and mortar stores that cell stompbox parts. Then again you can
This is a really cool service that manufactures open source PCB designs. You can order any of the open source designs on the site. Most of the stuff is not stompbox oriented. It takes a little google-fu to search up stompbox projects. You can also upload your own designs.
You have to order 3 PCB minimum for each board you order. The orders seem to get ganged with other orders so it sounds like your order doesn’t get printed immediately. That said the prices seem very reasonable.
Millenium problesm all solved with the help of R.G. Who kindly pointed out that I probably didn’t have a path to ground on the out put of the effect. Which was exactly right.
After having the Millennium work so well on the SHO, I decided to add one to a Fuzz Face. This Fuzz Face is the First DIY guitar effect I had built. It was built around 2000. Back in the “olden” days it was hard to get 3PDT switches. I seem to remember buying a Fulltone labeled switch from Small Bear, that cost about $13 at the time! So the carling switch was the say to go for DIY.
This is really Joe Gagan’s Easy Face, which is essentially a Fuzz with variable input cap and Si Q1. This thing sounds pretty good, though I think when I first built it I didn’t get it. Now days I like a lot.
The problems with adding LED to this Fuzz Face is that the circuit is Positive Ground. Nothing a quick Google search can’t solve these days, Of course all paths lead back to the DIYStompbox forum where I found a simple solution using a PNP-2N3906.
Managed to get this working in less than an hour. I used 10K current limiting resistor with and a super bright Blue LED. The Bezel is from Mammoth Electronics. I like these bezels the little stopper is made of rubber and fits into the bezel well.
I built this last week, see the previous post. Everything seemed fine on the bench. Today I gave it a test with the band. Seems like it is not working quite right. The LED lights when the effect is on. But, when the effect is off the light slowly turns on over a few minutes. Turning the effect on and off again resets the light. Not sure what is going, need to read the documentation over at GEOFX a few more times…
This is one of those things that has been around for a long time. Back in the olden days when the 3PDT switch was hard to get and cost as much as all of the other parts that went into a box. There was a need for a status LED that could be operated from a DPDT type switch.
Then there was the 3PDT revolution. The blue switches became cheap and plentiful. I had bought a few of the Carling DPDT switches before the revolution. Still having these around I threw one into an SHO clone. I figured I wouldn’t need an LED. Over time I found myself using this more often than anything else. I had built another with a 3PDT and an LED, but I gave this to a friend. You can’t let your friends run around using your products without and LED? They will start saying things to people like: “this thing is great, just wish it had an LED…”
So anyway, I finally decided I’d put an LED in my SHO, and of course I don’t have a 3PDT on hand! Which of course brings us back to the Millennium Bypass. I had never tried this before. I found a Vero layout, 4 by 5, on DIYStompboxes. Built the whole thing in 15 minutes. Worked like a charm!
The box I had was not originally designed for an LED. So I found some empty space and drilled a hole. I mounted the tiny circuit board from the LED, which was attached to the bezel.
I used a bezel from mammoth electronics. These look like many of the other chrome bezels of similar style. What’s nice about these is they have rubber, rather than plastic, plug to hold the LED in. This makes a nice tight fit and doesn’t leave you thinking it might come loose.
(Note sure what happened, but all of the pictures above seem to have imported upside down?)
Sounds like something from an old Bugs Bunny cartoon. Though it might have appeared in a Warner Bros. production it could have easily added to a sound track. Looks like it should be on the floor of your custom van, the one with custom paint and interior.
This is the Snarling Dogs Mold Spore Psycho-Scumatic wah. We’ll call it the Mold Spore from here on out. It is a combination wah and ring modulator. Yep, you read that right, wah plus ring modulation.
For those of you who are not familiar with ring modulation a short description is in order.
Ring modulation, also known as balanced modulation, is a process that combines two signals using a mathematical function. The two signals are the input, your instrument, and the carrier frequency. The carrier frequency, in the case of the Mold spore wah, is an audio frequency generated inside the device. The mathematical function is the sum and the difference.
For example, imagine you played the note A 440hz and the internal carrier frequency is 600hz. Feed these both into the ring modulation circuit and it outputs:
Generally speaking, this produces a non-musical tonal relationships. The classic sample of ring modulation you may be familiar with is the voice of the Daleks on Dr. Who.
The Mold Spore wah, not only provides typical wah sounds, it also provides ring modulation sounds and it allows you to control the carrier frequency with the treadle. You can actually have the wah and ring going at the same time and control both with the treadle, neat!
The Mold Spore wah sports several controls.
Range, with three settings, White Room, Voodoo and Shaft. This sets the range of the wah effect.
Preamp, which acts as a boost.
Mix, mixes the source with the ring mod sound.
Frequency, sets the carrier frequency.
There are two push button switches:
Range, which sets the range of the carrier frequency to either a higher or lower frequency.
Control which allows the treadle to control the carrier frequency or not.
The enclosure and general structure is pretty well made, very solid. The whole package is heavy and feels very solid.
Inside the wiring and soldering leaves a little to be desired. I’ve had the thing for some years and it still works, but have had to repair it a few times.
Recently, I broke it out for fun, and the ring mod was not working. After opening the box I noticed one of the chips had a hole, which looked to be burned from the inside out.
The chip was a MAX1044, this is a charge pump. The ring mod section probably requires +9V and -9V. The charge pump generates -9V from the regular +9V supply. This allows the mold spore to run off a standard +9V supply.
These chips also cost $2 to $5 ouch! Luckily I had a few in the parts bin. This particular chip was installed in a socket, where the other chips are soldered to the board, which suggests they had problems with this chip, or at list anticipating trouble. This made it easy to replace.
Anyway, I replaced the MAX1044 and the thing fired up immediately. He ring modulator working in all of its sonic glory. Of course the suspicion of something going wrong was in the back of mind. A quick check did not detect any chips showing any signs of over heating.
The Mold Spore runs off a 9V battery, but the charge probably drains the battery pretty fast. best to run this one from a power supply.
The wah alone is a very usable. The three settings provide a lot of choice, though I find myself using White Room most often.
The boost is a nice added bonus. I wouldn’t use it just for the boost alone.
The ring modulation is not an effect you will find yourself using often if it all. Then again if you’re in the mood to make dissonant noises it could be just the thing you’re looking for.
As explained above the effect is based on a non-musical function. In general this is true. There are times when the ring mod will produce musically interesting tones. Being able to control the carrier frequency with your foot allows you to ”tune” the effect as you play. Admittedly his is not as easy as playing the wah by itself. The addition of treadle control of the carrier adds a significant dimension to the ring modulation effect.
The ring mod can also produce interesting and musical sounds if he carrier is tuned to a pitch that produces musical tones around a tonal center.
These ideas give you two strategies to using the ring mod. Tune the carrier with your foot, or tune the carrier to a note central to a musical phrase or section.
The ability to control both the wah and the carrier frequency with treadle at the same time adds another dimension. Using the wah with the ring mod works best when tuning the frequency of the carrier and not controlling the carrier frequency with the treadle. Then again controlling both with the treadle sounds pretty crazy.
The wah works well with other effects. I get great sounds putting fuzz before the effect. This creates a really synthy sound with a octave down type fuzz. We’re talking MXR Blue Box type effects.
The Mold Spore’s sounds are both capable and unique. The ability to control the carrier frequency with the treadle adds new dimension to the ring modulator.