“Event Horizon” PT2399 Sequenced Delay Concept

[frequencycentral]

I just built a Midfi Clarinot, and I'm in the middle of a Magnus Modulus build, so I'm quite focused on PT2399 at the moment. Both these projects, which feature modulated delay time, got me thinking, as did danielzink's Seek Wah clone in the 'Picture's' thread. So I've got this idea for a PT2399 delay where the delay control is replaced by an eight step analogue sequencer. I'm pretty familiar with analogue sequencers as I've built a few for my modular synth, and I've come up with what I think are some interesting ideas.

There are two distinct parts to Event Horizon, the sequencer made up of a 4022 or 4017, an LFO and some logic, and the PT2399 delay itself. I'm not sure yet if I can run the summed sequencer output directly into the PT2399's pin 6, or if I'll need to use a vactrol or LED/LDR combo.

Running the sequencer would allow the delay time to be specified at each step. It would be possible to set up a chorus type modulated delay by selecting close but subtly different delay times for each step. Wider spaced delay times would allow more complex modulations. It would be interesting to set up delay times which are rhythmically related in alternate steps.

Stepping through the eight steps with the 'Manual' momentary footswitch would allow up to eight different delay time setting to be selected, which would be useful for gigging, selecting the right delay time for each song for example. So it's a delay with eight memories.

Pressing the 'Start/Stop' footswitch to stop automatically resets the sequencer, so when it's pressed again to start it will always commence at step one.

I'm thinking it might be useful to have the ability to override the internal LFO from and external source. Using a simple audio to gate converter the external source could be pretty much anything, from a click track to a drum machine to a microphone inside a bass drum.

It's going to be pretty 'knobby' with eight knobs (I'll use 9mm board mounted) for the eight steps as well as Speed, Feedback and Blend. A switch to select the number of steps, another to select auto or manual advance. Momentary footswitch for Manual Step and Start/Stop and the usual effect/bypass 3PDT.

Until I start breadboarding I can only imagine what it will sound like and how it can be used, but I think it should be cool. What do you think? Obviously, it's going to be a pretty busy breadboard to get all this running, but it should be straight forward enough. Anyone want to throw in any useful ideas that I've missed that wouldn't add too many more components/controls?

[Nitefly182]

I think you're going to need some sort of smoothing pot to ramp between steps. That way you could get reasonable modulation tones or back off the smoothness and get a weird noise pedal.

[frequencycentral]

I think you're going to need some sort of smoothing pot to ramp between steps. That way you could get reasonable modulation tones or back off the smoothness and get a weird noise pedal.

A portamento control is a good idea and easily implemented as part of the sequencer's summing mixer.

[thereverend]

i really like this idea. i hope you can get it to work.

[jacobyjd]

lol...man, Rick, you need to get this thing working and polished up so I can incorporate it into my already-in-progress sequenced wah/tremolo build!

I like the idea--definitely. In fact, a portamento control actually sounds interesting for a sequenced wah/tremolo, too...

[slacker]

Cool idea Rick. I haven't tried a sequencer but I've messed about with sample and hold and pseudo random generators hooked up to the Echo Base and you can get some interesting things happening. You can get cool arpeggiator type effects or with loads of feedback something like those mad Jonny Greenwood MAX/MSP sounds.

[frequencycentral]

Thanks Ian - what do you think  - can I hook up a control voltage directly to pin 6 of the PT2399? Or is a vactrol needed?

[Mark Hammer]

So this will really be a "Seek Whammy"?   That is, if one has a free-running sequencer, and ramping or smoothing between control-voltage changes, AND if there is still data in the RAM sampled at one rate and played back at a new rate, the net effect is to keep shifting the playback pitch of that content.

[cathexis]

Mark is most probably right in his post above. Fast speeds will induce seasickness. It's a very cool idea, anyhow, and I will follow this post closely. I've been planning to make a sequencer for the control jack on my A/DA flanger soon.
LARS

[bean]

I was actually just thinking about a sequenced delay this morning. I really like the idea. I have a nice compact breakout board for the sequenced wah and it could probably be ported to another design.

[Mark Hammer]

A more usable effect might be to use the sequencer to adjust wet/dry mix or regen levels, or maybe even a low-cut aspect of the wet signal.  That would keep your pitch stable, but introduce cyclical changes in how the delay sounds.

That being said, there is a big difference between a free-running sequencer yoked to a delay, and a stepped set of sequential control voltage changes used like a non-random access set of saved patches.

[slacker]

Thanks Ian - what do you think  - can I hook up a control voltage directly to pin 6 of the PT2399? Or is a vactrol needed?

I don't think you can just hook the CV up to pin 6. I'd use a vactrol or a transistor like in the Echo Base.

[jacobyjd]

A more usable effect might be to use the sequencer to adjust wet/dry mix or regen levels, or maybe even a low-cut aspect of the wet signal.  That would keep your pitch stable, but introduce cyclical changes in how the delay sounds.

That being said, there is a big difference between a free-running sequencer yoked to a delay, and a stepped set of sequential control voltage changes used like a non-random access set of saved patches.

I know this think would have the potential to be really chaotic--but...my first thought was to have a control to mix the delayed signal well below the dry signal. You could have crazy pitch-bending craziness in the background of your dry signal, but it wouldn't be complete chaos--you could get it to move at a standard rate...I'm imagining a kind of crazy ring-mod...

[frequencycentral]

Thanks Ian - what do you think  - can I hook up a control voltage directly to pin 6 of the PT2399? Or is a vactrol needed?

I don't think you can just hook the CV up to pin 6. I'd use a vactrol or a transistor like in the Echo Base.

Yeah, I just measured the voltage at pin 6 of my Clari at both min and max time, there very little difference, a few millivolts. So a vactrol it is!

[earthtonesaudio]

A current sink is faster and more linear.

[Renegadrian]

I just bought a couple of 2399...I believe this idea will find its way, after all you're much more into sequencers as I am, Am I right Rick?! (no, I'm left) <---Sorry for being stupid.

Stay tuned!

[frequencycentral]

......after all you're much more into sequencers as I am, Am I right Rick?!

Damn right, I'm mad for them. Here's a couple of 'soundscapes' i did a while ago just using modular synths/analogue sequencers. No keyboard, no drum machine, no overdubs, just loads of wires and knob tweaking.

http://dl.getdropbox.com/u/967492/Modular%20One.mp3
http://dl.getdropbox.com/u/967492/Modular%20Two.mp3

[JKowalski]

I don't know how useful this would be - for example, the delay speed constantly changing would be all out of whack with the sequencer resets, the echos would randomly change pitches and speed up/slow down - It sound like a noisemaker to me.

Give that, I want to see a vid of one! Step on it!

[tombola]

Did you ever get this working, Rick? I have an old Rebote PCB that I've never built, thinking about trying it.

[Taylor]

I didn't see this when it was new, but around the same time I pretty much made the same thing - I just hooked The Tone God's Vanishing Point to an optocoupler, aand put the LDR side where the PT2399 expects the time pot. Works exactly as you would expect. One thing to note is that the PT2399 has a slope in how fast it can change its time parameter - so at high sequencer speeds, you don't get instantaneous pitch change, more like a burbling random vibrato.