pt2399 Delay circuit – It works!!!

A couple of days ago, my pt2399 chips came in. Like I stated earlier, I got 10 of the chips for about 11 bucks on ebay. What a great deal!

After getting them I immediately went through the delay schematic that can be found in the datasheet for the pt2399. I wired it all up on the same bread board that had the wah wah circuit on it.

I had to grab a few parts from Rad Shack to get it all put together. One of the main things to think about is the need for only 5 volts. My bread board is wired (right now) for 9 volts. So I got a voltage regulator. Specifically, the 7805 5V voltage regulator from Radio Shack. It worked great. According to my multimeter, it puts out 4.98 volts.

I also couldn’t get a lot of the specific capacitor sizes, so I just used ones that were as close as I could get.

Of course, the first time I wired everything up it didn’t work. I have a tendency to go through it without checking my work for wrong wiring. After an hour or so of wiring and wondering, I put it to bed for the night.

I tried it again the next night and there was some delay. The potentiometers weren’t doing anything, which I thought was very odd. Then, I looked over at my guitar pedal board and saw that I still had my digital delay on. That was what was causing the delay, not the one I had just put together. I was so pissed at myself.

I went through the schematic again and found a ton of errors. All kinds of capacitors and resistors were in the wrong place. Wires were connected to empty rows on the bread board… it was a mess.

Now, she is all cleaned up (so to speak) and running perfectly. Check out the video.

The chip gets a little overloaded when you make the number of repeats too much. The echoes get louder and louder and drown out the original sound. Then it makes a weird noise and doesn’t work quite right until you turn everything off and unplug everything. 20 minutes later she works fine again.

I think I will shrink the size of the potentiometer that controls the number of echoes.

The other potentiometer is perfect. I might try a larger one to see if the delay time can be extended but other than that… it’s AWESOME!!!

Hope you like it and I suggest you try one of your own. It’s lots of fun. I have always wanted a second delay pedal.


9 thoughts on “pt2399 Delay circuit – It works!!!

    • Yeah pretty much…

      I looked at noystoise’s examples in his work… just to see what was really necessary and which capacitors I could change… but pretty much its strait off the data sheet… I think I only mucked with a few capacitor values…

      If I remember right…. I didn’t have all the right cap values so I found the closest ones… and just subbed them in… that worked great.

      It’s freaking amazing how awesome it is to build some delay and have it work… I was so happy when I finished it… and I have been able to use that assembly many times to test different things.

  1. Hy,

    At number 4 of the pt2399 there are two resistors, i assume a potentiometer and a normal resistor. What are these for, and could i use a pot too for the normal resistor? And how should i wire al that?
    Thanks, jonas

  2. Argh… It’s sooo frustrating! I’m trying to let this delay work for two months now, but i can’t get any sound out of it, exept for continuous pops, like pop pop pop pop… But i actually can’t say if it’s the delay making this weird sounds, because i’ve build it into a multi-effect (of which al the other effect work!). Have you any suggestions that could make my delay work? Thanks

  3. Did you try replacing the chip?

    I would also try to get one running independently. that way you can integrate it in and know that it was working when you started. If you wire it all up together then you won’t know where the problem is…

    Did you bread board it???

    The pt2399 can do some funny things… it gets overloaded and then you have to disconnect the power to get it to work again… that happens to mine. The right resistor value on the decay will stop that.

    That brings up another point… maybe you need different potentiometer values to get things working right…

    It’s not always just a science… some times there is an art too it too.

    DON’T GIVE UP!!!

    • Ok it looks like the chip works. I put a preamp in front of the delay to boost the input volume. Now i can hear a little bit of delay, it repeats my guitar just once. So i think now i will just mess a little with the potentiometers to find a good value. But there are still some things i don’t understand: at point 6 of the chip, how should i wire the potentiometers there? And are it two pots or is it one pot and one normal resistor? Thx

      • Were you every able to fix the problem?

        Hope it worked out. Let me know if I can be of any help.


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