[sdiy] Moog ladder filter transistor pairs matched or not..??

Jean-Pierre Desrochers jpdesroc at oricom.ca
Tue Feb 18 15:12:22 CET 2014

You are probably right Tom,
I remember now reading something like what you just stated..
In fact what I need to know for my future projects
is what are the 'picky' transistors that absolutely need matching..
in that design. I don't care spending some time
on my tranny matching rig to make sure the VCF
works as it's supposed to.


Le 2014-02-18 09:00, Tom Wiltshire a écrit :
> I thought it was the other way around - the top and bottom pairs need
> matching, but the ones in the middle don't matter so much. That's why
> the schematics that use the 3046 use it for those pairs. For example,
> The Elby version of Paul Maddox's Monowave:
> http://www.elby-designs.com/webtek/monowave/MonoWave-V12.PDF
> HTH,
> Tom
> On 18 Feb 2014, at 13:50, Jean-Pierre Desrochers <jpdesroc at oricom.ca> 
> wrote:
>> Hi list,
>> i'm about to build some VCF modules for my DOTCOM synth
>> in the next weeks. I'm gonna use the nice Moog ladder type VCF
>> like this one:
>> http://www.experimentalistsanonymous.com/diy/Schematics/Filters%20Wahs%20and%20VCFs/Minimoog%20ladder%20VCF%202.gif
>> Some DIYers used that Moog design and adapted it to their needs..
>> But when I check the info about the matching or not
>> of some of the ladder transistors, opinions differ from one
>> guy to another.
>> In fact, looking at the transistor ladder there are 5 pairs
>> of transistors stacked on each other. We'll call them
>> row 1 to row 5.
>> Most forums I browsed talk about transistor pairs rows 2,3,4
>> that need to be matched. Pairs on rows 1 and 5 need no matching.
>> But some DIYers say even rows 2,3,4 need not to be matched
>> for the VCF to work correctly..
>> What should I keep as a good info ??
>> JP
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