A viable solution[Was]Re: MM5837?

[Grant Richter]

Since you have a microprocessor involved, you could make a device that is 
controllable between randomness (noise) and repetition (pitched).
Electronotes had the pseudo random tone wheel waveform animator,
which used a short shift register as a "capture wheel" to skim off short
sections of the random noise and make them pitched.

Bernie gives a couple of references from the Journal of the Audio
Engineering Society. R. Burhans "Pseudo Noise Timbre Generators" Volume 20
No. 3 page 3 (April 1972) and R. Burhans "Harmonic structure of PN
sequences" (JAES Vol. 20).

Since the microprocessor could have many internal shift registers, you could
even set up multiples for chords and poly tones. The basic idea is to use a
short (8 bit) shift register as a capture wheel and keep inputting a new bit
from the long PSR sequence on some probability basis. The capture wheel will
appear to have a fixed pitch set by the recycle time, but the timbre will
continually morph as the the random bits roll through.

----------
>From: patchell <patchell at silcom.com>
>To: Harry Bissell <harrybissell at prodigy.net>
>Cc: Magnus Danielson <cfmd at swipnet.se>, 8brain at spiritone.com,
synth-diy at node12b53.a2000.nl
>Subject: A viable solution[Was]Re: MM5837?
>Date: Sun, Sep 3, 2000, 3:31 PM
>

>     Here I am listening to my chugga chugga (I found it, didn't even have
> to do so by
> inspection, I just listened to it, it is a whole lot worse than I
> remember), and a good
> solution to this problem is staring me right in the face.
>
>     If you would all please turn to page 147 in the good book
> (Digikey-July-Sept 2000),
> you will notice that the XC9536-15PC44C is only $3.30 in unit quantities.
> It would be
> entirely posible to put a 32 bit shift reg and XOR feedback into one of
> these little
> suckers.  I just have to dig up the article I have stashed somewhere that
> shows which
> cells to tap.  About a half hour at Xilinx Foundation, and I should have a
> hex file.
> (Although, I will not be back at work until this Wedensday).  I would post
> the hex file
> and schematic (and encourage others to post it on their site).
>
>     Anybody interested?
>
>     -Jim
>
> Harry Bissell wrote:
>
>> Likewise I have a schematic for one that I adapted from Popular
> Electronics.... and
>> used
>> in the Prophet V to replace the... (gawdawful) ... chugga chugga unit ! will
send
>> scan to
>> any who requests...
>>
>> H^) harry
>>
>> Magnus Danielson wrote:
>>
>> > From: patchell <patchell at silcom.com>
>> > Subject: Re: MM5837?
>> > Date: Sat, 02 Sep 2000 12:22:18 -0700
>> >
>> > >     All I can say is, good luck.  In one of my home made synths, I am
pretty
>> > > sure I have one of these things.  You might be able to talk me out of it
as a
>> > > last resort (I personally don't really care much for it, you can hear it
>> > > repeat, if you listen really carefully).  These went out of production a
long
>> > > time ago.  Keep me posted if you can't find one.
>> > >
>> > >     -Jim
>> > >
>> > > Romeo Fahl wrote:
>> > >
>> > > > Hello,
>> > > >
>> > > > I'm looking for an MM5837 ("Chugga Chugga") pseudo-random noise IC to
do
>> > > > some experimenting with.  Does anyone have a spare or know of a source
for
>> > > > one?
>> >
>> > Do you really require the MM5837? It is not too complex to cook up a noise
>> > source out of standard CMOS or TTL. If you go to the archives (Oh, I never
>> > thougth I would refer to them!) you will find a thread on the subject, I
recall
>> > being part of it, I even posted a ASCII schematic in there...
>> >
>> > If you really want a a 17 stage noise source it should not be too difficult
to
>> > make an equalent schematic, but a longer shifter is better. A 4006, a XOR
gate
>> > of choice and some clock generator (two of the XOR gates could be used for
>> > that) and you have an equalent.
>> >
>> > The MM5837 is a 17 bit shift register with feedback at the 14th tap. The
MM5837
>> > also has an internal oscillator which changes frequency with the supply
power
>> > (obviously!). Getting something equalent should not be too hard. Actually,
>> > a 17-tap shift register is a bit too short... it will beat too obviously.
>> >
>> > Anyway for some more info, check out:
>> > http://www.vego.nl/8/18/8_18.htm
>> > http://www.io.com/~ritter/NOISE/NOISRC.HTM
>> >
>> > Cheers,
>> > Magnus
>
> --
>  -Jim
> ------------------------------------------------
> * Visit:http://www.silcom.com/~patchell/
> *-----------------------------------------------
> *If you didn't buy a home in Santa Barbara,
> * You didn't pay enough!
> ------------------------------------------------
>
>