PT2399: Is It Possible To Have Infinite Repeats Without Sound Degradation?

[rring]

Lots of thoughtful description here in the posts > I Just want to FYI  one thing

The multi-pole switchcap filters such as the MAX7408 (I used in my circuitsalad delay design) or the MAX7410 - which is cheaper and comes in a DIP package; really improves the digital sampling noise artifacts tremendously, making long delay times with many repeats feasible.

These filters are very easy to use and easy to adjust to suit the crisp sound/less noise trade off - to ones individual taste.

No matter what it will end sounding like an "exploding garbage can" but I think many builders will be pleasantly surprised with reduction in part count, while getting improvement in performance, these filter IC's offer.

[Paul Marossy]

Lots of thoughtful description here in the posts > I Just want to FYI  one thing

The multi-pole switchcap filters such as the MAX7408 (I used in my circuitsalad delay design) or the MAX7410 - which is cheaper and comes in a DIP package; really improves the digital sampling noise artifacts tremendously, making long delay times with many repeats feasible.

These filters are very easy to use and easy to adjust to suit the crisp sound/less noise trade off - to ones individual taste.

No matter what it will end sounding like an "exploding garbage can" but I think many builders will be pleasantly surprised with reduction in part count, while getting improvement in performance, these filter IC's offer.

I did see your page recently, looks like something to give a try.

[Mark Hammer]

I gather these are, while not quite "brickwall" filters, more like "stiff cardboard wall" than foam.

I have to confess, I'd be a little skittish to include one more clocked device in a BBD project, but I imagine thoughtful layout and decoupling can successfully eliminate those jitters.

[rring]

yes these filters have a clk to filter cutoff ratio of 100:1... so a 100KHz clk gives you a low pass shelf of 1KHz. The point being it is very easy to eliminate clk artifacts. I did not have any problem with clk interaction between the PT2399 and the filter causing hetrodyning or spurious outputs - which you have accurately pointed out (multiple clocked devices) should be a concern.

[Digital Larry]

Semi-OT, but I recall reading some statement, I believe by Lee Jackson with respect to the "Mr. Springgy" pedal, where he claims to have had to "hand-select" the PT2399's.  Even though these are CMOS parts it's clear that they are hybrid analog-digital functionality inside.  If it was purely digital I would say this claim was silly, but I suppose there could be process variations in the op-amps, or the A/D conversion comparator, or the D/A stage(s). 

Anyone have experience that some of the PT2399s are better than others and if so, how?  While I'm a little hard core on the FV-1 currently, the PT2399s are cheap enough and don't require any programming, so one's thoughts do tend to drift towards more straightforward applications.

[R.G.]

I did it back when I was tinkering with other delay formats. It works, but the complexity of the circuits to do it exceeds the complexity of the PT2399 pretty handily.

I put it in the class of things that just because I know how to do them, it doesn't mean I *should* do them.   

[Paul Marossy]

Anyone have experience that some of the PT2399s are better than others and if so, how?

They seem to be all over the map. Some are noisey, some aren't. Some latch up on start up with anything less than a 1K resistor, others have no problem. That's a couple of issues I know of with them.

EDIT: And I've had some that were DOA - didn't work at all. Don't know if I messed them up or if they were duds from the factory.