[sdiy] Where is the DIY spirit? was: Filters

[René Schmitz]

Hello everybody,

I'm asking myself if we can't offer better advice to novices as where to 
buy the kits. I mean building a kit is mainly only improving your soldering
skills. 
IMO the challenge in DIY lies somewhere else. Its in understanding how these 
circuits operate, and why they sound like they sound. That means to learn
some 
electronics on your way. The fun when you have reached such a state, is in
being 
able to tailor your synth to your taste, rather then just being able to
pick from 
whats available off the shelf as a kit. 

I'm fearing that on the long run this community is starving, because the
oldhanders merely sell kits and the newbees simply put them together,
without learning how they work. (To say it more drastically: If all the
gurus here only had built kits, this community wouldn't be existant. Ok,
this is a bit exaggerated, but I hope you see my point.)

So much ranting, and now for the questions:

The IMO best sounding four pole filter is the SSM2040, followed by the moog
ladder, both give a classic sound. If I had to choose between one of them
I'd clearly prefer the 2040. 
I'd also prefer having a four pole instead of a two pole filter if I needed
to choose,
although a two-pole state variable has more sonic possibilities, but then I
find myself often only using the lowpass mode anyway.

For VCOs I'm not having much preferences, except that the circuit should be
stable, either thru tempco or heater compensation. And it should have good
tuning precision. There is nothing worse than a VCO that gets flat above a
certain frequency, if you do FM or ringmodulation between two oscillators,
or just run them in unison, it sounds unpleasant to crap. A basic setup
could do with just saw and pulse, but tri and sine are handy too. Much
better if your oscillators can span from LFO-range to the audio range, you
don't need specific LFOs then. For LFO use the circuit really should have
sine and tri. 

For VCAs I'm a fan of the diff-pair VCAs because they have better control
rejection then the VCAs with OTAs, also better noise performance. The
minimoog VCA is such a circuit.

Just a quick rundown, I hope that we can get the discussion into depth on
these issues.

Cheers,
 René


-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159