Varitone Question

[syddd]

Question around varitones - is there any benefit to having a toggle to select different inductors in the circuit? Or can every tone from toggling to a secondary inductor be achieved by keeping the primary inductor, and changing the capacitor values?

[reTrEaD]

Good questions syddd

You can get the same notch frequencies using different inductor values by selecting a cap value so the LC product is the same. But the 'tone' will be different, because depth of the notch and what happens outside that region will be different.

My opinion is, it probably makes the most sense to evaluate the effect through modeling, use one inductor in the guitar, then select cap values via a switch to select the notch frequency and adjust resistance values via potentiometer(s) to change the depth and shape of the notch.

Here's a post JohnH made in a thread a couple years ago with a little bit of information which applies here.
The Gibson Varitone

[syddd]

May 7, 2018 14:40:43 GMT -5 reTrEaD said:

Good questions syddd

You can get the same notch frequencies using different inductor values by selecting a cap value so the LC product is the same. But the 'tone' will be different, because depth of the notch and what happens outside that region will be different.

My opinion is, it probably makes the most sense to evaluate the effect through modeling, use one inductor in the guitar, then select cap values via a switch to select the notch frequency and adjust resistance values via potentiometer(s) to change the depth and shape of the notch.

Here's a post JohnH made in a thread a couple years ago with a little bit of information which applies here.
The Gibson Varitone

Many thanks! I am considering using toggles to alter both the resistance and inductance to complement a rotary capacitor selector from this.

[b4nj0]

If you use an LM700 series audio output transformer for the inductor (as many eBay Varitone sellers do) you could use the centre tap to do this and would then only need the one inductor.

I like your thinking; although you can hit the same resonant frequency with different combos of L and C, the "Q" of the circuit would change (at least in theory) and it would be interesting to discover how significant that change would present itself at the ears.

e&oe...