adding a sequencer or an envelope filter to a phaser?

[daverdave]

Hey all, I've made a vero layout for the envelope detector out of the meatball and I want to use it with the ross phaser. I'm not too clear on how to go about it, would I just add it in where the lfo goes to the stages or is there more to it? I was hoping maybe to add a sequencer as well, again, I'm not sure how to do it, but I'd like to have all 3.

[Mark Hammer]

Adapting envelope control to the Ross can be done in several ways.  You can have the speed increase when you pick harder, have the regeneration increase, or have the wet/dry mix become more intense.

To accomplish speed control, an LDR under envelope control would be placed in parallel with the phaser speed pot.

To have the picking strength intensify the phaser effect, you might have a 250k-500k pot in series with a 10k resistor to replace the 27k resistor that brings the wet signal to the mixer stage.  Then, as you play any LDR in parallel with the pot will drop the effective resistance lower to mix in more of the wet signal.

Envelope-controlled regeneration is a little more complicated, but do-able.

[daverdave]

I was hoping to sweep the phase stages with the envelope, is that what you mean by intensifying the phaser effect?
Thanks for the reply by the way.

[Mark Hammer]

Nope.  I was essentially describing envelope-controlled mixing, where the phasing would not be audible unless you picked harder.

[daverdave]

So would it be easy to control the sweep with an envelope filter?

[StephenGiles]

I think if you trawl through Jeugen Haible's site you may find some info in the Envelope-controlled regeneration front. Also, the electro-music.com site is a good place to look or ask for ideas.

[daverdave]

What's his site called?

[frequencycentral]

To accomplish speed control, an LDR under envelope control would be placed in parallel with the phaser speed pot.

Mark, is this the only way to do it? Would it not also be possible to mix the envelope into one of the control pins 1 and 16 of the 13700 LFO? Just curious, as I'm planning an eight stage Ross with two LFO's, so each LFO can control 4 stages each, or have both LFO's simultaneously control all eight stages, or have one LFO control the speed of the second LFO. I was planning to experiment with directly injecting a CV from the first LFO into the second LFO's control inputs, I'd assumed that the LFO is indeed a VCLFO in essence.

[frequencycentral]

What's his site called?

http://www.jhaible.de/index.html

[frequencycentral]

So would it be easy to control the sweep with an envelope filter?

Surely just apply the envelope to the control pins of the four phase stages, via a 10K resistor, just as you would the LFO? Though you may need to bias the control inputs with trimmer, lug 1 to +ve, lug 3 to ground, lug 2 to the control inputs.

[Lurco]

Surely just apply the envelope to the control pins of the four phase stages, via a 10K resistor, just as you would the LFO? Though you may need to bias the control inputs with trimmer, lug 1 to +ve, lug 3 to ground, lug 2 to the control inputs.

via a series resistor!

[frequencycentral]

Surely just apply the envelope to the control pins of the four phase stages, via a 10K resistor, just as you would the LFO? Though you may need to bias the control inputs with trimmer, lug 1 to +ve, lug 3 to ground, lug 2 to the control inputs.

via a series resistor!

[daverdave]

That sounds easy enough, I'll give it a try. How would I bias it though, I mean, how would I know it's biased?

[Lurco]

Surely just apply the envelope to the control pins of the four phase stages, via a 10K resistor, just as you would the LFO? Though you may need to bias the control inputs with trimmer, lug 1 to +ve, lug 3 to ground, lug 2 to the control inputs.

via a series resistor!

ah! you want the outputted voltage (or current) of that 10k envelope resistor to go to +ve or ground (depending on the extremer trimmersettings)?
my thought was that synth guys prefer mixing (adding) resistors for decoupling?

[frequencycentral]

ah! you want the outputted voltage (or current) of that 10k envelope resistor to go to +ve or ground (depending on the extremer trimmersettings)?
my thought was that synth guys prefer mixing (adding) resistors for decoupling?

I was thinking something like this:

[daverdave]

I'm still waiting on parts to turn up, but I just had another couple of questions. There's a buffer already at the start of the circuit so would it work ok to insert the input of the envelope detector from pad A on the tonepad layout (it's just after the input buffer) without using a seperate buffer for the envelope detector? And how would I go about biasing the output of the envelope detector to the control pins of the stages, is there a voltage it has to be to get the maximum sweep?

[frequencycentral]

There's a buffer already at the start of the circuit so would it work ok to insert the input of the envelope detector from pad A on the tonepad layout (it's just after the input buffer) without using a seperate buffer for the envelope detector?

Maybe it will work, I guess it would depend on the nature of your detector. Worth trying. You may need to experiment.

And how would I go about biasing the output of the envelope detector to the control pins of the stages, is there a voltage it has to be to get the maximum sweep?

The trimpot I suggested holds the OTA's open at the point fixed by the voltage divider (which is what the trimpot is). So you would get different sweeps depending on where the trimpot is set. Might be worth having it as a pot as opposed to a trimpot - maybe limit it's range at either end with a fixed resistor though.

What you're doing is quite experimental, I'm suggesting stuff that should work, but it's going to require some tinkering on your part ( !!).

[daverdave]

Thanks for the replies mate. I'll give it a go when the parts turn up. I'll keep you updated on how it goes. The envelope detector I'm using is out of the meatball, it's actually a pretty simple circuit, just a precision rectifier into a buffer driving an led/ldr as far as I can tell.

[Lurco]

ah! you want the outputted voltage (or current) of that 10k envelope resistor to go to +ve or ground (depending on the extremer trimmersettings)?
my thought was that synth guys prefer mixing (adding) resistors for decoupling?

I was thinking something like this:

even worse! when the trimmer is turned up, it will short +ve to ground 

[frequencycentral]

Oops, that connection between lugs 2 and 3 is an over sight, I'll remove it. 

EDIT: OK it's correct now, just click refresh to see it.