Overly ambitious modulated stereo dual digital delay - Input needed

Started by Philthy, January 19, 2017, 06:47:16 AM

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Hi Guys,

Further to this thread http://www.madbeanpedals.com/forum/index.php?topic=24629.0    I have been thinking about building the mother of all digital delay projects that is going to be well above my pay grade ;) Given this, I would like some input/advice. Thoughts as follows:

Aim: Mono or stereo dual digital delay with tap tempo and modulation and the ability to go parallel or series with the delays

Concept: JMK Paralyzer and two Electric Druid Digital Delays each with a TAPLFO.
              Some form of order switching to go parallel or series and mono or stereo.
              Single TT switch for both DD boards
              DD TT syncs the TAPFLOs (appears to be doable based on the comments on the ED site)
              Concentric pots for the delay and TAPFLO controls to save some real estate.
              Stack the delay and TAPFLO PCBs to save some real estate.

Switching options:
1. Parallel/Mono (delays blendable thanks to the Paralyzer )

                                               (Digi Delay 1 + TAPFLO 1)
Input > Paralyzer Input Buffer <                                     > Paralyzer mixer > Paralyzer Output buffer > Output 1
                                               (Digi Delay 2 + TAPFLO 2)

2. Parallel/Stereo
                                               (Digi Delay 1 + TAPFLO 1) > Output 1 (ie: bypass Paralyzer mixer and output buffer)
Input > Paralyzer Input Buffer <
                                               (Digi Delay 2 + TAPFLO 2) > Output 2 (as above)

3. Series/Mono (second delay blendable thanks to the Paralyzer )

Input>(Digi Delay 1 + TAPFLO 1)>Paralyzer Input Buffer<                                     >Para mixer>Para Output buffer>Output1
                                                                                    (Digi Delay 2 + TAPFLO 2)

4. Series/Stereo (second delay blendable thanks to the Paralyzer )

                                                                                    ______unused_______> Output 2
Input>(Digi Delay 1 + TAPFLO 1)>Paralyzer Input Buffer<                                     
                                                                                  (Digi Delay 2 + TAPFLO 2) >Para mixer>Para Output buffer>Output1
Some questions:
1. How to handle the output switching?  Could this be done on the order switch or maybe with a switching jack on output 2
2. Any obvious issues or improvements?
3. Any better alternatives to the Paralyzer?
4. Would I have phase issues with this arrangement?
5. Will all the buffers play nicely together?
6. Could I do something with the unused loop in options 3 and 4?



Oh man! You're shooting for the moon! Let's see if I can help at all.

1. I think that you could in theory use a DPDT toggle switch to be able to switch from stereo to mono. Essentially, the middle poles will be your returns from the delay circuits. One end of the switch goes back to the Paralyzer, then it gets mixed, then you go to your left output jack. The other side of the switch will go to the switch could go to the left and right outs.

Another option, in theory, is that you could use a pair of switching jacks. In this case, you never go back to the paralyzer, you just go to the output jacks. So when the right jack is not plugged in, it just gets tied in with the left/mono jack. This is a bit primitive, because there's no mix stage, so what you get is both outputs tied together. It's not ideal.

So, perhaps a better solution would be to create an actually true 'stereo panner' circuit. This is something that now you've mentioned it I can think about offering from JMK PCBs. It'd be a ways off in terms of development, but in these rare cases, you want to be able to split the signal off properly, then be able to keep the two parallel effects in stereo with proper buffers. Perhaps a Paralyzer could be hacked to do it, but more likely I can help develop the circuit, then you can build it on perf or a single sided layout or something... I'll have to think about this.

2. I think it's very ambitious, and the hard part about this is that ultimately you'll likely never use some of the features you're building. It's better to build the devices you use for the actual purpose you plan to use them for, rather than build it with lots of features you hope to use. Do you actually plan to switch back and forth between the Parallel/Mono, Parallel/Stereo, and Series/Mono settings?

I can see that you'd eventually settle into one of those settings, and just stay there. Personally, I would build it for Parallel, but hardwired to be in stereo. If I used it in mono, all I'd end up doing is use one of the delay circuits in mono mode, and then when in stereo, both delay circuits would be active. But that's just me.

3. See above. Basically, you could use it, or you could use just a part of it, or you could potentially use something different. Options aren't really available, unless you DIY them as opposed to using a PCB project.

4. I doubt it. More likely than phase issues is that you'd have sync issues. I'm not certain how precise the TAPLFO or Electric Druid Tap Tempo features are, but it's possible, as with the PTAP and the TAPTATION circuits are, that you'll end up with your projects out of sync.

5. There's such a thing as too many buffers, but it's unlikely that the circuits involved here are going to be the cause of major issuess.

6. Not sure.

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Thanks for your reply Jacob. I guess I was shooting for the moon somewhat with that post :o .

You are probably right re only using one setting, and that would be one of the mono settings but hey, modulated stereo delay is like chocolate - you don't need it but geez it's great when you have it.

I have a had a re-think and come up with a simpler arrangement. Deleted the Series/Stereo and rearranged the Series/Mono so that I may have some hope of working out a switching arrangement - maybe a 4P3T? Unfortunately some of the blending capability of the Paralyser will be unused though. See sketch.

Thoughts appreciated.