Three PT2399 Delay-Verb Layout Questions

[seedlings]

This is what I want to put together based on already existing ideas.  Two PT2399 in parallel feeding a third PT2399, with controls for feedback and delay time of each chip.  I do not know if it will 'work' as I've laid it out.  My breadbords have been used enough that the contacts are unreliable and I'm having trouble getting all three sub-circuits working at the same time.

But, if anyone here has time to check a few things, I'd be grateful.  The schematic is copy/edit/paste from the madbean sea urchin delay - with all original values.  This is my first attempt with DIYLC. That is one cool program.  I tried to get the circuit small enough to fit a 1590BB - this will be my first PCB etch attempt as well.  (Lots of firsts for me.)

Questions:
1) is it OK to feed all three PT2399 from the same LM7805?
2) is a 100uF enough for the main reservoir cap?
3) the sea urchin used a 33R dropping resistor to the LM7805, is this value still OK?  Would an LED be better to drop a couple of volts?
4) should pins 6 or pins 4 be connected for all the chips, or go to common ground, or simply remain isolated?
5) is it OK to directly couple (parallel) the ins and outs of the first two PT2399 subcircuits, or should a mixer pot be employed?  I don't really care if there is a slight volume imbalance between two of the delays, in fact it will probably add character.

Some of the cap values will be changed to taste.  Thanks for your input.

CHAD

[merlinb]

1) is it OK to feed all three PT2399 from the same LM7805?

It should just about manage. I think three chips will push about 80 to 90mA, IIRC

2) is a 100uF enough for the main reservoir cap?

Yes

3) the sea urchin used a 33R dropping resistor to the LM7805, is this value still OK?  Would an LED be better to drop a couple of volts?

Maybe drop it to ten ohms to be on the safe side.

4) should pins 6 or pins 4 be connected for all the chips, or go to common ground, or simply remain isolated?

Ground all the pins 3 and 4. Pin 6 is the delay pin.

5) is it OK to directly couple (parallel) the ins and outs of the first two PT2399 subcircuits, or should a mixer pot be employed?  I don't really care if there is a slight volume imbalance between two of the delays, in fact it will probably add character.

The ins to the first two chips are fine, but it would be better to use separate input resistors to the third chip.

You'll probably want to add some overall feedback from the third chip to the first two, too.

[seedlings]

4) should pins 6 or pins 4 be connected for all the chips, or go to common ground, or simply remain isolated?

Ground all the pins 3 and 4. Pin 6 is the delay pin.

I've read about noise when the digital and analog share a common ground.  I'll assume you haven't experienced any trouble.   Thank you for the helpful comments!

CHAD

[merlinb]

These chips run in the megahertz range, and you have to apply so much filtering to the audio just to avoid quantisation noise that I've never had problems with clock noise. Just keep the whole layout as small as possible when you come to a final product, and you should be OK.

[seedlings]

Bah! 

I can't get this thing to sound right.  The delay sound is too quiet and noisy... I don't have time to re-invent the wheel, so Mr. MerlinB - kudos to you... time to build an equinox or solstice.

Thanks for your help,
CHAD

[seedlings]

Total re-vamp of the circuit, but it's coming together now.  The first two PT2399 parallel circuits are finally up and working in a pleasing reverb sound.  Now if the third PT2399 can be added...

CHAD

[seedlings]

https://www.youtube.com/watch?v=sPTY9ZVENNw

This is how the breadboard sounds at the moment.  There have been a lot of tweaking and changes, and I haven't had the time to make a real schematic.  With only two chips, the sounds can get close enough to reverb for my purposes.  Adjusting the delay times and feedback is a little trial and error.

CHAD

[John Lyons]

The video is set to private. 

[seedlings]

The video is set to private. 

Should be fixed now, sorry about that.

CHAD

[armdnrdy]

Here is the Belton Brick patent block diagrams. Take a look how the three 2399's were implemented.

https://patentimages.storage.googleapis.com/US8204240B2/US08204240-20120619-D00007.png

https://www.google.com/patents/US8204240?dq=pt2399+reverb&hl=en&sa=X&ei=lPKXUZGRDMqM0wX4_YC4CA&ved=0CDsQ6AEwAQ

[seedlings]

Here is the Belton Brick patent block diagrams. Take a look how the three 2399's were implemented.

https://patentimages.storage.googleapis.com/US8204240B2/US08204240-20120619-D00007.png

https://www.google.com/patents/US8204240?dq=pt2399+reverb&hl=en&sa=X&ei=lPKXUZGRDMqM0wX4_YC4CA&ved=0CDsQ6AEwAQ

Yes. The delay in the video is basically the first two PT 2399 from the belton diagram with mostly 10k resistors. I can't get the third chip to do much besides oscillation, so I'll leave it with two.

CHAD