"Little Angel" - Super Simple PT2399 Mini Chorus

[toplak666]

I changed R1 to 1k and added a 10nF capacitor from pin 2 to pin 3 and it looks like that fixed it! At least one of those two things did... I don't know which.
I will take a good look at that link though. Might help me with any future builds. Thanks!

[Frances Rhodes]

hey y'all

i just built a birthday edition and it works pretty good but the effect is very subtle. i didn't go throught all 46 pages (but at least half of them) so i appologize if this has already been answered before, but would it be a good idea to lower R18? or would increasing R5 be a better solution?

regards

[miique]

Hello everyone, I built an Echo Base delay and I'm getting a clean signal, I suspect this could be caused by the PT2399 locking up, but neither a 100R nor a 1K resistor seem to be doing the trick, can anyone tell me how to apply mictesters' Little Angel fix to the Echo Base, if I'm making any sense at all?

[slacker]

To test if your Echo Base is locking up, unplug the power/battery, set the time pot to maximum resistance (longest time) and then connect power. If you still only get clean signal then your problem is not caused by it locking up. The only way the Echo Base can potentially lock up is if you start it with time pot set to very short times. No one has ever reported lock up as being a problem to me.

[garcho]

i just built a birthday edition and it works pretty good but the effect is very subtle. i didn't go throught all 46 pages (but at least half of them) so i appologize if this has already been answered before, but would it be a good idea to lower R18? or would increasing R5 be a better solution?

i need to look at the schematic but I can tell you that this isn't a "subtle" effect - if it's built right. I really doubt that you'll need to start modding values much to get super thick chorus sound, regardless of differences in personal taste. At least PT2399 super thick, anyway. I added a blend knob to mine specifically to be able to dial some back. I'd triple check your wiring and values and solder bridges, etc. or take some voltages and post them here. I bet it's an easy fix.

[Justus]

I just built a LA Birthday Edition but, like many others, have the problem of no real effect.  I hard-wired everything with no 3PDT switch, so any problem is in the circuit for sure.  I don't see any solder bridges and all the traces look good.  Here's my voltages, which don't seem too much different from Rick's posted voltages:

PT2399

1:  5.12
2:  2.49
3:  0
4:  0
5:  0.91 - 1.00
6:  0.81
7:  0.84
8:  0.91
9 through to 16:  2.49


NE5532

1:  2.2 to 4.01
2:  2.91 to 3.05
3:  2.62 to 2.82
4:  0v
5:  3.16
6.  4.00
7:  4.13
8:  8.58


I'm running this off a battery right now.  Any idea where I should start looking with a microscope?  This is my first pedal build, ever.

[bluebunny]

Those voltages all look pretty reasonable to me.  I would expect pin 2 of the PT2399 to show a bit of wiggle too - it's where the LFO (first half of NE5532) is going to (and that's clearly wiggling).  You might want to trace the audio path with an audio probe to see where your signal goes (and disappears?).

BTW, what layout are you using?  PCB?  Vero?  Some pictures of both sides might be helpful.

[samhay]

The PT2399 might have latched up. Can you hear any effect?

[Justus]

Here's the front and back (without the 78L05, as I didn't have one when I first populated the board).  The 78L05 is in there now, oriented correctly, I just don't have a new pic yet. 

I am not really hearing any effect.  I'm using an etched PCB from the latest Birthday Edition (it had the extra "4EVA" on there, but I wiped it off when I resized the image for printing so I knew which one was the right size).





Sorry for the delayed response, been out of town.

[Frances Rhodes]

hey y'all

has anyone tried jack orman's version of the circuit?

[Giglawyer]

hey y'all

has anyone tried jack orman's version of the circuit?

I am in the process of starting one...just cut the vero for it last night.  It might be a  few weeks before I get to it though...got about 6 others to box up and finish first...LOL...

[DWBH]

I am not really hearing any effect.  I'm using an etched PCB from the latest Birthday Edition (it had the extra "4EVA" on there, but I wiped it off when I resized the image for printing so I knew which one was the right size).

I had the same happen to me.
Effect was VERY faint, and the volume was boosted when engaged, and added alot of noise.
Basically gave up on it, ordered a new PT2399 from Banzai (the ones I have were bought on ebay). I'm etching a new board later this week, but honestly I don't feel very confident I'll get it working this time

[Frances Rhodes]

hey y'all

has anyone tried jack orman's version of the circuit?

I am in the process of starting one...just cut the vero for it last night.  It might be a  few weeks before I get to it though...got about 6 others to box up and finish first...LOL...

i can't have any pcb made for me so all i can do is point-to-point, the first i made took me over 15 hours to get through, but i was a little disappointed with my first angel so i want to give this other version of the circuit a try very soon

[Telvis]

I built the original layout but it did not work, I believe that is the problem with the IC PT2399. I will build the correction suggested by pin 6 Frequency Central, hopefully solve. Can I replace the 2N3904 for a BC547?

[Mark56]

I appreciate nobody has posted in this thread for quite a while, but I have a suggestion to put forward and I have the seemingly unsolved problem with the PT2399 locking up.

I bought the kit from Bitsbox in the UK using the V4 vero layout from here: http://tagboardeffects.blogspot.co.uk/2012/02/little-angel-chorus-rick-holt.html and as many others have seen I have the problem with the PT2399 locking up and it does not appear to matter where the controls are set. One sure fire way of knowing the chip is locked is that it gets warm and the input current goes up from 39mA to 145mA and the voltage on pin 5 & 7 increases to over 4V. I've tried all the fixes I can find and am now waiting for a replacement PT2399. Bridging pins 2 & 3 together resets it every time.

Would it not be possible to design a circuit that will trigger a momentary short between pins 2 & 3 to reset the IC when it locks up by using the reference voltage on pin 5 or 7 as these both jump to over 4V when the IC locks up, the biggest voltage increase is on pin 7?

Creating a fix of this nature should enable any PT2399 to be used and the existing anti lock circuit could be done away with. Seems logical to me but I'm no expert, just putting forward an idea.

I appear to have a PT2399 that is particularly bad for lock ups so this would be a good one to test any viable solution on as all the other fixes I have tried fail to stop it. Increasing the 10uF cap in the anti lock circuit to 47uF made it better, but it still can't be trusted. I am prepared to try anything that is suggested. Obviously a momentary 'on' switch to short circuit pins 2 & 3 would do it, but that is of no use when playing a live gig it needs to be automatic.

[anotherjim]

Afraid I have nothing positive to add, but am starting to get a theory of it...

2 things:
I think modulating pin 2 could be causing "crowbar" latch up of the chip. Theory is, internally, the circuits have some capacitance. Normally the reference voltage on pin2 is half supply, so about 2.5v. When the LFO raises the voltage, anything internally with 2.5v charge gets lifted with it, potentially  exceeding the power supply (2.5v+LFO increase). The same thing again to the neg supply when the LFO pulls pin 2 down. This can usually cause latch up with most MOS chips. Together with that, there could be a charge pump action going on via stray or designed PN junctions in the chip, generating excessive voltage versus supply. Since it's happening internally, you probably can't do anything about it, such as adding 2 reverse clamping diodes between pin2 and +5 and Gnd- but it could be worth a try?

The second worry, is that we don't know how much current pin6 can really, safely, sink. Recommended minimum 1k delay resistor is 2.5mA - that's about the limit for most MOS devices (such as standard gates) that aren't designed specially for higher current sinking.

Well, maybe a 3rd point, you could be too close to solar flares or the microwave...
http://en.wikipedia.org/wiki/Latchup

[Mark56]

Thanks for the reply. I just about grasp what your saying, but is it even remotely possible to create an anti lock up circuit that will do as I suggested?

I will be away from my PC until Tuesday so cannot make any further replies until then.

[maiko]

Id just like to say thanks to the guys who made this and shared it.

I built mine over the week end and it fired up right away.  I DIY'ed everything including etching the board.  Was very pleased with the result.   Got good range even if i only had 250k pot.    can only imagine when i swap it to the proper 500k

[frequencycentral]

Wow! 5 years old in a couple of weeks, I wonder how many L.A.'s have been built? I just listened again to my original soundclip way back on page 1, anyone who thinks this effect is too subtle might need to check their build...

[Cozybuilder]

Maybe a new thread for reporting completed "Little Angel" builds? I'm guessing in the thousands, I've done 2 of them.