Tremolo LDR, FET Or OTA?

[iainpunk]

another way to affect signal is a variable resistance driven by a motor of some sorts, everything from a slider pot and a drive rod (like a steam engine's drive system) or like in this video:

i might put one of those in a guitar to have motion activated tremolo/vibrato

[POTL]

another way to affect signal is a variable resistance driven by a motor of some sorts, everything from a slider pot and a drive rod (like a steam engine's drive system) or like in this video:

i might put one of those in a guitar to have motion activated tremolo/vibrato

yes, there is charm and mojo in such a design, I read about old tremolo with liquid inside the case, which closed and opened the circuit. I'll definitely try some ancient technology someday, like tape delays or leslie. But definitely not in the coming years.

[ElectricDruid]

unfortunately I can only buy That from local distributors. CoolAudio is almost out of stock.

Fair enough. I only really mentioned them for completeness sake. As I said, they make more sense with a bipolar supply, and often don't work at 9V. And it's not like there aren't lots of other options!

[vigilante397]

I don't have anything super meaningful to add, but I but I'm too lazy to use LED/LDR combos so I buy my vactrols at DigiKey. They're out there.

Which models?

This is the one I use for compressors and tremolos https://www.digikey.com/en/products/detail/advanced-photonix/NSL-32/5039800

[POTL]

I don't have anything super meaningful to add, but I but I'm too lazy to use LED/LDR combos so I buy my vactrols at DigiKey. They're out there.

Which models?

This is the one I use for compressors and tremolos https://www.digikey.com/en/products/detail/advanced-photonix/NSL-32/5039800

Thanks

[moosapotamus]

...For an OTA, you'd need to filter the PWM output and turn the result into a control current.

I'm interested in trying this method, but most of what I could search up on this topic seemed too complicated and, honestly, a bit beyond my expertise. Could anyone describe what an appropriate filter circuit for driving a LM13700 from the PWM output would look like?

[Guillemdc]

...For an OTA, you'd need to filter the PWM output and turn the result into a control current.

I'm interested in trying this method, but most of what I could search up on this topic seemed too complicated and, honestly, a bit beyond my expertise. Could anyone describe what an appropriate filter circuit for driving a LM13700 from the PWM output would look like?

Sorry to bring this up again, but I have the same doubt as moosapotamus. I think we gotta take the PMW out, filter it and turn it into a control current. I've been trying to do so to no avail with the output of a digital LFO I built with an Atmega chip but I just can't make it work :S.

I hope someone can help.

[Ben N]

ElectricDruid I did not consider VCA due to their cost and rarity. There may be cheap chips, but I only know about THAT and the cost of an effect with multiple chips would be very expensive.

[iainpunk]

a simple resistor and capacitor would do the trick, i'd put the break frequency of the filter at 1000 Hz, so that we can extract as much of the PWM as possible, without altering the wave form to much. if the LFO is too soft, and misses the sharp transient edge, just move the frequency up, when the pwm shines through, lower the frequency of the filter or higher the rate of the PWM

cheers

[ElectricDruid]

It works as you describe, more or less, but it's not entirely that simple. The trouble is that the Iabc input on the 13700 is two diode drops above it's negative supply (so above ground if we're on a single supply). The PWM signal runs from ground up to 5V. The lower portion of that range pushes the Iabc input below its usual level and turns the OTA hard off.

It's possible on some of my chips (like StompLFO, for example) to set the output offset level to 5V, and then limit the depth CV so that the output never goes so close to ground as to completely shut the chip off (which generally seems to thump like hell). That's the simplest way I know.

[iainpunk]

It works as you describe, more or less, but it's not entirely that simple. The trouble is that the Iabc input on the 13700 is two diode drops above it's negative supply (so above ground if we're on a single supply). The PWM signal runs from ground up to 5V. The lower portion of that range pushes the Iabc input below its usual level and turns the OTA hard off.

It's possible on some of my chips (like StompLFO, for example) to set the output offset level to 5V, and then limit the depth CV so that the output never goes so close to ground as to completely shut the chip off (which generally seems to thump like hell). That's the simplest way I know.

or you power the chip with 2 and 7 volts?

cheers

[ElectricDruid]

or you power the chip with 2 and 7 volts?

Yeah, I've considered that. It would work, but it doesn't strike me as "convenient"!