AND/OR Switching Part II: Active and Passive components

One of the goals with this switching system is to make it with as small of a footprint as possible. With the increased access to SMD services the use of the 14 and 16 pin CMOS chips for switching purposes are no longer a barrier which would take up large amounts of real estate. However, they are not without their drawbacks .

The challenge:

The BYP/CH1 and SEL/CH2 switches would need to pass the signal when not engaged. This is where we run into a road block. Its probably already apparent to most, but I struggled with it and figured I'd share it anyway, but the CMOS chips such as the CD4053 are electronically controlled, even when logic levels are low and you would expect that the SPDT would pass a signal, it will not if there is no power connected to the pedal.

This raises a small issue. Normal pedals using mechanical 3PDT bypass switches, are entirely passive. It doesn't matter if power is supplied to the pedal, when the 3PDT has its connections being met correctly it will pass the signal. This is not the case with the 4053.

I don't know how often people are trying to play through their pedals when they have their pedals unplugged. If power fails to your pedal board, I imagine it would be close to an outlet supplying power to your amp and trying to play anything would be pointless. Nevertheless it does present a challenge.

As I alluded to in the last post, this system would be very difficult to implement with a purely mechanical switching system. Instead I will be developing a microcontroller & CMOS system. If you haven't read through it already, I recommend checking out the GEOFEX article on the electronic bypass system. This project will be based on this and an of course expand upon it.

The first step is figuring out the signal paths and number of switches that will be passed through.

After sketching out some ideas, I have a rough draft where ≥10 SPDT/SPST switches would be required to move between the OR and AND switching. This corresponds to Channel 1 OR Channel 2 as well as Channel 1 INTO Channel 2. With this many switches involved at the moment, I think its safe to stop here for debugging purposes. Drawing anything further will get complicated quickly.

Given the digital nature of all of this we can already start to think of how a sort of "TRUTH" table could be set up to switch between modes and what each of the switches would need to do in order to achieve a given outcome.

Word to the frustrated:

When using photoFETs for muting, make sure you use a current limiting resistor. I had burned some out and not re-tested them and kept wondering, why isn't this muting?

  

AND/OR Switching System\\ Part 1

Part 1: The Gestalt

   The ability to control two different effects is one of the joys of having multiple pedals or multiple effects. To date, I have focused most of my attention on switching between channels in a "parallel" manner. However, while doing research for the DBA sound saw and the Kill Kill Filter, it seems that users were interested in the ability to run one filter into another. The challenge ahead is how to develop a system which could accomplish at least 3 modes of operation (1) A into B, (2) B into A, (3) A or B, and (4) A and B.

    Here's a version of a generalized schematic diagramof the switching systems we're interested in with. It should be noted that (1), (2), and (4) could use different grounding methods depending on your preference. 

    I have left off the LED switching systems at the moment for simplicity. Regardless, moving from (1) to (2) can be accomplished in a simple manner using the Geofex Juggler Effects Reverser.

 

    What we can see from this is that in addition to the Switching system to turn each effect ON and OFF, we require an additional 3 (or 4) SPDT switches to change the effect order.

    So the challenge becomes mostly focused on getting between mode (3) and either mode (1) or (2). As well as getting to mode (4) and making sure that there aren't any phase issues. If we can draw out the paths to get between these modes, then its just a matter of a couple more SPDT switches to change the effect order.

    Herein lies four of the starting challenges I've identified thus far:

A. The number of SPDT switches required.

  We are already at 3 or 4 to just move between modes (1) and (2) NOT including the LED indication. Adding in mode (3), and it should be clear that there is probably not going to be an analog toggle switch or rotary switch which will be able to accomplish this switching. In addition, we will need a way to cycle through states in a relatively easy way.

B. Switch life time.

    Part of the fun of the OR configuration is the ability to switch back and forth between effects/channels to quickly switch between different sounds. This will result in the "Channel Select" switch getting pressed more than the "Bypass" switch. Like everything, mechanical switches have a lifetime, can get worn out, and die on us, which present challenges with replacing them. Normally Open (NO) momentary switches have been used to toggle states of relays for pedals and can be used, but we'll need a way to address the toggled status of effects after power is disconnected. This is notably a problem in the OR mode.

C. CMOS switching and pop.

    To accommodate the anticipated large number of switches, we'll likely need to use CMOS chips for switching. In my experience, there has always been a popping issue for me when I have breadboarded this. We'll need to include a form of muting system to prevent popping from being an issue when switching between the AND/OR modes when the effect is powered up.

D. Method of indicating which MODE we are in.

    Switching between 4 modes, pretty much eliminates a single toggle switch (e.g. ON-ON-ON) to select the mode. I believe the choice is between (i) a rotary switch, and (ii) a push-button switch that cycles through the modes with some additional LEDs to indicate which mode is currently selected. I am leaning toward the pushbutton cycle selection since it is a new area for me to explore and doesn't take up as much space as a rotary switch. In my experience with Alpha Rotary switches (both plastic and metal) is that they stick up higher than the potentiometers, and often times require additional washers or an additional nut to get the right spacing/height with the inside of the enclosure. The issue with LEDs is finding the optimal way to communicate with the user which mode is currently active.

    At the moment, the solution seems to be pointing toward a microcontroller-based solution. I'm pretty sure this switching system could be achieved to a degree without a microcontroller. But one of my goals for 2021 was to push myself in a different direction. I think that incorporating microcontrollers into my effects pedals will push me into uncomfortable territory but ultimately improve my creations.

Beginning with The End

 Well 2021 is off to a strange start, and I have finished up a batch of pedals.  I've started a YouTube Channel, posted items to my Reverb Store, and created an Instagram account to keep people posted on different developments.

There are a couple existing projects I want to finish up and others I want to update and expand on. In no particular order other than my thoughts at the moment, here's what I've got planned for the year.

1. The AND/OR switching system is under development, and is somewhat of a priority since I have a fetish for dual channel designs. Moreover, I think my future designs will require the use of micro controllers to accommodate the ideas I have in mind.

If I can get this to work, I'll document the process for those interested. For two-in-one projects it just seems like it would be a cool option to switch between A or B, A->B, and B->A in with a simple interface..

2. I will be revisiting the Solaris this year. Belton has a new brick coming out that should be interesting to work with. Its based on the Cool Audio multifx chip, but at least it doesn't require me to do any SMD soldering.

3. I have been wanting to do a tremolo pedal for so long and I think I have some ideas. Laowiz suggested I try out the Gristleizer, and I think I will start to breadboard that. I've seen some cool videos and of course the VCA/VCF modes fit nicely into my fetish :)

While learning more about microcontrollers, I may try and put out something for a 

4. Modular Interfacing Longterm Fuzz is something I have been toying around with. Mostly to satisfy my crusade for the ideal fuzz for me. This will probably take the longest time to develop and may never be complete, but the basis of it will involve microcontrollers to simplify my life.

I don't want to get too far ahead of myself 4 projects for the year sound doable. The beginning always starts out strong, and right now since I have been drawing schematics and breadboarding most of December.

All along the way I'll put out some updates for the projects; the microcontroller work especially. I think it'd be nice to see simple microcontroller projects pop-up for other guitar pedal hobbyists out there.

Here's to a productive 2021

Best regards,

   Bradford

THE END: Dual fuzz dream eater

 So, I've been diving deep into the V1 Fuzz War again and again, and have another variant on the horizon.  Last year's Dark Sun was more of a re-imagining with a harsher edge, but I was still looking to capture the thick fuzziness of the V1 Fuzz War and something close to the Silver Armageddon.

Well after a couple months of testing, tweaking, and re-testing. I have (re-re-re-)designed a functioning silver Armageddon. This was largely based on the gut shots from a known source and the values from tracing my personal V1 Fuzz War.

As an overview,

 The End is a dual fuzz which allows you to select different filters via footswitch.  In addition, there are two toggle switches, 1 to allow more or less low frequencies to enter at 2 points in the circuit, and one to switch between the original silver Armageddon, and a personal variant for the fuzz/filters.

I made some small tweaks to the design to optimize performance, but this pedal "The End" is supposed to be as faithful of a recreation of the silver Armageddon as possible. In the next series of posts I'll post more details about 'The End'.

In this post I'll talk about options for the notch filter also referred to as "Filter 1":

Here is what the silver Armageddon's notch filter looks like. It provides a very deep cut that can be shifted up and down the frequency range so that you can cut out lows, mids, or highs. The notch ranges from approximately 100Hz up to 1.1kHz with an approximate 50db cut.

This may be too extreme for some guitar players when cutting the lower frequencies, but then again if you are interested in the V1 Fuzz War, you probably aren't interested in a typical friendly sounding fuzz. This thing can get harsh...Think MEDICINE harsh!!! Nevertheless, I wanted to add versatility to the fuzz and I've incorporated an option to change the depth and sweep for the filter to something a little more open sounding while still blown out and amazing.

As you can see, the notch is attenuated (-35db), which results in a louder sound throughout the frequency range from 150Hz through 1.2kHz.

On the other side (Filter 2), we have a tilt filter which functions like a BMP tone stack but the notch is shifted much lower than your typical BMP. This tilt filter is centered around 600Hz, a more useable range that shouldn't be as competitive in the mix.

This fuzz output from Filter 2 is hard clipped to give it an aggressive sound, but once again with the "add options mindset", I've added the option to lift those diodes, which adds a volume boost and a blown out sound to compliment the Filter 1 notch adjustment.

So in summary, the "Clip" switch on THE END will allow you to switch between the original silver Armageddon sound, and a more blown out variation that I've added.

More details to come soon...

The Journey to New AND/OR...

 While looking over how to improve the functionality of the Receiver Operator. It has occurred to me that there are a bunch of routing options that could make this pedal incredibly versatile. I took a look out at other companies who create multi-channel pedals and noticed a "gap in the market". There are a number of ABY switches out there, Lehle, Earthquaker Devices, Morley, EHX, to name a few. All of these are outstanding pedals in their own right in terms of straightforward use, or options galore depending on what you are looking for.  However, I have yet to see a pedal which can do what I am looking for.

The RecOp and the pedals it was inspired by are known for their dual channel nature. Let's call this "OR", after the A OR B function of the operation.  This is an easy to implement function using a 3PDT switch, which is what the new J Mascis Fuzz from the previous post most likely uses. The next step in the evolution would be driving A into B, and naturally following that would be driving B into A.

These aren't ABY type of options, but they aren't that different. The AB component remains the same.  The Y option is not in question, although with the creation of one design, another is born. We'll tackle that at a later date.

So the three functional goals for this design are:

1. A "OR" B

2. A "INTO" B

3. B "INTO" A

Ideally, the end product would be simple enough to control with a 3-way toggle switch so that any body could drop this design into their DIY pedal and have a wide range of control over 2 different effects in the same box.  Similar to the 3PDT/4PDT order switcher boards out there.

At present the RecOp can do Notch "OR" Boost, I have figured a way to re-route the signal as Boost "INTO" Notch, but the effects are not independent. In this first draft of the INTO mode switch, the bypass button turns the Notch on (which makes sense since it is on the left hand side below the Notch controls), and the Select button turns on the boost, which then runs into the Notch. If we only toggle Select, it does not engage the boost section. it just lets us know that when we do turn on the Circuit, we will be slamming the notch with the boost. 

In my mind this is a cool feature, but it is not exactly where I want to go with this pedal.

The challenge at present is the number of SPDTs that have to be used and changing the LED indication status to reflect how the pedal is going to work. For the "OR" function I am partial to DBAs approach of having dimmed channel indication in bypass.  For the "Into" functions (if they work as independent units) I don't think dimming is necessary, but a tri-colored LED would be nice as a sort of visual cue to which mode you are in. Albeit unecessary, LEDs always make things neat.

So I'll try and do a better job about documenting how I implement this and get more shots of the breadboard up in the meantime too.

Switches & channels

Switches, either mechanical or digital, provide opportunities to route different part of the circuits around in some interesting ways.

To start, I have always been a fan of having two channels on pedals, something attracts me to that sort of design. Probably my early exposure in pedals to the DBA soundsaw and kill kill filter.

Recently, there is a Big Muff by Wren and Cuff ("Garbage Face")  that has been released which allows for two different volume settings for a channel.

I can't say for certain how they implement this, but if I had to guess it would be like the old Beavis audio, two pots on a stomp with an LED approach. http://beavisaudio.com/techpages/switches/

Not a bad approach at all! Easy to implement, minimum parts count and greatly expands the sonic pallete of a certain pedal.  In fact the DBA KKF uses this type of control, to change the tone potentiometer. Move this over to the potentiometer for gain, and you can have two channels which allow you to vary the saturation of your dirt circuit. All of this with a 3PDT switch (Stomp or toggle pick your poison)

If you don't care for the LED indicator, you could get by with the DPDT. But wait!!! What about other options.  As far as mechanical switches go, we can move up the the 4PDT. Which depending on how we want to implement it for channel switching, we could get creative and allow changes to be made to 3 controls of a circuit, but would need to isolate components so they don't interact across channels. I.e. the we don't want the volume control for channel one to change the volume of channel two. Digital switching systems are more complicated, but offer a longer life-span and the potential for more parameters of the pedal to be channel switched.  This comes at the cost of more knobs to interact with though. Digital presets are the next evolution which allow you to have the base number of potentiomers and the ability to cycle through "saved" states.  The challenge with this approach is not being able to see what the preset was.

The NEW DBA ROOMS pedal looks to have 3 channels switchable on their "ALT" footswitch. While there are large knobs for Frequency, Depth, and Time, there is also a smaller 9mm potentiometers for F, D, and T which I am going to guess is tied to the ALT footswitch.

This of course depends on how the potentiometer is oriented in the circuit to begin with. This is most ideal for potentiometers set up as voltage dividers.


This is brief post covering aspects of mechanical switches for "multi channel" modifications to your pedal, but also serve as a backdrop to part of the process going into the Sound Saw REMAKE. The pedal toggles back and forth between the boost and the filter sides of the circuit.

Thoughts on the SoundSaw

Hey team,
 Glad you could join me, now let us begin.

SOUND SAW
what was the deal with that pedal anyway? Crazy awesome sounding demos on the old DBA website, but they are hard to come by and there is one schematic that has been floating around for years now.

Back in 2014-2016ish, I was helping Glass Hero screen some enclosures with the Sound Saw artwork until he disappeared (hope all is well). It was about that time that my life got complicated and I had to put a lot of things on hold and move states to a new job, now after moving to another state for another job, I feel like building pedals again. I have been ever so slowly unpacking my tools and reviewing old schematics I had drawn up to try and start being a little more efficient with my design process.

Part of this process is putting out a SOUND SAW REMAKE. I am looking at the instruction card from the original and tasking myself to recreate a pedal like this. Something that has the same functionality, but with improvements based on my knowledge thus far and what I would want, and something that adds to the original

After looking through the forums and customer reviews and feedback, I hope to incorporate those ideas and create an excellent REMAKE.  At the end of the day, I will probably email Oliver the results of my passion project and send him my REMAKE.

I have sent off for PCBs to test the backbone circuit of the pedal.

From here I will be developing the upgraded (deluxe) variant of the pedal.

I would really like to dig into some programming to make this process incorporate a challenge of a different dimension. Another reason is the relatively short foot switch lifespan of mechanical bypass pedals. With a pedal which you can toggle channels for huge variations in sound, a foot switch will most likely get plenty of use.  Once it is all used up, what is the customer left with? a dead foot switch. Let's try and avoid that from here on out.

I'll keep you all posted as I move forward with this project.

After this I can get around to....reverb pedal REMAKE.

Best regards