Building the Echo Base PCB

[Ginsengbob]

left side of bottom 220r is 9.43
right is 6.63

[Ginsengbob]

left side of lower 220r is 9.43
right side is 6.63

[mplindhout]

Howdy!

I bought your PCB, built the pedal, and all was working fine until a couple of weeks ago. (I mean, AWESOME effect this!)

Now, however, the pedal is fritzing out. It's still working —The echo works, the LFO modulation works, the volume knob blends— but the input is extremely loud and clip-distorted. I say "input" because the output (through the echo, out the jack) picks up the clip-distorted signal and nicely echoes that. So you can hear a decreasing distortion in the output.

Although I'm super-happy at having serendipitously created a fuzz-delay, I'd like some more control over the signal, and not breaking other gear further down the chain is nice as well

So, my question: In which components might this problem lie?

So far I've replaced both the TL072N IC's, the 2N5089 and the LM7805 transistors, but no dice.

[Taylor]

For me, the best way to debug that type of issue is to use an audio probe, and listen through the circuit starting at the input and moving until you find where things stop working as expected. This will help you zone in on the problematic area at which point you'll usually notice a bad solder joint or a part that's the wrong value.

http://www.diystompboxes.com/pedals/debug.html

[funkgang49]

Hi Taylor,
Building my 2nd Echo Base and this time I wanted to add a Tap Tempo board from GuitarPCB. I will be eliminating the Delay Time control potentiometer from the Echo Base board and using the Time control on the Tap Tempo board. My question is: are there any components, other than the Time potentiometer, that I need to leave off the Echo Base board and which pad do I connect from the EB board to the Tap Tempo board?

[Taylor]

Sorry, I don't know the details of combining those circuits. It looks like the GuitarPCB board is using the Taptation chipset made by The Tone God, who is a moderator here on DIYSB. If you search this forum for taptation I believe there will be several threads with info. I believe there's going to be a conflict trying to combine tap tempo with the Echo Base's modulation - the tapped tempo is never going to be right when you have modulation on, and it's possible that having the modulation section including the transistor that modulates the PT2399 connected at all is going to mess up the timing.

[funkgang49]

Thanks Taylor,
One more question:
I would like to be able to set the lowest setting of the modulation speed to a slower pulse - what component would I change and to what value?

[Taylor]

The 1uf cap on the far right of the board, left of the LFO SW pads, is the timing cap. If you increase the value it will shift the mod times into a slower range (twice as big would halve the cycle times, etc.). This is supposed to be a non-polarized capacitor, but if you can't get large value non-polar caps, you can connect two polarized caps with their negative leads together, then the positive leads to the two points where the original cap goes.

[funkgang49]

Taylor,
The Repeats knob on my build currently ranges from 2-3 repeats (with knob fully CCW) to infinite repeats (with the knob fully CW) - what component can I adjust in order to have less repeats fully CCW and just shy of infinite repeats fully CW?

[Taylor]

There's a 20k resistor right under the feedback pot on the PCB. It's in series with the feedback path. If you raise the value of that it should lower the total feedback available. Not sure about what value would get exactly where you want though, and since I'm not the designer of the circuit I'm not sure to what extent this will interact with the capacitors in that network and possibly change the filtering of the feedback. So the repeats might get slightly darker as you raise the resistor value(?), probably will still sound good but maybe put some sockets there and try different values?

[slacker]

From memory, people like 68k or 100k for the feedback resistor if they don't want run away feedback.

With the repeats pot fully CCW the wiper should be grounded so no signal can get through the feedback path, if you are getting more than one repeat then I would check the wiring of the pot, make sure all three lugs are connected properly. If there is still the problem after that then disconnect the pot or just lift the wiper or CW lug, you should then get one repeat. If you do then the pot is faulty and should be replaced, if you still get more than one repeat you have another problem and signal is leaking through the feedback path somehow.

[guitarman73]

Just finished building an echo base and there is a lot of hiss on the first repeat.  Does anybody have help regarding this problem?   Any help would be much appreciated.

I'm trying to upload a 30 second clip, but I'm not seeing how to do it on here.  Let me know and I can email it to you or if you can let me know how to post it here, I can do that, too.
It is hard to hear the hiss unless you are wearing headphones.  If you listen closely on the first repeat and you will hear the hiss sound.

Thanks.

[1878]

Finished this a while ago. Runaway repeats on second footswitch, tails always on & no switch for modulation.

[Taylor]

Looking good, cool art.  Is there a secret code spelled out by the highlighted letters?

[1878]

No, nothing so clever unfortunately  I had to change a black letter over a black background, so I randomly changed a couple of others.

[slacker]

Looks great, where did you find that image? I must have it

[1878]

I can't remember exactly, but I have it on the laptop (I think). I'll message you the link or the pic as soon as I find it.

[glops]

Does anyone know why I would be only getting 1 repeat? Everything else works perfectly, seems like I had this problem many years ago but can't remember how I fixed it.

[Taylor]

Problem in yer feedback path. Signal's going into and coming out of the 2399 OK, but not making its way from the 2399 output to its own input. Check around the parts under the feedback pot - the diodes and surrounding passives.

[glops]

Problem in yer feedback path. Signal's going into and coming out of the 2399 OK, but not making its way from the 2399 output to its own input. Check around the parts under the feedback pot - the diodes and surrounding passives.

Thanks, Taylor!