Here's a quick demo with a few different settings. I noticed that the modulation rate pot is only really noticeable until around 12 o'clock. Then the modulation takes a while to come on and may or may not catch the signal, if that makes sense.
alas (and alack) i have been too overwhelmed with the basic demands of life etc to get a bitsbox order in this week, so haven't got a 680n box cap to put this one together this weekend. which i was hoping to. so am kind of bouncing my above question as i'm sick of seeing it on my desk. it's cramping my desk style.
basically, using 2x 330n greenies parallel (660n total) will mean shuffling things around, as a parallel pair take up a lot more board space than a box cap. alternatively i do have a 1u film kicking around that could drop stright in, although that is a third over value. as it goes to ground i'm not sure how critical it is to be bang on 680n or just 'big enough'.
as for other odd things, am going with 33n for the 32n that doesn't exist, and TL072 for the MC32172p because that's what sonus used (and his demo is freakin' boss).
Tabby - I'm no doctor, nor do I really remember where I heard/read this, but I was under the impression that the very general rule of thumb is it's better to go larger rather than smaller when subbing cap values. Someone with more smarts can probably list a dozen reasons why this wouldn't be the case. Like I said, not sure where I got this info, or if I pulled it out of the aether of a fever dream.
Alternately, socket and try both while you patiently wait for the arrival of the 680n cap?
i have acquired that same general feeling re better going over value rather than under when the cap is being used as a battery, to store up a bit of power to smooth out supply spikes and have a little in reserve for headroom and high demand. i think a bit bigger is ok there. but as this is going to ground it’s not being used for battery properties.
as for decoupling caps, again, i think they are better bigger than smaller or they start eating into desirable frequencies. I think this is a decoupling cap of sorts, to trim higher frequencies out of the feedback loop coming from repeat pin 15 of the pt2399 to reduce recycling noise and self-oscillation.
caps for tone stacks I understand to be critical to be spot on (or max +/- 10%) as movement either way again is binning desirable frequencies to ground. which isn't to say you can’t create something 'desirable' in a freaky thin or scoopy way by using wrong values, but ‘desirable’ as in faithful to integrity of the original layout.
so a 'delay feedback loop decoupling filter' (i think, if that’s a thing). but beyond giving it a name I don’t know how to work out what value it needs to be to work. i’m only at that ‘recognition’ stage on the taxonomy of stomp science, ‘application’ al lot higher up.
anyway, rather than risk messing up one of my biggest builds for the sake of a cap, i decided to be strict with myself and leave it alone until i get the specified 680n film box.
and instead of soldering yesterday i spent the day in bed with a couple of freaky fassbinders and my german dictionary. i will learn german if it kills me, which is likely. and I’ve picked up some great chat up lines.
‘wurdest du mit ein kruppel schlafen wollen?’.
btw, as a fellow synthy fan with a taste for the odd, you might like this extract from 46m30s to 47m30s.
Hi Sonus. I am currently building the Echo Dream 2 and am at the stage of fitting pots and switches to the enclosure.
Could you clarify which switch does what in this build please?
Is switch 1, the DPDT, the sine/square wave switch or the wet/dry switch?
Thanks for any clarification you can offer.