MOTM

I have an Octave Cat SRM with the SSM2040 filter chip, and a MOTM 440  
filter. I can vouch for the fact that the 440 filter in the 'normal' mode  sounds 
(timbral response) just like the SSM2040 LPF in the Cat. As I use  it, the 440 
has a quieter background, although I don't know if that is  purely due to the 
filters themselves, or possibly the  VCA and other signal paths in the Cat. You 
wouldn't really notice too  much... until you listen to them side by side. I 
also notice when the Cat  breaks into resonance at high Q, the oscillation is  
louder (but the same tone), and is a bit less controllable at the  breakpoint 
than with the 440. The control aspect could be the age of  the synth and the 
use of an old slider for resonance on the Cat vs.  the better quality pot on 
the 440...I don't know. I haven't really  explored if the two react the same to 
overdrive. 
 
The 440 has also has a Bass switch you can flip to 'Enhance'.  This makes the 
low end stay beefed up at higher cutoff and  Q (compared to some loss of bass 
on the 'normal' 2040). Nice improvement,  and you can always switch back to 
the true original response if you want. It's  sort of like the loudness button 
on a stereo receiver.    
 
John Blacet did a module back in the '70's called the 'Phase Filter'. I  
believe it configured the SSM2040 chip into different filter modes. I wonder if  
the MOTM 440 could be modified to do the same?
 
-Karl.
 
In a message dated 6/22/2007 1:08:33 A.M. Eastern Daylight Time,  
djhohum@... writes:

>  This is hands down, my favorite filter. I wonder if the MOTM 440
>  really sounds like the real thing?

I don't know, it would be  interesting to hear from people who have
tried either the MOTM design and  or JHs design next to the real thing.
It's certainly a filter worth  building and if the discrete designs are
good, or perhaps even, perfect to  human ears, then that makes sourcing
a real 2040 less important for diy  efforts.







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