adding a sequencer or an envelope filter to a phaser?

[daverdave]

Right, I've rigged up test circuit with the meatball envelope detector and the ross phaser. I'm not sure how to wire the ldr side of the vactrol to the sweep pins of the phaser though, do I need to make a voltage divider with 9v on one side and ground on the other? Does anyone have any suggestions on how I should wire it?

[daverdave]

I tried using an ldr voltage divider with the ldr coming from 9v and a 1M resistor going to ground. It didn't seem to do anything though, I'm not sure if it's my envelope detector circuit. I know the phaser works. I'll try sweeping the phase with a pot and see if that works.

[daverdave]

Right, I rigged up a manual control to the control pins of the stages. I used a 100k pot with a 10k resistor coming from +9v to pin 3 of the pot, the 2nd pin of the pot going to the stages and the 1st pin to ground. It worked fine but when the pot was turned near to the 1st pin there was a wierd dip followed by a rise in volume, sort of like a strange click.
Anyone know a way to solve this?

If I can get it to sweep properly this way then I though using an ldr voltage divider might work, having a 10k resistor from +9v then a ldr under it going to ground, then using a 100k resistor in parallel with the ldr to set it's value. Any input would be greatly appreciated.

[frequencycentral]

I'm following your thread with interest, it would help to see a schematic of how you're marrying up the env detector to the phaser though.

[daverdave]

I don't have a decent schematic drawing program, I don't suppose you know an easy to use free one I can get?

[daverdave]

I rigged up the pot again the same as before, with a 10k resistor from 9v to lug 3, lug 2 to the phase stages, and this time lug one through a 20k resistor to ground, that got rid of the weird pop sound I was getting, and the sweep seems pretty good. Again frequencycentral, if you know a decent easy to use program for drawing schematics let me know and I'll post the methods I'm thinking of trying. I have a few ideas of how to connect the envelope.

[frequencycentral]

I'm almost ashamed to say I draw all my schematics using MS Paint. 

[daverdave]

That's well cool, you should ney be ashamed man. I'll have a do at drawing some and post them.

[daverdave]

This is how I intend to connect them anyhow

[daverdave]

Well I've just tested my envelope circuit and it works perfectly, so now it's just a question of connecting them together.

[frequencycentral]

Do you have a depth control, to set the amount of envelope that the phase stages see? It occurs to me that it might also be useful to be able to set 'where' the envelope sweeps from too - a bias control I guess?

[daverdave]

Yeah, the envelope has controls for sensitivity, attack, decay and intensity, that should provide enough control over the ammount of envelope. I reckon a bias would be usefull, not sure how to include it though, any suggestions?

[frequencycentral]

I think that little schematic I posted on page 1 would set how 'open' the OTA's are and so dictate the start point of the envelope sweep. You might want to add a resistor at either side of the pot though, as the whole travel of the pot may not be useful, and at the +ve end it could damage the OTA's. It would also work as a 'manual' control I also think.

[daverdave]

I think you're right, it would be almost the same as the manual control I tried with it, 10k from 9v and 20k to ground either side of a 100k pot. I'll rig it up and see what happens.

[Lurco]

I think that little schematic I posted on page 1 would set how 'open' the OTA's are and so dictate the start point of the envelope sweep. You might want to add a resistor at either side of the pot though, as the whole travel of the pot may not be useful, and at the +ve end it could damage the OTA's. It would also work as a 'manual' control I also think.

you really don`t want to wire a seriesresistor to the wiper?

[daverdave]

I think that little schematic I posted on page 1 would set how 'open' the OTA's are and so dictate the start point of the envelope sweep. You might want to add a resistor at either side of the pot though, as the whole travel of the pot may not be useful, and at the +ve end it could damage the OTA's. It would also work as a 'manual' control I also think.

you really don`t want to wire a seriesresistor to the wiper?

I'm not sure what you mean exactly, but if you're thinking that the current might be too hight for the ota's then I reckon they should be ok. I tried it out with a 10k resistor from 9v to lug 3 of the pot and a 20k from lug 1 to ground and it seemed to work fine. I'm not sure what pot would be best for the sweep, I used a linear and it seemed ok, might try a log and see if it sounds better.

[daverdave]

ah it works!! 

The one thing is the envelope only seems to sweep part of the phase, not the whole sweep, and the intensity control seems to shift the phase shift and you can hear the sweep better when intensity is set to 0. Not sure why, I think I need to do a bit more tinkering.

Sounds good though, like a weird envelope filter, could do with a bit more umph. I might try the regeneration mod Mr Hammer posted a while back, and add the extra stages mod. Should be a beast then. Just need to get the envelope to sweep more of the phase.

[frequencycentral]

I would guess that your envelope sweeps from about half the power supply up to a little below the +ve. Maybe the OTA's want to see a voltage swing thats nearer to being close to ground to close to +ve. I've used a env in a filter build I did that uses an LM324 which might do the job: http://www.diystompboxes.com/smfforum/index.php?topic=73021.0

[daverdave]

Would that sweep the whole of the phase you think?

[frequencycentral]

Would that sweep the whole of the phase you think?

I think so. LFOs tend to peak and trough either side of half the power supply voltage. Whereas most ENVs go from half the supply voltage upwards. So I'm guessing that's whats happening with yours. Why don't you measure the voltage at the output of your ENV when it's at rest and also at it's maximum. Oh, hang on, you have a LED/LDR combo in there too don't you? Hmmm, I'll have to give it some thought.........