Duncan Tone Stack Mod - Bridged T

[WGTP]

I am trying to figure out if I can mod any of the existing tone stacks to work like a Bridged T Notch filter, but have been unsuccessful.  The Fender/Marshal stacks won't work because there is no ground point.  The others I can't figure out how to route things to get the correct combination and flow.  Anyone else figure it out?   Maybe I could request a new one.

[Kleber AG]

OK... let me open it...
ready, select the "James" tonestack, now first
a) turn the input impedance(Zsrc) to around 1K
b) Put the "bass" and "treble" controls at max (100%)
c) Make R6(treb) at least 1M
d) R3 is by default 10k but change it to "1" (1ohm)
e) Now you have R1 and R4 to use for the Twin-T resistors, I use both with 33K
f) Now the caps, make C1 and C4 "1pF", change them respectively from 470pF and 3,3nF both to 1pF
g) Now you have C2 and C3 for the Twin-T caps, I use C2=47nF and C3=1nF

That's it, now you can sub values for the resistors R1 and R4 and for the caps C2 and C3 for trying out different frequencies cut/pass/scoop

I like R1 and R4 both = 33K and C2=47n and C3=1n

***Don't forget to always have R2 and R6 (potentiometers) at full/max 100%

Hope it makes sense and helps...
Kleber AG

[WGTP]

Great/Cool.  I sort of have mixed feelings here.  On one hand I was hoping it would be pronounced impossible, so I would look like I new what I was doing,    on the other, now I can SEE what is going on.       Thanks a bunch, your work is greatly appreciated.  Maybe Mr. Duncan will get a hint.  I will have to try it next.

I have found I like the filter with a .005fuf/.02uf - 10k/22k combo and a .005uf/.01uf - 22k/22k combo.  Smaller notches (I guess I'm not a major notch dude).  I'm still suprised at the smoothness and compression it seems to add, both contributing to a nice, fat, heavy sound.

You all really need to try this if your into modern distortion, it will really do a lot for those FF variants and mutant TS with too much midrange...  

[Kleber AG]

Yeah WG, that's nice if it could help

Have you tried with the program?
Another VERY cool thing is to change R3 to a pot (25K or 50K) on the "James" Tonestack, then you gonna have a level_notch/mid control/scoop/whatever, but that's so cool!!!
Maybe it's better with the values I told you, because it WILL gives a lot more variation through the pot travel... (try it)

Nice!!!!!!!!
Kleber AG

[Gringo]

Another VERY cool thing is to change R3 to a pot (25K or 50K) on the "James" Tonestack

Do you mean in the actual circuit or in the TSC? I'd really like to make some changes to the default tone stacks other than part values.

[Kleber AG]

Sorry, yeah into the actual circuit, but you can simulate that with the tonestack program at the "James" circuit.
I mean you need to keep changing R3's value simulating the variations a real pot would give you, while you keep watching the graphic curve.
For the program try R3 values from 1ohms to 50Kohms.
And for a real circuit try a 25K or 50K pot...

I hope it makes sense, cause it's not easy for me to explain myself in english, sorry... but if needed I can try again

Regards
Kleber

[WGTP]

Yes, I have tried it and it is very nice.  The notches are a little lower in frequency than I projected, but very helpful for SEEing what is going on with the filters.  I'm not sure how it works without a a ground, but seems to give correct result.  By using a pot to different resistors, you can get a different set of curves with the notch growing deeper and going lower, or getting deeper as it goes higher.  Your right you need to start with a big notch, so you can reduce it, for more variation.  

I'm sort of surprised this hasn't been used more commonly.  The Articles at Geo and AMZ are the only ones I'm I'm familiar with.  Your English is fine.  Better than mine and I live here.  Thanks again for figuring that out.  Now to built it into the Middle of a Vulcan.  

[Lonestarjohnny]

Kleber, your English is just fine, I tried the tone stack and Whow :shock: , very nice, lot's of choice's and good adjustability. now to try it with one of my builds.  
Thanks,
JD