PT2399 DELAY simple 'after chorus'' mod...

[pinkjimiphoton]

tried every permutation in the thread, but got zero chorusing.
it DID make the delay sound a bit thicker, but it also killed the runaway effect of the feedback.
also tried using a 470k fixed resistor and 500k and 1m pots with various caps, same thing. when i disturb the circuit,
it wiggles a little bit, or on really heavy attacks, but that's more like exceeding the power supply demands of the chip than
chorusing.
so, sorry, but for me? didn't work. tried it with three different chips. all reacted the same. 

[John Lyons]

I think it depends on the circuit.
I tried it on a circuit with a delay in series
with a reverb which are both in a feedback
loop. I got no chorusing either.
At very low resistance I got some cool
percussive repeats so I added it as a
sort of "Hard repeat" mode on a switch.
I need to try it on a simpler Rebote type
delay.

[deadastronaut]

had a thought this morning. just curious, anyone tried using the pt2399 onboard op amps for an lfo?

rather than just the usual caps across 9/10...11/12

might be handy...

[bean]

had a thought this morning. just curious, anyone tried using the pt2399 onboard op amps for an lfo?

rather than just the usual caps across 9/10...11/12

might be handy...

There's the One Chip Chorus: https://www.diystompboxes.com/smfforum/index.php?topic=92872.0

Also, I don't think this was mentioned in the thread so far, but if you put an LED from pin8 to ground (parallel to the 100n cap) you can sometimes get it to light up with repeats. Don't remember if there are any caveats with that. But combined with a photocell across the time pot it would make for some fun.

[deadastronaut]

hi brian, cheers man, ill take a look, and try those suggestions....still on breadboard

just been too busy lately to get back on it....

if i added an lfo to pins 9 10 11 12 it would kill the delay time repeats though wouldnt it?

[bean]

hi brian, cheers man, ill take a look, and try those suggestions....still on breadboard

just been too busy lately to get back on it....

if i added an lfo to pins 9 10 11 12 it would kill the delay time repeats though wouldnt it?

Yeah you'd have to add an external mixing stage to the delay output at pin12 then mix the repeats back to the input at pin1 in that case. I think that's the only way to free up LPF2 op-amp for an LFO? Maybe I could modify my Cave Dweller delay along those lines.

[duck_arse]

those opamps do shit inside, internal connections and stuff. the only free free oppie is 13 14. 15 16 as part of an osc might be interesting in that it also feeds stuff to the innards, whether youse likes it or not.

[bean]

I was wrong about the LED thing on pin8. It will light up but it clips the delay badly.

I did throw a new version of the Cave Dweller with Rob's modulation idea on the breadboard and it sounds pretty dang cool! I've got a few cap values to adjust then I'll put up a draft schematic for anyone who wants to give it a try.

[Ripthorn]

The belton brick uses one pt2399 opamp for lfo related stuff. It can be made to work (using the pin 13 and 14 opamp s mentioned above), though I don't recommend using those opamps for mixing signals, as they don't have a lot of grain for gain, being run at 5v and all.

[bean]

I ran out time to do any more on this for a few days, but here's what I came up with. I'm sure it could use tweaking. I recorded a quick sound sample to demonstrate the modulation with different pick attack. I neglected to cover really short delays with the modulation. This is a really nice discovery! Also, don't mean to take over the thread. This just fired up the old squishy brain this morning.

PS I just realized C12 is not on the breadboard. It should go to the input before R1, if used at all (it's not required).
You can also make MOD 1M and then use whatever value you want for R14 for added range.
There's a bit of underlying garbage in the delay so I'll work on dialing that out.


https://soundcloud.com/madbeanpedals/cavedweller2022-test

[culturejam]

This whole thing is awesome. 

[niektb]

Tried clicking your Soundcloud link Bean, but it says 'This track was not found'

[deadastronaut]

yep same here.....

like the idea of the pot brian...nice. as the warble changes with long and shorter delays i found.

[bean]

Tried clicking your Soundcloud link Bean, but it says 'This track was not found'

Huh, not sure why. Here's the link copy from soundcloud (I don't use it often so probably my error):
https://soundcloud.com/madbeanpedals/cavedweller2022-test?utm_source=clipboard&utm_medium=text&utm_campaign=social_sharing

yep same here.....

like the idea of the pot brian...nice. as the warble changes with long and shorter delays i found.

I tried tying the MOD pot to ground to stop the modulation altogether at the min. setting. It works, but the repeats start to duck/distort a bit (I had the resistor and pot reversed so the resistor goes to ground in parallel with pin8). Maybe someone can think of a way to eliminate the switch.

[niektb]

What's D1 for? to raise the voltage a bit?

[bean]

What's D1 for? to raise the voltage a bit?

Yeah it kicks it up to around 5.5-5.6v. I started trying that out with some low parts count delays/choruses thinking it might offer a little extra headroom at the internal op-amps. It's never caused a failure so I tend to put in all PT2399. I' haven't tested to see it shortens the delay time. Maybe that's a benefit with chorus designs. One thing I want to try out is using an LM317 and see what happens at different supply voltages. Just never got around to it.

One other neat little trick is if you put a 22R 1/4W resistor on pin1 then temporarily toggle it to ground, the delay repeats drop pitch steadily  as the current drains. It becomes non-operational after maybe ten seconds but springs back to life once you disconnect the resistor. So a momentary switch is a lot of fun.

[Mark Hammer]

Finally dickering around with a pair of Cavedwellers in series today (the first ones from 2012; I had a few populated boards sitting around).  It is interesting enough as is, getting some of those "dotted eighth" skipping effects.  But tack on the the 470N/470k pair between pins 6 and 8 on the first delay and...oh...my...goodness.  So thick and rich.  I just wanna move in and live there.

[deadastronaut]

Excellent mark, full on lush spaceyness...   

[Locrian99]

Anyone try this in the deep blue delay?   Looks like it should be about the same as the cave dweller...

[deadastronaut]

I cant see why it shouldnt work in any usual pt2399 topology based delay really....

Tack it on and see...