[sdiy] OTA performance (was SSM chip reissue)

[Tom Wiltshire]

I've got some evidence this is true. I built an 2164 SVF and swapped the 30/33K input resistors for 15K, thereby doubling the currents. This improved the situation somewhat, but it's only a octave's worth of improvement. But running the filter "hot" helps.

On 26 Apr 2017, at 09:06, Roman Sowa <modular at go2.pl> wrote:

> At low cut off frequency, when integrator currents are really small, Zeners are damping the oscillation, because most of the current is eaten up by the zener, not the cap - at that small current their voltage is way much smaller than, say, at 1mA, the top of VCF frequency.
> 
> Roman
> 
> W dniu 2017-04-26 o 04:11, David G Dixon pisze:
>> 
>> A couple of zeners across the BP cap ensures relatively clean sine waves.
>> However, I still haven't figured out how to get the sine waves to have
>> uniform amplitude at all frequencies.  One would think that the zeners would
>> ensure this, but they don't.  That's why, when I need really clean sine
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