[sdiy] Later MS-20 filter with 2164

[Antti Huovilainen]

On Wed, 30 Jun 2010, David G. Dixon wrote:

> I'm not really following you here, as there are no emitter followers in 
> the schematic I'm working off of (unless you are talking about the 
> situation inside the OTAs themselves).

http://www.synthdiy.com/files/2003/KLM-307.gif

The emitter followers I'm referring to are the buffer stages of the 
LM13600 (pins 10/9 and 7/8 in that schematic), which are simple two stage 
emitter followers with the first stage having a current sink load (with 
the current scaled by Ictrl in LM13600 and fixed in LM13700).

>> The two transistor (Q3 & Q4 in my copy of klm-307.gif) discrete VCA is
>> likely to affect the sound, so you'd need to tap the output of the LPF
>> directly for a valid comparison.
> I haven't used any discrete transistors; only 2164s.  And, as mentioned 
> above, I will not be reproducing the output circuitry of KLM-307.

That's what I assumed. I meant that the reference MS-20 should have the 
output tapped directly from filter output instead of regular audio out (as 
MS-20 seems to lack filter output jack).

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova