Most physically compact, full bandwidth digital delay? SPIN FV-1 or ...?

[polaris26]

Hello all -

What I am looking for is something that seems useful but I have not seen it anywhere - a simple, clean digital delay module (mono/no taps) that has more or less full audio bandwidth (say up to 16kHz) at up to 400mS delay time.  Looking at older tech, the BBD approach would take a string of maybe 5 or 6 MN3005 running at high clock speeds and who knows what the S/N ratio would end up at, and certainly not compact.  On the digital side, the PT2399 IC, which I have played with in the past, is just too noisy/degraded at those delay times for what I am looking for.  Also I do not like compander-based solutions since the feedback decay  "tails" can sound unnatural.  I am basically looking for something that sounds more like a Boss DD-2 with variable time, mix controls, no modulation. 

Would the Spin FV-1 be ideal (if not vastly under-utilized) for such a board?  I am basically looking for a board that is as physically compact as possible, just enough features to add a simple delay to existing circuits as an add-on.  Perhaps something like the D3lay design from PedalPCB but even smaller/simpler.  I know nothing about Spin FV-1 so if I were to layout my own board, I would have to ramp up with a dev board and such to get into that arena. 

Also is it true that the Spin FV-1 can be clocked by a variable external clock to get old-school variable delay times/modulations in hardware rather than software?   

Is there a more compact way to get a simple clean/full-bandwidth audio delay at this point in time?

Regards,
Dave

[Ice-9]

Yes the Fv-1 would be perfect for this idea, a simple circuit around the FV-1 is all that is needed and no need for companders etc. Running at 32kHz will give a maximum of 1 second delay. The key to getting the delay feedback to sound good is in the filtering of the repeats which can all be done in the code.
You could fit all this in a 1590A pedal if you want the size to be as small as possible.

You don't need to learn FV-1 coding if you don't want to as SpinCAD is available from Digital Larry which makes it easy to code up the FV-1.

[polaris26]

Hello Ice-9 - thanks for the reply.  Would an eprom be needed in a simple delay application?  I am not clear on the FV-1 workflow, but it seems that it involves buying a dev board to try out your patches before laying out a pcb.  Is this correct?  I don't mind learning the programming language if that would allow greater control over the end results.  I tried SpinCAD briefly and found the functions of the interconnections of the modules in the gui to be unclear.  I tried a simple delay patch and got unexpected results in the output file; not sure what I did wrong.  I see an option for sound card interface - can it do processing in real time (duplex)?  That would be most helpful!

Regards,
Dave

[potul]

An eprom is needed if you want a custom program. If you are fine with one of the built in, then you don't need it.

A development board is convenient but not 100% needed. If you have a means to program eeproms, you are good to go.

But, you need to think about your requirements before designing the pcb, although you can build a generic one that will fit most of your needs.  But you need to decide things like mono vs stereo, do you need an analog mix (dry signal mix), how many controls you want, etc....

[bluebunny]

Check out the Belton ABE-FX.  Rick (frequencycentral) used it in his "Stasis Leak" project.  It uses a Coolaudio V1000 chip.  It may be overkill for what you need, but apparently does 0.68s delay @ 48kHz.

[Ice-9]

As Mateu has mentioned, there is no need to buy an FV-1 dev board to develop a pedal. You will need to add an EEPROM to hold your own delay program though. The FV-1 has inbuilt programs that might be all you want but it is better to add the EEPROM as I'm sure once you get into it you will prefer to devlop your own effects (many available at the Spin site).  It isn't a difficult add n EEPROM and by adding a small 4 pin header to the PCB you can reprogram the EEPROM in place, this makes your pedal an actual development board in its own way.

another question is what size enclosure are you looking at using.
In fact if you wanted a ready built pedal to develop code on you would would not go far wrong buying a ready built 'Mr Black' FV-1 mini pedal and just reprogram the EEPROM with any code you want.

[ElectricDruid]

Check out the Belton ABE-FX.  Rick (frequencycentral) used it in his "Stasis Leak" project.  It uses a Coolaudio V1000 chip.  It may be overkill for what you need, but apparently does 0.68s delay @ 48kHz.

That sounds a lot like 1 second at 32KHz! E.g. Same as FV-1, 48KHz is the official max clock speed.

[polaris26]

As I research this topic more I realize how hopelessly behind the times I have fallen    Just catching up with tech others have been working with for years now.  I slept through the whole covid chip supply crisis, apparently.  Bluebunny - funny you mention Belton, because my original idea was something akin to a Belton reverb brick only for non-verb delay-based effects.  I don't have any specific enclosure size because I am thinking more as an adjunct to other projects that might be home-brew amps, pedals, mixers, etc.  Another board that looks interesting is the FV-1 submodule from Electro-smith (https://www.electro-smith.com/electro-boards/fv-1-dsp) but they are currently out of stock.  I will also check out the Mr Black pedal.  So much catching up to do - I really want to get into this DSP thing... 

Also - does anyone know if SpinCAD or some other visual programmer can do real-time simulation so you can hear the effect (or a close simulation of it) in real time as you play around with the design?

Regards,
Dave

[potul]

As I research this topic more I realize how hopelessly behind the times I have fallen    Just catching up with tech others have been working with for years now.  I slept through the whole covid chip supply crisis, apparently.  Bluebunny - funny you mention Belton, because my original idea was something akin to a Belton reverb brick only for non-verb delay-based effects.  I don't have any specific enclosure size because I am thinking more as an adjunct to other projects that might be home-brew amps, pedals, mixers, etc.  Another board that looks interesting is the FV-1 submodule from Electro-smith (https://www.electro-smith.com/electro-boards/fv-1-dsp) but they are currently out of stock.  I will also check out the Mr Black pedal.  So much catching up to do - I really want to get into this DSP thing... 

Also - does anyone know if SpinCAD or some other visual programmer can do real-time simulation so you can hear the effect (or a close simulation of it) in real time as you play around with the design?

Regards,
Dave

Spincad can do it. but it's more intended for debugging than checking sound quality.

[potul]

  Another board that looks interesting is the FV-1 submodule from Electro-smith (https://www.electro-smith.com/electro-boards/fv-1-dsp) but they are currently out of stock.  I will also check out the Mr Black pedal.  So much catching up to do - I really want to get into this DSP thing... 

I think this electro-smith is just using the on-board programs. You need something you can program.
Take a look at the projects in https://www.pedalpcb.com/
Some of the pcbs are quite generic and can be used for any effect. You will just need some way to program the eeprom, as they don't have a programmer header.

[potul]

I just realized they even have a dev board project. Looks interesting

https://www.pedalpcb.com/product/fv1dev/

[pruttelherrie]

  Another board that looks interesting is the FV-1 submodule from Electro-smith (https://www.electro-smith.com/electro-boards/fv-1-dsp) but they are currently out of stock.

I think this electro-smith is just using the on-board programs. You need something you can program.

There's a footprint for an EEPROM and the SDA/SCL are broken out to the header, should be programmable then.

[potul]

There's a footprint for an EEPROM and the SDA/SCL are broken out to the header, should be programmable then.

Oh you are right, I missed it. I didn't see the EEPROM and assumed it was not included in the pcb.

[Digital Larry]

Also - does anyone know if SpinCAD or some other visual programmer can do real-time simulation so you can hear the effect (or a close simulation of it) in real time as you play around with the design?

SpinCAD lets you simulate using a WAV file, which may not translate well to patches which are dynamically sensitive such as auto-wahs or compressors.  In general you should design the FV-1 system so you've got a fairly good headroom, though I don't know a way to do this other than to clip and then back off.

As far as how accurately it represents the sound of patches, I know there are a couple bugs (e.g. pitch shift down) and as I did not write the simulation code to begin with, I cannot really attest to it at all, other than to say I looked at a lot of it and it seems to do things the way the FV-1 docs say it does.  So, some things it simulates pretty well, and others, perhaps not.