“Event Horizon” PT2399 Sequenced Delay Concept

[cloudscapes]

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 made a similar circuit! I used an NPN as a ground pull on the 2399's time pin. the NPN modulated by whatever source.

[Taylor]

Right, that's how Slacker's done it in his Echo Base, but actually if you look at the Magnus Modulus it seems to be the case that you really can pump CV into pin 6.

See here:

http://www.diystompboxes.com/smfforum/index.php?topic=81668.msg677026#msg677026

And here:

http://www.diystompboxes.com/smfforum/index.php?topic=87813.msg743112#msg743112

I think I'll revisit this, because as I remember there were some really interesting and unique sounds available here. Using a CV or the transistor method would of course dial back the inherent portamento a bit - then we can add a dedicated portamento control just with a variable lowpass on the CV signal.

[Taylor]

I dug out my hideous perf board version of the sequencer I made last year, and hooked it up to an Echo Base PCB, soldering the LDR across the stock time pot, disabling the modulation.

It's a lot of fun. Pretty weird. I put the opto across the time pot to limit the excursion to a safe range. My optos have a max resistance of 500k, and previous experiments have shown me that this much resistance makes the 2399 lock up and stop making sound - what I read was that you need to refresh the DRAM with a clock cycle within a certain time range, otherwise it just forgets what's stored in the memory.

Also, by using this arrangement, the time pot acts like a depth pot when sequencing. Turning this down to a sensible level gives some funky but usable-to-normal-people vibrato/chorus sounds. I don't have it set up, but it would be possible to add a manual step mode like you see in ZVex's Ringtone. This would allow you to save n delay time presets, n being the number of stages in your sequencer. So you could use this as a regular delay pedal with presets, in addition to the funky sequencing.

[faptdivers]

Any chance of a sound sample? I'm really curious as to what this sounds but still have to wait a few weaks for my p2399's to arive.

[Taylor]

I'm going to try to do some. I may do a PCB for it, as it's surprisingly versatile and pretty unique. I might even add the ability for the modulation to control feedback amount as well - then you'd really have crazy stuff happening.

[tombola]

I'm very glad my bump had such a positive reponse!

My Echo Base PCB is (hopefully) somewhere over the Atlantic right now...

[Strategy]

I'm going to try to do some. I may do a PCB for it, as it's surprisingly versatile and pretty unique. I might even add the ability for the modulation to control feedback amount as well - then you'd really have crazy stuff happening.

woot! I vote for an extra CV input in parallel or that can insert and replace the seq CV.

- Strategy

[Taylor]

You mean an extra CV that is also controlling time in parallel? How would you use that, out of curiosity?

[Strategy]

Inject an LFO for more madness but to lend a random, non repeating aspect to modulation

Or have it switchable between onboard SEQ and external voltage source so not nec. both at the same time

but I am definitely silly enough to do compositions using multiple voltage sources. It is great for getting into babbling brook type effects where there is pattern with degrees of variation

- Strategy

[tombola]

I wonder if another useful, possibly more generally musical, effect would be seq modulating feedback, to create rhythmic delays. I used to have a great VST plugin called Metal Mickey which was IIRC an 8 step sequencer controlling delay time and/or feedback. It was great - I'll see if I can dig it out for inspiration

Edit: here it is: http://www.kvraudio.com/get/677.html

Screenshot pretty much explains whole thing.

[Taylor]

I wonder if another useful, possibly more generally musical, effect would be seq modulating feedback, to create rhythmic delays. I used to have a great VST plugin called Metal Mickey which was IIRC an 8 step sequencer controlling delay time and/or feedback. It was great - I'll see if I can dig it out for inspiration

Edit: here it is: http://www.kvraudio.com/get/677.html

Screenshot pretty much explains whole thing.

Yeah, I was thinking that would be cool too (mentioned it above). It's a pretty easy mod to add, so I will probably do it.

I think I probably won't put a CV in on the board, but it's the kind of thing that would end up in the mods sections of the PDF that accompanies the project. It would be useful for synth guys but not so much stompbox guys.

[Strategy]

I was thinking about getting echobase pcb, is there a CV input mod published in the documentation?

So, for Event Horizon, consider a clock input, a way to control the internal clock with pulses from outside, so people can sync the rhythm to drum machine triggers, square wave LFO, etc.

OK, I know, more synth oriented than pedal oriented...

Strategy

[Skruffyhound]

Well if this is turning into a project I guess I'll sign up. I really enjoy your projects Taylor, everything is well thought out, nice boards where components fit, clear instructions. I can stuff the board one night and play it through the breadboard the next. It's like knitting or meditation, I get a cool effect without any effort, kind of a rest between my own projects.

[Taylor]

Hmm, perhaps I should make my PCBs harder and messier, so as to be taken more seriously?  

I don't know if I have it in the doc for the Echo BAse, but the top of the LFO depth pot pretty much acts like a CV input. If you disconnect the LFO from there, maybe run it to a switch so you can have onboard LFO or a CV in jack. Then just connect whatever source there. May need some tweaking to get it in the right range.

[Taylor]

What sort of box and form factor would people want to build this in? 1590b ZVex-style? I personally don't like tiny boxes with tiny knobs, being a somewhat Lurch-shaped man myself, but that's just my preference.

I should also say that "Event Horizon" is a sweet name, but it's Rick's, so I would use something else.

[defaced]

I'd be fine with a BB or larger if necessary.  Sideways oriented boxes bother me.  I'm definitely in for at least one board. 

[frequencycentral]

I should also say that "Event Horizon" is a sweet name, but it's Rick's, so I would use something else.

I've been watching this thread develop with interest. Coincidentally, I just bought a bunch of 9mm 100k lin Alpha pots, and I have 4017's in stock too.

I would be flattered if you were to use the  "Event Horizon" name.

[Taylor]

OK, cool, well Event Horizon it is. Don't know if you intended a nod at "Vanishing Point" or not, but it's got a very... Bladerunner-esque feel to it in any case. I'm terrible at coming up with names for circuits.

I think I will try to either send CV straight into pin 6 ala Magnus Modulus, or use a transistor as in the Echo Base. The optocoupler approach works, but it would be nice to have more instantaneous changes possible.

The feedback sequencing control will have to use an optocoupler as an OTA or similar would just be too complex to add. For simplicity's sake the same sequencer controls for time will control feedback (with a switch so you can have time sequencing, feedback sequencing, or both). Since this tends to the experimental end of effects, I think that's an ok compromise and will still yield some pretty crazy sounds.

[Strategy]

The feedback sequencing control will have to use an optocoupler as an OTA or similar would just be too complex to add. For simplicity's sake the same sequencer controls for time will control feedback (with a switch so you can have time sequencing, feedback sequencing, or both). Since this tends to the experimental end of effects, I think that's an ok compromise and will still yield some pretty crazy sounds.

Wow, awesome!

I'm terrible at coming up with names for circuits.

Here are some imaginary pedal names. Now, design circuits specifically to fit the names.

The Cubist
Stay Puft
The Slider
Mossy Channel
Motion Detector
The Percolator

- Strategy

[Taylor]

Cool, I will try to use those, though there's already the ol' Harmonic Percolator.


So I'm thinking about knobs.   I started thinking about the knobs I'd want:

8 sequence step time knobs
1 sequencer speed
1 glide time
1 feedback amount
1 depth
1 mix

So that's 13 knobs... It would also have a sequence/random/step footswitch, a toggle for sequence or manual mode, and a rotary or 2 toggles for time/feedback/both sequencing. I have no problem with that, but it occurred to me that that might be too many for some folks. Anyone want to weigh in on what seems superfluous enough that it should be a mod instead of a stock feature? It matters because, with this many knobs, there absolutely have to be onboard pots on this. So I have to consider how it will be built before I can really do the PCB for the most part.