Dimension P - New PT2399 Chorus

[sundgist]

The input of Delay 2 is connected directly to the input instead of after the input capacitor. The quick fix would be to replace the jumper from D20 to K20 with a 0.1uF capacitor.

Input is on (L20) goes via C1 to (K16). There it splits to R4(K15) and jumper(K20)/R7(D18) to the delay inputs.

I'm not sure which side of the pots the layout is supposed to show, but make sure to use pins 2 and 3 on both pots.

Apart from the wiper on pin 2, pot pins are a bit of a guessing game for me. Thanks, I'll update the layout.

@egasimus : Thanks   

[CynicalMan]

Ah, sorry about the first one, I forgot to get the updated pic.

[sundgist]

So I finished building this and it worked.....         at least for a few minutes!  

There was a lot of noise from the output of delay 1. I checked voltages and pins 5,6,7 & 8 were quite different to those of delay 2. Whilst probing around debugging I managed to short something and out came the magic smoke. The regulator got pretty hot, thats had it.

Taking a break before getting back to it. It did sound nice while it lasted...  

This is the biggest problem with a tightly packed vero layout. Debugging is a pain in the butt.

edit: I think I found the culprit causing the noise. Whilst preparing the board I put a cut in the wrong place. I made a mental note at the time that I would need to move c2 and c3 over. I guess my mental notes are of the wipe clean variety!
I noted the current draw from my 9v supply was 70mA so I guess using the TO-92 package regulator would be fine.
Looks like this should work once I swap out the burnt regulator and check if anything else got damaged. Hopefully I can verify this layout pretty soon.

[sundgist]

Vero layout is now verified working.

And very nice it sounds too. Good one CynicalMan. If you've got two amps this does sound really lush in stereo.

TO-92 packaged regulator seems to work fine. Mine is max 140mA. On switching on, the current draw on my 9v supply jumps up to around 200mA before settling rather quickly at 60-70mA. I suppose this would be the power supply caps charging up, I doubt the regulator sees that much current.
I've used a 500k pot for speed, all I had to hand. At it's slowest, without the dry sound, you can't notice any modulation just a detuning effect which is adjustable with the depth pot. This sounds best in stereo.
I've socketed R2. I fancy playing around with a pot in it's place just to see what sounds it can make.

[sundgist]

Been playing with this a bit more.

A 10k pot in series with R2 gives a modulated slapback echo at max and stock chorus at min. There's a nice variety of sounds here with the different switching options.
I wouldn't go any bigger than 10k as noise starts to creep in above that. You could change R2 to 100R and have TZF at the pots min though I did find it gets quite whiney.
I'm keeping the 500k pot for speed. I like the double tracking effect when this is maxed, even more so with a longer delay.

In the end you get:

1 & 2 voice chorus, vibrato, slapback echo and stereo double tracking.

Not a bad little box of tricks.

[roseblood11]

what taper would you recommend for that extra 10k pot? I'm just placing my order...

[sundgist]

A linear pot was all I had and works fine.

[Gordo]

Verified my layout but note if you're using the L78L05 the regulator needs to be spun 180 degrees from how I drew it.  Nice one Cynicalman, I'm going to play around a bit with the delay resistors just because I can't leave well enough alone.  Then again that's what got me here in the first place 

Not my tightest layout but easy to work on.

[CynicalMan]

Glad that people are liking this! I'm waiting on an order from PPP to finish a Tremulus Lune, but once I'm done that I'll start on my build. I'll probably do a modified version of sudgist's layout; the vero board I have from Tayda is only 19 holes tall. And I'll play around with that delay resistor mod. Once I heard about that I started thinking about making some giant Echo Base/Dimension P mutant, but I don't really need that wacky a pedal.   (Although if I did, I might have thrown in a Clari(not) envelope follower too.)

[roseblood11]

How ould the bypass wiring look like for the version that the vero layout is based on?
The bypass signal has to go to both outputs, so I guess it has to be a buffered bypass?

[frequencycentral]

^^^

You're an actress??

[CynicalMan]

It's up to you. If you don't need stereo when bypassed, you could just wire the second output right to the circuit. If you wanted stereo bypass, you could buffer both channels, just buffer the second output, or have both channels connected when bypassed. This last one might cause issues with pedals with low input impedances if you're using it as a splitter, but for the most part it should be fine. If you want to use a 3PDT and an LED, you'll probably have to use a Millennium Bypass so that you can use one of the poles for each output.

Martin, how did you wire the bypass? Also, do you mind if I post your switching scheme on my site?

[sundgist]

Martin, how did you wire the bypass?

I havn't yet.... I don't have any enclosures or footswitches at the moment, but I've been pondering the stereo bypass. I found a switching schem for a 3pdt, which connects both channels in bypass (splitter) and allows the use of a mill bypass for led, either here or at the other forum. Hadn't thought about the need for buffers. I think the only things I would have plugged in after this would be my stereo rackmount effects or direct to mixer both of which have buffered inputs anyway.

Ok, found the thread. http://www.diystompboxes.com/smfforum/index.php?topic=95532.0

Also, do you mind if I post your switching scheme on my site?

Please feel free.

[roseblood11]

I built the "best of both" version, using sundgists veroboard layout. I also did both mods that he suggested (500k speed pot and that extra 10k pot in series with R2).
The circuit works, but it has noise problems. It's interesting that the outputs of both delays have a bit different noises: What comes from delay2 I would describe as "whining", whereas delay 1 produces white noise, but both noise sounds follow the lfo frequency.

- I wonder why the LFO inverter gets its Vref from the 7805. Wouldn't it be better to give it it's own voltage divider or at least share the voltage divider with the other half of the TL072?

- I don't understand why R23 is connected to R3/C6. Why not to R6/C11? Wouldn't that improve the decoupling of both outputs?

- Is it possible that the extra 10k pot in series with R2 produces the noise? (I used quite long wires...)  I connected it between R2 and the PT2399, maybe it would be better to move it to the other side of R2 (= between R2 and AL)?

btw: I made a little extra board with two output buffers and a millenium 2 bypass. I'll post that later.

[CynicalMan]

Where did you get your PT2399s? I've had similar issues with low-quality PT2399s from Tayda, but other vendors might have problems too.

- I wonder why the LFO inverter gets its Vref from the 7805. Wouldn't it be better to give it it's own voltage divider or at least share the voltage divider with the other half of the TL072?

U1a doesn't have a stable reference voltage source. The voltage on its non-inverting input varies quite a bit with the LFO signal because there's no capacitor filtering out the AC. I used the 5V source because it was convenient. The current going into the TL072 will be tiny, it shouldn't affect the power at all.

- I don't understand why R23 is connected to R3/C6. Why not to R6/C11? Wouldn't that improve the decoupling of both outputs?

It could be connected to either, the signal at both should be the same. I don't think that will affect the noise, though.

- Is it possible that the extra 10k pot in series with R2 produces the noise? (I used quite long wires...)  I connected it between R2 and the PT2399, maybe it would be better to move it to the other side of R2 (= between R2 and AL)?

That shouldn't matter either. If you want to check, just put a jumper across the pot and see if that helps, but I doubt it will.

btw: I made a little extra board with two output buffers and a millenium 2 bypass. I'll post that later.

Nice, I'm interested in seeing that. I was about to put Martin's mods on my site, but then I realized that I didn't have a stereo bypass system designed. I was thinking of something Millennium-based too. I still haven't built mine, but I plan to build it sometime in the next couple of months.

[roseblood11]

Still fighting the lfo noise... Maybe  I really have to buy some other PT2399s.

The depth pot makes some crackling noise when it's turned, is that normal?

------------------------------------------------------------------------

This is a little add-on board with stereo output buffer and millenium 2 bypass switching:
I used a TLC2272

[Xavier]

First, thanks Cynicalman for a GREAT project...........I am building this one shortly............

I only have a question about the stere version. SInce i have always used a stereo rig, in my case it's going to be ALWAYS in stereo, ...........will I still have signal through both outputs when the circuit is in bypass mode ? or only when the effect is on ?

[roseblood11]

That depends on the bypass wiring, which isn't included in the schematic at all. If you do it as I suggested directly above your post, you'll always have a signal at both outputs. I know that the layout of the output buffer circuit looks horrible, but it is small: I made it that way to fit between the footswitch/input jack (on the right side of the enclosure) and the two output jacks on the other side - in a 1590B.

[CynicalMan]

Yeah, I haven't really figured out the stereo bypass wiring. I suggested stereo as a mod to the original mono version, but I haven't got around to looking at bypass. I'd suggest looking at roseblood's bypass scheme, as well as the variety of threads that you can find here by searching "stereo bypass". You can either use buffers or use a 4PDT and Millenium Bypass. I was thinking of using the buffered signal at pin 15 of one of the PT2399s, but it has a slight boost so you'd need a voltage divider to bring it down to unity gain.

[GaryB]

Hi,
Lovely job CynicalMan, it seems to be just what I have been looking for.
A couple of possibilities come to mind though.
The LFO may be enhanced if something like the XR2206 function generator is used.
This device gives sine/triangle/square/ramp wave outputs with low distortion and a wide sweep range.
Unfortunately it needs a minimum 10V supply, but still might be food for thought.
Alternatively a small pic could be used as a function generator, the 12F675 or 12F683 comes to mind.
Also do you know about the microchip mcp6001/2/4 op amp?
5V operation, rail to rail input and output, high gain and very quiet.
I have used them successfully in a distortion/overdrive stomp box and they may possibly be better suited for the LFO and inverter than the TL072.
I know that I am entering this discussion late and I hope that these suggestions are not annoying.
Cheers