Introducing the "One Chip Chorus"!

[pinkjimiphoton]

check for solder bridges between the tracks, or an open somewhere..sometimes a trace can have an almost imperceptible break and screw ya up.

check the voltages, if they're not too far off, it may be the chip. there's an audio op amp section to the chip check around there especially...i'm on the wrong  computer to look up the data sheet for ya, but just hit google for pt2399 data sheet for pinouts and a ballpark of where the voltages should be in your build.

looks nice, man! you'll get it.

[bean]

I won't have time to verify this for a bit, but here is a 1590A layout for 1/8W resistors and monolithic/MLC caps. Should fit pretty easy.

[rhcp_schipper]

Here are the voltages I've measured and the pics of the wiring.

The voltages are way off the other voltages one page back, so thats not a good thing.

1   4.94           16   0.12
2   0.03           15   0.12
3   0.0             14   0.03
4   0.00           13   0.03
5   0.00           12   0.12
6   0.00           11   0.05
7   0.08           10   0.03
8   0.11             9   0.03

The Pics of the wiring.

Top:


Bottom:


Tim

[Pigyboy]

Hey Tim,

Unhook the switch section and just try to get it to work with and in/out only. Eliminate everything else and see what you get...

[rhcp_schipper]

Hey Tim,

Unhook the switch section and just try to get it to work with and in/out only. Eliminate everything else and see what you get...

Will try that tomorrow! Hope I'll get it to work!

[rhcp_schipper]

I've just unhooked the switching section from the PCB, and re-soldered every connection on the pcb.

Now I can get sound out of the thing, but I don't think it all right yet. At home I've got 3 Pt2399's, with one the of the Pt's I only get clean sound(no noticeable chorus at all), with another I get no sound at all, and with the last there is a chorus sound(no as nice as the the sound clip sounds), and when I have the pot at max the chorus pops every cycle it makes.

Extra info: That last Pt2399 came out of the little angel chorus I've bought from El musico Loco. This Pt2399 has the known startup problem, maybe this is some usable information.

For testing I'm going to buy some new Pt's!

Cheers,

Tim

[pinkjimiphoton]

tim,
mine drove me nuts too...

it wasn't really noticeable on chords at all...do you hear it more on single notes than chords?

[rhcp_schipper]

tim,
mine drove me nuts too...

it wasn't really noticeable on chords at all...do you hear it more on single notes than chords?

When the effect is working the chorus is pretty thick and good noticeable! Not only on single notes, especially when the chorus is maxed out.

Maybe I have to recheck all the solder joints again. Can't be a bad thing to do.

[Govmnt_Lacky]

My 2...

I have not built this particular version of a PT-based chorus however, I have built several of FCs Little Angels and I have found 1 undeniable truth...

IT ALL COMES DOWN TO THE CHIP!

Some chips just "work better" than others. Out of the 6 or 7 angels that I have built, I have probably seen 4-5 different results.

[pinkjimiphoton]

true that. i tried the  5 chips i had, and every one was different...so i bought 5 more from a different vendor, so i could see which one is "the one".

[frequencycentral]

Mojotastic PT2399? Awesome!

[pinkjimiphoton]

hi guys,
i think i got something screwed up, so advice would be hip, my newb posterior is afu atm.

it definitely works...it passes signal...but i can't seem to hear it warble like on the demo.

with headphones on, i can hear a chorus effect slightly, but the "lush"control doesn't seem to do anything.

i tried swapping out the 2 10k mixer resistors and subbing a 50 k pot (all i had atm) but didn't seem to make any diff at all...if i turned it toward the "wet" signal, just kinda lost volume some. still no real warble.

i did mess with the resistor between pins 4 and 6 some...and ended up wiring in a 50k pot instead. now i can dial up a distinct one slap echo maybe a 1/4 second long or so. so i know the chip is working. for $#*^s and giggles, i tried feeding back the output to the input for a couple repeats...a little noisy, but very warm and tape echo-y. could get about 3 slaps. messed around with trying to inject the output at different points back into the circuit with a couple interesting results, but nothing really useful...

sorry for the rambling on and on...

what i guess i need to know is what parts should i check to see if the lfo is working? i know the chip is working, but don't have enough knowledge yet to really understand how to check the lfo.

advice as always appreciated!!

thanks guys...

[pinkjimiphoton]

k, tried a couple things...read on at your own peril.

added a 50k pot in series with r1 as a voltage divider...can go from stock, to doubling, to one slap about a half a second. at long times, it's noisy and almost unusable. i like it tho, reminds me of a tape echo.

also added a 250k pot between pin 7 and the bottom rail, with the third lug grounded.  this adds to the "lush" control, and seems to be a master volume and boost for the delayed signal. seems to add a lot of compression, too.

like i said, at your own risk. i am a newb having fun, to me these are happy accidents.

i love this thing, anchovie.  


thanks!!

edit: also shorted across r9, it wasn't needed on my build. chinese pt's....who knows what they are...  lol

[deadastronaut]

^ nice one jimi, i haven't had time to bread this yet, been too busy..

when the delay is long is it the same-ish as a rebote delay?...i know its an inherent trait of the pt2399 to get dirty on long delays but i'd like mine to be a chorus/delay too...coz i'm greedy...

any chance of one of your famous vid demo's on it?...

[pinkjimiphoton]

hi rob, i will post a video as soon as i can. never tried a rebote, so i don't know...it's a VERY tape like echo, it sounds alot like my echoplex and even warbles some.
if i can get my girl off the laptop with the webcam one of these days...lol...

i need to chase down a very LOUD switch popping problem first..this things been driving me nuts!!


anybody got any tricks for making a feedback loop other than just connecting input and output? if i do that, i get the original and 2 distinct slaps...would a buffer fix that?

no idea how to add more filtering, but the delay gets a weird ascending "zip" sound that's modulated over about a half second...really faint, but noticeable.

i like it best just at the point you can notice a double...sounds awesome.

will try to make a video later...beware of stupid pedal tricks volume....5? 7? lol

[pinkjimiphoton]

please excuse the crappy sound...the soundcard in this laptop sucks.

mods are a 50 k pot between pins 4 and 6, and a 250k pot between pin 7 and the bottom rail, and ground.

i can tell the lush knob works, but just barely. you can actually see where the pt locks up in the video. every time it locks up, it wobbles more.

anyways...

[Earthscum]

Hey all, before I forget... the micro-sized layout I promised several pages ago, lol. 1.2" x 1.5", scaled for 300 DPI Print. You'll need to mirror the image for toner transfer etching, I have it set up for silk screen transparencies.

I have the ground plane extending under the chip in an effort to isolate the power side from the signal side (at least I think that's what my idea was). Also note either resistors OR trimpot for the output. Lush control is set up as a trimpot in case you want to make a "No-Knob OC Chorus" NoKnOCChor? 

Anyhoo...

[deadastronaut]

@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?...

[anchovie]

I promise I'll get round to verifying my own vero layout with my own parts! Finished the new tube amp at the weekend with the intention of doing this next, but I've now got someone's bass amp in the garage that I've been offered money to repair.

[meffcio]

Hey all, before I forget... the micro-sized layout I promised several pages ago, lol. 1.2" x 1.5", scaled for 300 DPI Print. You'll need to mirror the image for toner transfer etching, I have it set up for silk screen transparencies.

Hey, what software did you use? Is there a possibility to export the pcb to a pdf file, probably by using PDFCreator? Printing is proved to be better then.
The layout is really fantastic.