Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!coherent!dplatt
From: dplatt@coherent.com (Dave Platt)
Newsgroups: comp.sys.mac.hardware
Subject: Re: SID Board: UPDATE!!!
Message-ID: <55852@coherent.coherent.com>
Date: 4 May 90 19:58:59 GMT
References: <8223@rice-chex.ai.mit.edu>
Reply-To: dplatt@coherent.com (Dave Platt)
Organization: Coherent Thought Inc., Palo Alto CA
Lines: 29

In article <8223@rice-chex.ai.mit.edu> mikec@rice-chex.ai.mit.edu (Mike E. Ciholas) writes:

> The difference in frequency between 'C' and 'C#' (sharp) is about 5.5%.  If
> I went with the first circuit, could you hear the 1/38th interval?

I certainly couldn't, I would think.

> I may be possible to "pull" the resonator frequency slightly.  I'll see if I
> can find a way to do this without an adjustment (it is usually done with
> some sort of trimmer capacitor).

Maybe the board could have a provision for a trim-cap, which people
could include or omit at their own choice?

> My personnal favorite is #1.  People who have already bought parts can still
> use it, the freq difference is minimal, and it is cheap.

I like approach #1 for another reason... it has a low fundamental
frequency.  This may make it easier to keep the SID from radiating EMI
which would interfere with radio/TV reception.  Using a higher-frequency
resonator or crystal (e.g. approach 4 or 3) would raise the relative
level of the higher-frequency overtones, and might make it harder to
shield the SID to meet the FCC Class B emission limits.

-- 
Dave Platt                                             VOICE: (415) 493-8805
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