[sdiy] Buchla/Bergfotron modifications

[Gergo.Palatinszky at nokia.com]

Hi,

Interesting modifications? 

-> Check the archive about "linear detuning"  - J.H.-knows the best
(but please discuss about it with Juergen beforehand (copyright) ...
Somewhere he mantioned that it shouldn't be Doepferized :O))

Br,
	Pala

>-----Original Message-----
>From: owner-synth-diy at dropmix.xs4all.nl 
>[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of ext 
>Aaron Lanterman
>Sent: 2006. december 5. 7:23
>To: Synth DIY
>Cc: Manu Raghavan
>Subject: [sdiy] Buchla/Bergfotron modifications
>
>
>Another of my students (Manu) is working on building a 
>Buchla-style triangle core VCO.
>
>I did an evil thing on my midterm quiz, which is I gave them the Buchla
>259 exponential converter schematic to analyze - in Buchla's 
>original handwriting. Uhm... this didn't go over so well, and 
>required a lot of during-exam clarification. Not a good idea 
>on my part. I still feel guilty about it.
>
>So, I didn't really want to throw the Buchla 259 schematic at 
>him to work from, lest he immediately try to set it on fire. I 
>suggested he try hacking at the Bergfotron triangle-core (if 
>nothing else since it's a 1 V/oct converter):
>
>http://hem.bredband.net/bersyn/VCO/VCO%20Buchla%20core.gif
>
>Part of the way my final project is structured is that their 
>final design can't be purely an existing design - they must 
>modify it in some at least vaguely interesting way.
>
>Manu has the original Bergotron up on the breadboard. It's not 
>working yet, but I'm sure he'll get it working, right Manu? :)
>
>Anyway... I'm less picky about fancy modifications here, since 
>VCOs are inherently such finniky beasts.
>
>Anyone have a favorite modification the've wanted to try but 
>haven't had time to?
>
>I was thinking of (not sure if any of this would change the 
>performance or
>not)
>
>* Use the allegedly superior LM319 (it's what Paul uses in his 
>VCOs) instead of the LM311.
>
>* Use the higher-input-impedance CA3140 instead of the TL072 
>as the integrating op amp
>
>* Both of the above...
>
>I want to keep the four-BJT-OTA (vs. replacing it with a 
>LM13700 or 3080, as Mark did), since I want to be able to use 
>an NPN pair in the expo converter.
>
>I gave him a CA3083 for the expo converter (Ian often 
>recommends it), and was thinking the spare transistors could 
>be set up as a "heater" as in Q3, Q4, and A2 of Figure 1 of 
>the AN-299 ap note:
>
>http://users.ece.gatech.edu/~lanterma/sdiy/datasheets/opamp/AN-299.pdf
>
>Any other assorted ideas of easy but interesting modifications?
>
>- Aaron
>
>P.S. That CA3083 - I remember Harry, I think, telling me to 
>tell students put the substrate pin the negative rail, or the 
>transistors would act weird - am I remembering that right
>
>P.P.S. I love my job!
>
>---------------------------------------------------------------
>--------------
>
>Dr. Aaron Lanterman, Asst. Prof.
>and Demetrius T. Paris Junior Prof.    Voice:  404-385-2548
>College of Electrical and Comp. Eng.   Fax:    404-894-8363
>Georgia Institute of Technology        E-mail: lanterma at ece.gatech.edu
>Mail Code 0250                         Web:    
>users.ece.gatech.edu/~lanterma
>Atlanta, GA 30332                      Office: Centergy 5212
>
>
>
>