Introducing the "One Chip Chorus"!

[mwynwood]

My new PT2399's have arrived.
I just ripped one out of the package and chucked it into the socket... and it worked perfectly!
Thanks for you help - now it's modding time

[anchovie]

i'm gonna try adding a simple transistor boost after it to see if i can get it up to unity or slightly above.

Much easier to do what Pat did and change the 680k for a 330k - increases the gain of the first stage. Or you could put a 1M trimpot there and tweak to taste.

My new PT2399's have arrived.
I just ripped one out of the package and chucked it into the socket... and it worked perfectly!
Thanks for you help - now it's modding time

This is excellent news!

[pinkjimiphoton]

tried using a 430k resistor in place of the 680k...made it seem to distort too much.

went thru 20 pt2399's. 4 work in the circuit, but all 4 mess up after a couple power ups. what a drag. gonna try the chips in my delay, and see if they function there.

noticed the reg gets extremely hot with some of the chips, assuming that means them chips are shorted.

when all was said and done, used a 30k trimmer for r 11 and 12, found a couple "sweet spots"...and replaced the 1k resistor (r1) with a 10k trimmer.

when it WORKS, it works great. still can't figure why it acts so weird...

wondering if it's oscillating above my hearing range, may stick it on my scope later and see if i can see anything.

the bitch is, when it works, it sounds great..but sometimes it just doesn't seem to matter. powering up repeatedly works sometimes, sometimes adjusting the "lush" control (which now works...go figure) does it too.

gonna keep playing with it, do ya think adding the npn and stuff to pin 6 is worth trying? will the trimmer still work between pins 4 and 6? it's nice to dial in a "sweet spot" there...

thanks!

[Magnus]

Hello,
here's my Layout based on the schematic from page 1, I have not build it yet, so it is not verified...
...but I am very sure that it is ok and will work, I compared it to the stripboard-layout and also to the schematic

http://img861.imageshack.us/img861/8206/onechipchorus.jpg?http://imageshack.us/

I hope that I soon will have the time to build it!




Greetings from Germany
Magnus

[mwynwood]

Here it is all boxed up in a "blemished" enclosure from Mammoth I got for about $5!  

I swapped R3 from 680k to a 470k to bring the volume of the effect up to match the bypassed volume.
I swapped C12 from 100nF down to 10nF to brighten up the effect tone up to match the bypassed sound.


Thanks to everyone for their help!

[deadastronaut]

cool, nice build....any clips?

[mwynwood]

Just recorded a short sound clip: http://soundcloud.com/mwynwood/my-lush-chorus-pedal

[deadastronaut]

nice one marcus:  sounds really nice,  i think i'd like a speed control on it, i'll have to get round to breading this for sure, cool...

[mwynwood]

Thanks man 
A speed control would be great - even if it were just an internal trimpot.
Let me know how you go!

[deadastronaut]

hmmm, got this on breadboard at the mo...not working yet.

i'm using this schematic
http://www.diystompboxes.com/smfforum/index.php?topic=92872.msg796348#msg796348

...one dumb question though, where do the vr's go...to the lush pot?..

going by magnus's layout?....


hmmmm...redone the breadboard a cople of times..., got clean sound , no chorusing...

[deadastronaut]

bumpy!!!

:ok so the vr's go to pin 2 of the pt2399...cheers james,.

[anchovie]

They join together, so the Vr point on the right half of the schematic goes to pin 2.

[deadastronaut]

cheers man.!!!..

[danielzink]

Definitely like the sound of this - can anyone sort a speed control though ?

I think that's what's missing to make this perfect.


Dan

[anchovie]

Based on schematics for standalone Phase Shift Oscillators, the Lushness control should be the speed control. But using one of the PT2399 op-amps for the LFO forces the use of the chip's voltage reference as the ground point for the oscillator and makes wacky stuff happen. There is a subtle change in speed, and also a change in LFO shape, and it's all completely unplanned and unpredictable!

If you want full LFO control, you'll  need at least a Two Chip Chorus.

[deadastronaut]

^ right, i got it going yesterday, and yes, i got lush chorus ( think walking on the moon /police) i tried different values for the 22k..i lowered that and got a much more warbled chorus...

but the chip locks up now and then ...i also moved the connection to the 10k / post 10k as taylor previously suggested, and got that pitchy vibrato too...

then i conected a pot to pin 6 and messed around with delay....great fun, but i too would have liked a speed control, so i guess its knock up an lfo, and sort out that lock up fix...

thanks for the cool project james, its the first time ive breaded a pt2399, and messed around with it,  its a blast....nice one!....  i'll try ricks little angel later too as it has lfo and see how that goes...i'd like to get the vibrato mod on it now too......

cheers guys.

[bluebunny]

Here's my verified layout for OCC.  I've been enjoying the challenge of squeezing stuff onto those little 25x9 boards.  This is the squeeziest and breaks a couple of my rules (some resistors standing up, one diagonal resistor!, etc.), but I'm kinda pleased I managed it.  Though no doubt Adriano could manage it on something half the size! 



Note four regular links in yellow, and one rule-breaking large link feeding Vr to pin 2.  Watch out for breaks underneath the horizontal caps and resistors.

And here's the finished article:



A couple of the elecs look a bit drunk - I think they've been squished a bit, hanging around waiting for a home.  And those two mahoosive greenies were not exactly what I had in mind...

Anyroad, now working on putting it in a box (sorry to disappoint - it's not going in a 1590A!).

[Perrow]

... (some resistors standing up, one diagonal resistor!, etc.)...

Couldn't C11 move one snap to the left and let R10 go straight down? I don't see any break under C11 so it should be ok, shouldn't it?

And surely R4 and R5 can be stretched another hole and be flattened.

[deadastronaut]

@marc: any problems with pt2399 lockup...?

[bluebunny]

@marc: any problems with pt2399 lockup...?

Nope, not so far...