[sdiy] (oops) EN #76 question

[Tim Ressel]

The PDF was given to me as reference material for a project I was consulting on. The circuit in question is on page 8 of that document btw.

My question was more about how the 8b circuit worked and if there is a mistake or oversight in the operation. A random source that can only hit 8 different levels seems a bit useless no matter how gaussian it is.


 
Tim Ressel
Circuit Abbey
503-750-9331
timr at circuitabbey.com



----- Original Message -----
From: Dave Manley <dlmanley at sonic.net>
To: Tim Ressel <timr at circuitabbey.com>; Neil Johnson <neil.johnson97 at ntlworld.com>; synth-diy at dropmix.xs4all.nl
Cc: 
Sent: Monday, November 26, 2012 5:04 PM
Subject: Re: [sdiy] (oops) EN #76 question

You should ask Bernie.  He may not be too pleased to hear there is a pdf (see his faq for why).  The free stuff is on electronotes.netfirms.com/free.html

Note he did give permission to:

www.synthsource.com/ens76/vco1.html

-Dave

-------- Original Message --------
From: Tim Ressel <timr at circuitabbey.com>
Sent: Mon, Nov 26, 2012 02:52 PM
To: Neil Johnson <neil.johnson97 at ntlworld.com>; synth-diy at dropmix.xs4all.nl
CC: 
Subject: Re: [sdiy] (oops) EN #76 question

>I have a PDF of the page from EN. Is it kosher to post it here?
>
>
>
>
>
>Tim Ressel
>Circuit Abbey
>503-750-9331
>timr at circuitabbey.com
>
>
>
>
>________________________________
>From: Neil Johnson <neil.johnson97 at ntlworld.com>
>To: synth-diy at dropmix.xs4all.nl 
>Sent: Monday, November 26, 2012 11:43 AM
>Subject: Re: [sdiy] (oops) EN #76 question
>
>Tim Ressel wrote:
>> I am looking at Electronotes #76 figures 8a and 8b. 8a shows an 8-bit dac made from discrete binary-weighted resistors. We've all seen this type of dac.
>> 
>> Figure
>>   8b shows a dac that has gaussian distribution. The thing is, this
>> circuit will only produce 8 different levels, as opposed to the 256
>> levels of the 8a circuit. Am I missing something here?
>
>Its the usual trick for generating a sine wave with pseudo better than 8 bits resolution, by sacrificing other waveforms.  You feed in a bit pattern that turns on multiple 'bits', which then sum to give each sample of the sine wave.  So what you're seeing is not a Gaussian distribution but a sine wave.
>
>Neil
>-- Modules and more :: www.cesyg.com
>Homepage :: www.njohnson.co.uk ::
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