Mods for a PT2399 delay kit

[nonoxxx]

Hello,

A friend ask me for building him an analog delay,  I am more confident with OD/dist, so I will build him the bluelay kit from Musikding.

But I was looking at the spec sheet of the PT 2399 chipset and I don't find a lot of informations (the only thing I see is how to modify the time of the delay). Do you guys know a page with more information than this page ?
     http://www.diyaudiocircuits.com/tutorials/pt2399-digital-delay-analog-echo/
In fact Iwould like to know what we can  do with the OPAMP and LPF stages.

Thanks

[swever]

I've sucessfully breadboarded a small time delay and built a pcb version of sea urchin dealy

The second one did have a problem with distorted repeats. This thread helped me to find a solution.

What exactly do you want to do with opamps and lpf filters and why? 

[anotherjim]

This is worth reading...
http://sound.whsites.net/project26a.htm
This chip is something of an enigma. As you noticed, the official datasheet leaves a lot out. Some of what you read elsewhere is based on observations of it's behaviour. There appears to be variable quality in manufacture of this chip. What one experimenter gets working with their particular chip, may not work the same with yours.

[EBK]

This is worth reading...
http://sound.whsites.net/project26a.htm
This chip is something of an enigma. As you noticed, the official datasheet leaves a lot out. Some of what you read elsewhere is based on observations of it's behaviour. There appears to be variable quality in manufacture of this chip. What one experimenter gets working with their particular chip, may not work the same with yours.

In other words (the Hollywood version):
"The [PT2399] is a very mysterious and powerful device, and it's mystery is only exceeded by it's power."

[Mark Hammer]

I like to insert a bit of additional (and switchable) lowpass filtering in the feedback loop so that each repeat loses a little more high end.  Helps to compensate for the accumulation of noise and grit over repeats, and also allows for a less distracting delay sound when the repeats are cranked.

There will generally be a fixed resistor in the feedback path.  I divide it into two common values, and calculate the needed cap-value to ground between the two resistors to achieve the sort of rolloff I want.

[samhay]

>In fact Iwould like to know what we can  do with the OPAMP and LPF stages.

With reference to Merlin's musings on the PT2399:
www.valvewizard.co.uk/PT2399_Data_Notes.pdf


(click/view image for bigger version)

You'll see that there are a bunch of op-amps with output and inverting input pins available.
However, OPAMP-1 has its output tied to the digital innards of the chip, so is only really useful as an input stage (though is handy as it lets you do active mixing of dry and wet inputs (repeats) ).
Likewise, you can take the signal from INTEGRATOR2 OUT, but most folk feed this into OPAMP-2 to do some filtering.
As OPAMP-2 doesn't have input or output tied to anything, you can use it like any inverting op-amp and build a filter to suit your needs and wants. You could alternatively re-purpose it for something else. e.g. I believe some one-chip choruses use this as the LFO stage.

[nonoxxx]

Thanks, for all your reply , today I will check all your links and docs.

[nonoxxx]

What exactly do you want to do with opamps and lpf filters and why? 

In fact I don't know , but I can't solder a component on a board if I do not know exactly the role of this component. A

[nonoxxx]

I finished the musikding kit and testing it since 2 days, It sound awesome with the stock parts ( I have just swap some of the electrolytics caps for film)

https://www.facebook.com/AnalogBeastEffects/posts/1858018911137323 (it's my humble facebook page where I show my projects and pedal builds for me or for my friends )

I will now try to learn how this chip work for chorus , do you have any suggestions of documentations /ressources.

[Plexi]

I take note into a paper (old fashion mode  ) with a lot of notations, schems, and tricks with PT2399's.
When I found it, I'll share.
The most one I remember is where you have to jump some resistor to have tails.

BTW: do you read or look some schem of the Madbean "Dirtbaby"? It's a Deluxe Memory Man based delay with 2399