Conceptual Help on Swell Circuit Blocks

[turdadactyl]

Can someone point me in the right direction on the concepts behind a swell effect?  Is this simply a matter of slowly discharging a cap?  Is it more like a compressor circuit with a really fast attack and slow release?  Looking for a jumping off point to go start learning.  Thanks!

[blackieNYC]

Much like a gate, input may be split to a voltage controlled amplifier, and a DC converter - which will then be a control voltage to tell the VCA to turn on or off.  Or in this case, how fast to turn on and off. See the Gator at guassmarkov.net
http://gaussmarkov.net/wordpress/circuits/gator-clone/

[Kipper4]

It's a tough gig.
Getting the raise in volume, the decay and trying to ensure the gate is shut when you play another note/chord.
Here's a quick demo of what I managed to do.


Cant wait to see what comes up.

[turdadactyl]

Sweet, Kipper!  That's exactly what I'm going for...but I'm debating what else to pair it with, like a fuzz perhaps.  Where did you get started with this?

[turdadactyl]

Much like a gate, input may be split to a voltage controlled amplifier, and a DC converter - which will then be a control voltage to tell the VCA to turn on or off.  Or in this case, how fast to turn on and off. See the Gator at guassmarkov.net
http://gaussmarkov.net/wordpress/circuits/gator-clone/

Thanks.  I went and checked out the documentation on the original PAiA Gator.  Definitely looks like the attack/delay pot is controlling the charge time of a cap, which thereby affects the attack (in a true ADSR sense).

http://paia.com/manuals/docs/5730pages_200.pdf

[Kipper4]

Here's  a messy thread.

http://www.diystompboxes.com/smfforum/index.php?topic=113273.20

[idiot savant]

The gator circuit is pretty interesting since it uses the V- pin as the control input from the envelope follower. I'm not really sure what the benefit of doing it that way is.

The problem I've always have with envelope follower style swell pedals is the extreme discipline you need in your pick attack to get them to swell when you want. I've made a few circuits with a manually triggered envelope generator that I found was much easier to control. Take a look at the DOD FX-15 for an ideas on that approach.

Here's a couple I've done:

one with an analog envelope generator:


and another with a digital envelope generator:

[idiot savant]

oh, and just for fun, here's a follower style gate using a tube for the control element.




cheers!

[Groovenut]

Here's another take on the effect from a slightly different perspective (well... mine  )

http://www.diystompboxes.com/smfforum/index.php?topic=113778.msg1054098#msg1054098

[Eb7+9]

Can someone point me in the right direction on the concepts behind a swell effect?  ... Looking for a jumping off point to go start learning...

the most natural kind of "fade" response is exponential // almost begging for an R-C circuit here ... wherein a switching block (auto version) or physical switch (foot triggered) is used to short the cap back to starting position ... a normally closed soft-switch works well in the foot triggered version ... CV can go up or down from starting position, depends on style of interface circuitry  following it ... several ways to convert this CV to voltage gain function, optically or otherwise ... one way would be to buffer the CV and use that to shut off or turn on the LED in an opto-isolator, etc ... I've tried it, and it's tricky to get right ... it's much easier going the OTA route ... all  you need then is a CV to current converter, again the simplest is probably a linearized differential pair ... OTA gain is proportional to bias current which is, in turn, made isomorphic to CV thru the linearity of the CV-to-Ibias converter  ... add a volume control for sake of flexibility ... make R variable in the RC circuit and you have yourself a SPEED control ... done