"Little Angel" - Super Simple PT2399 Mini Chorus

[merlinb]

With no power I get 3.74 uf between pin 2 and ground,definitely enough to kill the chorus effect.

EDIT: This was measured with nothing but the meter + IC connected at pin 2,and the rest of the circuit still set up.

In circuit your meter is registering the impedance to ground from pin-2, which includes the LFO capacitors, so it's a false reading. There is no internal capacitor on pin 2.

I built a new seperate LFO with a TL072.
Got it modulating between 2V and 3V,but when I connect it to pin 2 it just stabilizes to 2.5V

How / where are you measuring those voltages?

[Earthscum]

Brymus... try the pin 4-6 fix. I know 95% for sure that it shuts up the chip up, and my SPRV is more stable. I think we've all missed a big part of the PT2399 design, isolation of digi and analog grounds. My thinking is that your chip may be sensing the warble through the delay pin and compensating for it somehow. I fixed my LFO problem, lol... new battery, but it seems like my LFO is a bit more "active" in the circuit, if that makes any sense. It's gonna take some more checking, but I think the digital ground thing may be what stabilizes quite a few of these anomalous glitchy builds that obviously should have worked just fine.

[Govmnt_Lacky]

Thanks for the explanation Merlin !

I breadboarded this,well 3 times actually double checking all my connections.
And I could not get any chorus,any warble to be accurate.
Turning the rate pot would yield a wah like effect while turning it,but turning the speed knob gave no change.
I tried different IC's,my PT2399's are a year or two old at least,I can get delay from it by increasing the 100R just no chorus.
Its like my LFO isnt oscillating I tried TL072, RC4558 and (NE5532 the only one to yield the wah sound) the rest had no modulation.
I get 2.5V at pin 2 but its stable doesnt wiggle at all.

Any suggestions ? 4 hours of this and I put everything back in the bins ,I will try again this weekend.

Any news on this Brymus?

I want to build the new layout so I am keeping an eye on this 

[Brymus]

With no power I get 3.74 uf between pin 2 and ground,definitely enough to kill the chorus effect.

EDIT: This was measured with nothing but the meter + IC connected at pin 2,and the rest of the circuit still set up.

In circuit your meter is registering the impedance to ground from pin-2, which includes the LFO capacitors, so it's a false reading. There is no internal capacitor on pin 2.

I built a new seperate LFO with a TL072.
Got it modulating between 2V and 3V,but when I connect it to pin 2 it just stabilizes to 2.5V

How / where are you measuring those voltages?

There was nothing connected at pin 2 ,I unhooked the LFO from the circuit when I measured the capacitance at pin 2.
So any capacitance couldn't have come from the LFO on another board that was disconnected at the time.

I was disconnecting the lead from pin 2 to my LFO and measuring the voltage there on the flying lead from the LFO board,not pin two.
With my DMM connected to that and ground it would fluctuate between about 1.8 and 3.1/3.2 VDC the speed knob would make it bounce between voltages faster or slower.
I can change the voltage divider and other resistor/s to get a greater voltage swing but am unsure what is safe to apply at pin 2 ?
Since the Vref is supposed to be 2.5V,I thought 2-3V was right.

I had a show Saturday afternoon ,and DIYSB was down all day today for me.      ( ? any one else ? )
So I havent tried anything else,I am thinking anout getting new chips and trying again.

I mean I can get delay,lots of delay ,and reverb from the chip by changing the 100R resistor to ground.
So the chip isnt latched up,if its delaying right ?

I appreciate the help and reply's if anyone has any ideas ,it is still on my breadboard.(both the LA and the seperate LFO)
I will post the voltages in my next post if that will help.

[makaze808]

Hi, is the  new layout OK to build yet ?  Thanks.

[deadastronaut]

Archangel?? .....

[Pigyboy]

On a second look my build of the birthday angel works but not really right and my experience with the angels is if it don't work and there are no visible mistakes is build a new one. Even if the birthday version works I didn't do a good enough job on the build to cram it in a little box either,
So I built a new one from the original 1590A and built one of mctesters fix boards and when I hooked it up using the 5 volts supply line it didn't work and made the 2399 & the 7805 hot real fast. I measured 40 mV at the output to pin 6. When I hook it up to the 9v line I am getting 29mV and everything works without getting too hot. I don't know what the math is here but maybe someone can help out here with what is going on.
Here is a little trick with the 100uf cap

I shoehorned it between the two IC's and took the connections from corresponding points on the top of the board.
You can also see I socketed R1 to see if the circuit would work with out the fix....

Cheers.
Chris

[deadastronaut]

@chris

did your original page 4 version work ok?..still waiting to build this...

[Pigyboy]

@chris

did your original page 4 version work ok?..still waiting to build this...

The one from page 9 for the 1590A's definitely works with the pin 6 fix (like the one pictured above)  I am not sure if anyone got the BDay version to work totally right yet. Turns out the sound out of mine is really weak compared to the one above.

[askwho69]

@chris

did your original page 4 version work ok?..still waiting to build this...

me too hahahha wanting to make this REALLY!!! @@ but im so confused which the best layout and verified with no mistakes... man its hard to scan on this threadtoo many pages!! like reading a whole book!

[deadastronaut]

thinking about  bread boarding this, so i can tinker with it,  will an 072 be ok, instead of 5532 ?...

[Scruffie]

@chris

did your original page 4 version work ok?..still waiting to build this...

me too hahahha wanting to make this REALLY!!! @@ but im so confused which the best layout and verified with no mistakes... man its hard to scan on this threadtoo many pages!! like reading a whole book!

There might be a new layout today if this last bit of the puzzle goes well 

[deadastronaut]

cool,  

edit: would an 072 be ok?..

[Scruffie]

Another Layout for the Birthday Edition! Not my neatest and 3 jumpers but it seems okay and there should be plenty of space for components.

Onboard Pots (Mounted on the back) to fit a 1590B with battery.

Unverified





54.61 x 52.07mm

Enjoy.

[Brymus]

cool,  

edit: would an 072 be ok?..

I got a 072 to modulate as an LFO.
But no matter what type of IC or LFO I used I couldnt get the Vref to fluctuate at the 2399.
So all I got was delay.
I am waiting to get some different 2399s and try again,because I love the soundclips.

[Scruffie]

How well does this function as a vibrato, is it worth adding pads to the PCB to lift the 10k off the input out the circuit with an SPST?

Sorry if this has been answered but yeah... 35 pages to read through.

[deadastronaut]

^ no idea , but i like the idea of having the delay option/switch too...as bryan said!..if it can be done... .. options!..


:just got an ne5532 to try...

[askwho69]

^ no idea , but i like the idea of having the delay option/switch too...as bryan said!..if it can be done... .. options!..


:just got an ne5532 to try...

which layout did you try rob?

[Pigyboy]

Can someone explain what R7 - 330k does in the circuit? I dropped it to 27k then 1.2k and it still works good but is way less hissy. The only problem is I need to have them boxed up to really tell it is less noisy. Going to try to jimmy-rig another in a box today to check the 330k side by side with one of a lower value R7....

[merlinb]

Can someone explain what R7 - 330k does in the circuit? I dropped it to 27k then 1.2k and it still works good but is way less hissy. The only problem is I need to have them boxed up to really tell it is less noisy. Going to try to jimmy-rig another in a box today to check the 330k side by side with one of a lower value R7....

It doesn't do anything,* really it should have been replaced with a wire link from the start.

*in alternative circuits it would serve to reduce the output offset of the opamp, but that is no important in this case, so it just adds noise.