Reverse Delay - first module prototype

Seems like a great example of where clock-phase instead of clock-pulses could solve a lot of gnarly problems with detection logic and so on. Much simpler. We talked about it here:

In thinking about it again, I would propose the phase-signal to be a saw-wave, so sharp leading edge (falling ramp) because you would get the trigger signal from the leading edge for free.


Ah, thanks so much Lars! I’d seen some of those standards discussions when searching, but hadn’t read this one!

In looking at Marbles, I was specifically thinking of some of my experiences trying to get Impromptu’s clock to sync to an external FH-2 from Expert Sleepers. I had a really good experience syncing Clocked to the FH-2 using the P24 setting. But I had less good experience using slower clock inputs and getting a solid sync.

At that time I was thinking I should sync all my external equipment to FH-2, and send the P24 clock into my computer to sync VCV, and I’d only have half round-trip latency that way.

But, my Marbles module is so good at syncing to even slow clock signals that I gradually switched to using it as my ‘main clock’ externally, and I offset the roundtrip latency in VCV with a scope and a loopback cable and a second Clocked module.

This looks like:

So I thought, Marbles is doing some kind of clever clock recovery magic.

But, within VCV, Clocked is rock solid. It’s only when I introduce external clock signals that it gets wobbly at the lower pulse per quarter note levels.

Anyway, I need to do some more careful reading of that post before commenting further, but that was my thought process before now.

Yeah, jitter, it’s the worst thing and pure poison for clock/tempo detection logic, and it seems like Marbles is good at handling it, but it’s also pretty complicated logic as can be seen. Clock-phase would not solve that, it would just pass on the jitter as it’s just a “varying clock speed”. For smoothening out jitter I don’t think there’s any way around complex logic.

However, in a “perfect world” all you need is BPM-CV and clock-phase. We just need to get all the hardware vendors on board :slight_smile:

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That’s my feeling as well, I was pretty surprised by how hard good-sync was to obtain, and yet how well Marbles did it.

I’m going to give it a try to just import the Marbles code rather than rewrite it, and try to make it work for clock sync on this module. If it works, that will be a good excuse for me to make the code public so other people can use it as, hopefully, a drop-in clock recovery device.

I’m a better C programmer than C++, but I feel like this is a good excuse to tackle some object orientation.

Haha, yeah, I think VCV Rack comes as close to a perfect world for hardware ideas as I’ve ever seen! But I’ve lived for too long in the other hardware world, I can’t put both feet in one or the other now it seems :slight_smile:

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Definately give it a try. You might run into some 8V and 5V levels in Marbles that really should be adapted to Rack standards but otherwise - great if it works! Would be very worthwhile as a stand-alone “clock-detection” module! And yeah, the “standards” and levels in Eurorack land are pure anarchy compared to the sensible voltage standards in VCV Rack. A few, simple standards goes an awful long way…

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Haha, very true. I admire the work of standards makers, it seems like such boring bureaucratic work, and yet they have clearly made the world a tangibly better place and all of our lives so much easier and better-off.

Still can’t help but think about that old joke, ‘You know the great thing about standards? It’s that there are so many of them to choose from!’

Makes me laugh to myself and groan internally as well :slight_smile: It’s as painful as a good pun!

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BTW, if you’re into that kind of thing I can’t help the instinct that there’s some gold to mine here by looking at phase locked loops for this kind of problem.


I haven’t tried it out, but the RPJ Circular Ride looks like it can give Chronoblob a run for its money, and it is polyphonic.

Also this one is polyphonic, and stereo:

Thanks, saw the announcement on Dave’s modules but haven’t tried them yet!

CircularRide is great, but doesn’t have a send/return loop, and neither does Surge XT Tuned Delay. The regular Surge delay isn’t poly either (yet).


the AS delay has a send/return loop
both the mono and stereo version, tho they are not polyphonic

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I finally read the Chronoblob documentation, and now I understand what Send/Return you are referring to. Now I understand why those blue modes never did much for me!

My Venom Recurse will definitely not help in your use case. It recursively sends/returns a signal to/from a polyphonic module, with each pass going through a different channel. The signal never gets mixed, so it is not feedback.

You want output fed back and mixed with the incoming signal, with the option of inserting additional modules in the feedback path, all on the same channel. (Actually you want a polyphonic version of that feature, each channel with its own feedback loop). I can see how that would be a great feature.

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Yep, there isn’t a poly delay with feedback loop yet. It’s fine, I can just use 16 Chronoblobs with the sends into a merge, it’s the same thing but poly patching is just easier and looks neater! Effects in the feedback loop are great fun, particularly frequency shifters, Clouds and modulation.

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My first handmade hardware synth had a one or two defeatable PLLs in it, I would would generate different frequency signals and then cross connect them using a repurposed multimeter knob that could short different connections together. And then I would power starve the circuitry so the PLL would have different clock recovery rates. It was quite fun, the PLL gave it a real sense of life and responsiveness.


Well, would still love to see /hear this crazy patch. Put it on Patch storage, go on, go on go on now! Mrs Doyle has a lot to answer for!!

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Crash issue: Sometimes when I add Taps into a patch, it crashes VCV Rack, not all the time, but often enough it’s definitely a problem. But I’m not sure what’s causing it. If anybody has any hints for determining the cause, let me know. The logs don’t seem to spell it out for me, but I haven’t caught the logs often enough to have a clear take on it.

I don’t feel like the module uses an unusual amount of resources, so maybe it’s a pointer that is too slow to initialize, or a similarly unexpected divide by zero? I’ll look for those this weekend and anything that anyone else suggests.

Clock input: In the meantime I’m making progress on the improved clock input. I find that input surprisingly useful, thanks again to @rasmus7 for suggesting that and for sharing his patch with me, where I could immediately hear how useful it would be. It was totally different from the way I imagined using the module, but now it feels essential.

Final design thoughts: I am feeling better about keeping the location controls in the final version, at first I thought the reverse tap location control would be too squirrelly to use, but when I am using two Taps modules, it’s great for creating stereo reverse effects.

Which also makes me wonder if I should make it a stereo module. I’m mentally kicking the polyphony can down the road for a bit while I worry over these different thoughts. Maybe maybe it stereo would also be a good way of dipping my toes into the polyphony problem. But, then again, maybe getting a mono Taps module into the library would be a good first goal.

The more I use it, the more I think of @alefnull’s comment about there not being anything else quite like this in the library right now.

Request for feedback: So if there was a slimmed down, early version to put into the library pipeline, that kept all the controls as they are right now, stayed mono, and maybe added voltage control to the different parameters, does anybody have any requests, or suggestions, or feedback on what would make it feel like a more polished module? I am planning to re-do the faceplate, but haven’t had a vision for it yet.


I think it’s probably fine for library as it is. If I want stereo, I just use 2 or 3 and pan them. I would say get it out there, and work on an update if you have time. I’m slightly obsessed with polyphonic effects, so that would be my first feature request, and also a way of smoothing parameter changes. Other than that, it’s good to go!

@ady34 go on then, I’ll try and upload that patch tomorrow. I was going to record a quick demo, and OBS decided to be an arse and stop capturing windows so I need to fix that first.


You have given a futuristic idea. Psy