Dimension P - New PT2399 Chorus

[nocentelli]

The 2206 seems to work on 9v in the catalinbread pareidolia - maybe at reduced performance as it's only producing a single simple waveform?

[roseblood11]

I still can't get rid of the background noise. There's too much constant hiss and noise that changes with the lfo.

What I did:
-tried more than 25 different PT2399 from 4 different suppliers
-added an extra voltage divider (from 9V source) for the LFO inverter (to decouple it from the 5V supply rail)
-tried different 5V regulators.

What else could I do?
-Maybe use better parts for C16 and C19? (I used cheap parts from tayda for everything)
-Increase the values of C18 and C20?
-Add a 100R resistor before the 7805?
-use shielded wire for the pots (but the noise doesn't change if I move the wires)?

I still don't understand, how the noise gets into the audio signal...

I built the "best of both" version using sundgist's vero layout and added two output buffers, wired as shown above (where I posted the vero layout of the buffer).

[samhay]

I also built the 'best of both' version recently using sundgist's vero layout. Thanks CynicalMan and sundgist - nice job.
It sounds good - very lush - and there are no major noise issues (for a PT2399 build). I added a switchable 50k delay pot to the 1st delay chip, which adds yet another dimension (pun intended). I also added a mono A/B output selector switch and the only issue I have with it is that there are too many options available - I don't do too well with making choices.
roseblood11: My version is true bypass - mono in/stereo out with a Millennium bypass using a 3pdt. Have you tried removing the output buffers?

[roseblood11]

Have you tried removing the output buffers?

No, but how should they cause this noise? If the lfo noise would find its way into the buffers via the supply rail, it would be audible in bypass mode, which is not the case.

[samhay]

Ah sorry, I missed the fact that the noise changes with the lfo.
I am using a 78L05 regulator (it doesn't get very hot), as was Gordo I think. The filtering may be a little different for a 78L05 vs 7805, but the caps seem oversize anyway. I guess you have tried a few different op amps?

[bluebunny]

Just built mine (see Pictures thread), and it sounds great.  I've gone for the modded v1.1 circuit, with switches for dry on/off and 1/2 voices.

Thanks Alex!

[axelrod]

 Nice sounding chorus , but I have a fair amount of hiss and LFO noise . I would give up features for less noise if possible . I used the best of both vero . How much noise is normal for a PT2399 ?
Thanks

[samhay]

The PT2399 gets progressively noisier the longer the delay time. In this circuit, it shouldn't be a problem. Seeing as roseblood11 has had problems too, it would seem that there is something going on though.

[axelrod]

So far I played with different power supplies ,PT2399's , some TL072's , replaced the 78L05 for a 7805 and added a voltage divider for pin 5 of the TL072 . A lot of hiss is gone  but the chewing of the LFO is still present . I'm thinking more ,better filtering but don't really know ...

[chemosis]

noob question. how does one wire the switches since theres only 4 wires for the 2 spdt switches?

[chemosis]

if they were spst switches then id understand but since there spdt switches I don't understand because that would be 4 wires for 6 terminals

[jpalmer5948@gmail.com]

there are many very good diagrams showing 3pdt or dpdt switches...look at guitar pcb, they have alot of good info in their instructables...as well as circuit parallels and series/mods...

[paderuski]

I made the mono version 1.1 with the two switches for voicing and dry control. No noise issues to note but I was wondering if there was a simple way to increase the delay time without impacting on the performance of the circuit? I would assume its to do with the delay resistors and changing the values a bit. I wanna achieve more of an echo-like effect or get more voices on there somehow. However, more voices probably requires more PT2399s which might be a hassle on the veroboard circuit I already made. 

Thanks very much for the circuit diagram, it made things an awful lot easier for me.

[John Lyons]

Anyone have the Schematic(s) for this?

[Ben N]

Anyone have the Schematic(s) for this?

There are live links for schem, layout on p. 3 of the thread. Cheers, John!

[John Lyons]

Oh,ok. I glossed over those. Thanks.

[bluebunny]

In case you just need some images, here are the originals from my stash:

v1.0



v1.1



v1.1 stereo



v1.1 modded



^^ I've built this last one a number of times.

[Ben N]

I don't know if this is really the place to mention this, but asbestosaurus at the "other" forum just posted a simple chorus design using the Mitsubishi M65850P, an out-of-production but still available  cheap, digital delay chip with 15-200ms delay intended for karaoke machines--not much good for an echo, but maybe ideal for ADT/chorus/vibrato/reverb with that super-short low-end range. Might make for some excellent possibilities.

[John Lyons]

Thanks for posting those Schematics Marc!
I'll check that project out Ben.

[bms19]

anyone kept a schematic, both links to them are dead...
Cheers
Benoit