GRAB AND GOGO: Delay and overdrive from a single PT2399

Stompboxes circuits published in magazines, books or on DIY electronics websites.
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allesz
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Post by allesz »

Hallo, I just completed it yesterday, and it sounds very good (some soundclips coming soon).
It's a very basic PT2399 delay with only time and repeat controls (it does feedback too) and fixed level.
Since I left out the op amp between pins 13 ad 14 I decided to try and make an overdrive out of it; again I only put two controls, gain and volume.

Of course there is space for improvements, but for a very simple pedal that you grab and put on your guitar bag for little jam sessions it's very nice and it gives the basic sounds I just can't leave home without: echo and dirt, id does a nice reverb too.

It works on a single 9V battery for a couple of hours too :shock:
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allesz
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Post by allesz »

Here is the link for the clips: start clean, then overdrive with gain low and volume high.... then higher gain... then I play with the delay:

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Post by frequencycentral »

Great idea! :D

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Post by allesz »

Thank you Grand Master (and inspiration) of perfect perfboards.

The overdrive section is very simple and with a lot of space for change/improvement... I will have to test it with different amps and guitars to decide what I really like.

btw the (bad) recordings are done with my chinese tele, sd broadcaster bridge pickup, going in a vht special 6 head (triode mode, boost off) and in a 1x10 closed back cab.

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Post by storyboardist »

Here's (an attempt) at perf and PCB layouts. The switching kinda threw me, but I think I got it figured out. It's laid out so that you can have a switch for each effect. Let me know if you find any mistakes. Checked it over a few times and I think it's right.

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allesz
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Post by allesz »

Great work my friend! :applause:
Two minor correction:
1: the electro 1uF cap you put on the overdrive out is really just a 1nF ceramic cap that cut some excessive sizzle.
2: delay in and delay out are just in and out for the (always on) buffer: the signal from the imput jack gets switched between overdrive in and (buffer) in. When the signal coming from the input jack goes to overdrive in, overdrive out goes to (buffer) in... so for the overdrive you need at least a dpdt switch.

For the delay a spst switch would be enough... if you don' use status leds of course.

Really nice and compact layout... now I want to make another pedal: the prototype got quite messy...

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Post by storyboardist »

Ok. I think I got it sorted now. Let me know if this is right.

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Post by Nocentelli »

I just started doing a very for this (looks like a lot of fun from not many parts), and I got to the gain control and it looks a bit odd: is the diodes pair always in series with the 220k? I would have thought they wouldn't do much.
vanessa wrote: 20 Aug 2007, 17:51 You can't arrest someone for reverse engineering something.

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Post by allesz »

Great work storyboardist.
Just a note: SW1 is delay out, and SW2 is the output (dry, dirty, and delayed), when SW1 and SW2 are connected you get delay.

Btw, thank you for a perf layout: never understood vero (it's just me, I know).

Hallo Nocentelli, you got it right: the 220K is in series with the gain pot and the diodes; the circuit distorts even without diodes, but the sound has an uneven decay... and diodes makes the sound smoother. With the 220 K resistor, at minimum gain and max volume you get a light volume boost; an overdrive has to work like this to me.

I attach a switching scheme that will clarify the switching scheme :)
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GRAB AND GOGO SWITCH.bmp
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Post by storyboardist »

You're more than welcome on the layout. I've had mixed results with vero as well, so I typically stick to perf and PCB.

Isn't the output (dry, dirty, and delayed) coming off that 100nƒ cap coming off the emitter off Q1? Or is that the buffered out? Sorry for the slow uptake on this one. I haven't messed with buffers before.

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Post by allesz »

Yep: the output is always coming from that 100nF cap. It is not a True Bypass effect (I admit it :oops: ).
If you read the pt2399 experiences tread I started almost three years ago, I came to the conclusion that I don't like true bypass delays; or, at least, I can't make a true bypass delay that sounds good.

The overdrive section comes before the buffer when it'on, just like if it was a completely different effect box.

Your layout made me whant to do another pedal, in a bigger enclosure and, maybe, with an extra fuzz circuit.... look at my terrible job: I screwed the layout and had to add some components on the fly (the switch wiring was also wrong when I took the photo): that 2,2M resistor floating in the air is just embarassing...
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Post by allesz »

Just a little update and report on my build, after some test in the field (aka rehearsals... :wink: ) and mods.

The silicon diodes provide little dirt, so I replaced them with germanium ones and got a little more dirt when you open the gain up; note that, as pointed out by Mr. Nocentelly, with the gain at zero they are not working and the unit gives only a slight, if any, boost.
Speaking of volume and output, the overdrive has actually little boost capability, so maybe it's better (still not tried it) to replace the 10K volume pot with a 100K one.

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