[sdiy] Room 211... Envelope Follower or Pitch to Voltage on a chip?

[harry]

Hi Cynthia....

Pitch to voltage conversion is quite difficult. It might be easy to convert
something like an electric drill or blender, that has a fairly predictable and
repetitive pitch.  Other sounds that are not 'monophonic' are usually impossible

to convert (what is the 'pitch' of a C7 chord...?)

There are two common ways... the tachometer circuit and the ramp/hold circuit.
The tachometer is slow to acquire a pitch, and will track slowly. its fine for a
motor
because the motor can't change speed instantly anyway... and is usually running
for a long time.

The Ramp/Hold will acquire a voltage within two cycles of the incomming
frequency...  but you need to be sure that there are only two zero crosses
per cycle. this is very difficult in real life.

For the "musique concrete" sort of thing your friend is doing... I'd recommend
the Korg MS-20 circuit.  It has a built in trade off for speed of acquisition
and the
output ripple(it is a tach circuit)... and the pulse generation method is VERY
clever
and has a wider range than most tach circuits.

The PV-1  (by Bob Moog - used with permission, me, and distributed by EFM)
is a circuit board that uses the ramp/hold method. It can convert any clean
waveform
by itself...and with some additional circuitry you could do Guitar, Voice, etc.
There
will be a delay of two cycles... for guitar that might be 24ms... a long time
IMHO.

H^) harry

Cynthia Webster wrote:

> Hi All!
>
> I was at this crazy event last night, essentially someone rented out an
> entire motel Lock, Stock & all 30 rooms - upstairs and down, in a balconied
> courtyard surrounding a swimming pool, and had a different artist performing
> their works in each room.  A great Idea actually!
>
> They charged $20 bucks a head for folks to make he rounds and buy drinks and
> hot dogs while viewing lots of crazy art projects over a 24-hour period.
> Quite a scene, as It was certainly "a Happening" and I was somewhat honored
> to help my friend Bob with his feedback piece in room 211...
>
> He had contact mics placed around the room, which fed into his board and
> then on to his Macintosh laptop running Super Collider software -  and then
> out into the room via amplifiers and speakers.  It was a casual and friendly
> clean room that was mostly un-attended.  The message on the door read
> basically.  "Hey, do what you want in here, watch tv, play some records,
> or even take a shower if you like - just know that your sounds are being fed
> into multiple delayed feedback loops and amplified out to the rest of the
> world!
>
> I was soldering some last minute connectors for his project, and showing
> folks what could be done with Train whistles and rubber mallets on flower
> vases filled with contact microphones!  it was interesting to see just
> how many people were attracted to a crate full of vinyl records to muse
> through and play.  Of course the sound from the TV and the turntable were
> seriously altered.  (i.e. Wacked!)  :)
>
> Bob said that he'd like to eliminate the laptop and build a stand alone box
> to do this patch that he has been perfecting lately...
>
> (*this*  was of course music to my ears!) and I pulled-out out my art tablet
> and started to draft out an analog equivolent of what the software was
> doing...
>
> it turned into reams and reams of paper!
>
> What with all of the pre-amps, envelope following, filtering, and granular
> synthesis (LFOs controlling VCA & VCFs chopping), I ultimately concluded
> that what he really needed was four or six ARP 2600's running side by side
> to do the piece!
>
> This all leads me to ask you fellow friends and Do it Yourselfers -
> If anyone makes a combo pre-amp, envelope follower on a Chip kind'a thing?
>
> or I was thinking to use Don Tillman's famous FET preamp
>
> http://www.till.com/articles/GuitarPreamp/index.html
>
> and wonder if there are VCA/Envelope Follower chips, or sub-assemblies
> anywhere?  As the needs of this all in one box - Analog for laptop solution
> are quite complex!
>
> Aside from CEM Curtis and SSM Chips-  what else is (Currently) out there?
>
> The logical next step would be to seek the ultimate Pitch-to-Voltage circuit
> as well.  (I was wondering if anyone has tried using a car tachometer chip
> to do pitch to voltage conversion)?
>
> The main idea here is to make many channels of this patch thing for my
> friend so he can use many microphones - without a room whole full of
> modulars.
>
> Ha!  I feel a bit like like John Henry must've felt against the Iron Horse!
>
> Ideas certainly appreciated by all.
>
> Cynthia

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