Echo Base - a new PT2399 delay

[Mario44]

Hello everybody

It's my first reply here.
I built 1st version of echo-base according to anonymousfacelesscoward http://chawk.files.wordpress.com/2008/02/echo_base_pcb.pdf , but got a problem.
Board is self-etched. Everything was soldered very carefully. Jumpers in their places.
I used 1,6M instead of 1,5M, 40k(39k), 46k(47k), 1N4007(1N4001) and BC558(2N5089- i know i used PNP, my mistake, but before i had BC547 and i had same problem, however 4066 switches properly). Whole rest is same as in the schematic. 4066 bypass is working, 2399 is also working(100% sure, I had it in my rebote 2,5),
connections between pots and switches are OK(checked extra by measuring instrument). Got checked voltages with slacker's one's. I have only slight changes in few points.
PT2399
1. 5v
2. 2.5v
3. 0
4. 0
5. 2.89v [3,09V]
6. 2.5v
7. 0.5v [0,67V]
8. 0.5 v [0,68V]
9 - 16 all 2.5v

4066
1. 4.6v
2. 4.6v
3. 0.4v [0,7V]
4. 0.4v [0,7V]
5. 0
6. 0.45v off 4.5v on [0,4V off/ 4,35V on]
7. 0
8. 9v
9. 3v on 0.32 off [1,81V on/ 0,4V off]
10. 4.6v
11. 4.6v
12. 8.5 on  [8,7V]
13. 8.5 on [8,9V]
14. 9

U3 - all good
1. 5v  2. 5v  3. 5v  4. 0  5. 5v  6. 5v  7. 5v  8. 9v

U1
1. changes
2. 5v
3. 5v
4. 0.8v [ changes between 0,7~0,8V]
5. changes
6. 5v
7. changes
8. 8v

BC560 on/off
E. 0V
B. 4~5V
C. 1,14V

2N5089(BC558)
E.0 V
B.9V 0V off
C.9V
I've looked over 70pages of this thread but I didn't find exact problem.

The problem:
The signal is very quiet and noisy. I have to turn up my amp to 50% of power to hear sounds.
I get only 1 repeat and its distored(humbuckers pickups, I could take out diodes but i want this thing to run first)
When i had my audio probe connected I could hear LFO working. The signal in the input(U3) was much quieter than in the output.

When I took tl072 from my rebote out, the sound with repeats was the same as in echo-base, quiet, noisy and distored 

So i come to conclusion, something makes U3 opamp not working properly so my echo-base runs without a buffer, like rebote 2,5 without opamp. Maybe there are too much 2M2 resistors in the input(before pin 2 and between 2 and 1)

Any ideas how to debug this thing, gents?

[Marcvv]

I have been searching the forum but could not find what i need.
Is there an easy way to add an expression control to the echobase modulation speed that can be used with regular expression pedals?
Most expression pedal use a 10k pot and the speed contol is 1M.
Thanks.

[nocentelli]

I have been searching the forum but could not find what i need.
Is there an easy way to add an expression control to the echobase modulation speed that can be used with regular expression pedals?
Most expression pedal use a 10k pot and the speed contol is 1M.
Thanks.

I would first try to use a LDR in place of the modulation speed pot: You could then use the expression pedal to control the brightness of an LED rigged up facing the LDR and control the speed this way: I have used the light/dark section (2N3904 + two LEDs) from Rob Deadastronaut's lightwah schematic with a Roland EV-5 expression pedal in place of the sensitivity pot and it works well in similar contexts: I'd put a small resistor from + to 9v the expression pedal lug3 to reduce the chance of accidentally frying the expression pot.

[Marcvv]

I have been searching the forum but could not find what i need.
Is there an easy way to add an expression control to the echobase modulation speed that can be used with regular expression pedals?
Most expression pedal use a 10k pot and the speed contol is 1M.
Thanks.

I would first try to use a LDR in place of the modulation speed pot: You could then use the expression pedal to control the brightness of an LED rigged up facing the LDR and control the speed this way: I have used the light/dark section (2N3904 + two LEDs) from Rob Deadastronaut's lightwah schematic with a Roland EV-5 expression pedal in place of the sensitivity pot and it works well in similar contexts: I'd put a small resistor from + to 9v the expression pedal lug3 to reduce the chance of accidentally frying the expression pot.

Thanks for the suggestion and sorry for replying late. Seems like I need to do some tweaking. I hoped someone had already found out how to do it. I will try your suggestions.

[mordechai]

Is there a vero layout available for the "extra delay time" mod involving the second PT2399 chip?  I would like to know how to incorporate this mod into the PCB for the Echo Base from MusicPCB, or if that's even possible.

[slacker]

I've never seen a vero for it, I think Yorick was the only person who ever built it. No reason it can't be done to the musicpcb version, you just need to find the right places to connect it, might need some traces cutting which might be tricky.

[mordechai]

Well, I am game for giving it a try.  I ordered two boards so if I mess one up I can figure out how to correct the mistakes.

I have a question about the mod, though.  In the picture on your gallery, I can't tell if two wires are supposed to be electrically connected, or if they just intersect on the schematic but aren't supposed to actually connect.  here's the pic, and I have circled the confusing area in red and highlighted it with an arrow:



I'd really appreciate some clarification if possible.  Thanks!

[slacker]

They are not connected

[mordechai]

Thanks...one more question about a mod.  I am implementing the waveshape pot mod, and I am not sure about where a connection is supposed to go.  I am talking about the wire leading to the 10-50K resistor...since the mod breaks the simple connection between Pin 1 of U1A and the 240K resistor, I don't know if the 10-50K resistor wire now connects to Pin 1 of U1A or to the 240K resistor.  At the moment I have it going to the 240K as such:



But do I have that right, or should it be connected to Pin 1 of the op amp?

[mordechai]

Bump...

Any help on this?  Should that 10-50k LED be connected to pin 1 of the op amp and NOT to the 240K resistor?

[slacker]

The resistor stays connected to pin 1. Having said that It might actually work like you've shown and would give an indication of the waveshape.

[mordechai]

I'll give it a try both ways and report back.  I wonder if the effect of the waveshape control would change somehow depending on where that resistor is connected...?

[Mario44]

has anybody idea how solve my problem?

[slacker]

Hi sorry for not spotting this earlier. First a stupid question have you put the opamps in the right way? They're both upside down so pin 1 is at the bottom, if you've put them in the wrong way they're probably dead and will need replacing.

If they're in correctly, then we need to figure out where the problem is, if you probe on pin 1 of the opamp in the top right corner, is the signal there the same volume as the input or is it already noisy and quiet?

[Mario44]

No problem, thanks for reply anyway.
Meanwhile, I managed to redo buffer section from version 2 http://jonandtina.net/static/images/echobaserev2-changes.png
I took 47n out and cable going to wiper and connected new pcb i made for that buffer(I wanted to save big one from cuts)
The op-amp was and is oriented in a good way. I also bought few new opamps more and all of them work. However effect is still the same - no repeats, distorion, no modulation, quiet signal.

I guess, by pin 1 You mean pin 5 now, so INput of buffer. When I probe the INput I get quiet signal in comparison to pin 1, or 2(OUTput of the buffer)
Bypass system works(with LED) and tails mod also works. I can hear quiet distored oscilation. Level, time and feedback pots are affecting that noise also.
It still looks like the buffer doesn't send enough signal through pt2399 to make it sound properly - thats my only feeling

The difference between version1 buffer and version2 buffer for me is, that
in v1 there was one louder repeat than dry signal everytime when I produced sound from probe, while
in v2 i have no repeats, but only noise and still quiet dry signal.

[slacker]

If you turn the level all way down so there's no delayed signal does the clean signal sound Ok, it should should exactly the same as going straight from guitar to amp? If it sounds Ok, I would trace through the circuit from the input towards the PT2399 and see where it starts to get distorted and quiet.

[Mario44]

Now I tested this circuit with my guitar... and shock. I didn't check that before(only with my probe) but now the buffer works  . Like You said, lvl turned down and I get clean signal like with guitar and amp only.
Bypass and tails still OK. Problem begins with repeats now. They get a little noise, first repeat is as loud as I set it via lvl pot, but rest of repeats are quieter or dissapear. I can get repeat louder than dry signal, which is also good for this circuit.
Still no modulation and sometimes the signal becomes oscilated and distored in one. The time pot works only half range - from long repeat to medium(I don't know if that is default property)

I'm not sure how I can get sure if circuit is good in some points with my probe, if it wasn't telling me truth about the buffer.

EDIT: I have touched this effect in few places and I found a way to make repeats in proper sound level and somehow for a while the modulation worked.
I'm going to check cables once again.

[bluescage]

Hello everybody,

I built the echo base with the layout of Sabrotone.
At first it worked ok, but then when I switched it off and/or on again, there was only a distorted signal.
I started debugging but could'nt find anything wrong. With the level ccw, the result was the same, so I figured it was in the buffer. I replaced The TL072 . No result.
I got me a usb oscilloscope and discovered that when this distorted sound came, the output opamp was oscillating at approx. 533KHz. When I removed the output cable, all was quiet. I tried different resistors and caps but no improvement. I think the combination of cable and amplifier input made up a tuned circuit.
At last I replaced the TL072 for a NE5532 and yes, now it works fine!
Mayby if anyone has the same problem, this is useful.
Best regards
Ad

[Mario44]

I finally sorted out this effect. Everything was about crappy cables(and buffer). Got few mods more: lfo kill switch, 2,2u pop cap, and changed 20k feedback resistor to 180k variable one.
Btw, one more question. Should "mod depth" pot affect "time" pot?
When my modulation is off and I turn down mod depth pot I can get slapback echo, but when I start turning it back slowly the time between repeats comes longer and there's no slapback.
Is that normal?

However its nice project. I love this effect   
Here is how my pcb looks.

[slacker]

I got me a usb oscilloscope and discovered that when this distorted sound came, the output opamp was oscillating at approx. 533KHz.

Interesting information, I don't think I heard of that problem before, thanks for sharing. With the TL072 you might be able to stop it oscillating by putting a 100 Ohm or similar sized resistor in series with the output. That might stop it by isolating the output of the opamp from the cable capacitance.