PCBs with pots and LED

22/7 PCB

I just built a PCB project without the LED taken care of on the board, what a headache! In the old days everything was like that but we have evolved since then! in my most recent projects I have been following the layout used by PedalPCB. I feel like they have hit on an arrangement that works well.

Here’s my proposal: Let’s make this a standard! If everyone does it this we all know what to expect, it’s easier for everyone to wire board, and the build process is easy. It also makes for a clean build which leads to more successes and less debugging.

Here you can see the wiring is pretty neat and tidy. Notice the input and output jacks ground to the board on the left and right sides. The wire run is short and obvious. Also, see the four wires in the center of board run in a straight line to their connection at the stomp switch. This helps make the wiring self documenting.

What way not be obvious from these images is that the pots and LED are also mounted to the board. This reduces the off board wiring and gives you a secure place to mount the and supports the LED.

Here you can see all of the pots, switches, and LED mounts to the board. This is clean neat and reliable. The board and LED have a secure mounting place.

What am I proposing here? A convention for laying out your PCB:

  • Pots mounted to the board
  • LED mounted to the board
  • 4 connections at the bottom of the board:
    • Effect In
    • LED Switch
    • LED Ground
    • Effect Out

Why? It makes building guitar pedals really easy and less error prone.

  • Mounting pots to the board saves on wiring, and makes a secure place to mount the PCB, and avoids mistakes.
  • Mounting the LED on the board saves wiring avoids mistakes and gives you a place to securely mount the LED.
  • Using the 4 connections at the bottom of the board avoids mistakes and makes wiring the switch, often a source of errors, easy and less prone to errors.

Here are a couple wiring diagrams for the project PCB above.

Check out my projects page for a closer look at building these projects. You can order boards from the PCBWay shared service, then follow the build guide on my site.

If you’re interested in making your own boards I can highly recommend using the the PCBWay.com service. All of the boards pictured here were manufactured via PCBWay.

The Music of the Krell

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.

Watch the movie here: https://archive.org/details/ForbiddenPlanet1956_201707

I thought I should try my hand at recreating the music of the Krell with circuits I had made!

Krell 1

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.

Krell 2

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.

Krell 3

This time I used the Fuzz Factory as an oscillator. This pedal will oscillate on some settings usually when turn down the Stability and turn up the Drive, Comp, and Gate.

I also added the Zvex Seek Wah. This is a wah controlled via an 8 step sequencer. Imagine a wah pedal stepping through 8 different positions of the foot pedal.

Krell 4

This demo makes use of the Deadastronaut Tremshifter. The Tremshifter is both a tremolo and phase shifter in one box.

Krell 5

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.

Carling DPDT 316-B-PP

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.

Available at smalll bear

I built this Klon clone with buffered bypass which only requires DPDT. I used the carling here. The original Klon Centaur used these carling switches.

Harvesting Parts!

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.

Stomp box enclosures and shielding

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.

Resources to get started making stompboxes

Getting Started

Someone asked me about getting started building stompboxes, so I thought I’d put it all in a forum post, for your enjoyment and edification.

Become a member of both of these forums. Search, and read what’s posted there. Post your work, and your questions. Lot’s nice knowledgable people.

Probably the oldest stompbox forum around. Really friendly and helpful people. Lots of good info.


Another great forum, this one has been around for a while.


This forum, ostensibly, caters to the subject Madbean PCB projects, but the people here talk about everything. Not much traffic as the other two forums.



Probably the best kits out there. This would be a good place to start.



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

Mouser All purpose electronics supply.

SmallBear The original stompbox supply

Mammoth They have everything, good quality, order boxes in colors, and pre-drilled

Pedal Parts Good prices for boxes

Tayda Cheap, good range of parts.

Futurlec Good prices, slow shipping.

Bitches Love My Switches (Yes, that really the name) great prices, prompt shipping. Good for switches, knobs, and jacks.


After building a few kits try building from just the PCB. You’ll have to source your own parts.


These are very well done PCBs. I have built the the delays.



Here are a few more sources for PCBs, I haven’t tried these



After you make a few projects you might want to try making your own PCB.


This site is something special. It allows people to upload their PCB designs, and open sources them to the greater community. The prices look good.


Experimenting and making your designs

Get yourself some parts and a breadboard. Build a test rig, and an audio probe, and you’re in business. Besides the forums above, these sites have some information and projects to try.


Download the Stomboxology Article: Going Discreet. This is a great primer on transistors.


Sort of the grand daddy of stompbox info




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.


I just placed an order for a few PCBs. I’ll post again when the order comes in…

Millenium Bypass – Working!

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.

Millenium Bypass, not so fast

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…

Millenium Bypass

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?)