Echo Base - a new PT2399 delay

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

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Here's something I've been working on for a while, it's a PT2399 based delay called Echo Base. It started out with some ideas for mods for a Rebote, but after playing around for a while I thought I might as well start from scratch and design something new.

The main features are:-
1. It's got an LFO that modulates the delay time for chorus/vibe/tape flutter effects, a bit like a DMM.
2. Shock horror, it's not true bypass, that's because....
3. It can do delay tails, where you bypass it and the delays die away instead of being cut off instantly.

Here's the schematic

The bypass is done using CD4066 switches and works like this. The signal goes through the input buffer which sends the dry signal straight to the output buffer, the signal also goes through the first 4066 switch (A) and into the PT2399. This section is mostly from the appnote on the datasheet with a few values tweaked, but with the output taken from pin 14 like on the Rebote 2.5, doing this taps off just the delayed/wet signal. The wet signal then passes through another 4066 switch (B) and gets mixed with the dry signal via the Level pot.
When the effect is on both of these switches are open. When it's bypassed one of the switches closes depending on the position of the Tails/Boss switch. In Tails mode the input switch (A) is closed, cutting off the signal to the PT2399,  the wet sound then dies out naturally.
In Boss mode the output switch (B) closes so the wet sound is instantly cut off, the input to the PT2399 is still open. This is how Boss pedals work, hence the name.

The modulation is a simple triangle LFO hooked up to a PNP transistor in series with the delay time pot. It took quite a bit of experimenting to get this working nicely but I think it's a neater solution than using a LED/LDR combo.

Here's some sound clips, they're just guitar >> Echo Base >> Condor >> Soundcard.

Slapback Bypassed then effect
Rhythmic repeats Bypassed then effect
Chord stabs showing the longest delay time
Chorus Bypassed then effect
Heavy vibe Bypassed then effect
Slow vibe Bypassed then effect
Pitch bending
Delayed vibes
Example of delay tails This starts with some (bad) distorted lead then the distortion and the delay are turned off and you can hear the echoes dying away behind the clean playing. The switch pop is from the distortion pedal.

Here's a guts shot of the finished pedal, vero layout to follow shortly :)

Thanks go to R.G. and The Tone God for their electronic switching articles and Francisco Peña because if it wasn't for the Rebote I wouldn't have built this.

Enjoy :)


hey that's a great build! Makes me wanna to make one myself.


Nice work. 8)
Thank You!
That's one for the ever expanding "to do" list.
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That looks really nice. The modulation is cool and I really like the idea of it not chopping the tail off the repeats when you bypass.
Does it come with an Ion Cannon? :icon_wink:
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Delay Tails! I've had that idea before, but I didn't know how to do that.  :icon_biggrin:
Now, a feedback loop (both internal and external) in that and it's done. :D


Cheers for the replies.

Quote from: soulsonic on August 27, 2007, 04:54:11 PM
Does it come with an Ion Cannon? :icon_wink:
No Ion Cannon, but I'm glad somebody got the reference :)


What can I say, I'm a child of the 80's.
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Great work Ian, looks superb and a nice clean vero build too :D
Now i need a few chips .......
"Success is the ability to go from one failure to another with no loss of enthusiasm"
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the vibe is even heavier than DMM!!

i did "echo tail" mod on my rebote2 by using a momentary switch
with a effect loop anyone can get the fabulous sound easily

Ed G.


All great sounds and effects!


Vero layout would be great Slacker  :)
Can't wait.
"Why can't I do it like that?"

John Lyons

Great sounding clips and nice work on this one! I dig the modulation addition and the delay trails.
I've always though about incorporating a steep LPF and or HPF to the rebote ala dub style echoplex and space echo sounds.
I'll have to put that on the list of to dos

Thanks for sharing this.

Basic Audio Pedals


Sweet slacker .....:o
Yup a wet only effects loop will do tricks  ;D
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Wow! Ian, that is a great effort. I'll need to build this one.



Very nice!

I'm glad I waited with my Rebote.. Got all the parts lying around allready!



Good work. I tried the LFO with a transistor. Mine didn't work so great, so I switched to and LED/LDR. It sounds like your is working very well. I like the idea of powering the LFO from the 5v supply.

I have been thinking about PT2399 delays a lot lately. A couple questions keep coming up.

First, the PT2399 chip runs off 5V so the signal fed into it should be kept in a range of 0 to 5V. The PT 80 delay uses a NE570 to compand the signal. But the Rebote and others usually use an op-amp with a gain of about 1 as the input buffer. My Rebote sounds pretty good. Is there a chance of clipping? Would it be better to use an input buffer with a gain of something like 1/2 and recover gain at the output buffer?

Second, most of the examples I see use inverting stages for the input and output buffer. An inverting stage at the input is more prone to noise. This is due to the need for large input and feedback resistors. Larger resistors create more noise but are required to keep the input impedance high. Then again my Rebote sounds good. Maybe the metal film resistors produce less noise, or any noise they create adds "mojo" to the sound.


Nice Job Ian, this is very impressive indeed!  8)
Thank you!!


sounds really great.  the vibrato is impressive to say the least... :)