Introducing the "One Chip Chorus"!

[pinkjimiphoton]

@jimi: nice demo as always man....i see what you mean, more of a delay than 'lushy chorus' cool mods though......

shame as anchovies original clip sounds really 'lush'..nice and rich chorus...

and merlin's clip was really warbly...i thought merlin added an anti lock-up thing to it?..off pin 6?...i may be wrong though...anyway, i like that reversey sound too...


@david: so have you built it?...does it 'chorus'...does it lock up?....can it make tea?...

i want the lushy chorus tho!!
lol!!

it's neat, but i really wanna get the sound of jim's box, not what i ended up with. it COULD be a chip issue, but i tried 10 different ones from 2 different vendors. weird!!
a search on pt2399 led to a pdf from merlin here that explains a LOT of what's going on. if i could find it in my archives of saved info, now,...lol..

[Earthscum]

I use Illustrator or Inkscape to do my layouts, after creating them by hand on a printed 'perf sheet' and pencil.
I do have it saved as PDF, but nowhere to host. Besides, if you need it any clearer than 300 DPI, you're getting a bit too picky. That is standard 'photo-quality' resolution. The traces aren't anywhere near fine enough to warrant anything higher.

[Taylor]

@Earthscum: It looks like the center pin of the regulator is not grounded in your layout. Simple enough to bend the lead over since the ground is right there, just thought I'd point it out for those building using it. Nice layout! I want to build one of these when I get some time.

[meffcio]

I use Illustrator or Inkscape to do my layouts, after creating them by hand on a printed 'perf sheet' and pencil.
I do have it saved as PDF, but nowhere to host. Besides, if you need it any clearer than 300 DPI, you're getting a bit too picky. That is standard 'photo-quality' resolution. The traces aren't anywhere near fine enough to warrant anything higher.

You're probably VERY right, but you see.. it's just my habit. I'm just sure about the quality of printng when all my pcbs are vectorized in pdfs, and I can simply open up some PDF editor, and put a lot of pcb drawings on one sheet of paper, and it all prints great.
But since you're just right, I won't make any problem with that. Thanks for your briliant layout, I'll be building this soon.

[Ripthorn]

duuuuude....

it was an almost microscopic break in one of the rails!!! 


but,

now it works great!!   



reminds me of my old boss dimension d!   

the vero is now VERIFIED, fwiw!!   

thanks anchovie!!  gotta box it up, will try and post clips this week.

I know this is a little old, but did the break change any of the pin voltages?  Trying to troubleshoot mine.  I don't get any chorusinfg, though I do get signal passing through.

[pinkjimiphoton]

yes, i was getting maybe 2 volts to the ic

[arma61]

Hi m8s, need your help!!

I've built is as per schematic on 1st page and as per Scruffie  layout, it's almost working but.... it takes 4 to 5 secs to become operational! in those secs lot's of noise, whistles etc, then it sound normal (not really as the soundclips, I need to work on that later, though voltages look good). So any known reason for it to be so slow to bristle up!, I don't thinks it's "latching" , just takes time to warm up.

Thx m8s for help
Armando

Edit, I also printed out the whole thread but didn't find any idea....

[anchovie]

I think my breadboarded one had a start-up time, just not as severe as yours. The phase-shift LFO didn't give me instant response when changing the pot setting - if I rotated it quickly I'd have to wait for the oscillator to "catch up"!

[arma61]

thx james

though my one is doing this everytime I switch it, I mean the signal not the power, the pot does nothing while I waiting it to warm up.
If it's the LFO, is there any cure to keep the LFO "active" while idle?

I've refreshed all the soldering but still same problem. Is there any voltage I can measure to see what's going on?

Thx

[pinkjimiphoton]

mine is on acid too, i hoped to add it to the pedal board cuz when it works it sounds great...but sometime it just....goes crazy...warbles all over. this seems to be minimized if i run it with a dedicated ps, but i never know if it'll work or not. real temperamental. maybe i need to try it again..;p

[anchovie]

thx james

though my one is doing this everytime I switch it, I mean the signal not the power, the pot does nothing while I waiting it to warm up.
If it's the LFO, is there any cure to keep the LFO "active" while idle?

I've refreshed all the soldering but still same problem. Is there any voltage I can measure to see what's going on?

Thx

I sadly have no idea! Looks like I was really lucky with the one I breadboarded to test the "LFO from a PT2399" theory. I don't even know how a phase-shift oscillator works, I just saw a schematic for one and that it only used one op-amp.

This project should be filed under "experiments" rather than "pedals to gig with". 

[Gordo]

Anyone had any luck with this?  I've been chasing the dragon trying to get that great sound from first post but so far have only got what sounds like a slapback echo.  No LFO.  I've had no luck with perfboard, Madbean's layout or Earthscum's layout.  A number of different PT2399s from a few sources...well you get the idea.  I've built entire amps in less time

This is destined to become my modern equivalent to a Fuzz Face: "I know it's really simple but I can't get it to sound right..."

I need to go lie down now.

[Gordo]

breep, breep, breep.

(crickets)

[earthtonesaudio]

It seems a better place to stick the lfo is the vco input, pin 6, through a current limiting resistor.  I haven't tried it though, just a thought.

[anchovie]

When I first had the idea for this, I thought I'd set up the phase-shift LFO and then work out where to inject it into the chip. As it turned out, the LFO uses pin 2 as its ground connection and caused wobble for me anyway so the modulation is more a product of grounding the LFO at Vr rather than feeding the LFO output to pin 2.

I had a lucky break with mine. I'd suggest that anyone else wanting to try the circuit does so on a breadboard, and don't spend more than half a day debugging it. If it doesn't wobble, possibly check the LFO on a scope. If you still can't get it to work, save the headaches and build another chorus!

[pinkjimiphoton]

mine works, but it's wicked temperamental...but i added a delay time pot to it, and a little feedback thru a pot...mAkes a nice double, but i can't really get a chorus out of it usually...but sometimes it just goes crazy, sounds like a broken taper delay...cool, but too intermittent to be useful. every power up it makes a weird noise that kinda sounds like bra-aa-aa-aaapzip before it does anything, sometimes it gets stuck there and i have to power it down. it's weird, i tried 15 different pt2399's and they all sound different, 10 from one vendor, 5 from another...and they all work in my echo fine, but not in this circuit. i'd love to see this nut get cracked, cuz when it works  it's real nice and silky, almost sounds like doing it with tape.

[Gordo]

every power up it makes a weird noise that kinda sounds like bra-aa-aa-aaapzip before it does anything, sometimes it gets stuck there and i have to power it down.

Yupp, getting the same noise and I'm also getting varied results using different chips.

i'd love to see this nut get cracked, cuz when it works  it's real nice and silky, almost sounds like doing it with tape.

Anchovie, like Jimi says, I just liked the sound of the original post.  I'm not even a big chorus fan, just thought yours sounds killer.  The fact that it was dead simple was icing on the cake.  I'll shelve it for now but will definitely come back to it.

[pinkjimiphoton]

i don't like chorus either, but this thing, when it works, sounds special...really organic, and not all fake like most choruses.

[anchovie]

Perhaps a better way to obtain the sound that I got would be to replicate the LFO shape using an isolated chip and use it with a more stable pt2399-or-whatever delay circuit? I described it earlier as being like someone dipping on the whammy bar repeatedly.

On a scope it looked like a sawtooth with a short fall time and long rise time. Should be easy to set up with a 555 but might introduce ticking into the power supply (CMOS 555 perhaps?). Or another quiet solution that allows the duty cycle to be altered in the right way.

The one-chip challenge that I set myself was fun, but I'm not going to cry if another op-amp or suchlike appears!

[Gordo]

Yeah, I'd thought of that.  I did a layout for the Dimension P that worked out so at least I have my PT2399 mojo back but the coolest part of this circuit was being in on your "aha" moment.  Nice to see one of the forum's regulars dip over the threshold from time to time.  Just wanted to validate it.

Well, that and the cool sound clip 

For all the times I've let the magic smoke out, it would be cool to put it back in...