"Little Angel" - Super Simple PT2399 Mini Chorus

[Groovenut]

If the fix is in the build from the start, would there be any reason for it to ever latch up? Assuming (for simplicitys sake) that the cap in the fix is fully discharged between any switching off/on (accidental or otherwise) while depth is below 1k.

Things are complicated by the modulation of Vref, because that also affects the internal pin 6 circuitry, so it depends on how the LFO starts up. Best bet would be to improve the latch up fix by putting the 47R resistor in series with the emitter instead of collector, and increasing the charge time (increase the 68k to 220k say). Alternatively, put a couple of diodes or an LED in series with the emitter and eliminate the 47R resistor completely; this will increase the time before the transistor starts conducting.

On the original the operating voltage on pin 6 was ~.7 volts. Do we need to match this voltage with the diode/LED on the emitter or can we use any generic red LED?

[PereatMundus]

hey hey.
So my L.A.'s been sitting halfway built for far too long now [along with (no joke) 13other pedals  ]
Last package of parts arrived today thou, gonna head out and fetch em tomorrow and start finishing the projects.

So went through the thread again and as usual the info is all over the place and spread around.
Quote's below from what I reccon is the only needed info. To help next random person from reading through the
whole thread again for the X'th time.

I dont remember now but can posts here on the forum be edited "forever" ?  so the first post easily can be updated
with the newest version of the schem / layouts avalible etc?  that might [if possible] be a good thiing to do

From what I can tell the pin 6 fix still is no unilateral successful fix?
the PT2399's acting somewhat different and reports beeing all over the place as to why and when it looks up.
But.. it does help thou?
[I got a few of em to try with (in a couple of other delay pedals) so hope Ill find one who works, just curious mostly]

Pin 6 fix - Is this what Merlin was describing?

I guess so, sort of anyway, check quote's below.

So is there an updated schematic with these fixes...?

If so I might do an Onboard Pot 1590B with room for battery PCB...

Schematic for the Birthday Edition:

^^^

Well I was gonna save this as a surprise for LA's 1st birthday in August, but........




I wanted to keep it 1590A-able, but also add good things like the Pin 6 Fix and a seperate vref for the audio path. Here's the lowdown:

• Pin 6 Fix: D1/C16/Q2/R21/R22
  I did add a little Pin 6 Fix subcircuit to a PT2399 that I know won't work without. It still has issues, but I think raising R22 to 100R and C16 to 47uF will sort it
• Audio vref: R23/R24/C17 - suggested by merlinb as a way to reduce noise dumped into the older version's 5v vref supply by the PT2399
• C4 changed to 3.3nF - might be a bit darker but will be less hissy

 
As it's planned to be 1590A-able, hopefully all the electro caps should be able to be bend over 90⁰ to lie flat against the PCB. C16 might be the trickiest.

I PM'ed this layout last week to a couple of people who expressed interest in verifying it, so you never know, it could be verified within a day or so. The layout does need a little tidy up, as I notice the pad sizes are not all the same size.

mictester over at the other place has developed a little sub-circuit to prevent the PT2399 from locking up:

 "The PT2399 datasheet warns about having a low value resistor from pin 6 to ground during the power-on reset that the IC does automatically. The reset lasts 400 ms. I keep pin 6 with a higher value resistor for longer than the reset period. I tried it, and the three ICs I tried it with did not lock up. With the 2N3904 I used, the delay was pretty much identical to that from a 100R resistor. "

It would appear to be verfied twice. Should solve people's problems with some PT2399 not liking this circuit.

[Gorilla0815]

Hey guys,

isn't the layout wrong about C17? In the schematic, there is a 47uF cap, in the layout a 10uF. I have to say that I'm not really into this whole schematic-thing. Does it make the sound different?

I'm talking about the birthday-edition, to prevent confusion.

Greets

[slacker]

Yeah, you're right C17 should be 47u according to the schematic. In this case it doesn't matter, either value will do the same job, with no effect on the sound.

Welcome to the forum

[Gorilla0815]

Ok, in this case I'll continue soldering Thanks!

And Thanks! 

[geiristudio]

Hi there, I just finished putting this: http://www.sabrodesign.com/wp-content/uploads/2011/04/LittleAngelRev1.gif together and it passes audio when bypassed (duh!) and when active but nothing happens. I can hear a tiny change in the guitar tone but the knobs don't do anything and there's no chorus going on.

I tried powering on-off a few times, shorting out, powering on with the depth maxed out and everything I've read that works for some people but nothing works for me.

I've checked the circuit 5 times and it is soldered 100% like the schematic. I've made lots of pedals and all of them work.

Any update on the lock up ?

[Seven64]

Hi there, I just finished putting this: http://www.sabrodesign.com/wp-content/uploads/2011/04/LittleAngelRev1.gif together and it passes audio when bypassed (duh!) and when active but nothing happens. I can hear a tiny change in the guitar tone but the knobs don't do anything and there's no chorus going on.

I tried powering on-off a few times, shorting out, powering on with the depth maxed out and everything I've read that works for some people but nothing works for me.

I've checked the circuit 5 times and it is soldered 100% like the schematic. I've made lots of pedals and all of them work.

Any update on the lock up ?

i used that layout and it worked perfectly the first time, and 8mos later still hasnt locked up or anything.  check your circuit again or try a different pt2399

[mthibeau]

Hi there, I just finished putting this: http://www.sabrodesign.com/wp-content/uploads/2011/04/LittleAngelRev1.gif together and it passes audio when bypassed (duh!) and when active but nothing happens. I can hear a tiny change in the guitar tone but the knobs don't do anything and there's no chorus going on.

I tried powering on-off a few times, shorting out, powering on with the depth maxed out and everything I've read that works for some people but nothing works for me.

I've checked the circuit 5 times and it is soldered 100% like the schematic. I've made lots of pedals and all of them work.

Any update on the lock up ?

i used that layout and it worked perfectly the first time, and 8mos later still hasnt locked up or anything.  check your circuit again or try a different pt2399

I build that layout a few weeks ago, it does lockup from time to time, but I think that my be due to the PT2399 I used (a recent order from Tayda). The layout works great though, and when it locks up all I do is power off/on and it works again.

- MikeT

[geiristudio]

I'm either changing the PT2399 or building another circuit to see if it works. I'm 100% sure that the one that's locking up is correct so it might be the IC.

[Seven64]

Hi there, I just finished putting this: http://www.sabrodesign.com/wp-content/uploads/2011/04/LittleAngelRev1.gif together and it passes audio when bypassed (duh!) and when active but nothing happens. I can hear a tiny change in the guitar tone but the knobs don't do anything and there's no chorus going on.

I tried powering on-off a few times, shorting out, powering on with the depth maxed out and everything I've read that works for some people but nothing works for me.

I've checked the circuit 5 times and it is soldered 100% like the schematic. I've made lots of pedals and all of them work.

Any update on the lock up ?

i heard an audible differance between the tayda/futurlec/smallbear pt2399's and op-amps in this circuit.  i have kept the tayda in the circuit, but admittedly i havent played on the pedal for prolonged amounts of time (prolly has <6 hrs total)

i used that layout and it worked perfectly the first time, and 8mos later still hasnt locked up or anything.  check your circuit again or try a different pt2399

I build that layout a few weeks ago, it does lockup from time to time, but I think that my be due to the PT2399 I used (a recent order from Tayda). The layout works great though, and when it locks up all I do is power off/on and it works again.

- MikeT

[geiristudio]

I changed the IC, no change. The circuit is definitely right in every way and nothing is touching that isn't supposed to touch. I've tried all methods posted here and nothing works.

Is there anything I can do ? This is very strange. I know how to build a pedal and this just won't work. I've done more complicated vero layouts than this.

[Suicufnoc]

Has anyone had success running this thing at 6 volts?  I'm thinking I'm gonna up the 78l05's ground reference with a diode and get about 5.7v out of it.  Probably not worth it for the 1ms less time it will get me, but I'll gain a little headroom too I guess.
Tomorrow I'll be building my vero layout with treble pre/de-emphasis and a little extra treble roll-off to kill a little hiss.  I'll post when it's verified.

[garcho]

I breadboarded the Birthday Edition schematic tonight, it sounds awesome! It reminds me of an old Ibanez I had years ago. Thick and chewy, with lots of character. Easy to put together from that nice schematic, too. Thanks Rick! (and thanks to PTC, Small Bear, and the everyone at the forum!)

[bluebunny]

Just wanted to say thanks to Rick and all those who have contributed to this lengthy thread.  This was my third build (in this lifetime) and I finally got around to plugging it in and having a test run, having built the board a couple of weeks ago.  Sound came out, which is always good, but no chorusing.   

This is where re-reading the thread helped enormously - the more I read, the more I understood what each part of the circuit was doing.  And it became apparent that I wasn't getting any LFO to pin 2.  Lo and behold, I found a track-cut that wasn't...    (I veroed.)  Soon remedied: now I have a sweet little chorus which I am once again motivated to drill a case for!  And some ideas for mods, perhaps...

Thank you all again.  Here's to the next one!   

[thedefog]

there is an error on the layout. It says Q2 should be a 3906 pnp, but it should be a 3904 npn, correct?

Edit: guess this was updated

[cobexonly]

I've finished making a little angel ... and the sound is GREAT!!! .... thanks rick 

[cobexonly]

I love the way it sound  , but I have a little problem with LA chorus, sometimes willing to work and sometimes don't want to work .... when not working I have to unplug the power first and plug in back. And I did change the value of R1 to 1K, C1 and C3 already changed to 100nF, but still sometimes work well sometimes don't work anyway. anyone can give solution to my problem? 

[Barcode80]

a few posts up there is a circuit you can add in to prevent lockup

[cobexonly]

I've read from previous pages and I found to avoid the lockup from PT2399 is by substituting the value of resistor R1, capacitor C1 and C3 with the value that I mentioned above. Is there another trick that I missed? please let me know .... 

[bhill]

Don't know if anyone else has mentioned this, but if you are getting intermittent operation out of your LA, check what your power is reading. I found out the hard way on a used pedal board that someone had tried the 100r + huge cap trick for a noisy cheap wall wart that ended up with 8.1 vdc with only four pedals hooked up. At that voltage level both my LA and Echobase lfo's quit. Worked just fine when the One Spot powering the internal power strip did not get loaded down by the R/cap mentioned above. It went from 8.1 vdc to 9.54 vdc just eliminating that cludge. This worked both for the original with the pin 6 fix daughter board, and the birthday edition I built just to have everything on one board.