After spending my sweet time going through a few boosters – it’s time to make them better.
Adding some sort of tone control to a guitar pedal is a great way to make it better. In this post I’ll explore some of the ways to get a useful tone stack for your build. I’ll be looking at something real simple – like an adjustable filter and Big Muff style tone control which are one knob controls.
I’ll shift focus then to amp stacks that might be interesting to explore like 2 knob Vox style or 3 knob Marshall style tone control.
If you want to skip all the text – just jump into video straight away.
Getting the Schematic
How do we go about getting the schematic? It is common to use an existing pedal for inspiration – Big Muff tone stack is a very popular tone stack to use. Maybe a certain amp tone is something you fancy. If you have a certain tone stack in mind that you already know of – it is probably easy to find it nowadays.
One easy way to get us going is to use Tone Stack Calculator application. I’d recommend starting there. It’s a Windows app that is very easy to use and I used it for this post.
Here are some screenshots:
You can turn pots (virtually) and see how that affects frequency response.
There’s a similar online version of it (unaffiliated as far as I can tell). It removes dependency on Windows, and adds more tone stacks.
You can use SPICE to draw schematic and do all of this yourself, but why bother, the apps make the process way easier. Of course, if you need to try out something that’s not in the apps, or you need more control over what you’re simulating, then SPICE is the way to go.
Another way is to find a schematic of a pedal you like and just use that. For example, go to Electrosmash’s ProCo Rat analysis and see tone control there. Super simple, very easy to try out.
Or just search for a schematic of an amp you like – say Fender Bassman. Fender Bassman 5F6 introduced a tone stack that was later copied by nearly everyone. I’ll try out 2 variants – Marshall and Vox style stacks found in Tone Stack Calculator. But by varying component values you can get a lot of different tone stacks.
What are we building?
One note to be made is – all of the tone stacks I’ll be looking into are passive tone stacks. They are attenuating the signal so it is a good idea to use them with a booster to compensate for the loss.
If we look at the boosters that I created before as building blocks, and we look at tone control as another building block – by combining them we get a new pedal, more versatile.
With that – let’s do exactly that. I’ll use LPB-1 for this, it is the very simplest we can start with:
By simply plugging in a tone stack in between amplifier and volume control we get an improved pedal. For the examples I chose, it is as simple as that. Maybe it won’t be for everything, and not for all pedals, but that’s the general gist.
Tone Controls to Try Out
Here’s a bunch of controls to try out:
Single knob tone controls are normally titled: Tone. Simple Low Pass filter like the one found in ProCo Rat is there because it is really simple and easy to try out. It is actually titled: Filter on the pedal – which it is ?. The purpose of it, in a distortion pedal, is to filter out some of the harsh sounding higher order harmonics, so don’t expect much out of it.
Big Muff style tone control is very versatile and affects the sound significantly, yet, it is very simple to implement. Definitely something to try out.
When we get to two or three knob controls – things get a bit more complex. Mostly because we have 3 pins per pot, and things easily get very messy when breadboarding:
The component count is still low – Marshall stack has 3 caps, 1 resistor and 3 pots, but that’s a hell lot of wires.
Trying This Out
I did a simple explanation of what I’m doing and I breadboard all of the tone stacks. Here’s the video with most of the above covered in it:
What I learnt was that a simple filter is very simple but not great as a control. The main purpose of it is to control harsher higher harmonics in a distortion pedal, so not that great for a booster.
I liked Big Muff tone stack, very good range of tone control, no wonder it is very popular.
Vox was very good too in terms of range, but what is most important I think is that a single tone control gives a big range of tone control. Two knobs give smaller change per knob but overall, across both knobs should give the same range but with more control. Ditto for the three knob controls.
To be clear, I’m not talking about overall sound, I’m just talking about range and control over tone. Great thing about DIY is that everything is tweakable so there’s a lot of material to experiment with.