Loophole Vibrato Mod...

[JakeFuzz]

I really like the sound of a vibrato control and have been looking at a possible add-on mod for the loophole. I just don't see any way of making it simple. I am looking at porting the clock and voltage controller from the Payback project. In theory it is simple, turn the unused logic gate into a clock and have it modulate the power supply voltage on the ISD chip through a 2n5088 transistor. Here is Tonegod's site on the payback.

http://tech.thetonegod.com/payback/payback.html

What does everyone think? too complicated? Routing everything looks pretty messy and a few traces need to be cut (including those grounded gate inputs on the CD4001!) The transistor board itself will be very tiny though.

[JakeFuzz]

Another thought is that you could just use another dual gate chip (CD40107) to avoid having to reroute the CD4001. It would still be pretty darn small.

[JakeFuzz]

Hmmmm... I wonder.  

Now I just need to get the balls to cut up my board and test it out.

Sorry about the MS paint blobs, just trying to simulate what my solder joints are going to look like  

[nzCdog]

Cool!  2 more knobs would make this pedal a tweak-beast!
Would you have the the Vibrato on/off switchable too?

[JakeFuzz]

Cool!  2 more knobs would make this pedal a tweak-beast!
Would you have the the Vibrato on/off switchable too?

You could. It would just be switching the green line between the vero and the blue trace (constant 5 volts to modulated 5 volts). That probably doesn't make any sense but I can draw it up later. I definitely want to see what the depth range is. I like the vibrato because it sounds (well in the PGS vid) like a really old/warped tape playback, sort of driving home the low fidelity thing this effect has.

[nzCdog]

The PGS demo does sound awesome

[jtn191]

did I miss something? what PGS video?

[JakeFuzz]

Here is the one of the Zvex lo-fi loop junky with vibrato.

[JakeFuzz]

Hmmm, Tonegod is using a Schmitt trigger action NAND gate, I cannot find an 8 pin - 2 device Schmitt trigger IC. I wonder if the vibrator will work normally with just a normal comparator IC.

Update: yeah I am pretty sure that oscillator needs a Schmitt trigger, shame to use a whole cd4093 for just one logic gate...

[JakeFuzz]

Updated to CD4093. Also need some filtering now that the post regulator cap has been spliced off. Move C17 to where R15 is, jumper the de-tune switch, put a 22uF electro where C17 is and the wiring should be the same as before! To add a vibrato on/off switch just add a switch that opens/closes the "To REC switch" connection. That should do it.

[cjkbug]

Wow! that didn't take long Paul. I'm excited to see how his works out. Are you gonna have to ditch the detune function  to pull this off?

[JakeFuzz]

Wow! that didn't take long Paul. I'm excited to see how his works out. Are you gonna have to ditch the detune function  to pull this off?

Yeah I really want to see if it works. It is so simple I don't see how it could go wrong. I am pretty sure you could maintain the de-tune function by moving the filtering cap to the Vero and just wiring up the switch normally, I am not sure how it will react with the vibrato though...

[JakeFuzz]

Would this work maybe for a modified de-tune feature? The base bias for the 2N5088 is still controlled by the depth pot to the 5 volt source. The collector voltage is varied to a specific value (between 0 and 5 volts) using the pitch knob. When the NC switch is pressed it switches the 5 volt collector connection to the voltage selected on the pitch knob and if the depth knob allows a significant conduction between collector and emitter the ISD supply voltage will be set specifically to the de-tune value and the pitch will go to a specific value. Of course I have no idea if this will work or not but that seems like overkill with knobs and switches to me... awesome 

[nzCdog]

Dude you NEED to proto these, I'l drooling at the very idea of these cool mods!  Let us know how you get on!!! 

[JakeFuzz]

Dude you NEED to proto these, I'l drooling at the very idea of these cool mods!  Let us know how you get on!!! 

Yeah I am definitely including these on my loophole build. It might be a while before I get to it though.