Author Topic: Modern delay chips?  (Read 413 times)

Fancy Lime

Modern delay chips?
« on: February 07, 2021, 01:54:11 PM »

I've been asked for advice on buying a digital delay. I did some digging only to find out that, apparently, there is none on the market that has the features I seem essential: tap tempo, subdivision including triplets and quadruplets (they all have the super annoying dotted either although those can easily be tapped in directly if you have a bare minimum of feel for rhythm), kill dry, a neutral typical digidelay sound, infinite repeats. Are these unreasonable features? Anyway, looks like I need to look into DIY solutions.

Can you guys recommend a good chip set for that sort of thing? There are so many cheap and fairly decent sounding digidelay around (if only they managed to not try to emulate bloody tape echos or "cosmic shimmer" or some such nonsense all the time) that I'm sure something suitable must exist. Kind of like an FV-1 but for delay.

Cheers and thanks,
My dry, sweaty foot had become the source of one of the most disturbing cases of chemical-based crime within my home country.


Re: Modern delay chips?
« Reply #1 on: February 07, 2021, 05:25:10 PM »
I suppose the obvious question is "How long?"

FV-1 is the clear winner up to 2 seconds. Up to 4 seconds..dunno, two FV-1's maybe??

I had a crack at it with dsPIC and got 4 seconds, but it has a bit of hiss. You need an external codec for better quality - I was deliberately keeping it simple and through-hole. If you go with an external codec, you can get excellent quality. Here's one example (more features than you need):

I don't know of a single-chip solution. It's possible that there's a processor out there that includes decent A/D and D/A on the chip along with enough RAM to make a good delay, but there are so many I haven't found one yet. From a design point of view it is *far* easier to keep the noise level low if the codec is a separate chip away from the processor's noise.

I've been stuck with this same problem myself, so one project that someone has been helping me with is a little daughter board solution for long digital delays. Think of something like the Teensy or Basic Stamp (I've been thinking of it as "Delay Stamp"). It's 25 x 64mm, with rows of 0.1" spaced pins down the sides, like an overgrown chip. The board has a processor, codec, lots of RAM (8 seconds) and a full VCO running the master clock, so you can easily add modulation (I know, I know, you said you didn't want tape wobble simulation!). We've got as far as me having three prototypes on my desk, but I haven't had a chance to play with it. The plan is when it's finalised to get a pile of them manufactured and then sell it as a plug-in module you can easily include in your own designs, with all the hard super-tiny-SMD and digital stuff done for you. The on-board firmware needs to be flexible enough that people can do things like build simple loopers and layer sounds as well as delays but also simple enough that there aren't a million confusing options to set up. That's the next bit to sort out.

« Last Edit: February 07, 2021, 05:37:19 PM by ElectricDruid »

DIY Bass

Re: Modern delay chips?
« Reply #2 on: February 08, 2021, 04:10:00 AM »

DIY Bass

Re: Modern delay chips?
« Reply #3 on: February 08, 2021, 04:49:54 AM »
FXcore is also a newer take on FV-1, but still with the same amount of RAM, so no longer delay times.

Fancy Lime

Re: Modern delay chips?
« Reply #4 on: February 08, 2021, 09:51:31 AM »
Hey guys,

thanks for the input! The Daisy and the FXcore look really interesting. Alas, they still seem to be in the early adoption stage, meaning documentation is likely still a bit thin. I'll have a look at the Daisy first and see if I can figure out if that would work for me.

OTOH, 2s are plenty for my purpose, so I might try an FV-1 after all.

In the meantime, Tom has given me an idea: Why not use a simple existing delay and just design an external "tap translator". Here is a quick rundown of how I want to control the tap tempo:

-There are two momentary switches: S1 and S2
-Tapping S2 sets the subdivision count. So tapping it three times sets the subdivision to 1/3, tapping seven times to 1/7, and so on. Tapping it again after it was not tapped for more than 2 seconds or so starts the counter anew.
-Tapping S1 at least twice sets the "basic tempo".
-After the second tap on S1, two pulses are being sent out via the "tap out" to the "tap in" of some effect. The pulses are spaced by the basic tempo divided by the subdivision factor. If no subdivision was set, 1/1 is assumed. If Si is tapped more than twice in a given time, the double pulse is sent out after each tap (except the first of course), with the basic tempo factor updated to the last to taps, respectively (subdivision remains the same).

This would allow to get arbitrary subdivisions without the need to use your hands. Ideal for progrock with changing times signatures. How is such a thing not on the market as we speak? Baffling. Shouldn't be too hard to get working with an attiny or pic. And then I could use a Boss DD-8 or DD-3T, two of my favorite sounding delays. Does anyone know what kind of input they expect on the tap in? NO or NC?

« Last Edit: February 08, 2021, 09:54:11 AM by Fancy Lime »
My dry, sweaty foot had become the source of one of the most disturbing cases of chemical-based crime within my home country.


Re: Modern delay chips?
« Reply #5 on: February 08, 2021, 11:43:32 AM »
On one of my projects I used an ATTiny for tap tempo, subdivisions, and manual time adjustment using an encoder. The tap tempo used a footswitch, the subdivisions used the button on an encoder (could be pressed with the foot) and the manual time adjustment was the normal encoder. This also produced a CV out and a tempo LED blinking. It's totally doable, but I don't know why there aren't many commercial offerings like that or like you describe.
Exact science is not an exact science - Nikola Tesla in The Prestige