Drolo FX Twin Peaks Tap Tremolo build

[strungout]

Hey guys. Another mix-and-mash project.

I was looking for something new to build (for me at least) and I found David Rolo's Twin Peaks Tap Tremolo thread on here, based around Tom's (Electric Druid) TAPLFO chip. Went to listen to some soundclips and it sounded great! I couldn't find a schematic, but I asked David directly and he sent me the v2 one (thanks again!).

It's a multi-trem. Classic, Harmonic, and modulated Treble only or Bass only. The TAPLFO give you 16 waveforms (8 for the first set, and add a switch for a second set of .

The only thing missing was the envelope follower part which is present on the Twin Peaks v5 model. So, I added my goto, the EF from the MXR Envelope Filter, with the sweep direction switch mod.

I breadboarded it and started messing around with stuff... For the audio section that splits the signal into bass and treble, I didn't change anything. I messed with the filters some but reverted them, it just sounds great as is.

Moved on to the LFO section. I used the TAPLFO 3 so, I didn't have to get a 20MHz crystal (needed for the TAPLFO 2). I added the envelope follower on another board and connected it to the junction of the rate input. It worked right out of the gate, so I thought, ok, it should also work for the other inputs. It was just a matter of whether it does something interesting.
The EF outputs at 2V at max, I think, when I measured.

Modulating the shape input was weird, not very musical. The transition happens too fast. Sounds jumbled.
Tagged on the multiplier input, it did much the same as for the rate, but a bit more dramatic.
Depth works well. The tremolo fades in (or out) as you would expect.
Symmetry is a subtle effect. Maybe too subtle... On the datasheet it's called Wave Distort. It changes the duty cycle, sort of like a squish/stretch effect. I think it worked better straight into the symmetry input pin. Would the 1k/100n network mess with that any? At first, I didn't have those on the cv inputs, the pot wipers went straight to their respective pins. They're there to filter out possible noise? I'll have to check again though, just to satisfy my curiosity. I have to rebuild the circuit on my breadboard cause I pulled some components out to put them in the pedal.

My build modulates rate, depth or symmetry, chosen with a DPDT (on-on-on) switch. I subbed the optos with VTL5C3 instead of the VTL5C1. Works great from smooth to helicopter mode. I removed the attack pot from the EF, for minimum attack, and it didn't seem very useful to me. I increased the decay resistor (R36) to 1.5M for a longer decay. Still, the decay slope causes a kind of abrupt return to the cv set from the pot... I guess I can't expect decay smoothness from this or any EF. There was some ticking, but the optional 100n (C22) solved that.

David's original Twin Peaks thread: https://www.diystompboxes.com/smfforum/index.php?topic=103714.0

Schematic:



Pics:

[ElectricDruid]

Wow, it's a beast, Frank! That's a tremolo with *all* the knobs on!

The 1K/100n filters *are* there just to filter a bit of pot noise. They're an optional extra. My earlier chips didn't do any internal filtering of the ADC results, so it perhaps mattered a bit more. The recent designs include digital filtering of the ADC results on the chip, so it's not really necessary any longer.

There's only one more thing to say:

We want sounds!   We want sounds!   We want sounds!   We want sounds!   We want sounds!   We want sounds!

[antonis]

Absolutely crazy..!!! 

[strungout]

Thanks guys! But the praise goes to the ones who make this possible!

Ask and ye shall receive! Demos:

https://soundcloud.com/user-165425177/sets/tremellow-demo/s-pqrjnV5T9JF?si=8011e9a02cd94f1fbadaec3adfd591af&utm_source=clipboard&utm_medium=text&utm_campaign=social_sharing

I needed some time to put 'em up The chain goes guitar > tremolo > M-Audio Air USB interface > PC. Sounds ok. The titles say what you need to know.

[ElectricDruid]

Ask and ye shall receive! Demos:

Thanks! Those sound good. My favourite is the Rate Up one, the way the tremolo slows down as the notes fade away is lovely, sounds like everything is slowing down and dying.

The Sym ones are interesting too, because I can tell something is going on, but I can't hear what. In my view, anything that gets you away from repetitive WooWooWooWoo modulation cycling over and over is a good thing (and not just for tremolos, either), and that manages to do that, without being obvious about it. Like it.

[moid]

Thanks for posting these, I was wondering what it would sound like. I like the Rate Up and Rate Down the most myself - the others sound like a 'normal' tremolo to my rather lo fi ears, but those two samples do something I haven't heard a tremolo do and I like that.

[strungout]

...My favourite is the Rate Up one, the way the tremolo slows down as the notes fade away is lovely, sounds like everything is slowing down and dying.

Going kinda dark there... I like it! Perfect for autumn

I found it less abrupt than I thought. There are sweet spots to find... As in, the Depth knob has to be set to barely be active to get the most out of the effect. On my breadboard I have an LED incator for the envelope, so I can see the effect of it. If it's too bright (which depends on where the respective pot is set), it won't have much movement. I'm wondering if I should maybe change the linear depth pot to audio taper, to more precisely set the sweet spot.

I'm also wondering if this pedal would benefit a oneshot chip addition. The attack/decay would be more controlled, if I understood correctly how it works.

As for the sym, I think it follows what's in the TAPLFO3 datasheet? The first portion (180 degrees - treble modulation) gets narrower, while the lower portion (bass modulation) gets wider. Basically, the length is changed and back. I think. Vice versa for the down direction.

One question, Tom: what's the max voltage rating for the cv inputs? I don't see it in the datasheet. I'm just concerned about maybe damaging the chip if I feed it a burst of more than 5V.

@moid: glad to be of help! Keep hanging around, your ears will learn. Mine did. But as I said, the movement is subtle...

[ElectricDruid]

One question, Tom: what's the max voltage rating for the cv inputs? I don't see it in the datasheet. I'm just concerned about maybe damaging the chip if I feed it a burst of more than 5V.

The max voltage rating is 5V, but there are protection diodes on the chip, so it's the *current* that makes a bigger difference. Too much voltage will turn the diodes on and they'll dump it to the rails - clip it, basically. Too much current will fry the diodes and then the chip will die. If the current is limited by a series resistance (like the 1K's in those 1K/100n filters you have) then you should be ok. There's a calculation you can do for the size of the resistance you need to protect against a certain size of over-voltage. For +/-12V Eurorack use, I worked out that 2K2 was fine, so 1K should be enough for 9V.