SV: Re: [sdiy] CEM3328 seems to only have buffers at the end

[Antti Huovilainen]

On Wed, 22 Feb 2006, karl dalen wrote:

> That picture dosent tell me anything!

The picture should tell you that Moog core clips at roughly 1/4 the signal 
level compared to OTA filter (due to OTA nonlinearities cancelling 
better).
Practical meaning is that if you set up Moog & OTA filter so that core 
sees same signal level, the self oscillation amplitude is 4x for OTA _and 
therefore any clipper in feedback loop affects OTA more than Moog when 
other things are equivalent_.

> Here is something for you to do.
> Draw up the ladder stage in the simu machine,
> add some bias and "unbalance the ladder"
> what do you get.

Somewhat more distortion and more even order harmonics. The general signal 
level isn't really affected (tested with 10mV mismatch). In OTA filter any 
DC offset only affects the DC offset of the output signal for constant 
cutoff.

Now I challenge you to do the same tests without simulation. Oh, and 
you're not allowed to spend more than 15 minutes on it ;) (do you now see 
the point of simulation?)

> Antti, what is it you are trying to prove?

Prove?
That Moog ladder distortion is not due to the input differential pair 
alone (or even mostly - all stages are more or less equivalent).

Antti

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