DIY Q-Filter

[idsnowdog]

Today I built a Q-Filter and it does work! I had been reading about the Gibson Varitone and the Bill Lawrence Q-filter and I saw a number of DIY diagrams, so I gave it a try. Both circuits are some kind of variable choke that changes tone when the pot is turned.

The DIY schematics called for a 1.5 henries inductor, 5k resistor and a .02 capacitor. Since I didn't have the 1.5 henries inductor I used a small audio transformer from an old PCI modem card. I used the transformer since I read that a person could use whatever small value audio transformer they like and achieve largely the same results. I'm not sure what the value of the transformer I used is?

The effect is very subtle, but I do notice a difference. As I turn the pot, I can hear the bass and midrange decrease and the resonant peak of the tone shift towards the treble range. I haven't tried a Varitone or Bill Lawrence's Q-filter, so I don't know how close this is to either of them? I think I will order a 1.5 henries inductor to see if there's much of a difference.

Has anyone else tried building one of these? I would like to have a larger tone shift, so hopefully Artietoo will read this and tell me what other value components I can try.

Bill Lawrence Q-Filter installation help - The Gear Page
http://music-electronics-forum.com/t13641/

 

[Jessie's ghost]

Re: DIY Q-Filter

You would mount this in the guitar, then, or in a pedal?

 

[idsnowdog]

Re: DIY Q-Filter

I'm thinking of putting it in my strat's instead of a tone pot. I want to play with component values first. Right now I have it as an external unit that I can aligator clip to the input lug of a volume control.


*edit*
I bridged the other side of the transformer and the effect is more pronounced now. The bridge is marked by the red lines.

 

[TheLivingDead]

Re: DIY Q-Filter

Nice!

 

[Jessie's ghost]

Re: DIY Q-Filter

*edit*
I bridged the other side of the transformer and the effect is more pronounced now. The bridge is marked by the red lines.

I bet you could change the sound by different amounts by bridging it with different resistor values.

 

[hamerfan]

Re: DIY Q-Filter

I have a Bill Lawrence OBL Q-Filter lying around.
Having used with different pups i would say, it sounds a lot like parallel wiring of the coils with a humbucker. With a JB i had the chance to you use it with a DPDT switch.
After that i used it in a Les Paul in the neck employing the useles Tone Pot.

 

[idsnowdog]

Re: DIY Q-Filter

Today I built a low-cut circuit and together with the mid-cut circuit it really brightens a signal. What is interesting is when I cut midrange and bass the tone becomes bright and super tight. Also it is interesting when I cut the bass but leave the midrange alone. Of the two circuits the bass-cut is the most effective and the mid-cut circuit becomes more noticeable when used together with the bass-cut. I would still like to tweak the mid-cut circuit to create a more effective circuit. I'm thinking I would like to integrate the two circuits into one by using a concentric pot.

 

[Boppy]

Re: DIY Q-Filter

Interesting. I've played ES-345s with the Varitone rotary pot. I've always wondered what they would sound like with a Strat or a Les Paul. Let us know, SnowDog, and by the way, thanks for all the alluring titty-girls in your avatars

 

[idsnowdog]

Re: DIY Q-Filter

Interesting. I've played ES-345s with the Varitone rotary pot. I've always wondered what they would sound like with a Strat or a Les Paul. Let us know, SnowDog, and by the way, thanks for all the alluring titty-girls in your avatars

The varitone on the 335 is more effective than what I am currently experimenting with. The Problem that I have is I don't know what to do to modify these circuits to make them more effective, so I am feeling my way into them by trial and error. The frequency bands effected are narrower than expected and their center aren't what I expected.