Designing a Variable Crossover Pedal

[comradehoser]

So, I'm impatient about the Great Eastern XO Crossover Pedal, and I'm thinking of having a stab at it. Unfortunately, my ambition far exceeds my ability to electronics.

I'm thinking this:

State Variable Electronic Crossover

ESP Audio Projects - Continuously variable electronic crossover using state variable filters.

sound-au.com

With effects loops might be the XO?

Oh, and a bandwidth selector, dry blend, signal inverter, phase, and balance controls.

Y'all think it's doable? Anything I need to mind with the implementation? Can I just assemble everything modularly, or do I need to compensate in the main circuit for adding elements

 

[simoneogle]

So, I'm impatient about the Great Eastern XO Crossover Pedal, and I'm thinking of having a stab at it. Unfortunately, my ambition far exceeds my ability to electronics.

I'm thinking this:

State Variable Electronic Crossover

ESP Audio Projects - Continuously variable electronic crossover using state variable filters.

sound-au.com

With effects loops might be the XO?

Oh, and a bandwidth selector, dry blend, signal inverter, phase, and balance controls.

Y'all think it's doable? Anything I need to mind with the implementation? Can I just assemble everything modularly, or geometry dash spam and do I need to compensate in the main circuit for adding elements

Yes, it’s doable. The ESP state-variable crossover can provide the core high/low split, with the effects loops, dry blend, phase inversion, bandwidth, and balance controls built around it.

The key is buffering: use a low-impedance input buffer and buffer the crossover outputs before the effects loops and summing stage. Don't add controls directly into the filter’s feedback network unless you recalculate the circuit, since they can alter its frequency response and Q.

Building it modularly is a good approach—prototype the crossover first, then add the loops and mixing/switching stages.

 

[comradehoser]

Yes, it’s doable. The ESP state-variable crossover can provide the core high/low split, with the effects loops, dry blend, phase inversion, bandwidth, and balance controls built around it.

The key is buffering: use a low-impedance input buffer and buffer the crossover outputs before the effects loops and summing stage. Don't add controls directly into the filter’s feedback network unless you recalculate the circuit, since they can alter its frequency response and Q.

Building it modularly is a good approach—prototype the crossover first, then add the loops and mixing/switching stages.

Aye Aye, Cap'n!

I'm waiting for a PPCB sale to order some new boards, then I'm going to town with a whole lotta components, including the ones for this.

Haven't sussed out the modular add-on circuit bits, but now I will.

Thank you for the encouragement that I needed to tackle this with my dumbness! This will be a major step forward in my learnings.

 

[JohnnyCreepy]

Now you got me waiting for Point-to-point variable hi/lo crossover with fx loops -thread in build report section.

Circuit topology would be like?
input buffer -> splitting to hi/lo -> hi/lo fx loops (with buffers) -> mixing stage -> output stage

Is phase switch needed when doing x-over loops? FX loop for instrument or line level? How about fx loop section output impedance? Is variable impedance possible here? How about a toggle switch for pickup sim before loop?

 

[comradehoser]

Now you got me waiting for Point-to-point variable hi/lo crossover with fx loops -thread in build report section.

Circuit topology would be like?
input buffer -> splitting to hi/lo -> hi/lo fx loops (with buffers) -> mixing stage -> output stage

Is phase switch needed when doing x-over loops? FX loop for instrument or line level? How about fx loop section output impedance? Is variable impedance possible here? How about a toggle switch for pickup sim before loop?

Well, you know PTP is how it's going to go. In theory, anyway. It might not be a 125b enclosure project, hahaha.

I think when you are splitting, filtering, and summing, yeah, the phase can invert and will need to be controllable. I think the dude in the ESP audio projects that I linked to above talks about it, actually.

Are you asking about instrument and line level as a decision or a feature? Haven't thought about fx loop out impedance. Pickup sim/impedance control before loop might be useful for primitive fuzzes in the loop(?)

Thanks for giving me things to think about.

 

[anevilspar7an]

As a utility having a polarity switch is a must. You can add an instrument level/ line level switch at the send and return of each loop, since if you are using line level equipment with your rig you want to bring that up to line in the send and down to instrument on the return. I vote no on a pickup simulator since that can either be a stand alone pedal or incorporated into the fuzz itself. You can have variable output impedance on the buffer using a potentiometer with a 100 ohm resistor in series before it so it doesn't bottom out.