Doubt about article on old module Pluck Follower

[sergiomr706]

Excuse my nerdiness, but I want to add this to a 2399 delay I have,
http://hammer.ampage.org/files/Device1-11.PDF
and well, on page 7, where it says IC2 should be a BIFET op amp, or other op amp with very high input impedance, I d like to hear some suggestions about a useful ic

Thanks a lot

[Rob Strand]

What they are really trying to say is using a JFET input opamp has a low input bias current, so the input bias current won't discharge the cap.   Pretty much any JFET/MOSFET/CMOS input opamp will work.

Actually, I'd have to calculate out how much of a difference that really makes since both IC's  have 1M resistors on the input.  You might get a small DC offset, probably not a big deal.

[tonyharker]

You probably wont find anything better than a CA3140 or a CA3130  BiMOSFET input op amps.

[sergiomr706]

Fast response! Thanks a lot to both of you

[Kipper4]

What's the application for the envelope detector and larger
?
In your pt2339 design.
Lm358 l.p. amps  work well in some cases.

[sergiomr706]

Mt idea is very simple I want it to start hearing ir delaying the notes when I stop playing not having delay if i play a lot of notes.so after using a first envelope extractor, I think that basically I need pick final control voltage output to interact with the pot labelled dry /effects or blend .it's just a deep Blue delay clone

[PRR]

In Anderton's day, opamp inputs often sucked. The TL072 series is *the* obvious choice today. I'd even use it at IC1: the '741 is old and now costly, the '072 is real cheap. Don't worry that you need two '072 to cover three opamps- they are cheap enough to squander.

[Kipper4]

Have you considered a tails mod.
Im sure it could be done (to a point) with and envelope detectror.
If you use a vactrols ldr as part of a voltage divider (Which is essentially what the mix pot is) to cut off the delayed signal.
However it gets tricky when trying to get within a short time frame. Ie enough time to hear the first repeat if your playing a lively piece.
Google up rectifiers (envelope detector)
maybe a  Peak detector.


edit.
oops I forgot this. So we can see what we're working with.

http://3.bp.blogspot.com/-bEMBMvJwA5Y/TwrbbnpmzoI/AAAAAAAAAbw/EQ70PKQOFes/s1600/seaUrchin_Schematic.gif