EQ/Preamp Build - Starting Point

[LaceSensor1]

Hello I have decided to design/build my first effect pedal. I have and idea for a pedal that doesn't exist on the market. There are many similar pedals that would accomplish the same goal however I'd like my own custom design so that I may pick and choose the controls, and component values to my taste. The idea is simple however I don't know where to begin. It would be greatly appreciated if someone could recommend some books and webpages to help me get started. Just a heads up I have a mechanical engineering degree so I am familiar with basic circuits and fundamentals of electronics. I have never designed any circuits so this will be a bit of a challenge for me but I believe this is within my capabilities.

EQ/Pre-Amp

Low Cutoff (HP shelf -12 or -24 dB) + 3 way toggle (120 Hz, off, 240 Hz)
Parametric Mid (w/ variable freq.) (w/ narrow q toggle)
High Shelf (cut/boost)


For the parametric mid section I found this circuit online that seems like it might do the trick. However I'd be curious to know what are my options here for the most commonly used circuit types?

Using a capacitive gyrator to simulate an adjustable inductor.

http://www.geofex.com/article_folders/eqs/paramet.htm

[LaceSensor1]

https://drive.google.com/file/d/1W2ceKLf5yyOGp2ul9pVMcKgp97rQpGQp/view?usp=sharing
https://drive.google.com/file/d/1W2-S_EAElqvxACSTJ3c-xq9B3S-0y_Jv/view?usp=sharing

[marcelomd]

Hi,
Rod Elliott's site is a great place to start: https://sound-au.com/index.html

This is his article on equalization: https://sound-au.com/articles/eq.htm

The projects and articles there are really good. Check this bass preamp project: https://sound-au.com/project152-1.htm. There's a low cutoff, parametric mids and shelf bass and treble.

[Vivek]

Welcome to the group !!!

Always live life assuming that everything is within your capability !!!

Your specifications remind me of the SON OF KONG EQ pedal used by Frank Zappa

https://spontaneousaudio.com/products/son-of-kong/

https://www.youtube.com/watch?v=y6da1mHPlbA


For the mid section, you could consider the MT2 mid, explained very well by ELECTRICDRUID here : https://electricdruid.net/boss-mt-2-metal-zone-pedal-analysis/

[niektb]

Also, I think as shelves I think you can take a look at a Baxandall Tonestack

[Vivek]

It's difficult to change the slope of a Baxandall


And it's difficult to change the frequency of a Baxandall since too many components need to be changed.

[niektb]

It's difficult to change the slope of a Baxandall

And it's difficult to change the frequency of a Baxandall since too many components need to be changed.

If I understood correctly, the slope doesn't have to be changed on run-time. But the frequency is doable, there is a single capacitor version:
https://www.guitarscience.net/tsc/baxandall_2.htm#RIN=600&R1=22k&R2=22k&R3=22k&R4=10k&R5=10k&RB=100k&RT=100k&RF=600&CB=47n&CT=560p&RB_pot=Linear&RT_pot=Linear
So all you need to do is switch a cap that's parallel to Cb

As for the gyrator-based mid-control, ElectricDruid did something for his distortion pedal a while back: https://electricdruid.net/designing-the-hard-bargain-distortion-pedal/

[Vivek]

Yes you are right, a one cap Baxandall can have switched caps easily.

The hard bargain mid looks like the mid of a Baxandall

It normally has very low Q at low to mid boosts/cuts, and can sometimes act more like a volume control

[LaceSensor1]

Hi,
Rod Elliott's site is a great place to start: https://sound-au.com/index.html

This is his article on equalization: https://sound-au.com/articles/eq.htm

The projects and articles there are really good. Check this bass preamp project: https://sound-au.com/project152-1.htm. There's a low cutoff, parametric mids and shelf bass and treble.

Wow this is fantastic. I was reading through some of his pages and projects. Looks like everything I'm looking for is here. Thanks again, this is great information to stumble upon.