Echo Base - a new PT2399 delay

[decc]

No reason there couldn't be a "PTAP4" for this as the code scales just fine. We would need a second dual digital pot and move to the next size up micro-controller for the additional 2 analog pots and second chip-select line. (I think the ATtiny48/88 is next at in 28-pin package. We could also sacrifice an LED output and stay with the 14-pin DIP depending on how you want the serial/parallel arrangement to work.)

There's a separate PTAP thread here if you want to discuss this further. Don't want to de-rail the Echo Base discussion or anything.

[exterm]

hi everybody
i've finally find some time to work on my non working echo base! (thanks Slacker!)

so i find one error on a strap and the delay works fine!!!, but the modulation is not working

the "mod depth" pot add some delay time, (the time pot too!), and "mod speed" pot do nothing.
can you give me some advice... i'm lttle bit lost héhé

thanks

[ashaxx]

can anyone help with a small problem i have, i wired it all up and it worked fine i came to check again the next day to carry on doing some more and the mod speed pot doesnt seem to be doing anything at all, everything else is fine, thanks

[mth5044]

I don't really have any idea, but do you have the depth pot up at all? I don't think the speed pot will do anything if you don't have any depth on.. dunno though. Might want to check out the mod IC too.

[edd29]

can anyone help with a small problem i have, i wired it all up and it worked fine i came to check again the next day to carry on doing some more and the mod speed pot doesnt seem to be doing anything at all, everything else is fine, thanks

that's the same problem when first build this pedal,  don't use 9v battery coz it easily drain your battery
use power supply 9v dc regulator  and double check your layout compare it  to schematic.

[ashaxx]

tried it with mains supply and it worked must just be batteries dont last very long with it or something, thanks

[slacker]

Yeah thats a known problem with the design, the LFO stops working once the battery voltage starts to drop. I don't use batteries so I didn't find the problem when was designing it.
It's caused because the LFO bias voltage comes from the 5 volt regulator so when the battery is new the bias voltage is about half the supply voltage so it works properly. As the supply voltage drops the bias voltage stays at 5 volts so it gets too high compared with the supply voltage and the LFO stops working.
It's possible to modify the design to make the LFO work on lower battery voltages, but by the time the LFO stops working the battery is probably already pretty much dead anyway. Think of it as a low battery indicator 

[beatnik]

hi everybody

how can i add a led pulsing in time with the delay time?

[Barcode80]

hi everybody

how can i add a led pulsing in time with the delay time?

you can't.

[Taylor]

I'm pretty sure someone in this thread made an add-on board to do just that. Was it ruled out as not working properly or something? This is what I don't like about these long threads - it's so hard to find individual topics that cropped up without reading every page again.

[R O Tiree]

Yes you can.

TEH CLICKY

Basically, it counts up to 684,000 and then resets. The left-hand chip counts to 1,000 and resets, sending a clock pulse to the right-hand one every time it does so. The right hand chip counts up to 684 and then resets. The number comes from a bit of arithmetic applied to the table in the PT2399 datasheet.

When the output at D10 goes high, the LED flashes briefly.

[slacker]

Thanks for posting that Mike, I had a look but I couldn't find it.

I believe Auke Haarsma has done a version using a PIC instead.

[BootCut]

Hi.

I've been trying to build this on perf board. I found some incorrect voltages on U1 and U3. When looking closer to the layout and schematic I'm getting confused. For example, in the layout there is a 2M2 (R3) between pin 6 and 7 on U3. But in the schematic there is a 10k in this position. There are more of these "errors" around U3. I can't say if it's errors or if I'm reading it the wrong way.

Can someone explain?

[doitle]

I've been trying to look at this, the datasheet for the PT2399 and a few other PT2399 based echo/delays trying to figure out what is needed to get it operating in its most bare form. What is the absolute minimum to get it to echo/delay. I want to try to start from there and see if I can come up with anything neat off of it. Just need to get some free time together to really figure out how the chip works.

[slacker]

Hi.

I've been trying to build this on perf board. I found some incorrect voltages on U1 and U3. When looking closer to the layout and schematic I'm getting confused. For example, in the layout there is a 2M2 (R3) between pin 6 and 7 on U3. But in the schematic there is a 10k in this position. There are more of these "errors" around U3. I can't say if it's errors or if I'm reading it the wrong way.

Can someone explain?

The pin numbering on the schematic is wrong compared to the vero layout, not sure about other layouts. U3A with the 2M2 resistors should be labelled with pins 5,6 and 7. U3B with the 10k resistors should be labelled with pins 1,2 and 3. I'll correct the schematic.

I've been trying to look at this, the datasheet for the PT2399 and a few other PT2399 based echo/delays trying to figure out what is needed to get it operating in its most bare form. What is the absolute minimum to get it to echo/delay.

The datasheet has schematics that show the basic configuration, or look at the original Rebote delay that’s pretty much straight from the datasheet with some buffers added. R.G also has a very basic circuit over at geofex.

[~arph]

Look for the midfi clari(not) schematic, that is the most minimal parts usage of the pt2399 I've seen as of yet.

FOUND IT:  http://www.diystompboxes.com/smfforum/index.php?topic=74294.0

[doitle]

Yeah heading close to the clari-not is a bit more what I mean. I want to maybe take that reference design and only keep what is absolutely necessary to get it to function to see how spartan it can be. Then build off of that.

[BootCut]

Hi.

I've been trying to build this on perf board. I found some incorrect voltages on U1 and U3. When looking closer to the layout and schematic I'm getting confused. For example, in the layout there is a 2M2 (R3) between pin 6 and 7 on U3. But in the schematic there is a 10k in this position. There are more of these "errors" around U3. I can't say if it's errors or if I'm reading it the wrong way.

Can someone explain?

The pin numbering on the schematic is wrong compared to the vero layout, not sure about other layouts. U3A with the 2M2 resistors should be labelled with pins 5,6 and 7. U3B with the 10k resistors should be labelled with pins 1,2 and 3. I'll correct the schematic.

But even if I compare the perf board layout to the PCB layout by "anonymusfacelesscoward" I can't get it right.
I have put numbers on the pins in the pictures below. That is how I believe it should be, based on the connection between pin 3 and 5. In the perf board layout, R3 is connected between pin 6 and 7. R3 is a 2M2 resistor. In the PCB layout there is a 10k between those pins. Are the values in perf board BOM wrong?

[slacker]

Ok I see what you mean now, the PCB layout follows the schematic, I didn't realise that. Sorry if what I said before confused things.

The PCB and vero layout are both correct though. The TL072 is a dual opamp, it's 2 opamps in one package, pins 1,2 and 3 are one opamp and pins 5,6 and 7 are the other one. They are both the same so it doesn't matter if you swap them over.

[BootCut]

Ok, thanks slacker! I found an error on my board causing the wrong voltages. But it still doesn't work. It is like it's always in the bypass mode. The signal is going thru, but there is no effect no matter how I swith the bypass.

These are the voltages:

PT2399
1. 5v -> 5
2. 2.5v -> 2.5
3. 0 -> 0
4. 0 -> 0
5. 2.89v -> 2.87
6. 2.5v -> 2.4
7. 0.5v -> 0.8
8. 0.5 v -> 0.8
9 - 16 all 2.5v -> 2.5

4066

1. 4.6v -> 4.7
2. 4.6v -> 4.7
3. 0.4v -> 1.4
4. 0.4v -> 1.5
5. 0 -> 0
6. 0.45v off 4.5v on -> 0.79 off  4.4 on
7. 0 -> 0
8. 9v -> 9
9. 3v on 0.32 off -> 1.7 on  0.38 off
10. 4.6v -> 1.5 off  4.4 on  (should it be different when off?)
11. 4.6v -> 4.4
12. 8.5 on -> 8.7
13. 8.5 on -> 8.7
14. 9 -> 9

When the effect is off depending on which position the tails/Boss switch is in either pin 12 or 13 will be 1.25v the other will be about 8.7 volts.

The TL072 voltages are

U3 top left of vero

1. 5v -> 5
2. 5v -> 5
3. 5v -> 5
4. 0 -> 0
5. 5v -> 5
6. 5v -> 5
7. 5v -> 5
8. 9v -> 9

U1 bottom left of vero, this is the LFO

1. changes -> changes
2. 5v -> 5
3. 5v -> 5
4. 0.8v -> 0.8
5. changes -> changes
6. 5v -> 5
7. changes -> changes
8. 8v -> 8

The voltages on the 5089 should change depending on the position of the bypass switch.
E. 0 -> 0
B. 0.63v off 0 on -> 0.61 off  0 on
C. 0.89v off 8.5v on -> 0.82 off  8.6 on


When I'm doing audio probe testing on the PT2399 there is no signal at all, except from pin 11 with a loud noise and hiss.
I can follow the input signal on the outputs on U3A and U3B. But I can't find it anywhere else on the board.

Any ideas of what could be wrong?

Thanks!