"Little Angel" - Super Simple PT2399 Mini Chorus

[Thomeeque]

http://dl.dropbox.com/u/967492/Little%20Angel%20Demo.mp3

 Oh, that sounds promissing*! And I'd say that delay time is pretty short actually (just short enough for proper chorus)! Please, measure it if you have a minute.. Thanks a lot! T.

*to be specific: I miss slower speed and at the slowest speed on the demo I'd say modulation sweep is not ideal**..

**EDIT2: Maybe just increasing of the LFO -> V_ref decoupling cap value (10uF on the schemo) would help it.

[Brymus]

Whats your voltage out the 7805 ?
I have everything except that to try this...
Also hows the volume ?
I noticed no volume pot is it more than unity ?

[~arph]

I'm going to try this tonight with my favorite sine LFO..

EDIT: The 7805 puts out 5V

[~arph]

By the way, you do realize a lot of boutique builders will now start modulating pin two right?  

No relation between voltage and delay time by any chance I suppose?

[frequencycentral]

It has more of a vibe feel to it.. come to think of it.. how does it vibe without the clean mixed in?

Wet only, a little latency is discernable when playing: http://dl.dropbox.com/u/967492/Little%20Angel%20Wet%20Only.mp3

Sounds great! Is the sound at 0:11 (the first time the effect is used) at the slowest speed?

Wet/dry mix, slowest speed, maximum depth, though easy to tweak for even slower and deeper: http://dl.dropbox.com/u/967492/Little%20Angel%20Slowest%20Speed.mp3

Whats your voltage out the 7805 ?
I have everything except that to try this...
Also hows the volume ?
I noticed no volume pot is it more than unity ?

Voltage out of 78L05 is er, 5 volts. Unity gain. I tried a mix pot earlier in the experiment but it screwed with the unity, so I dropped it and went for fixed resistors.

By the way, you do realize a lot of boutique builders will now start modulating pin two right?  

They will have to ask my permission first surely?  

[Renegadrian]

Nice clips, Rick!!! I have to try it soon!!! (hopefully in September...)

[Slade]

Genius work, you have just released another simple (beginner) chorus for this world. Simple design and sounds fantastic, almost like if you were young.

[12Bass]

Cool!  I'm also curious to know the delay time.

[slacker]

Sounds good, I'll have to have a play with that. Presumably the modulation still works if you stick a resistor between pin 6 and ground, so this could also be used to modulate any PT2399 based delay.

[mth5044]

You could modulate Vref and delay time 

[tiges_ tendres]

I had gotten a Belton Brick based delay/reverb to sound pseudo chorus-y by starving the voltage.  I didnt investigate further because if you starve it too far, the chip freaks out and makes random, awful noises.  It kind of made it sound like a Deluxe Memory Man.

There is no reason you couldnt do the same thing to those reverb modules, which probably are just a bunch of PT chips in the brick.

[caress]

Sounds good, I'll have to have a play with that. Presumably the modulation still works if you stick a resistor between pin 6 and ground, so this could also be used to modulate any PT2399 based delay.

exactly.  nice to know there's a super simple way to voltage control these...  great job, rick!   

[Mark Hammer]

That is frighteningly good for two chips.

[Hides-His-Eyes]

A new chapter in modulation pedals, I hope

[Thomeeque]

So I'm now waiting for you clever guys out there to suggest any improvements.......

 OK

 

 It's just a quick draft adressing my previous notes mostly, consider at least non-inverting input buffer and "No DC" mod.

 About the LFO buffer - it would be maybe cool to adjust LFO out to work around 2.5V (~PT2399 V_ref), then decoupling 10uF cap (which makes shape of sweep dependant on speed in IMO not very pleasant way) could be removed.

 T.

EDIT: GIF slightly updated (+"Placeholders for.."), you may need to refresh page..

[frequencycentral]

Thank you Tomas! I will try these mods soon. I have already added the 'no DC on output' mod, as well as adding a 100R to ground from pin 6 instead of directly grounding it, on Arnoud's advice. Interesting that you suggest non-inverting input buffer, I was under the impression (perhaps mistakenly?) that the output of the PT is inverted, therefore assumed that the inverting buffer I lifted from the Rebote 2 was appropriate? It's important to be mixing in-phase signals here, so I'll try it and report back. As for the LFO, I'm going to have to experiment some more to get it wobbling either side of 2.5v, but yes it will be worthwhile as the 10uF coupling cap certainly does affect the waveform. I see you added LPF's similar to Rebote, probably a good idea. I am also considering adding a 'bright' pot/cap to ground from pin 14. Maybe I should also try adding the wet/dry blend pot back in now there is no DC there!

[~arph]

I've seen some different cap values for the 9 - 10 and 11 - 12  connections(  datasheet ).
I recall seeing a schematic that had a switchable parallel cap at the pin 9 -10 cap. I believe it was labelled  HP/LP. So that cap supposedly has influence on the bandwith.. I'm curious what different caps do there.

I'm interested in everything pt2399 related as there might be improvements to my 4xpt2399 series delay. (which I still plan to release here)

[Thomeeque]

Thank you Tomas!

 My pleasure!

I will try these mods soon. I have already added the 'no DC on output' mod, as well as adding a 100R to ground from pin 6 instead of directly grounding it, on Arnoud's advice.

 Was there audible difference? Did you measure delay times with 0 and 100R by any chance?

Interesting that you suggest non-inverting input buffer, I was under the impression (perhaps mistakenly?) that the output of the PT is inverted,

 Both in and out LPFs of PT2399 are inverting so at the output you should be back at the same polarity (if delay line itself does not change it of course - you could actually check it as a part of delay time measuring experiment ).

therefore assumed that the inverting buffer I lifted from the Rebote 2 was appropriate? It's important to be mixing in-phase signals here, so I'll try it and report back.

 There should be no difference for effect itself - you take dry and wet path from the same point so phase at this point is not relevant. It can by only important for the "outside world" (rest of you setup) in some special circumstances (like processing signal splited for more amps) that phase of passing dry signal is not inverted.. it's sort of "good practise" I'd say..

 Btw. Rebote 2 inverts phase twice (at input and at output), so it's (-1)*(-1)=+1 again

 Btw2: Electric Mistress does not care

As for the LFO, I'm going to have to experiment some more to get it wobbling either side of 2.5v, but yes it will be worthwhile as the 10uF coupling cap certainly does affect the waveform. I see you added LPF's similar to Rebote, probably a good idea.

 Yes, it is again case where proper filtering may be important for "outside world" in some special circumstances.

 Again, Electric Mistress does not care

I am also considering adding a 'bright' pot/cap to ground from pin 14. Maybe I should also try adding the wet/dry blend pot back in now there is no DC there!

 Why not? Even the "wet/dry blend pot" is one of the features I have found useless on chorus (..and phaser ..and flanger) for me (when it's there I just set it 50:50)..

 T.

[frequencycentral]

.....as well as adding a 100R to ground from pin 6 instead of directly grounding it, on Arnoud's advice.

Was there audible difference? Did you measure delay times with 0 and 100R by any chance?

Non that I could hear. I haven't done any measurements yet........

Maybe I should also try adding the wet/dry blend pot back in now there is no DC there!

Why not? Even the "wet/dry blend pot" is one of the features I have found useless on chorus (..and phaser ..and flanger) for me (when it's there I just set it 50:50)..

I'd agree with you there, I have no use for wet/dry mix pots, and leave them 50/50. But others may find it useful, so there will be extra pads on the PCB for that option.

[cpm]

if only we had a more detailed technical data on the PT2399...