NE570 Attack/Decay??

[Jaicen_solo]

Anybody ever fiddled the attack time on an NE570 compander to produce slow gear style swells, or short decays???
Is it possible, or am I insane?

[oskar]

It's possible indeed. You can reach the vca-part in this chip separately. See Craig Andertons - Rocktave Divider.
I think it would be a better idea to try an OTA though ( LM13700... it's in production ).

skar

[Mark Hammer]

In fact, the NE570 is used in more or less such a manner in the PAiA/Anderton Rocktave octave divider.  The decay is set to be just a bit faster than the attack so that the companding is asymmetrical (That's what D1 does http://hammer.ampage.org/files/rocktave.pdf ).  The result is that the octave portion decays before the fundamental signal gets too weak to provide good tracking, keeping the output signal "neat and tidy".

Can the C(avg) value be tweaked to achieve attack times that feel like "swells"?  I dunno.  My hunch is not enough to make a quick and easy "Slow Gear".  Worth sticking a 47-100uf cap on pins 1 or 16 to find out, though.  Certainly won't blow the chip.

Note that the C(avg) value affects both attack and decay in each 570/571 section.  If you wanted to have a slow attack and quick decay, you'd need to configure one for compression with a slow attack, and the other section for expansion with a fast decay, like the Rocktave.  Really and truly, the NE572 is better suited to this task since attack and decay parameters can be set separately.  Of course finding an NE572 is another matter.

[oldschoolanalog]

http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016+688606+2371775&N=1323038+4294818368+2371775&Ntt=*572*&Ntx=mode%20matchall&Ns=P_SField&Mkw=572&Msb=0&Ntk=Mouser_Wildcards
Top of the list.

[Mark Hammer]

$6.83 in singles?  Sheesh.  And I thought Radio Shack charged too much when they used to carry them for $2.99!

Just note that there is a surface mount and a through-hole version.  Don't get them mixed up if you order one.