Chorizo, the Argentine chorus.

[chi_boy]

Look for any trace sits between 2V and 7V, i.e., it is biased above ground. For example, you could connect pin 5 to pin 3 in your layout (I mean this one www.....org/download/file.php?id=11665&mode=view ), since that sits at 4.5V. That wouldn't spoil your ground plane under the IC. There is signal on pin 3 of course, but that doesn't matter since it is within the headroom of the op-amp (it must be, since U1a has to handle the same signal!) All you're trying to do is turn unused op-amps into buffers that don't go anywhere or feed anything.

Well, I learned a think or two with this one.  Thanks for the training.  It's great for the Dirty Bomb, but not so much for Chorizo.  Both rails are easy to get to, but no bias voltage is close at hand.  It looks like it would be a major rework to stabilize the op-amp the right way.

[GodSaveMetal]

Hello after doing the little angel chorus, I thought of making one, also using the PT2399, but with a sinusaidal wave generator on the LFO. The result was this, a warm chorus on a PCB no longer easy to do and with very few components.

NOTES:
* depth control can be 250k or 500k, the higher value, the lower the effect attack.
* R19 is the resistance responsible for controlling the delay time of chorus, you can put a 5k potentiometer in series with R19 to have a time control.
* Speed ​​control depends on C1, C2, C3 and R2. Enlarging the three capacitor or the resistance we can get slower repetitions, achieved in configuration C1 = C2 = C3 = 470nf and R2 = 100k have a balance between fast and low speeds.
* 78L05 voltage regulator is invested in the circuit because it had not as a component in the libraries of the eagle, but is the correct posisicion Layout.






Downloas PCB http://www.mediafire.com/?c3yap3cqj01yp56

Ppaappoo you are from Argentina?? I'm from Peru!!! you post this on Zonadiyer of Argentina??? I want to make this with the mod you suggested of adding a pot of 5k to control the tempo it is right??? you prove the pedal yet??? thank a lot it is a good work!!!

[ppaappoo]

yes I'm the same, I've sent a PM!

[ppaappoo]

HI, i have some questions about the buffer at the end.

the questions are in the image

[frequencycentral]

Yeah use the 5v as vref, connected to the bottom of R11. You'll also need a cap on the output of the opamp, and a 100k resistor to ground after it. As an alternative, you could consider a diff amp as the output stage.

[Fender3D]

You'd better avoid C4 and C12, enter with R10 and R16 in pin 13, R11 from pin 12 to vref and add a 10k between pin 13 and 14.
this way you'll have a better wet/dry mix and since ic1c and ic1d are inverter, you''ll get a proper in phase signal.
Better again you might add a filter cell on ic1c and a "restorer" on ic1d, to lower hiss... just 2 resistors and 2 caps

[Thomeeque]

You'd better avoid C4 and C12..

Shouldn't one stay? DCs at outputs of input buffer and PT2399 differ..

Btw. adding output mixer gives possibility to remove boost (2x) from input stage (=bigger dynamic range).

My (repeated) advice would be to turn input buffer into non-inverting buffer, it's IMO better noisewise and one or two resistors could disappear now (but fx would become inverting again).

Better again you might add a filter cell on ic1c and a "restorer" on ic1d, to lower hiss... just 2 resistors and 2 caps

Yep, pre/de-emphasis, IMO good idea.

And R17/R18 and R14/R15 pairs could be IMO merged into one resistor each - these "triangles" are leftovers from removed 2nd order LPF filtering

T.

[GodSaveMetal]

Please somebody help adding a layout or a scheme whit the modifications proposed??

[Thomeeque]

Please somebody help adding a layout or a scheme whit the modifications proposed??

OK, something like this (quick redraw of something of mine, I have not replaced all values by exact Chorizo ones, e.g. capacitors around PT2399):



RP1, RP2 and CP form pre-emphasis, CD and RD de-emphasis - if you don't want to use it, remove them all and replace RP1 by wire.

T.

[ppaappoo]

I did the changes you suggest are good?

[Thomeeque]

I did the changes you suggest are good?

Yes, you may just consider lowering impedances in mix/feedback networks (for less noise):

R8 = R10 = R16 = R23 = 10k
R22 = R24 = 2k2
C18 = C4 = 22nF

and bigger value for output cap for less low cut in some conditions:

C17 = 1uF

T.

[ppaappoo]

well, thanks to Thomeeque this would be the final circuit. Thanks

[ppaappoo]

ups

[Thomeeque]

well, thanks to Thomeeque this would be the final circuit. Thanks

Yep, perfect, just one small change yet I have forgot about above:

after "merging" resistors in PT2399 LPFs, values of feedback capacitors C13 and C11 have to be adjusted to get same filtering curve from 1nF to 3.3nF (it should be 3-times bigger = 3nF exactly, but 3n3 is IMO close enough).

Good luck T.

[Fender3D]

Grr Thomas 
the symbol you have for PT2399 is cooler than mine..

I'll steal it for my library.... 

[Thomeeque]

Grr Thomas 
the symbol you have for PT2399 is cooler than mine..

I'll steal it for my library.... 

Be my guest

T.

[Fender3D]

thanks man,
for the sharing, but when I was typing my reply I stole it already... (or better I drew it down, since I'm using KiCad) 

[Govmnt_Lacky]

Has the output buffer been finalized for this?

Is there a PCB layout with the buffer change?

Looking forward to this one 

[StephenGiles]

Had a "mini bife chorizo" in BA today!!!

[ppaappoo]

here is the pcb "NOT VERIFIED YET"

http://www.mediafire.com/?39my8ukybhelech

Note: red trace under tl074 is a wire