Zpsdx possible mod? And I have another question

[Matt]

I was trying to find a way to make the modulation on the zp sdx sweep unevenly like a univibe compared to a phaser and thought about this mod by Mark Hammer.

"  The Ross actually uses anLM13600 to implement the same LFO circuit that the first issue Small Stone used with a pair of CA3094 chips.  As you know the SS eventually changed from 6 chips to 5.  Looking at the original Small Stone LFO, I decided to try out some things included there and they work very nicely.  I run a 22uf-47uf cap to ground from the LM13600 side of the 10k LFO resistor that goes to pins 1 and 16.  This adds some lag to the turnaround time at the high point of the sweep at the fastest speeds."

Maybe I am just hearing things but it seems to change the lfo sweep ever so slightly on the modulation section of the sdx.

Anyone have other ways to change the sweep of the lfo to make it sound more "random" or warbled?
I connected a 47uf cap from lug 3 of the depth control to groung.

[midwayfair]

You can add some ramp with a resistor in series with a diode across the speed pot. This may duplicate what you already did with the cap.

But random? No. Not without ripping out the entire LFO and using something different.

[Matt]

You can add some ramp with a resistor in series with a diode across the speed pot. This may duplicate what you already did with the cap.

But random? No. Not without ripping out the entire LFO and using something different.

Any suggestions on resistor value and diode as a starting point?

[midwayfair]

You can add some ramp with a resistor in series with a diode across the speed pot. This may duplicate what you already did with the cap.

But random? No. Not without ripping out the entire LFO and using something different.

Any suggestions on resistor value and diode as a starting point?

Any generic silicon diode. Maybe ... 100K or so. Hard to say. No resistance would be completely sawtooth. The symmetry control on the Tremulus Lune is similar.

[Matt]

I'll check it out thanks!

[Matt]

Instead of starting another thread, I figured I'd just ask another question here. 

Dont know the best way to describe what im after but here it goes.  Does anyone know of a way to modify the modulation section so that I could shut off the lfo and manually change the depth, making it a detuning effect?  And I would want it to be switchable so that I could retain the stock modulation as well.

[midwayfair]

Instead of starting another thread, I figured I'd just ask another question here. 

Dont know the best way to describe what im after but here it goes.  Does anyone know of a way to modify the modulation section so that I could shut off the lfo and manually change the depth, making it a detuning effect?  And I would want it to be switchable so that I could retain the stock modulation as well.

A continuous detune effect requires the time pot to constantly be made to go slower. The charge/discharge circuit in the Multiplex does this a little bit, until it runs out and the time pot stabilizes. You could simple add an expression jack to use a treadle to control the time (you'd need a 50K expression pedal, though ... an EB with an 82K resistor across it would get close enough) manually.

The better solution may be to make the time pot very quickly lengthen when you play a note. This requires an envelope that drives a variable resistance element negative. Put the variable resistance element in series with the time pot. Of course, you also need a very short decay so that it's ready for the next note in line.

[Matt]

Instead of starting another thread, I figured I'd just ask another question here. 

Dont know the best way to describe what im after but here it goes.  Does anyone know of a way to modify the modulation section so that I could shut off the lfo and manually change the depth, making it a detuning effect?  And I would want it to be switchable so that I could retain the stock modulation as well.

A continuous detune effect requires the time pot to constantly be made to go slower. The charge/discharge circuit in the Multiplex does this a little bit, until it runs out and the time pot stabilizes. You could simple add an expression jack to use a treadle to control the time (you'd need a 50K expression pedal, though ... an EB with an 82K resistor across it would get close enough) manually.

The better solution may be to make the time pot very quickly lengthen when you play a note. This requires an envelope that drives a variable resistance element negative. Put the variable resistance element in series with the time pot. Of course, you also need a very short decay so that it's ready for the next note in line.

Thanks for responding, I do appreciate your time, knowledge and input with this project.
The expresssion jack wouldn't be an option for me because I don't want to give up the pedal board space.  .....I have no earthly idea how to go about the second thing you suggested, and it sounds really complicated.  Maybe that's not the way to go about it.

Let me back up a bit.  The first time I stumbled across the idea of using some sort of detune was when I breadboarded a cave dweller, used a 9 volt battery to test it, and found that the repeats were out of tune.  After eliminating the possibility that I wired it wrong somehow, I connected it up to a 9 volt dc wall wart.  The detuned sound went away.  So it would seem that somehow the weak battery caused the detune.   

Anyway, after playing it for a while, I decided that the cave dweller wasnt goint to do what I wanted.  The zpsdx seemed like a better choice.  I love the sound of the sdx but. Iwanted to incorporate this mod.  I have very little electronic knowledge outside of being able to follow a schematic.  So I don't know what it was about the battery that caused the detune?  Voltage, current or other?  I figured that since they are both pt2399 based delays, the mod should work on either circuit.   Since then, I've been trying to find a way to recreate that sound in a more reliable way. 


Any ideas?