[sdiy] Discrete opamps vs IC's opamp in Moog 904x designs cloning..

Jean-Pierre Desrochers jpdesroc at oricom.ca
Mon Jun 2 16:06:33 CEST 2014

I'm in the process of cloning a Moog 904B module
with its original circuitry.
The only thing I would change are the followings:

Both opamps for CV mixing and stages freq cutoff originaly made of 
parts and transistors..
I heard the MOS-LAB, in their 904B clones used
2 separate 741 opamps to replace the Q1,2,3,4,5 and Q6,7,8,9,10 

I think any single opamps could be used as far as I
use the same feedback resistors, trimmers and surrounding parts..
741 seam a bit old to use in new made designs..
I was thinking of using 2 x TL071, one TL072 or something like that.
What about it ?

Second question:
I'd also put buffers for both input and output of this filter
still using TL07x opamps. I'm hesitating in using 2 separate TL071
or only one TL072. I'm just curious about any
possibilities of 'crosstalk' between both opamp parts
that could cause oscillations easily..
Maybe 2 separate TL071 would be the best or it doesn't
matter in this type of design..(??)


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