Digital Potentiometer? (How does tech21 do it, and can I?)

[LowWay]

I was wondering what it would take to make some of my favorite pedals more like the tech 21 pedals with preset memories. I would love to be able to set up some of my effects to have song specific settings I could recall with a single foot switch.

So what is their secret at Tech21? I don't have one to open up. Do they use digital pots? If so, can I get them? I'd be willing to put some of these pedals into custom chassis and build a custom switching system to make it all work.

I would probably hire out some of the design work to local IE students at the university (I have had success with this in the past). My dream is to build a controller unit that would turn on or off a bunch of effects, and control their parameters. It seems relays would be the tool for switches, but I was wondering what to use for knobs, and I would like to have the physical knobs for setting the parameters, like the tech 21 pedals, but then the ability to store and recall the setting.

thanks for any insight.

[Swimming Bird]

Best guess is rotary encoders. As I recall they output in Gray code (binary code for switches).

Looks like you have some research to do. Good luck and let us know how it goes.

[grovest]

Yes, presets are great.

For someone who wants lots of knobs but presets too, perhaps you should look into VST or other computer-based effects that can interface with an external MIDI knob / button / switch controller.

There are such things as digital potentiometers. I suppose they could be controlled by encoders or traditional pots. A digital pot, plus control knob, plus memory and microprocessor is "all" that you'd need to do this. Wait, here's a notion. What about linking your knobs by belt to some servos with custom control to accomplish this without modifying your analog pedals?

[Taylor Livingston]

Indeed, can be done with a regular pot into a microcontroller controlling a digital pot like an MCP42050 (this is a dual digital pot). You need to write the code for the MCU of course. This would be a fairly monstrous build if you wanted your pedals to be physically detached from the controller unit. Even if you integrated everything into a single case, it's a very large undertaking for a one-off unit.

[Bassman203]

This sounds like a cool idea, but wouldn't it almost be cheaper to buy multiples of the same pedal units and a switching system?

I haven't done any price checks, just raising the question out of interest.

[JimmyM]

Originally Posted by Bassman203

This sounds like a cool idea, but wouldn't it almost be cheaper to buy multiples of the same pedal units and a switching system?

I haven't done any price checks, just raising the question out of interest.

the vt deluxe will be $280. two vt pedals is $300.

[Taylor Livingston]

Originally Posted by JimmyM

the vt deluxe will be $280. two vt pedals is $300.

True, but not particularly relevant.

If the only pedal you want to be programmable is a VT, then you're in luck. But this guy wants his entire pedalboard to be programmable, so designing and building a system to do that would be very expensive. Completely possible, but expensive if you have to hire someone to program and build it. It's cheaper per item when you can sell 10,000+ of them like Tech 21 will. It only has to be programmed once. But if you're only making one of these, that development cost is divided by one instead of 10,000.

That said, a cheaper but less convenient solution would be to just have a few preset resistors per parameter selectable by toggle switches. You couldn't save presets on the fly, but it drops cost from thousands to tens of dollars.

[LowWay]

I have built some pretty elaborate digital systems in the past with some EE undergrads for a few hundred. You'd be surprised by how cheap you can get some of these talented guys for, especially if they can use the project as a class project for credit (as they often can).

I've considered servos, and still may go this route. I've considered finding the values for my favorite settings and building the toggle suggestion above. I like to do my preliminary research before hiring the students to make sure I can try to do something I'll be happy with.

If I can build some presets for a handful of pedals it is probably smaller and no more expensive than 3 or 4 of each envelope filter I'd like to be able to save presets for. PLus it should be able to fit on my existing pedalboard (I hope). We'll see if I get this one off the ground. If I do, you can bet I will be posting about it here.

rob