Dimension P Chorus

9/29/2014

EDIT 2014-10-20
I added a soundclip.

Here is a PT2399 based chorus by Distorque. I was a bit hesitant about this one because of the PT2399, but it sounds great. Very lush and deep. :) Original thread here.

If anyone wonders, depth lugs 1&2 are supposed to connect from two point on the board. It's not a typo :)

32 Comments

agung setiadi zainal abidin ashole he

10/13/2014 02:43:51 pm

Hy mr fredrik
i was build this chorus too, and its working. But theres noise problem (ticking and hiss). maybe pt2399 problem ?

Fredrik Lyxzén link

10/13/2014 07:45:17 pm

Hallo
Yes, the PT2399 chips are noisy. Some are noisier then others. I had to try a bunch of them to find the less noisy ones. I still have some noise with my build, but it's no problem now unless i'm using it with alot of distortion.

Mictester

4/7/2015 09:18:16 pm

As shown, there are several problems with this circuit:
1. Each PT2399 needs its own 78L05 - this helps to reduce heterodyne whistles as the clocks pass each other.
2. The modulation oscillator should not use 5V for bias - it should be 4.5V - I used two 10k resistors and a 10u filter capacitor. If you use the 5V supply, the oscillator output will be asymmetrical and will "hit the rail" in one direction - leading to ticking.
3. It's worth introducing some pre-emphasis before this circuit, and rolling off the extra treble afterwards - this method (also used in FM broadcasting) will give a significant reduction in noise.
4. It's worth experimenting with the values of the timing resistors. Keep one at 100R, but the other one has interesting sounds at 150R, 180R, 220R and other intermediate values - I used a 100R resistor in series with a 500R pot padded down to 300R.

Fredrik Lyxzén link

4/10/2015 08:20:52 pm

Thanks for bringing these issues to my attention. :)
The schematic was the most recent one I could find, but I guess the inventor gave up on improving on it. Maybe a modified version is called for. I will play around with it when I have time to spare. I didn't have any LFO ticking in my build, but it was quite noisy (why I didn't box it)

Thanks!

Phil Gemmell

2/25/2019 04:47:37 pm

Which pin is the modulation oscillator? Where should 4.5v go?

Phil Gemmell

3/20/2019 04:11:37 pm

Is "hitting the rail" likely to cause oscillation? I'm using separate 78L05s but getting harsh squealing after about 20 seconds of running. Turning off and back on doesn't stop it. I'm going to use an lm317 at 4.5v tonight and see how it performs.

Philip Gemmell

3/23/2019 02:50:03 am

Mictester has excellent advice on this build. I have built one and it runs perfectly and quietly. Using a 78L05 for the 1st PT2399 and an LM317 network producing 4.5v for the 2nd one. The LM317 does get warm so don't bury it in anything.

The voices and dry switch all work. With the voices off it's more of a tremolo wobble but rich chorus with it on.

I look forward to someone designing a triple PT2399 chorus one day.

roseblood11

8/18/2015 06:46:47 pm

This circuit sounds so good that it's really worth to improve it. I built it, but never boxed it up, because I couldn't get rid of the noise. Have you ever tried to include mictesters suggestions? If you could solve the problems, this could even work as a commercial pedal (or at least sell a lot of pcb's...)

Fredrik Lyxzén link

8/20/2015 04:15:07 am

I agree that this would be worth improving using those suggestions to start off with. A dual layer PCB layout with a proper groundplane would probably take care of most of the noise issues alone. But I would feel bad selling PCB's and making money out of someone else's work, even if they gave me their permission. For now I'll stick with just selling PCB's of my own designs.

roseblood11

12/4/2015 02:29:57 pm

This was such a great project, but there never was a "final" version...
In the original thread there is this "best of both" version with two switches and a stereo output. If someone could add all the improvements that mictester suggested and the stereo output buffer and switching scheme that I posted to the thread, this could become the best DIY chorus around. And a lot of people (including Mr "Distorque", I guess) would be very happy to have a pcb for it!

TazFr

5/6/2018 06:14:54 am

Very very great work. Convinced it could be the best DIY lusch chorus (in stereo!) Hope one savior could prototype PCB including best of both world + all improvements... I would for sure be the first one to buy it !

Doxasound link

10/16/2018 08:59:30 pm

Built another one of these and had a lot of oscillation and noise. I followed Mictester's first suggestion and supplied each PT2399 with it's own 78L05 and that alone quieted most of the oscillation. Now I really have to turn my amp unrealistically loud to hear any LFO ticking.

I also made sure to use tested and legitimate pt2399 (from Mammoth Electronics). Cost a pretty penny, but was well worth it! Noise free!

tazidore

10/17/2018 02:23:44 am

Thanks Doxasound, very interesting post. I'll follow your suggestions.
Keep on soldering!

darpi

1/14/2019 02:43:37 am

Hvat with input buffer and poor opamp as NJM2904L, LM358 in LFO

Fredrik Lyxzén link

1/14/2019 02:51:29 am

Sorry, I don't understand your question. If you have any question regarding the design, please ask in the freestompboxes thread. I did not design this effect, I just made the vero layout. Cheers / Fredrik

Phil Gemmell

3/21/2019 04:39:56 pm

Ok. Built and complete. Instead of a 2nd 78L05 I used an LM317 with R1 at 150r and R2 at 390r. This produced 4.5v to power the 2nd PT2399. No ticking, no oscillation, no hissing, just chorus.

timothy

2/27/2020 05:04:39 pm

right now since I don't understand the switches I just have 2 of the wires that are supposed to go to the spdt switches connected and I get a nice vibrato.

Brit

8/22/2020 05:08:09 pm

How did you go about this on vero? Having a hard time adding the lm317 and both r1 and r2. Thank you

Harry link

7/14/2019 06:52:49 am

Hi i built this one but a subtle effect on depth and no response on speed pot... i tried changing pots but nothing happens... by d way does it mean that the two depth labelled in the vero should be connected each other?

timothy

2/26/2020 05:40:25 pm

I have the same exact problem. still trying to figure it out. ill let you know if I do

Phil Gemmell

2/27/2020 12:12:48 am

Hi Tim, depth 1& 2 are linked. Easy to just link it at the pot and run a single wire to the board.

timothy

2/27/2020 04:49:02 pm

thanks for the response. I don't quite understand how to wire the switches. theres only 4 wires total for 2 spdt switches? how does one wire these spdt switches?

Phil Gemmell

2/27/2020 04:58:44 pm

There is a standard numering of switch terminals. Google spdt on on switch pinout and it should explain the numbers.

jyt

2/6/2020 06:22:51 pm

this must be the same one not?
https://www.diystompboxes.com/smfforum/index.php?topic=94435.0

djyt

2/6/2020 06:49:31 pm

Sorry did see the link on the first post, same one. But does anyone have a revise schematic of this

Dylan A Stratman

4/1/2020 10:18:47 pm

Hey there. I just finished this the other day and I am having an issue with the voices switch, where as I’m only getting any chorus/vibrato sounds with it connecting v2-v3. Any ideas?

mictester

7/13/2021 10:10:59 am

I've just noticed - on the Vero layout above, the TL072 pin 8 is not connected to the supply! You've missed a link,

Fredrik Lyxzen

7/15/2021 05:35:10 am

+9V is connected through the 100R resistor

Fredrik Lyxzén link

7/13/2021 12:14:37 pm

+9V is connected through the 100R resistor.

Ted Schoenling

1/21/2022 11:59:58 am

Okay. I built this the way it was laid out and while it worked, there was the clicking and swooshing noise.

I added a 2nd voltage regulator and voltage divider and that did help a little but not enough.

I then got some 'good' PT2399 chips and swaped in and out with the ones I got from Tayda. That did nothing. I also changed the TL072 for a lower power chip, and that did help a little but still not enough.

So I went all out. I built 2 boosters, one treble and one a little more full range. I then built a low pass filter with a cutoff around 1.6KHz. I put the treble boost in front, then on the output I put the low pass filter. this worked but it was quiet so then I put another boost after that and bam, I have a quiet, working circuit. It looks like a hack job but the low pass does work quite well at removing noise.

Ted Schoenling

1/22/2022 08:32:34 am

Didn't like the treble boost in front.. so I used the baxandal layout on this site and THAT did the trick.....

Derek

2/21/2022 01:28:25 pm

Why is there a cut on D-N? The fifth pin on IC1 doesn't appear to go anywhere. I'm guessing part of the original designer's unfinished work?

Dimension P Chorus

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