Echo Base - a new PT2399 delay

Started by slacker, August 27, 2007, 04:33:19 PM

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thanks Slacker!
so what place do you recommend? I'm going to place a 1:1 gain effect, like an harmonizer, whammy, etc.. I want the first repeat effected (the dry, and then the second repeat re-effected again, so effected two times, and so on..
If I put it before the join between 10k and 47k on pin 16/15, it should sound as natural as possible, right?
what is happening on the signal with that filter on 16/15, and what with the filter after 14/13?


If I wanted to add a tone control that would effect the repeats only, at what point would I insert it? I am thinking of adding a simple tone knob, maybe using the Stupidly wonderful tone control ( or similiar) to better control the tone range of the repeats, while attempting to preserve the tone of the original signal. Is this even possible? Has anyone done this before? Can anyone suggest a suitable tone control? Any suggestions? Slacker?

sorry for the flurry of questions, and thanks in advance for any guidance,

friends dont let friends use stock pedals.


Roger: I've done what you are proposing; the tone stack goes in the same place as the FX loop, as discussed in the posts immediately prior to yours. I used a variation of the SWTC along with a gain recovery stage and internal trimpot to set the output of the gain recovery stage. In testing I found that if you dial out the bass the repeats sound louder and you need less gain recovery, but if you cut the treble the reverse is true. Ideally I would have preferred a dual-gang pot so that the gain recovery could be inversely proportionate to the amount of treble being cut, but my enclosure didn't have room for a dual gang pot.


Thanks for the great ideas, Andrew. I was reading the post about adding the FX loop and thought that the insertion mentioned might make sense, so that is why I asked. Woul you be willing to give any details on
1) your variation on the SWTC?
2) what you did for a gain recovery stage?

I'll bet that there are more than a few of us who are interested in this concept and would love to see the details of how you did it.


friends dont let friends use stock pedals.


Sure Roger, but I did nothing original.
I used Jack Orman's variation of the SWTC -
and the gain recovery stage was based on a Trotsky Drive / Electra distortion without the clipping diodes and using an old NEC transistor form a bunch of stuff I picked up in a surplus place in Tokyo. Any simple clean boost will do the job, but my build is supposed to be lofi and the modded electra added to that nicely. My build is still full of bugs which I might look into today, but the EQ / gain recovery portion works fine.
Just make sure you don't boost the signal above unity gain. You'll know it if you do  :D


thanks for the detailed tips, I am off to the breadboard!!!

really appreciate it

friends dont let friends use stock pedals.



- what other op-amps can I use instead of the TL072´s?
I´ve got NE5532AP and OPA2134PA here...



They should both work fine. I'd use the OPA2134 for the buffers and an NE5532 for the LFO.

Fuzz Aldryn

I used a TL062 for the LFO as it has less current draw because I had/still have a minor problem with ticing. It helped to calm it down a bit without generating any noticable noise but it's still there. So I would say don't care to much about the OPs as long as they are Dual OPs.


Mine doesn't have any ticking and I spent quite a lot of time making sure it didn't, I wonder if it might be a layout issue, which one did you use?

Fuzz Aldryn


If I wanted to put this board into a 1590b and didnt need the controls for the modulation section, could I just jumper where the modulation control pots go?or is there a better tactic ? I want to build a 3 knob echo base in a smaller case,leaving off the pots for mod speed and depth....just using the controls for delay level, repeats, and time.

forgive me if this was covered somewhere else in this thread, but my eyes glazed over after reading all 21 pages.

Any suggestions?
friends dont let friends use stock pedals.


If you don't want the modulation at all then on the schematic remove U1 and everything connected to it up to and including the BC560. Then replace the 39k resistor with a 100R resistor and remove the 220R resistor and 47u cap connected to "LFO+"
If you compare the values on the schematic to the layout it should be easy to see which parts to remove, it's basically everything bottom left on the anonymousfacelesscoward layout.

If you've already built it and don't want to remove everything just pull U1 and remove the mod speed and mod depth pots and the BC560, and replace the 39k resistor with a 100R.



I see exactly what you are saying on the schematic and layout, and thanks again for the quick response, the great tips, and the versatile circuit!
friends dont let friends use stock pedals.


Hi everyone, I've just finished building an Echobase and am stumped by a problem I'm experiencing.  Let me preface this by saying I just joined this great community last month, and that this is my first-ever circuit build.  Since the first day, I've been eating up all the wonderful information found here and have been so impressed with the generosity of everyone in this forum.  A special thanks to Ian for this great project.

When I felt up for the challenge, I read and re-read this entire thread, absorbing the knowledge and noting various issues folks had with their builds.  I also practiced my soldering skills by building a passive A/B switch, and a TB Dual Looper, my first two stompboxes.  Needless to say, the last few nights have been incredibly frustrating as I have tried to troubleshoot the problem with my build.  Any tips and insight would be appreciated.

1.What does it do, not do, and sound like?
With effect on, and all knobs set to minimum, I can hear the dry signal fine, which means there is no problem with the TL072's. 

Also, with Time pot at 12o'clock, and everything else at minimum, I hear only the dry signal.  This is a good thing.

After turning up the Level, and Time pots (and leaving others at minimum), and a quick guitar strum, I hear a very, very faint repeat of the chord, but I really have to strain to hear any semblance of what I played.  Any repeats after that (if I can hear them) are incredibly distorted. In fact, no setting enables me to hear what I consider an actual set of clean, delayed repeats, at least nothing anywhere near Ian's original sound clips. One other way to describe it is that whenever I play a note, I can tell that there IS a delay, and that the Time, Feedback, Depth, and Speed knobs function if I turn them, but I don't hear what I played being repeated or affected in any clear fashion.  It's like my note gets thrown down the side of a waterfall and I'm listening and listening, but hear only a faint echo, which quickly gets overcome by noise from all sides.  Increasing the Level knob only turns up the noise(and of course, after 2 o'clock, the whole thing melts into self-oscillation like a Roland Space Echo - I'm assuming this is ok, bc it's part of the Echobase appeal to me). All the while, the clean signal is clearly audible throughout this. Also, the bypass switch works, and the tails/Boss switch works too.  I have seen others post a similar issue as mine, but I was not able to fix it by checking for shorts around the pot connections.

2.Source of the circuit (URL of schematic or project) =  I used John Lyons' PCB, based on anonymousfacelescoward's layout. All jumpers confirmed.  No solder bridges that I could detect.  It all fits into a 1790NS enclosure.

3.Any modifications to the circuit? NO.

4. Any parts substitutions?

Parts all stock except for:
a) 78L05 instead of 7805
b) 2N5087 instead of BC560
c) TIME POT: 50k lin instead of 47k lin
Note: I looked up each transistor's datasheet and confirmed that I placed the E,B, and C in the correct sockets, remembering that the orientation for 78L05 and 2N5087 are both opposite from the 7805 and BC560, respectively, in the layout.

5.Positive ground to negative ground conversion? NO.
6. Out of circuit battery voltage => USING 1SPOT 9V pedal power supply.

7.  Voltage at the circuit board end of the red battery lead = around 9.5
8. Voltage at the circuit board end of the black battery lead = around 0
9. Voltages: Oddly, voltages on the PT2399, the two TL072's, and the 2N5089 all match the voltages provided by Ian.  The differences appear solely with the 4066, as you'll see:

U4 - CD4066

--PIN - (Ian's Voltages)
P1 2.88 (4.6)
P2 2.88 (4.6)
P3 .03 (.4)
P4 .02 (.4)
P5 0 (0)
P6 .44 off - 2.88 on (0.45v off 4.5v on)
P7 0 (0)
P8 8.45 (9)
P9 nothing (this pin leads to the LED) (3v on 0.32 off)
P10 2.88 (4.6)
P11 2.88 (4.6)
P12 7.78 on (8.5)
P13 4.92 on (8.5)
P14 9.5

Is this something really obvious that I'm missing?  I just don't understand how my readings are almost half of what they are supposed to be.

I know the voltage regulator works, since the other IC's show 5.04v.  Is there a chance that the 4066 is malfunctioning? Why would it only read 2.88v if everywhere else on the circuit appears to be getting the proper voltage?  Should I change the voltage regulator?  Does it have any relevance at all?

I haven't had a chance to systematically troubleshoot with the audio probe (I have a 21-month son and pregnant wife so I can only work on this a couple hours a night) but will do so ASAP. I would also post some pics but am at work and may do so later if it would help.

Thank you anyone who can offer any insight for this frustrated noob. Through the distortion, I can almost hear the glory of the Echobase.


Wow, building this as your first project, that's quite impressive. I hope the frustration of debugging it doesn't put you off building anything else :)
Looks like you've done the right things so far to try and debug so hopefully we can get it to work.

The strange 2.88 volt readings might be caused by your meter, some meters give false low readings when trying to measure voltages where large value resistors are involved. There's an explanation of why here if you're interested
If you want to see if this is the case you can remove the CD4066 and measure the voltages of the pads that are giving you 2.88 volts, if they now give you nearer to the correct voltages then it means the CD4066 is bad, if not it's probably just your meter.

Whilst the CD4066 is removed you can also try this to see if it is causing the problem. Get a couple of short pieces of wire and use them to connect pads 1 and 2 together then do the same thing with pads 10 and 11. If you've used a socket just jam the wire in the holes, if not temporarily solder those pads together. This basically hardwires the pedal into the on position, if the problem is just caused by the CD4066 you should now hear it in all it's glory :)

If not let me know and we'll have to try something else.


Thank you, Ian! I'm thrilled to have some concrete steps to take tonight.  I'm really hoping it's just the 4066 gone bad.
At this point, I think I'd be okay with having the the pedal 'always on'.   :)

Will report back...


So I removed the 4066 from the socket and hardwired Pads 1-2, 10-11, but still had the same sound problem.

Then I measured each socket hole as well as each joint on solder-side and got slightly lower values than before (with exceptions). See below.

-PIN - My original voltages -  (Ian's Voltages) - After 4066 removed
P1 2.88 (4.6) 2.02
P2 2.88 (4.6) 2.02
P3 .03 (.4) 0
P4 .02 (.4) 0
P5 0 (0) 0
P6 .44 off - 2.88 on (0.45v off 4.5v on) .85 on
P7 0 (0) 0
P8 8.45 (9) 9.42
P9 0 (3v on 0.32 off) 0 on
P10 2.88 (4.6) 2.02
P11 2.88 (4.6) 2.02
P12 7.78 on (8.5) 7.78
P13 4.92 on (8.5) 8.98
P14 9.5 (9) 9.5

So I put the 4066 back in.  Bypass, tails/Boss, LED all work fine.

So clearly it wasn't the 4066 gone bad, which I think means that you're absolutely correct about the DMM bringing down the measurements, but since there is still the identical sound issues, does this mean there is likely a short somewhere?  And is it possible that too much solder can be a problem? Is it possible that it's any of the transistors? Over the course of the build I did have to take them out to orient them correctly. Could this have damaged any of them? (Even though they appear to be oriented correctly, based on the pinouts I looked up) Again, when I turn each of the pots, they seem to function as they should.  What do you think I should do next? Maybe after you've heard the sound clips below it might be easier to diagnose.

Here are two short sound clips to give a clearer idea of the problem I'm having:

Each clip has 3 takes showing various combinations of Level/Time. 3 guitar stabs per setting.
1st Clip
Take 1: Time knob at 12. All else at minimum.
Take 2: Time at 12. Level knob at 9o'clock.
Take 3: Time at 12. Level at 12o'clock. Then turning Level up to 3o'clock.

2nd Clip
Take 1: Level at 12. Time at 12.
Take 2: Level at 12. Time at 2.
Take 3: Level at 12. Time at 3.

I also used my audio probe to try and detect anything else. I traced the audio from the TIP IN, and it was a clean signal all the way to the 4066.  It's still clear on Pins 1 and 2.  But terribly distorted at 10 and 11.  Maybe this is obviously a symptom of the problem, but thought I'd lay it out in case.  I wasn't sure how the "SIG D IN/OUT" and "SIG D OUT/IN"  on pins 10/11 from the datasheet work.  Could this mean there is something in between the 4066 and PT2399 that is wrong?  And by the way, probing all the pins on the PT2399 yielded not a single clear signal.

I've also included a pic of my build.  I don't expect you to study my soldering, but it's just to give you an idea of how I put everything together, in case there's some glaringly obvious mistake that I made. Note that the colored wires going to the pots are not uniform for all the pots. They are just what I had available, and helped me to keep each pot's lugs connected to the correct point. Also, added a 4.7k resistor to the LED (because my first one burned out).

Thanks Ian (and to anyone else following this).


From the sound clips and everything else it sounds like the CD4066 is working properly. Did you try jumpering the pins with it removed just to make sure.
It sounds like the problem is somewhere around the PT2399 as the sound is clear going into it but not coming out.
Sounds like the PT2399 is doing something because you can hear a delay and the knobs seem to be working.
Out of interest on the clips where is the Feedback pot set?

I would try audio probing around the PT2399 again and see how your results compare to these.

Pin 16. very quiet signal
Pin 15. delay
Pin 14. loud delay with cyclic noise
Pin 13. nothing, or possibly a very quiet signal
Pin 12. delay with hiss
Pin 11. very quiet delay with hiss
Pin 10. very quiet delay with hiss
Pin 9 . delay with cyclic noise and hiss

I would also double check all the resistor values attached to the PT2399 because if any of those are incorrect they could be causing the distortion. If you've got a spare one try swapping the PT2399, someone who was having problems similar to yours had a bad chip.

Your build look pretty neat, looks like there's some big blobs of solder but so long as they aren't touching anything they shouldn't be they are fine.


Yes, I removed the 4066 and jumpered the pins on the socket.  Same values as I reported.

The Feedback, Depth and Speed knobs were all kept at minimum in both clips.

Tonight I will check the resistor values and see if I can try swapping out the PT2399. Will also re-probe, referencing your values.

Thanks Ian.