Little Angel Chorus - NYE

[amz-fx]

Over the holidays just a couple of months past, I laid out a pcb for the Little Angel Chorus. After building it, I found that a few changes were needed to get the most out of it with my rig.

I made an number of mods to the circuit, which I have called the New Year's Edition to differentiate it from previous versions, since the changes are significant. Complete schematic and other details are in my blog.



Build and enjoy!

Best regards, Jack

[Mark Hammer]

Thanks Jack.  Nice to see you here, and that you haven't forgotten us.  Mods much appreciated.

[amz-fx]

Thanks, Mark.

It should be easy to build the circuit on the previous perfboard layouts with only a simple mod or two to the layout. The jfet startup is optional and the bipolar version can certainly be used. The two mods to the LFO are the most important and helped my pedal out the most (bias and reduced resistor on pin 2).

Best regards, Jack

[Govmnt_Lacky]

@Jack

Did any of the new mods increase its usefulness?

What I mean is that ALL 3 of the LAs that I built were flat and weak in the chorus department. Hardly any real "chorus-y" sound came from them. I know that opinions differ and some may like a very, very, very subtle chorus but.... I was greatly dissapionted 

How did yours turn out?

[guitarkill]

@Jack

Did any of the new mods increase its usefulness?

What I mean is that ALL 3 of the LAs that I built were flat and weak in the chorus department. Hardly any real "chorus-y" sound came from them. I know that opinions differ and some may like a very, very, very subtle chorus but.... I was greatly dissapionted 

How did yours turn out?

If you read the blog he linked it's explained there.

[amz-fx]

@Govmnt_Lacky -  When I first finished the pedal it sounded flat and weak, as you described. I initially thought I had a bad PT2399 so I tried a couple more but they were all the same. (prime chips from Small Bear) The only way the sound was getting into the range I liked was with the Depth knob cranked wide open.  I listened to some of the sound clips on Youtube, and they all sounded just like my pedal, so I figured that was just how it sounds. Like you said, a lot of players like a more subtle chorus, and that's okay. I like a little more depth to the sound so I started testing some mods.

The LFO noise was not a hard thump, but more a whoosh-thump that sped up/down as you changed the oscillator speed. I tried a mod that I knew would kill thump from that type LFO and it did nothing, so it had to be coming from inside the PT2399, probably in the bias network. The LFO was also skewed.  When I changed the two bias resistors on the LFO, the wave straightened out and the thump disappeared.

The PT2399 does not go down low enough in delay time to do a good chorus...  it really needs to be 15ms to 25ms (at most) to get a good chorus sound and the chip cannot get there. I tried all kinds of mods to make it work and none of them were very successful. The 2399 is just not meant for chorusing, and the MN3207 chip will beat it every time.

Here is what the modded Little Angel is good for...  it stacks VERY well with other chorus units.  Place it in series after another chorus pedal and the sound becomes much more complex and rich. I don't have two working LAs or I would try that combination too.

best regards, Jack

[bluebunny]

Place it in series after another chorus pedal and the sound becomes much more complex and rich. I don't have two working LAs or I would try that combination too.

Hmmm... interesting idea, Jack: two LAs in a box?

[samhay]

Place it in series after another chorus pedal and the sound becomes much more complex and rich. I don't have two working LAs or I would try that combination too.

Hmmm... interesting idea, Jack: two LAs in a box?

Or a 2-PT2399 chorus?
http://www.diystompboxes.com/smfforum/index.php?topic=94435.0

[Scruffie]

I wonder if the little angel might fare better with some feedback... I know not typical for chorus but it's not a typical chorus... hell why not a fixed phase stage in there too 

[bluebunny]

Or a 2-PT2399 chorus?
http://www.diystompboxes.com/smfforum/index.php?topic=94435.0

Built that too, Sam.  Sat on my bass "board" for a gig or two, but I prefer it on guitar (and have since sold it to a tame guitarist).  It's two PTs in parallel.  I'd be interested to try two in series.

[samhay]

Or a 2-PT2399 chorus?
http://www.diystompboxes.com/smfforum/index.php?topic=94435.0

Built that too, Sam.  Sat on my bass "board" for a gig or two, but I prefer it on guitar (and have since sold it to a tame guitarist).  It's two PTs in parallel.  I'd be interested to try two in series.

Fair enough. I have one too, but don't use it very often for various reasons.
You're quite right that two PT2399s in series would make for a different effect. One downside is that the cumulative delay might start to become a problem.

[amz-fx]

Fair enough. I have one too, but don't use it very often for various reasons.
You're quite right that two PT2399s in series would make for a different effect. One downside is that the cumulative delay might start to become a problem.

The direct guitar signal is passed through the chorus pedals so there is no delay on that path... also, the delay parts are sweeping up/down and canceling or reinforcing the various frequencies. It is a nice rich sound.

regards, Jack

[samhay]

^The direct guitar signal is passed through the chorus pedals so there is no delay on that path
Quite right.

In light of this thread, I put a Little-Angle-like chorus together on the breadboard last night - Thanks for the motivation Jack, it is indeed a fun little circuit. I made a few more mods, and will have to post them somewhere once they are a little more finalised. It definitely benefits from more depth though (I have probably settled on a 4k7 to pin 2 of the PT2399).

[vigilante397]

I realize I'm a little late jumping in, but is there a PCB layout to accompany the schematic? I've been looking for a new chorus for my board and would like to give this one a try 

[Cozybuilder]

I finished my build, a few small changes, nothing that hasn't been posted before. This is deeper and slower than the LA, thanks to Jack for making some good improvements on a design that is deceptively difficult to get to sound right.

Gut shots




The Lil ArchAngel


Schemo

[nocentelli]

i'm guessing that the JFETs under the PT2399 form a rate-indicator and millenium bypass combined, so the on/off connection goes to the effect output in bypass. Is that right?

[Cozybuilder]

Yes, the Mosfets (wrong symbol  , sorry for any confusion; I used 2N7000) are my way to see the LFO rate on your effect on/off LED, using Millenium Bypass switching, with minimal current draw on the LFO. I would suggest reversing the order of them, as the LED still flashes as drawn (very weakly) in bypass mode.

[psychedelicfish]

As far as improving the sound of PT2399 choruses goes, the biggest improvement I've found is to run it on a higher supply voltage. If you look at the datasheet the absolute max supply voltage is 6.5V, and the max recommended voltage is 5.5V, so there's a bit of room. I've run them at 6.5V for reasonable periods of time and had no problems, and it's had a very noticeable effect on the sound of the thing. You can raise the supply voltage by sticking a diode between ground and the ground pin of the regulator, or use a variable regulator.

I wonder if the little angel might fare better with some feedback... I know not typical for chorus but it's not a typical chorus... hell why not a fixed phase stage in there too 

I've played with PT2399 choruses and feedback a bit, it doesn't really have much effect on the depth of the chorus, but it adds a definite flangey swirl in the background. It's subtle compared to an actual flanger, but it's definitely there.

[samhay]

I wonder if the little angel might fare better with some feedback... I know not typical for chorus but it's not a typical chorus... hell why not a fixed phase stage in there too 

I've played with PT2399 choruses and feedback a bit, it doesn't really have much effect on the depth of the chorus, but it adds a definite flangey swirl in the background. It's subtle compared to an actual flanger, but it's definitely there.

I added feedback to my 'Cherub' chorus and I guess I would have to agree. Also, you can't crank the feedback up too high or you can start to hear the repeats quite clearly.

[amz-fx]

As far as improving the sound of PT2399 choruses goes, the biggest improvement I've found is to run it on a higher supply voltage. If you look at the datasheet the absolute max supply voltage is 6.5V, and the max recommended voltage is 5.5V, so there's a bit of room.

I bought a 78L06 regulator at the same time that I got the rest of the parts, and planned to try a higher voltage, once I had the project working. I haven't put it in yet, but it's good to know that there may be some positive effects from +6v or more.

Thanks, Jack