4 pt2399's in series / long clean delay..

[Mbas974]

Little bit OT...   question concerning the FET Switch (as per merlinb schematic).

What is the meaning of the 10u Cap in the switch ?
I tested the switch trying to turn on a LED
Connecting a superbright LED between source and ground and 1K resistor between drain an 9V.
The switch works, but in both case LED is ON,
when switch is OFF, LED is just less brighter than ON.
Removing 10u Cap LED is totally turned off when switch is off.

Thanks.

[Jdansti]

In addition to Larry's suggestions, does anyone know if it's possible for the PT2399 to access external RAM. If so, can it be done with just a few components?

[slacker]

No there's no way to add external RAM. I think R.G. once suggested that you might be able to tap the digital signal off one of the pins, so you'd just be using the analogue to digital converter in the PT2399,  in which case in theory you could connect that to some RAM but it wouldn't really be practical by the time you'd added everything else you'd need to control it.

I've just started playing with a DsPIC micro controller hooked up to some serial SRAM, this gives you potentially up to about 8 seconds of delay at better quality than a PT2399, I'm a way off having anything resembling a finished pedal though.

[deadastronaut]

^ wasn't that the 2395?..

anyway,

^ 8 secs...

ian, that sounds uber cool...i know sweet fa about programming etc though


i think i may just tinker with this a little more, 4 is defo better than 3 either way....and defo cleaner than 1 anyway, and i love the modulation/chorus to shimmer vibrato...very nice.

ive started on a preliminary layout just for kicks..should fit  1590bb upright, same as chasm reverb etc....see how it goes.

[psychedelicfish]

i think i may just tinker with this a little more, 4 is defo better than 3 either way....and defo cleaner than 1 anyway, and i love the modulation/chorus to shimmer vibrato...very nice.

Good. Your work so far is too good to give up on.

ive started on a preliminary layout just for kicks..should fit  1590bb upright, same as chasm reverb etc....see how it goes.

Make sure to keep traces as short as possible, especially those between the +5V and Vref filter caps and the PT2399's pins.

You should also try bigger caps (470nF-4.7uF?) from pins 6 and 7 to ground. Definitely try a small value resistor between pin 4 and pin 3, and connect the emitters of the transistors direct to pin 4.

[deadastronaut]

cheers ed,

put 220n's on pt1 and pt 4  (in/out) on pins 6 7 ground..they work fine..  (on 2/3 it got a bit out of control feedback wise..

3/4 isn't there an internal 10r anyway?...i'll give it a go though..

and i'l try the emitters to pin 4...


had fun this morning, jumping the out of pt 1 to 4in .. and out of pt3 to 4 in...

pt3-4 is best..long delay and bounce bounce bounce....very cool, like a reverb in between kind of...great option.


@larry: i'll order up one of those compander chips and try that..might be an improvement. ...i'm going to need a rack for this..

[loylo]

Hey Rob,

Your thread reminds me of this old one:
Echodeck - Quad PT2399 delay/reverb/chorus

I don't know if you know this and if it may be of any help for you.
As far as I can remember, it also deals with the need of compander/expander.

I hope you'll succeed in your build.  

[deadastronaut]

thanks loylo, i'll have a good read through that.

hopefully arnoud 'arph' will chime in on his experience/knowledge with the pt's too...

cheers..


edit: i'd love to see this dead link...erm ..link.
http://www.diystompboxes.com/smfforum/index.php?topic=85946.msg720538#msg720538


edit2:

i was reading about the echoreck at the end of that thread link from mac (cheers mac)

hmmmm......split the outs?.. switches for each or 2  pt's , hmmmmmmm    kinda makes sense......just thinking aloud!....

[deadastronaut]

i re-arranged my breadboards. and the layout..

i now have all the controls on pt1 , much better and less noise, i looked back at my vid and realised thats how i had it then...so went back..works great.

just need to get the feedback/repeats how i want them....with controllable osc + fet bypass tails

been having lots of fun with the 'divisions' sounds @#$%ing awesome with 1-4,  3-4.....2-4 obviously just halves, ...but yeah, very reverb like too..very cool.

back soon.

[Invertiguy]

Can't wait to see what comes out of this! I just ordered several pt2399 to breadboard it, can't wait to try it out!

[knutolai]

the hiss was more prominent due to that 220n on pt4, which made the delay level way above input level.(which i liked)

Did you try attenuating the signal at the 13-14 pin opamps? According to Rring this process leaves you with less hiss than using a 100n cap + gain=1 at the 13-14 pin opamp. I haven't had time to try it out yet, but if everything fails it might be worthwhile trying using this mod to all 4 pt2399s and see what happens. From the looks of it you will need a gain=0.2 when using a 470n cap between pins 9-10.

[samhay]

Sounds like you are back on track Rob - nice work.
I had been wondering about tapping the outputs of each PT2399. Glad to hear that it is worth while.

[deadastronaut]

blah blah...

[deadastronaut]

Still tinkering...for those interested  heres a couple of clips of the 4 PT's jumping..  pt1-4   pt1-3  pt1-3&4......not necessarily in that order...but you get the idea...all done at the same tempo..

https://dl.dropboxusercontent.com/u/7464107/DELAY%20HEADS-TAPS%20..mp3

https://dl.dropboxusercontent.com/u/7464107/DELAY%20HEADS-TAP1..mp3


very, very  cool  and even better with chorus modulation......been playing with this a hell of a LOT... ..  managed to get the humpup  behaving better too..

[loylo]

Sounds like you can play One of These Days or Run Like Hell, it's very Binson like! 

[deadastronaut]

yeah you can..

reminds me of my old watkins copycats  i used to use too.....its the same principal .....but with long delay too

and without the ...thump.........thump.....thump....thump........of the dodgy tape loop.. ...could have done with this many years ago...i spent a fortune on loops

and always had to make sure the level was turned down when turning on....or....thump.....thump....thump....was imprinted on my new loop.... ...grief no more..

i wish i still had both of mine, they go for a pretty penny nowdays for some strange reason..

[deadastronaut]

little update...

[slacker]

Sounds lovely Rob, very clean. We need photos of that breadboard setup

[deadastronaut]

cheers ian, yeah its getting there.. that was all on the shorter delay setting, i'm using a 1m pot, but the adding a 1m resistor to it for longer delays, (haven't got a 2M pot )


as you can see i used ceramics just for now as they are just easier to pull to ground and a bit of space saving etc..

but really the circuit isn't massive, i'm pretty sure going by my preliminary pcb layout that i can get it 1590bb-able...(welll i was until i started adding switchng )  

which will be toggles..not a massive rotary..

anyway..

input/output and first pt....current mirrored to the other 3..



3 pt's in series ...and lfo.



still a bit of tweaking here n there to do...as always....but i'll be glad to get my 2 breadboards back for other mad stuff i intend to mess with....

and mrs astro will be happy that she doesn't have to hear....BING....BING....bing.....bing....bing....bing...... everyday too i'm sure.....

[Jdansti]

>and mrs astro will be happy that she doesn't have to hear....BING....BING....bing.....bing....bing....bing...... everyday too i'm sure.....

LOL- I was told to put my headphones on when I played your demo. Some people just don't appreciate a fantastic effect!