vanishing point/a sequenced phazer

[lightningfingers]

hii stompbox builders

I have a 4 stage phazer here- I built it with a view to using the vanishing point instead of an lfo. The phazer is a generic one, 4 opamp stages, using 2N3904s as the resistive element:


The collector(s) go between the cap and the opamps + input..

Some questions: In the schem. you will notice a 150R resistor in series with he LDR, this is because if i take it below 150R the transistor starts being MORE resistant?? Any idea why this would happen?

Also the pots for the vanishing points sequencer stages, what is a good value? Im not going to use LEDs: im really not into drilling that many holes :shock:

TIA

[lightningfingers]

Heyyy where'd the edit button go?

It looks like the transistor should go to 4.5V, but i'm using a bipolar supply for the opamps

[The Tone God]

I have a 4 stage phazer here- I built it with a view to using the vanishing point instead of an lfo. The phazer is a generic one, 4 opamp stages, using 2N3904s as the resistive element:

Ah yes the sequence phaser. I've already built one. Its fun to run the phaser in vibrato mode. Can anyone say pseudo-pitch shifter ?

Some questions: In the schem. you will notice a 150R resistor in series with he LDR, this is because if i take it below 150R the transistor starts being MORE resistant?? Any idea why this would happen?

Could the base input be leaking into the signal ?

Also the pots for the vanishing points sequencer stages, what is a good value? Im not going to use LEDs: im really not into drilling that many holes :shock:

What ?!? Your not into drilling holes ? I can't figure out why. You do need some kind of gate between the stages. I choose to use LEDs to serve as indicators as well as gates but you can either leave the LEDs inside the case, for testing purposes, or replace the LEDs with plain old diodes.

As for what value pots I think I suggested 50K to someone. It depends on what LED/LDR combo you have. I was going to order some parts probably this week so I could give a better suggestion as to what parts to order. When I do I'll post my findings.

Andrew

[lightningfingers]

I was planning on using some 1N914s as i had a bunch lying around. As for indicators--well thats what the little white mark on the knob is for right? :wink:
I'm going to use a transistor to tap an LED off the sequencers output, that might give a decent indicator of speed setting etc.

Could the base input be leaking into the signal ?

it seems obvious that it might do that now...how could i stop that from happening?

Thanks for the help-i'll buy a few different pots and see how it works out.

Stay tuned (and phazed) :mrgreen:

[The Tone God]

I was planning on using some 1N914s as i had a bunch lying around. As for indicators--well thats what the little white mark on the knob is for right? :wink:

lol, thats true. Those didoes should be ok. I would use those too or something similar like 1N4148s.

I'm going to use a transistor to tap an LED off the sequencers output, that might give a decent indicator of speed setting etc.

You could tap off the sequencer clock with another gate/transistor and get an LED that blinks with the clock pulse. That would be pretty easy.

it seems obvious that it might do that now...how could i stop that from happening?

I would think switching to FETs might be easier. I use optocouplers to solve those problems.

Thanks for the help-i'll buy a few different pots and see how it works out.

Stay tuned (and phazed) :mrgreen:

I would love to hear how it works out. Posting what value you use will be helpful for others as well.

Andrew