Any projects for a clean, long digital delay (similar to boss)

[Praying_V]

Hey everyone.  What would it take to build a digital delay circuit in the vein of the boss digital delay pedals?  Is programming involved?  Can I use PT2399s in series to get up to the delay time I want, or will I degrade the sound quality with each successive delay chip, like with analog delays?

[petemoore]

  I think you'll find the performance offered by digital delay pedals on the market aren't easily matched with DIY projects.
  There is a digital section to this forum, I haven't visited lately.
 

[TELEFUNKON]

will I degrade the sound quality with each successive delay chip, like with analog delays?

not like with BBD delays, but will degrade due to multiple AD/DA conversions

[Praying_V]

I already own several commercial digital delays.  If I can build one, I can customize it exactly how I want it.  With a delay-line effect loop, for example.

I guess there's no simple chip like the PT2399 but with longer delay times?  Well, I'm sure there's not, or we'd already be using it...

[tommy.genes]

Somebody here did some experiments with, I think, four PT2399 chips in series, all wired to the same controls. I couldn't find it in a search, however. Maybe you can do better.

You should also look into the PT2395 chip (carried by Small Bear just like the PT2399), which uses an external DRAM chip for delay memory. According to the data sheet, the PT2395 can support up to 256k of DRAM for 800ms of delay, so you've already more than doubled the published 342ms delay time of the PT2399.

Things could get really interesting, though, if you start piggybacking the DRAM chips. To avoid a lot of retyping, see the discussion in these posts HERE.

Piggyback one extra chip and get a max delay of 1.6 seconds, two extra chips gets you 2.4 seconds, three extra chips gets you 3.2 seconds, etc. And all this is done with only one pass through the A/D and D/A convertors. The only downside is that piggybacking DRAM chips in this manner increases your minimum delay time as well as your maximum. It shouldn't be too hard, however, to use a switch to chose between the first DRAM only versus the whole DRAM stack, thereby getting you the best of both worlds.

This is an idea I've wanted to try myself, but I never had time, as usual. If you do anything with it, please post your results for the rest of the group to see.

-- T. G. --

[puretube]

Same "usuality" here...   

[Praying_V]

Is a DRAM chip readily available from the typical parts suppliers?  Probably only in a surface-mount package...?  Is there any actual "programming" involved, or would I still be able to simply construct the circuit by arranging the parts correctly?  I'm gonna look into this more.

[tommy.genes]

Small Bear also carries the 41256 DRAM chip which works with the PT2395. I think these small DRAM chips - who uses 256k anymore? - are also abundant in older consumer electronics, especially in karaoke machines and similar devices, should you want to go the salvage route.

And there is no programming involved. It's already done in the PT2395 for you. I can't comment, however, on your being "able to simply construct the circuit by arranging the parts correctly." 

-- T. G. --