From gstopp@fibermux.com Thu Dec  7 09:42:47 1995
    7 Dec 95 12:42:42 +0500
    5 Dec 95 19:50:32 +0500
From: gstopp@fibermux.com
Date: Tue, 05 Dec 95 16:35:21 PDT
Encoding: 35 Text
Subject: Re: Linear FM on SEMs?

     Regarding adding linear FM to the SEM VCO - 
     
     Get ready for techno-blab - looks like experimentation would be needed 
     here, as the exponential converter uses the Moog-Hemsath method 
     meaning that the reference amplifier has the (-) input going to ground 
     rather than the (+) input due to the inversion added by the 
     high-frequency track transistor (I'm getting this out of a book). So, 
     the advice would be to take a resistor of about 300K and connect it to 
     either the (+) input or the (-) input of the 741 reference amp (A3 for 
     VCO 1, A8 for VCO 2) and apply the modulating voltage to the other 
     end. If it goes the wrong direction (frequency gets lower as the 
     voltage goes up), try the other input. If the sweep range is too 
     narrow, use less than 300K. If the sweep range is too sensitive, use 
     more than 300K. If none of this works, try something else. If the VCO 
     blows up (which I doubt would happen), don't blame me.
     
     Good luck!
     
     - Gene
     gstopp@fibermux.com


Subject: Linear FM on SEMs?
Author:  MAGER@bitstream.mpls.mn.us at ccrelayout
Date:    12/4/95 7:27 PM
     
1) I'd like to implement linear FM on at least one oscillater 
per SEM.  does the SEM include a log-->linear CV
converter on the way to it's VCOs' CV inputs like many 
other synths, and does anybody have tips for bypassing
it?  I'd like to have CV patch points w/ exp & lin response 
so that I could avoid the frequency shift inherent in 
exponential FM, but still CV the pitch (or 'average pitch') 
around with the min-sequencer/kenton/whatever.