Adding a HF filter to Joe’s Vulcan and Tim’s FET Driver Wow!

[will]

Hi,

I added Doug Hammond’s signature 2 stage high frequency filter, that Doug used on the Meteor and on his Highway 89, on the output of Joe Davisson’s Vulcan and Tim Escobedo’s FET Driver circuits.

Wow! It improved the highs of both effects tremendously. The 1st stage of the filter starts rolling off the highs around 6K and the second stage rolls off just above 15K. I am really happy with the sound of both effects.  

Vulcan:

I found that at some drive levels there was a high frequency weird aberration happening. I guess there was too much high frequency harmonic clipping happening for my ears. I tried originally using the treble tone control on my amp it muddied up the sound. This filter seemed to cut the junk out but the great balance remains.

The circuit seems so much more like a good high gain tube amp overdriven. It’s a great powerful sound.
The Vulcan is higher gain type sound, turning down the volume; the sound becomes clearer but still has the high gain tone. The volume seems to operate partly like a blend control blending in the desired degree of clean with the overdriven tone. The nature of the sound seems to largely remain at all drive or guitar volume levels.

FET Driver:

I built Tim’s FET Driver 3 or 4 months ago and really liked it at low gain it has a great tube like sound. At high gain the high frequencies seemed too harsh, “not tube like” with the above HF filter this effect sounds fantastic. It goes from clean to heavily overdriven very naturally, very versatile. The FET Driver has a much greater range of great sound than the Vulcan. Its high gain overdriven sound is not as powerful sounding as the Vulcan but it sounds great.

In comparing the two I do notice how the Vulcan diodes are compressing the signal, where the FET Driver is more dynamic.

I’m really happy with the sound of both of these effects. Really Great stompbox designs. :wink:

Regards,
Will

[Gringo]

Could you please explain what you did with more detail (drawings welcome )?

I'm still tweaking my vulcan, and i'd like to try what you did before boxing it.

Thanks in advance!

[WGTP]

I think I saw a variable version of this in the FAQ's section.  I believe it is a double pole - 12db/oct filter and a dual gang pot can be used for the resistors.  25k to 100k pots should work.