Black Current Vibrato & Stutter effect

[Freppo]

Hi there Folks!

Here is a original design I've been tinkering with for a while.
I finally called it finished and boxed up a prototype pedal.

Please let me know what you think, and if you see anything that can be improved.
More info, schematic and vero layout at: http://www.parasitstudio.se

cheers
/ Fredrik

[kaycee]

Freppo, that looks great, sounds great and it's very cool of you to share the project. I like that you kept it to one control and a switch and wasn't tempted to over feature it. 

The chop Trem is a bit like the Vox repeat percussion. Have you managed to keep the clock noise out of the audio?

[Luke51411]

I've been looking for a unique tremolo to build, I think I'll add it to the list

[Freppo]

Thanks guys for commenting. I'm happy you like it

Kaycee - to aswer your question: indeed, the biggest challenge was to remove the clock-noise from the audio.
I managed to make it very quiet until I had boxed it.. Now I have a faint ticking.
It can't be heard while playing and I think that shielded offboard wiring would do the trick, so it's no biggie.

cheers
/ Fredrik

[kaycee]

Might I suggest that you try removing the LFO ground from the audio ground and wire it direct to  power ground?

[Freppo]

Using separate grounds are usually a bit tricky, but I like the idea
When I make a PCB layout I will have this in mind.
Thanks! / Fredrik

[Davelectro]

Sounds great!

IMO a buffered input would be useful to protect the input RC filters from different source impedances.

[anotherjim]

Sounds great!

IMO a buffered input would be useful to protect the input RC filters from different source impedances.

+1 to all.

Freppo,
I see you used an amp for a "hard" reference. You could reuse that as an input buffer and get away with resistor dividers for Vref,  but make 2, one for the audio amps and one for the LFO circuit.

[kaycee]

Using separate grounds are usually a bit tricky, but I like the idea
When I make a PCB layout I will have this in mind.
Thanks! / Fredrik

Might not work, so I suggest that you try it on your proto before the effort of making a PCB.

[Freppo]

Sounds great!

IMO a buffered input would be useful to protect the input RC filters from different source impedances.

+1 to all.

Freppo,
I see you used an amp for a "hard" reference. You could reuse that as an input buffer and get away with resistor dividers for Vref,  but make 2, one for the audio amps and one for the LFO circuit.

Thanks for all the suggestions!

I don't think a input buffer is really necessary.. But I guess wouldn't hurt either Maybe just a simple transistor buffer.
All the filters at the input(s) do is to remove a bit of the high "radio" frequencies that translates into hiss when amplified.
The 2.2nF and 330pF cap was added in the last minute when listening to noise with my guitaramp cranked. 
The RC filter that sets the crossover frequency to achieve the vibrato'ish sound is placed after the inverting amp.

This circuit require a bit of amplification to reach unity, because the two signalpaths that are mixed together at the output.
My first version actually had both input stages as buffers (one inverting and one non-inverting)
To achieve unity gain I had a amp at the output.. but that was too noisy and also amplified the ticking.
So insted I choose to have some gain at both input stages and passive summing = much less noise.

I've already tried with two resistor divider Vref for the audio amp and LFO, but it was not helping much with the ticking.
By buffering the Vref almost all ticking went away, so that's why I stuck with that. But good thinking
The ticking is not really a problem.. It's very faint now, and probably because of my messy offboard wiring.

I really appreciate your advice and ideas!

Cheers / Fredrik

[bluesdevil]

Hi Fredrik!
Just finished soldering up your Black Current pcb layout and noticed you did away with one of the 47R resistors that's in your schematic and vero layout..... was it just used to decouple LFO from rest of power supply and you decided it was not needed when doing pcb layout?
Also in the pcb layout you have a TL022 for the 3rd IC, but have TL062 in schematic and vero layout.... just a typo?
   I'm surprised nobody has reported back from building from your pcb layouts with these questions, but I'm glad to be the test guinea pig!!
Gonna fire it up right now with a TL062 in the LFO........ can't wait!!! Hopefully will report back with success.

[bluesdevil]

Okay went ahead with the TL062 and fired up nicely! I just realized you mentioned doing away with the twin divider resistors in your last post... sorry about that.
No ticking or noise, but I may add a level pot because the "stutter" mode seems to jump in volume a bit. The "vibrato mode reminds me of R.G.'s "Vibra-Tone" Fender Brown face amp tremolo project. I built it up years ago from Markm's layout. Thanks again for the very cool project... now on to the Raygun Chaos Fuzz!

[Freppo]

Okay went ahead with the TL062 and fired up nicely! I just realized you mentioned doing away with the twin divider resistors in your last post... sorry about that.
No ticking or noise, but I may add a level pot because the "stutter" mode seems to jump in volume a bit. The "vibrato mode reminds me of R.G.'s "Vibra-Tone" Fender Brown face amp tremolo project. I built it up years ago from Markm's layout. Thanks again for the very cool project... now on to the Raygun Chaos Fuzz!

Thanks for the build report. I'm glad you like it!  
TL022 or TL062 both work fine for the LFO and I skipped the 47r resistor on the PCB layout because it wasn't necessery.

cheers!
/ Freppo