[sdiy] Digital noise generation

[Fredrik Carlqvist]

You can always experiment with different polynomials. Is your polynomial
stage maximized (i.e. an M-sequence)? Each register length has many
polynomials with different properties. I use a 23-bit register with two taps
that is maximized and it has no obvious "snaps". With a longer register, the
snaps will be sparser. But if you're not stage maximized, snaps may come
more often.

There is a good discussion of this at
http://www.newwaveinstruments.com/resources/articles/m_sequence_linear_feedb
ack_shift_register_lfsr.htm

At the bottom of the page there is a complete list of M-sequences up to N=24
and selected M-sequences for larger registers.

Hope this helps.


Fredrik C



-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Antti Huovilainen
Sent: den 8 mars 2005 17:53
To: Magnus Danielson
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Digital noise generation

On Tue, 8 Mar 2005, Magnus Danielson wrote:

> I assume you meant 200 kHz to 1 MHz.

Yes.

> What polynomials did you use?
> If you dig in the Synth-DIY archive I published a list up to length of 64.

I tried both N = 23, M = 18 and N = 31, M = 28. Both suffered from the 
same problem. Strangely, at least N = 23 case sounded okish if FSR was 
clocked at 44khz.

Repeat time was not a problem for either as I only listened for a few 
seconds, which was enough to convince me that the result was intolerable.

> Did you use a parallelized version?
> I can help you with that if you need.

No. What's the difference to normal LFSR?

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova

Ps. What's the url to the archive?