"Little Angel" - Super Simple PT2399 Mini Chorus

[azrael]

Hm....This looks like a fun build. Anyone able to do a demo of it doing Paradise City chorus tone, or at least verify that it can do that?

[radio]

It surely! Thanks for the supplementary amount of motivation.

(I mean the sound sample  )

I got 2 PCB s on the way for this modulation effect.

If I should succeed with both ,I have one I ll try to tweak

a little bit.

Regards JM 

[Pigyboy]

Hi everyone,
I think I stumbled onto something here. The first of these I built with a 5 volt L78L05 positive voltage regulators and all worked fine and then I built 2 with a L78L06 6 volt regulators. The first one started to work but then stopped and the PT2399's were getting hot but I didn't pay attention to it. I couldn't get it to work again so I built another and again it didn't work. I put in a 5 volt L78L05 this morning and it fired right up. I think this may be G-Lacky's problem so check it out if you are having problems.
Chris

[Govmnt_Lacky]

Hi everyone,
I think I stumbled onto something here. The first of these I built with a 5 volt L78L05 positive voltage regulators and all worked fine and then I built 2 with a L78L06 6 volt regulators. The first one started to work but then stopped and the PT2399's were getting hot but I didn't pay attention to it. I couldn't get it to work again so I built another and again it didn't work. I put in a 5 volt L78L05 this morning and it fired right up. I think this may be G-Lacky's problem so check it out if you are having problems.
Chris

Sorry Chris.... I wish it was that easy over here. I just checked and the regulator is a KA78L05AZ from Fairchild and it is reading 5.01V on the output. I am going to check the "stupid" things again before I shelf this thing! 

[Pigyboy]

Hey Greg,
Check it all out again and feel the chip for heat. If it is getting hot at all swap the regulator. I would swap it out just to be sure and check your pinouts for the regulator just to be sure. Good Luck. This thing drove me crazy but it is great when it works.
Chris

[Govmnt_Lacky]

This may be an odd request but....

Could someone post a picture of this chorus on an oscope? I set mine up as follows:

Frequency: 440Hz
Amplitude: 80mV
Wave: Square wave

I could really use a "working unit" to compare to.

When I engage the circuit, my square wave become more "sawtooth-like" with "spikes" in the middle of the peaks and valleys. These "spikes" never get larger or smaller however, they do change with the pots. When I turn the speed pot, the spikes move more rapidly/slowly back and forth along the peaks and valleys. When I adjust the depth pot, the "distance" in which the spikes travel along the peaks and valleys becomes longer or shorter.

Confirmation with a working unit on an oscope will give me a bit more sanity. 

[BoxOfSnoo]

I wonder if a regeneration pot might be more useful as a sort of resonance control?

It's on my breadboard right now. 

How did this turn out, BTW? 

I just breadboarded mine, and it sounds good, but I'd like to give it a bit more "thickness".  It seems a little subtle to my ear, for some reason.  I already tried lowering R12 to 2K to try and get it slower.

[Pigyboy]

From looking at the datasheet I think you can manipulate the delay by changing R6. Yes

[azrael]

PigyBoy, how would you say this design is for hitting the "Paradise City" intro tone?

[Pigyboy]

PigyBoy, how would you say this design is for hitting the "Paradise City" intro tone?

Hi Azrael,
Do you mean the 'bmwaaa-bb-bmwaaa-bb-bmwaaa-bmwaaa-bmwaaa' part at the start of the song? 

[azrael]

Hmmm...wait, I'm evaluating your use of onomatopoeia.....


Not how I would characterize it, but....I believe we're talking about the same thing? The very first guitar part of the song.

[BoxOfSnoo]

I wonder if a regeneration pot might be more useful as a sort of resonance control?

It's on my breadboard right now. 

How did this turn out, BTW? 

I just breadboarded mine, and it sounds good, but I'd like to give it a bit more "thickness".  It seems a little subtle to my ear, for some reason.  I already tried lowering R12 to 2K to try and get it slower.

Heh heh... Mr. DMM tells me that I needed to *RAISE* R12.  I changed it to 7.5K and it's pretty sweet about there.  The delay pot is handy just for tweaking that extra little bit of space in it.  Now if I can figure out how to give it a tiny bit of regen I'll be ready to perf this baby!

[Pigyboy]

Hmmm...wait, I'm evaluating your use of onomatopoeia.....


Not how I would characterize it, but....I believe we're talking about the same thing? The very first guitar part of the song.

I think you can get that tone with this box.

[kristoffereide]

Anybody want to make me a board? Or tell me where I can order one with the info provided here?

[frequencycentral]

Anybody want to make me a board? Or tell me where I can order one with the info provided here?

Here: http://www.guitarpcb.com/apps/webstore/products/show/1690146

[Pigyboy]

Has anyone seen the problem of the PT2399's latching up and not turning on the effect? I am not sure if this is due to a bad set of chips. I was using a 6 volt regulator and found the chip and the regulator getting hot so changed to a 5 volt regulator and it seemed to work but now I am getting reports that the same problem is intermittently re-occurring.
Any thoughts?
Thanks,
Chris

[frequencycentral]

Hmmm. I've read similar in one of the other recent PT2399 design threads. There could be a number of culpits:

• Bad set of PT2399, as you say.
• Speed that the PT2399 is running at, ie 100R resistor. As the data sheet shows only minimal ms difference between 0.5R and 1K, maybe we should try a higher value and see if the bug goes away.
• Some PT's don't like their vref being tampered with? Not sure of the solution if this is the case, as the Little Angel depends on this to get the effect.

[Earthscum]

That's the issue I came across with the Sewer Pipes. It wouldn't let me use anything less than 560R. When I would turn it on, I would get a small double-pop and then only the OP Amps would be working. I don't think I even hand anything coming out of the mod/demod sections. Even just setting up the chip for a normal datasheet delay yielded the same results. I swapped in other PT's and got the same thing, then I tried the ones from different source and they worked fine with the 100R.

The ones that don't like short delays are the ones I got from Tayda, but they are different than the first one I got from them. The 2 I originally used are from Steve (smallbear), and the first one I got from Tayda, and they have no problems with the 100R at all. The one from Steve have a nicer case, while the ones from Tayda look more like National chips... square, boxy, dull case. If I get a hankerin, I'll post pics of the different ones. Just gotta get into a case for a pic of one of them.

[Pigyboy]

^^^^
Thanks for the input FC &ES -
So in the end did they all work by raising the resistance to 560R?  Does it affect the effect?

[Earthscum]

Ya know, I use a 10k pot with a 100R limit on mine, and I usually find it turned up to about 1.5-2.5k minimum for bass, so I don't think a 560 would make too much of a difference... maybe just a little bit of tone change.

I really wish they'd make a chip like the 2399 that does .1-5mS and 4-40ms or so. The 2399 effectively covers most of the longer range, and can easily do longer with multiples, but short delay lines are still kind of a pain.