question about gyrator eqs on main page

[Sensei Tim]

quick question on the gyrator eq layouts on the main page:



if i only wanted 3 bands, can i leave band D disconnected (i.e. no pot)?

[Neil mcNasty]

Yes! I think that should do it...

But even better:
Leave out (or remove) R1 D, R2 D, C1 D and C2 D (keep the link!)
If you then also connect the (now) unused pin-5 to Ground, you prevent that op-amp section from doing weird stuff , like starting to oscillate by it self...

Here's a nice trick/mod that I often do with Parametric EQs, and can also be done with this:
I design it/strip it down to one op-amp section/band, and then I add the components that sets the frequencies (in this case: only R2, since the rest has the same value all over) to a rotary switch that enables me to switch to the frequency that I need for the occasion.
That way I cut down on the size and complexity of the circuit + there is less circuitry to pass trough, which results in less stuff that can affect the signal.
If i need more bands, I just add/insert another section.
This is specially handy when building rack modules for the studio, but works very well for pedals as well, since you can cut down the size and number of pots quite a bit...

[Sensei Tim]

awesome!  thanks for the tips!

I have a cool idea in mind that i hope will materialize in the next month or so. stay tuned ;)

[Sensei Tim]

So I built this up omitting all of the components for position D and I’m getting a very low output vs the input signal.  I’m wondering if grounding pin 5 will help.