<HTML>
Hello,
<P>I just wanted to let you know that I have just finished a VCO based
on the ASM-1 VCO.
<P>Instead of using a 3140 in the relaxation oscillator, I used a 3130
as originally proposed in Electronotes (ENS-76, VCO option 1). The 3130
operates on a 0 (pin 4) and +15 V (pin 7) supply. It goes from some mHz
to around 110 kHz with 30 pF as the discharging cap and slightly higher
with a 22 pF cap.
<P>For the FET I've used a 2N4391 and the exponential pair is formed by
a pair of matched 2N3904.
<P>The VCO has Saw and Square outputs as in the ASM-1. For the Triangle
I have used the overdriven transistor configuration. The Sine output is
made with another FET as suggested in the original Electronotes article.
<P>I am now trying to make the linear detuning that Jürgen proposed
for the SEM VCO clone, but I am not quite sure how to implement this in
the ASM-1 (EN) VCO.
<P>As far as I understand the linear detuning is done by introducing a
small constant current _after_ the exponential converter, right? Could
someone please tell me if the follwing circuit (extracted from Jürgens
schematic) will do the linear detuning:
<P><TT> +15V</TT>
<BR><TT> |</TT>
<BR><TT> +----------+--+---------+</TT>
<BR><TT> |
| | |</TT>
<BR><TT> <
| - 150nF |</TT>
<BR><TT> < 1k
| - |</TT>
<BR><TT> | | /
| |</TT>
<BR><TT> +-------|v |
|</TT>
<BR><TT> | |\
| |</TT>
<BR><TT> <
\ | <</TT>
<BR><TT> < 4.7k +---+--vvv---><
47k</TT>
<BR><TT> |
| 10M <</TT>
<BR><TT>
v
|</TT><TT></TT>
<P><TT> gnd to neg.input
gnd</TT>
<BR><TT> of 3130</TT><TT></TT>
<P><TT>transistor is BC560C.</TT><TT></TT>
<P>Thanks for all the feedback regarding the 3130.
<P>Nothing beats plugging in a new circuit and realizing it works!
<P>-Isac</HTML>