Echo Base - a new PT2399 delay

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

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Quote from: slacker on January 30, 2010, 04:02:47 PM
Any NPN transistor should work instead of the 2N5089, I would just use a 2N3904.

The schematic for the mod switching is in another thread

thanks a lot this wil be fun, i wonder if its possible to connect it directly to the led or if it has to go through the 4066


Yeah you can just connect the LED and resistor directly to pin 1 of the LFO, putting it through the CD4066 is so the switching turns it on and off.


Quote from: slacker on January 31, 2010, 06:26:50 AM
Yeah you can just connect the LED and resistor directly to pin 1 of the LFO, putting it through the CD4066 is so the switching turns it on and off.
ok thanks maybe ill make it atlast ive been cirkulating around i for some months now, i moved from south america to europe so i been paused in the diy for some time


Hi everyone,

As you can see I'm new to the board so first of all a big THANK YOU to slacker for this awesome pedal and all his feedback to other people creating mods..I've gone through all 40 pages in the last couple of days and I've learned a lot! So yeah I'd like to build some version of the Echo Base myself (without the modulation bits)..unfortunately I only discovered it when I had already ordered all parts for a Rebote 2.5, but I'm pretty sure I can improvise with the parts that I have.. Since I've got quite some customising coming up anyway I've been trying to really understand all the pin assignments of the PT2399. The data sheet is a joke except for pins 1-6 which are pretty much self-explanatory, and I can't find the description of pins I thought I remembered from somewhere early in this thread..but let's try, based on the audioprobe-results:
16. LPF1-IN very quiet signal
15. LPF1-OUT delay
audio in, which makes sense since the signal has to go through an LPF first before being digitised.. Do I get it right that this is actually the input and output of an OpAmp, the two resistors before 15/16 controlling the gain? (sidenote: if I use a 10k/47k combination on the setup that I've got on my breadboard right now (pretty much the "typical configuration" setting from the datasheet with 10k/15k) I get some serious distortion, which might indicate just that.) And the 470pF cap between the two pins acts as yet another LPF?

14. LPF2-OUT loud delay with cyclic noise
13. LPF2-IN nothing, or possibly a very quiet signal
Anybody got a clue why there should be another LPF in the chip, particularly one for the output?

12. OP2-OUT delay with hiss
11. OP2-IN very quiet delay with hiss
10. OP1-IN very quiet delay with hiss
9 . OP1-OUT delay with cyclic noise and hiss
Pretty clueless, particularly about 9 and 10.. Can anyone with more experience with the PT2399 tell me what difference the cap between 9 and 10 makes? Here somebody mentioned an effect on the internal clock bleeding through (which I also encounter when turning the delay pot past 40k), the post isn't clear about influences on other sources of noise though..

A lot of questions for a first post I know, but hopefully some of you can share your experience with customising the thing..will go straight back to meddling with it myself now ;)



Oh wow, so I had the truncated version of the datasheet all along.. My bad in that case, sry  :-\


I have a question. I built one of these recently and I love it. I use it all the time. But I've noticed that when I have it plugged in, whether bypassed or on, it introduces a small hiss into the signal. I know it's the Echo Base because if I remove it the hiss goes away. Has anyone else had that issue, or knows maybe why?



Thanks for that! I'll mess with the buffers a little and see how it goes.


OK I'm now ready to build an echo bass is there a final layout with all the changes and noise reducing updates Ian made?

I will be making my own PCB layout but would like to have the latest layout.



No sorry I haven't done a schematic with all the changes on it yet.

The 3 schematics here show all the mods I've made to mine


New here.  Maybe somebody could help me with something.  I want to build this delay, and I read somebody mentioned before that they added a momentary switch to increase oscillation to like a dub/infinite level on the fly, which to me sounds like an awesome idea.  But in reading all 40 pages it was never really explained how to wire that up.  Anybody know how? ???


Here's how I've done it.

10k - 100k is probably good for the resistor after the switch, or you can use a pot so you can dial in the amount of feedback you want.

Welcome to the forum :)



I'm gonna make one of these delay (first on breadboard ) and I'd like to add a kind of "dirt" or tinny saturation on delayed signal like , according to what I read, the real tape echo units do . Any ideas about incorporating that thing (setable with a pot)  ? 


Hi! If voltages on pins are correct, is it still possible that the IC is damaged? Cause yesterday it worked fine, but after cleaning and renewing joints it makes a lot of crackle noise on repetitions and bad distortion (not the saturated one)... I don't have other PT to substitute and  i've checked PCB and wiring 1000 times.... everything's good...


Yes it's possible to get all the correct voltages and still have a damaged PT2399. Does all the distortion stop if you turn the Level pot all the way down? If it does then it's probably a bad PT2399.


Well it's not a distortion injectec in the signal path by the PT2399. No backgound noise or anything like that.. This crappy distortion appears just on the delayed signal, i tried to remove the PT and probe the signal on pins 16 and 15 and the sound is clean, so it's not a bad capacitor or resistor on the input. No problems on buffers or 4066... The distortion it produces is something like a bad biasing of a, kind of fuzzy crappy, it's not a saturation it's an ON-OFF distortion like if there was a distortion threshold somewhere  >:(  ??? :( 
The problem came out after renewing joints and after cleaning mounted PCB with alchol.. I could have burnt the PT i think but it seems to work... Voltages are ok and it makes delay.... don't know


I'm a big fan of this effect, and I wanted to build another of these with less noise and some tweaks, so I did a new PCB design and had some professional PCBs made up. I have some here if anybody's interested:


Just as I ordered a board from John, this comes out  :icon_neutral:

Oh well... it does raise 3 questions:
1) Is John's board based on rev 1 or rev 2?

2) Are these the correct changes in rev2? (Except for the 1M resistor on the input)

3) Can these changes be made to the existing John Lyons board?  The toughest one might be what looks like the input buffer, but I'm not experienced enough to know what the differences are between the old and new.  I've read all 40 pages several times but pointers would be greatly appreciated.

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Sorry about that, it's really just a bunch of mods that that were already out there for the original. After Taylor did his PCBs I just thought I'd put them all together on one schematic. John's board will be rev 1. There's one other change that you've missed, that's the 2u2 cap connected to pin 7 of U1B, I don't think the PCB already includes that.

None of the changes are critical and apart from the new buffers and they can all be added to the original PCBs if you want them, the flashing LED might be a bit tricky.
To be honest I would just build it as rev 1 and then see if you need/want the mods.
The 2u2 is just there to stop a bit of ticking from the LFO that some people reported, I never had a problem with it, so if you don't get any ticking you don't need it.
The 10u cap before the mod depth pot reduces the interaction between the pot setting and the delay time. Basically on the original as you turn the pot up the delay time gets a bit longer, this bothered a few people. Again I'd build it without and see if it bothers you, if it does it's simple enough to add it.
The flashing LED mod (the 10k-50k resistor) is only really worth doing if you also add the modulation on/off switch.

The new buffers reduce the background hiss the pedal has, a few people complained about this and to be fair the original is quite noisy. Most people who have built it seem happy with it though, or if they aren't they haven't told me about it :)
If you do find it too noisy it's pretty easy to build the new buffers on a piece of vero or perf board and add them to the pedal, I don't think you can modify the PCB to include them, but I might be wrong.