Introducing the "One Chip Chorus"!

[ggsmailroom]

I just built one up on Vero/Perfboard - sounds really crazy, but I am afraid mine is not working correctly.

Sine wave is very disturbed sounding ( just moves in a very unuseable step ) and it also has pulsing distortion. I love the tone of the Chorus - it just needs to be adjusted.

I want to add mods as well, so this will be a great troubleshoot lesson! Ill post pics this evening.

This is my first post, I am excited to be a member here now, have been at BYOCs forum since 2007.



Patrick G

[earthtonesaudio]

Welcome Patrick!

[anchovie]

I've replied to your PM, Patrick. I'll put the gist of the answer in the thread for posterity!

The electrolytic from pin 2 to ground was a real "trial and error" component for me as it interacted with the whole character of the LFO. In this circuit it does a lot more than just filter Vref! Could be worth trying different values.

[ggsmailroom]

Alright Anchovie...

YOU RULE!!

The C2 E.C. Cap in the layout is crucial for fixing the distortion/hiss issue. a 47uf cap fixed all distortion issues, although there is a very faint pulse to it when you have it engaged in the background - but its only audible once the volume on your amp is turned all the way up. A 22 uf was nice, but the background pulse was louder. 100uf was too thin on the Lush signal. 47uf seems to be the sweet spot for getting subtle to lush chorus.

I do have one final issue - I do notice a drop in treble and output volume when I have the circuit going through my break out box compared to my clean signal un affected.  - Can this be fixed or is this an issue others have noticed? Also, is there a way to add a Rate knob?

[ggsmailroom]

Hey guys, here is my One Chip Chorus all boxed up - I call it the Lunar Chorus (weve had some great moonlit nights here in TX lately, so it fits)

I opted for a 330k instead of 680k, which gives more output. I also changed out the EC from 10uf to 100uf that goes to Pin 2 - eliminates any noise issues and gives you a perfect chorus! Socket these areas and see what you like

I love how it sounds and will get a demo up ASAP!

[mwynwood]

That looks amazing!
I'm a bit of a novice, but I've just built this based on the Vero layout on the first page.
I read through the thread and I'm not quite sure why it's not working
It passes signal ok, but no chorus effect.
I'll keep fiddling! Thanks heaps for this - i can't wait for it to work!
Is there an updated Vero layout? (I guessed the polarity of the caps...)

[anchovie]

(I guessed the polarity of the caps...)

You don't need to (and shouldn't!) do that - look carefully at the layout and you'll see a darker stripe on the electrolytics that denotes the negative terminal.

[mwynwood]

ah!  Thanks for that! I'm used to layouts with the terminals marked + or -
Probably didn't help that I printed it out in low-quality B&W... haha

[ggsmailroom]

Mwywood - Thanks for the kind words!

All you need to figure out whats up with your build is an audio-probe - look it up and you'll get somewhere really quick.

[mwynwood]

Thanks Pat - I've just put together one kinda like the one here: http://www.diystompboxes.com/smfforum/index.php?topic=79707.msg658079#msg658079
I followed the circuit through, and on the other side of R3, there is no signal (hole 13d on the Vero)
I've checked R3 and it's reading 680k on the multimeter, so I assume it's ok.
I don't want to be spoon-fed or waste anyone's time, but if anyone has any good trouble shooting tips or has an idea of a simple beginners mistake I could have made, that would be great
Thanks!

[ggsmailroom]

Sounds like something connecting to that side of R13 is causing problems to me

[danielzink]

Here's another take on the one chip chorus. This one has deeper modulation, so it generates a very thick warble, more like the deep settings on a LA. It also has an improved latch-up fix that may be useful for other projects.

I *think* this is based on the updated version. Please check before attempting - it's late - I'm tired.

Any way to slow this one down ?

It's alittle too "wow-wow-wow-wow-wow" all the time.

Plus - a pretty good thump when turned on - even without an LED indicator - gotta check and see if something leaking DC - or maybe I just need an RPD.


edit: plus I'm getting a pretty good volume drop - it doesn't seem to be quite at unity.
Dan

[geiristudio]

I've been trying to debug my vero layout for a long time now. I've changed chips, traced everything over and over again. I'm just getting farting sounds coming from the pedal.

I've built a lot of pedals before but it always seems that pedals containing PT2399 chips are hard to make.

I'm using PT2399 chips from Tayda. Have any of you tried them ? Out of 10 chips, I've managed to make one rebote delay and that's it. I haven't gotten 3 other rebotes, 2 little angel and one of these circuits to work.

[mwynwood]

I've been trying to debug my vero layout for a long time now.

I sympathise! Were you working of this Vero too?

I wonder if there is an error with it, or if there is an updated version?

[rousejeremy]

I think Photon verified this layout and if you look a few posts up you'll see a finished pedal using the same layout.

[bacanador]

Nice

Have to try this one out. But it seems it would be hard to get the LFO to work.

Phase shift oscillators are hard to use in my experience, they will not always oscillate. I don't quite understand this one, I guess I just have to build it and try.

[mwynwood]

I've never done this before... but I've had a go a debugging by following the instructions here:
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0
I'm working off the Vero Layout I posted a few posts above.
It passes sound, but with no chorus effect. 
I hope I get this right... here goes:

V1
Input = 8.69
Common = 0
Output = 4.97

D1
A = 9.57
K = 8.68

IC1
 1 = 4.97
 2 = moves between 1.90 and 2.80
 3 = 0
 4 = 1.75
 5 = 4.94
 6 = moves between 1.90 and 2.80
 7 = 0.20
 8 = 4.59
 9 = moves between 1.90 and 2.50
10 = moves between 1.70 and 3.10
11 = moves between 0.50 and 3.80
12 = moves between 2.30 and 2.40
13 = moves between 2.00 and 2.90
14 = moves between 1.90 and 2.90
15 = 0.85
16 = 4.78
Thanks for your help 

[pinkjimiphoton]

yah, i did verify the vero layout...it works, but of the 20 chips i bought from different suppliers, almost all of 'em were wonky in this circuit..i'd say it's the chips, not the circuit.

i've had everything everyone has described, from lock up to insane distortion to bizzarre noise to even a low-pitched motorboating. switch chips, and it's a different problem.

switch the damn chips to other projects, and they all exhibit issues, too...so it's definitely the chips.

but when ya DO get a good one...it does sound nice.

i could never really get the lush pot to do much, unfortunately, but i think it's more because the damn chip locks up so easily.

i undid the mods i had done to it before, but did make one change...i took out r1, 1k and replaced it with a 10k trimmer, so i could play with the delay time a little..1k sometimes seemed just a little too little...and this way, it can do a nice double, with the trimmer cranked...

i like it right about 3.43 k the best, fwiw

[mwynwood]

Thanks Jimi - I've just ordered 10 more PT2399's.
Hopefully one of them fixes my problem
Good idea about the trim-pot too, I might give it a go once it's all working.

[pinkjimiphoton]

if you move that trim pot and there is ANY wiggle, the pt2399 is working...most of 'em will, but some seem to start self oscillating either above my hearing range, or motorboating..giving em a little tweak seems to help.

i don't know why it doesn't self-modulate sometimes...it seems almost like the attack of the guitar is what gives it wiggle. but tweaking the trimmer you should be able to get enough time to get it noticeable ...really kinda subtle.  i still can't get it to sound as good as anchovie's demo...thinking of trying to mod the voltage divider for a little more delayed signal, but i don't think that's the problem...getting it to modulate is, at least for me.

when it's working, it sounds almost like a boss dimension c...you almost can't tell it's on, but switch it off and you know it's not there. slight volume drop too, but i'm gonna try adding a simple transistor boost after it to see if i can get it up to unity or slightly above.