[sdiy] Noninverting integrator / 2-opamp Biquad

[jhaible at debitel.net]

Remember the discussion a few days ago?

Now I found that this odd little circuit 
- NIC creates negative reistance to undampen
a passive RC circuit - has been used in the
famous Orban Equalizer 672A.

That's a mix between graphic and parametric EQ:
Parametric, but with small sweep range for each
band. This is more than compensated with the
use of 8 of such parametric bands!

(Absolute) bandwidth can be adjusted independent of
center frequency, and all this with ordinary pots
(no dual pots, as in a 3opamp biquad)
Center tapped pot for gain, but probably just to get
an exact 0dB detent.

www.orban.com  - I think they have a download area.

JH.


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