My sharkfin build works great and is a lot of fun to play.
However quite often it looses it's randomness over time (e.g. after being engaged for 1 or 10 minutes, that's also random :o) and stabilizes on a fix melodic pattern. Going back to a random behavior can be achieved easily by either re-engaging the pedal or slightly moving the speed pot. So there's a work around. Furthermore to me there seems to be no dependency to any of the tuning settings...
Any idea on how I could mod the pedal so that it permanently stays in a random state?
Ah, the cursed drift. All of the F/SH I've built present this behaviour to some degree. The only solution that has satisfied me is the stomplfo chip from electric druid. The random wave makes for a rock solid and truly random sample hold with no drift or patterning.
Thanks! Does it replace any of the existing chips?
No, unfortunately. The circuit needs to be designed for the chip. The electric druid filterfx project uses the chip to great effect with a Sample Hold and many more waveforms
what a pity :'(
http://me.aquataur.guru/musicstuff/fsh-1.html
aquataur suggests using the b/e junction of the noise transistor (i.e. base to -9v and emitter connected to the opamp) and leaving the collector open. this is a change from the original fsh-1 arrangement, and I can attest that it seems to be a more reliable way to get random blipping from pretty much any old transistor. when I tried out the original arrangement, I had to try out quite a few different types before I got one that was reliably random.
Well, let me translate that for not-so-well-educated people like me.
I "simply" have to twist two legs of the transistor Q4 as marked in the attachment (yellow arrow, lower left corner), right? Whereas I do not have to but anything into the middle hole...
Quote from: fritz on December 10, 2021, 09:20:10 PM
Well, let me translate that for not-so-well-educated people like me.
I "simply" have to twist two legs of the transistor Q4 as marked in the attachment (yellow arrow, lower left corner), right? Whereas I do not have to but anything into the middle hole...
This is exactly right. See my post here:
https://www.madbeanpedals.com/forum/index.php?topic=29884.msg289196#msg289196 (https://www.madbeanpedals.com/forum/index.php?topic=29884.msg289196#msg289196)
thanks. i'll try it today...
... and it works! great!!!
i have the impression, that the type of randomness also changed a little bit. the former one quite often had a sort of "dotted note" aroma. but maybe it's just a matter of tuning...
nevertheless no steady pattern any more or at least only for a very short period of time.