Quick / Slow switching in sequenced pedal?

[Bernardduur]

OK, here's the deal:

I made a high pass / low pass / band pass filter pedal and added a sequencer to it; it works like a charm! But I want to look a bit further......

I now use two LDRs and a LED for the effect. The effect has a glide effect as a wah wah pedal. I would like it to be more "choppy" as in it does not glide but jumps from one to the other.

Is this possible by replacing the LDR with something else?

[TELEFUNKON]

resistors/pots

[Bernardduur]

Hmm, no, I just replaced the pot with a LDR to let it be controlled by the sequencer

[The Tone God]

LDRs have a slow response which contributes to the "smoothness" of the switching. One problem that can occur if you switch too fast is popping particularly if you switch between stages with largely different settings. Some people don't like this so the LDR is a good indirect way to squash that bug. In order to do quicker switching you will have to use something other then a LDR. Maybe a FET of some type or a switching IC.

Andrew

[TELEFUNKON]

switched resistors/pots

[Bernardduur]

Ah, yes, I am already switching between 10 pots, so that is normal..... Just the change between different pot settings is my problem

[zachary vex]

OK, here's the deal:

I made a high pass / low pass / band pass filter pedal and added a sequencer to it; it works like a charm! But I want to look a bit further......

I now use two LDRs and a LED for the effect. The effect has a glide effect as a wah wah pedal. I would like it to be more "choppy" as in it does not glide but jumps from one to the other.

Is this possible by replacing the LDR with something else?

LDRs are what you want for quality audio.  remove the LDRs from two vactrol model VTL5C9 and use those instead.  you might want to use the LED from that one as well... or you could put two of those vactrols' leds in series or parallel and leave them intact. 

you could also try using an H11F3 or H11F1 photofet optocoupler, but they usually add distortion to audio circuits... however that can sound interesting too.

[Unbeliever]

If LDRs aren't 'fast' enough for you, you might need to change your circuit to use OTAs then. It might also be worthwhile rejigging your circuit so that a smaller changes in the LDR resistance result, still, in the filter change you want. The less the resistance of the LDR has to change, the 'faster' it will be to change. Personally, I'm guessing you won't like the pops likely introduced by an 'instant' change of resistance anyway.....

[Paul Perry (Frostwave)]

Any hints as to the schematic? I would have thought any step sequencer would have been fast enough with a led/ldr!

[soggybag]

What about a H11F (I think that's the part number) photoFET? Or a regular FET?

[Processaurus]

Sounds like a cool project... 

Some photo resistors have a faster response than others, might be worth auditioning a couple types. 

Also check this out if you didn't know already:

p.s.  the light sensitive resistors are called LDR's, Light Depending Resistors, also known as "Photocells" at ratshack.  Cadmium Sulphide (CdS) reacts best to green light wavelengths, Cadmium Selenide (CdSe) reacts best to red light wavelengths.

[Bernardduur]

Any hints as to the schematic? I would have thought any step sequencer would have been fast enough with a led/ldr!

Sequencer

filter; scroll down to super tone control

I don't know if I use Cds or Cdse cells (and my source doesn't know either); will try some stuff here

[Bernardduur]

OK, I got it!

I found some NSL-32's I had left from my Mu-Tron III copy; they work great!

Thanks all for the advice

[brad]

There's a sequencer on GEO that switches between pots rather than LDRs.  I used it to do exactly what you're after, but with Tim Escobedo's PWM.  The only probelm is that it doesn't have step indication LEDs.

[Processaurus]

There's a sequencer on GEO that switches between pots rather than LDRs.  I used it to do exactly what you're after, but with Tim Escobedo's PWM.  The only probelm is that it doesn't have step indication LEDs.

Awesome! I love that the controller is 10x more complicated than the audio path.

If you want LEDs, you can use another multiplexer chip to ground the cathode (with a series current limiting resistor) of one of 8 LEDs  that are always getting V+ on their anodes.  The LED multiplexor's address lines can be hooked up in parallel to the corresponding address lines controlling your chip switching between the pots.

sometime I'd really love to see a sequencer hooked up to a formant type filter, so you could make vowel sequences, to play along with a vocal part.

[Paul Perry (Frostwave)]

Awesome! I love that the controller is 10x more complicated than the audio path.
sometime I'd really love to see a sequencer hooked up to a formant type filter, so you could make vowel sequences, to play along with a vocal part.

1. You mean like your brain and your throat?

2. Can you say Zvex ooh wah? (Okay, it's covered at geofex as well).

[brad]

If you want LEDs, you can use another multiplexer chip to ground the cathode (with a series current limiting resistor) of one of 8 LEDs  that are always getting V+ on their anodes.  The LED multiplexor's address lines can be hooked up in parallel to the corresponding address lines controlling your chip switching between the pots.

Did that too...and you should have seen the size of the perf!!  I think the circuit ended up having 6 ICs (2 for the PWM, 3 for the sequencer, 1 slave for the LEDs).

This is the shematic I based it all on from GEO btw: http://www.geofex.com/FX_images/ud-rand.gif

Compare it to this sequencer, and you'll see why LDRs are so much better  : http://compiler.kaustic.net/machines/vanishing-moon.html

[Bernardduur]

Wow...... that IS much bigger

[nelson]

Am I right in thinking a "step" function could be added to a 4017 based sequencer simply with a momentary DPDT footswitch?

If you create one clock signal with the momentary then hold the clock inhibit pin high on release of the footswitch the output should move one pin and stay there.

[The Tone God]

There's a sequencer on GEO that switches between pots rather than LDRs.

With The Original Vanishing Point I switched acutal pots with a multiplexer. The reason I did it that way was to reduce the problems of getting the LDR in the right range. Using the multiplexer also produced "stronger" switching as it is faster then the LDR.

Am I right in thinking a "step" function could be added to a 4017 based sequencer simply with a momentary DPDT footswitch?

If you create one clock signal with the momentary then hold the clock inhibit pin high on release of the footswitch the output should move one pin and stay there.

You just use a SPST switch with a deboucing R/C network feeding that to the clock input. Another option is to disconnect the leg of the speed pot feeding the input of the gate and connect the footswitch there so you can switch between auto and manual clocking.

Andrew