Making a generic envelope follower

[R.G.]

OK, that's a 4017 to count cadence, two 4053's to let you have three throws per pole (sample, open, discharge), a 4093 to do misc gateing. Isn't there a single peak detector circuit there to generate the "sample me now" pulse?

[Vsat]

As requested previously, I have the updated CD4053 schematic here....
Now if someone will tell me how to post the schematic to the list, I will do so...
Mike

[puretube]

you gotta upload it to a website of yours, (or photobucket or the like),
and the post the link to that here...
(either link to the URL of that pic,
or insert the URL xxx your url of that link to the pic as an "IMG"

[R.G.]

To post a picture to the forum, first you have to upload it to any web page where it can be browsed. You can't (that I know of) upload it directly to here.

Then to post it, you enter a message and put in the  terms "img" and "/img" around the picture url, but where I have quotes, use the left square bracket "[" and right square bracket "]" to enclose img and /img. As in (img)www.website.com/folder/imagename.gif(/img) but using square brackets [ ] instead of parentheses.

[Vsat]

Thanks R.G. and Puretube...
Let's see if this works:

http://putfile.com/pic.php?pic=11/32315330961.gif&s=x12

(image hosting courtesy of www.putfile.com)

Regards, Mike

[Vsat]

OK... Harry's updated schematic is online now

[Peter Snowberg]

I'm a bit late, but welcome to the forum Harry! Nice to see you here.

The 4017 / 4093 would easily disappear into an Atmel ATtiny12 or an 8 pin PIC. At first I was thinking great, now it's only three chips. A second later the need for a voltage regulator brought it back to four. Oh well, at least it's a total of just 11 pins for the digital section.

Mr Coffee,
I have an RNC1773 and absolutely love the thing. It does indeed use a 68HC705P6A clocked at 4MHz.

I've never looked around the board with a scope as it runs, but it uses a MAX318 along with buffering from a TL074 in what looks like a sample and hold at first glance. I don't see any diodes after the sidechain input so it looks like it does all the peak detection in software. The control voltage for the VCAs is supplied by an 8 bit D/A. I would love to see a schematic, but it looks like it may be a somewhat involved software/hardware hybrid setup.

It has two algorithms to choose from while running, regular and super nice. Super Nice mode is a set of three different algorithms running in series with the output fed to the VCA. You get the performance of three compressors in series, with noise from a single opamp and a THAT Corp. VCA. Very cool design!

[MR COFFEE]

Ooooooooo, this is such a great thread. My FAVORITE subject!!!!!

Many thanks to Harry and Vsat for posting the cool schematic. The CD4093 is there just to give a nice sharp, squared-up quick reset signal for the S & H's, then?

Nice way to get the op amp output node up one diode drop to overcome the Vf on the S & H diodes, Harry.

Just a thought... couldn't we simplify the circuit just a little bit more by bumping the output of the input buffer up another diode drop and replacing the 3 op amp buffer\rectifiers with 3 good-quality pn diodes, as long as the following stage had a fairly high input impedance? The S & H circuits only have to hold up the charge on the .01 uf caps for 15 ms. Diodes don't leak that much, do they?

Hey maybe we can get this thing really small yet. 

[MR COFFEE]

And Peter,
I'd love to hear more about the RNC - I haven't ever had one to study\trace out, but it seems like a fantastic design! They *do* sound really nice according to everybody I know who has played with them.

Hmmm, 3 algorithms in a row... didn't Mark MCQuilken designed this thing? Wonder if he'd join this discussion if we asked nice - anybody here know him?

[TELEFUNKON]

another pitch detector:
http://www.pat2pdf.org/patents/pat4351216.pdf

[MR COFFEE]

Hi TELEFUNKON,

Nice patent circuit to check out, but this thread was on Envelope detectors, not pitch detectors. 

Takes a lot of circuitry to "bust humps" and derive a pitch signal from an electric guitar string.

[TELEFUNKON]

don`t worry, Bart.
early contributors to this thread will welcome that p-file.
it`s a crossover topic.
crosses over into the DSPDIY too.
this thread has touched the pitch detection (aka fundamental extraction) realm
a couple of times.

[TELEFUNKON]

after I just had a phenomenal idea for the perfect env-fol, (whose patentworthiness has yet to be checked...),
maybe it would be interesting to see what Mr. Bissell thinks of :this (older)  quadrature approach...

nice idea! ( 30 years late!   )

now where have I heard THAT "Blackmer" before?