Blending Wah Inductors...?

[01downer]

Hi guys
I've had this idea for a few days now about being able to use a blend pot to switch between 2 inductors and have a blend of the 2 as well

Problem is, i have no idea if this is possible along with no idea how i would wire it up. Ive done 2 inductors on a switch before but cant find any wiring diagrams showing a blend pot being used.

I've got a 500k blend pot a red fasel a halo and a gcb95 as the victim

If this mod is possible and someone has a wiring diagram of how to do it i would be extremely grateful for your help!

Thanks everyone

[tubegeek]

Do you have a schematic of what you are trying to modify?

[01downer]

Afraid not. Sorry

Im just curious if its possible to wire up 2 inductors on a gcb95 wah and use the pot to blend the tone of the 2 inductors at once along with fully clockwise inductor A only and counter clockwise inductor B only.

Almost as if they were wired to a 3 way on on on toggle but a blend pot instead of the toggle is what im hoping to accomplish

In my head it seems like it could work somehow but I've been wrong quite a few times so thats why im here looking for help from some more experienced guys


Ive searched wiring diagrams and all i came up with was diagrams on how to do it with spdt on on on toggles. No blend pot diagrams that i could find.
Im hoping someone will be generous enough to post a wiring diagram for me or diect me to a site that has one.... hoping atleast

[PRR]

Any significant resistor in the inductor circuit of a Wah will spoil the effect.

Variable inductors of large value is one of the toughest problems in practical electronics. There's no real good answer. Designers beat all around the bush to find other ways.

The Wah is a variable tuned circuit. The inductor works against a variable capacitor (a real cap, an amplifier, and a gain control).

If you read on Tuned Circuits, you will find a Mass And Spring analogy. The tuned circuit resonates, "bounces", at a specific rate. Just like a car with bad shocks(dampers). Any resistance in the tuned circuit reduces the bounce. Adding your "blend pot" will be like putting good high-friction shock absorbers in the old car. 500K in a typical Wah circuit will be like clamping the bumper to a tree-- it may slide a bit but won't bounce at all.

[01downer]

Oh. Bummer.
Thank you for taking the time to reply though

[tubegeek]

PRR: what do you use as a reference for passive filters? I have the Active Filter Cookbook which is wonderful but I don't really know of a great resource for passive EQ theory.

[Digital Larry]

You could conceivably get more sounds out of two inductors and something like a 4-pole 5-way "super switch" that allows complex pickup wiring combinations.

1) Inductor #1
2) Inductor #2
3) 1 + 2 series in phase
4) 1 + 2 series out of phase
5) 1 + 2 parallel in phase
6) 1 + 2 parallel out of phase

However this most likely does not accomplish the goal of any of these settings 3 - 6 being "between" 1 & 2.  More likely, #1 "large" and #2 "small" in series +/- phase could give (inductance wise):

1) in phase: L1 + L2
2) Out of phase: L1 - L2
3) short across L2: L1

I suggested that L2 be relatively small compared to L1 (total seat of the pants guess = 25%) so that the inductance variations are not too significant.

[01downer]

Thanks for all the info everyone!
The general consensus im getting is that using a blend pot won't work. I will probably hook them up to a dpdt on on on toggle and see what tones it puts out with both 100% active

[electrip]

Put the inductors in series and a potentiometer as a variable resistor shunting one of the inductors.
Not perfect but dc-resistance remains always low.
Log-pot indication.
Not tested in wah but worth a try.

electrip

[01downer]

Thanks man! I will give that a try

[electrip]

Ok,
this one will not blend between a red and a yellow fasel
but between a lower and a higher inductivity.
(between value of the unshunted inductor and sum of inductance of both inductors)

If you have a small audio transformer you can use one winding as the inductor
and connect to the other winding a potentiometer as a resistor.
High resistance means high inductivity - shorted secondary means low inductivity.
Q-factor will be f***ed up for the inbetween values but dc-resistance will be always the same.

Or you could connect a capacitator to the secondary for some 'complex' effects.... 
At least the Q-factor won't be damped.

electrip

[01downer]

Im thinking of removing the q resistor all together and soldering 100k trimpots directly on the legs of the inductors so each one can be individually tweaked

[PRR]

> 1 + 2 series in phase

What is in or out of phase on two separate inductors?

If they are on the same core it makes a big difference.

If they are "apart" it makes no difference.

In radio-work, air-core, coils can be separated and still couple, in or out of phase.

But at audio we get "no" useful inductance unless we use something better than air for the coil. (Exception: low impedance midrange coils like loudspeaker tweeter crossovers- and even then we need a whole pound of copper to get 8 ohms at 2KHz.)

Since our cores conduct flux 100X to 1000X better than air, even if you clamp two inductors together, the difference in or out of phase is negligible.

One, the other, series, parallel.... 4 useful connections of 2 coils.