Tone Stack Help

[Schappy]

I am building a Vulcan and want to add a SWTC tone stack.

How do I go about figure out the (starting) values I will need?

[Schappy]

I basically need to learn more about the cutoff frequencies that are desirable.

If anybody can give me some advice Id appreciate it.

[nick d]

Not sure what you mean by SWTC , but have a look at the Tone Stack calculator from DuncanAmps - it has Fender,Marshall,Vox,BMP and several others-I have found it very useful and informative. Hope this is helpfull , good luck with your tweaking!

[amptramp]

You will find the Duncanamps tone stack here:

http://www.duncanamps.com/tsc/index.html

[Schappy]

SWTC- Stupidly Wonderful Tone Control

[nick d]

DOH! Saw this a while ago , seems to be a high-pass filter with a very variable cut-off freq. I would try Mark's suggested values (R=1K , P1=10K , P2=50K , C=18n) then play around with R and C to see (hear!) what happens. As to which frequencies are needed depends on what you're playing (guitar , bass , keyboard, etc.) and what sound you want. Like all good cooks say "Season to taste" !

[liquids]

the SWTC (stupidly wonderful tone control) is an interesting variation on the rat's simple tone control...but keep in mind that the rat tone control is following (being driven by) a low output impedance op amp signal, and then the tone control is followed by a standard voltage-divider volume control.   This arrangement is where the SWTC does it's best work, as that mitigates a lot of the variables and the advantages of it are best utilized.

So really, you've values depend on what it's following and what you want.  Keep in mind that this tone control works by shaving highs.  The amount of cut is constant, but as you turn the control, the FREQUENCY of the cutoff changes.   These are all passive tone controls

This is different than a graphic EQ slider or something like an even-valued BM/BMP (big muff) tone control,  where the frequencies affected by the tone control are more the constant, but the amount of cut is the variable.

Anyhow, it's good to tweak by ear but the RATs tone control values make sense if you are using the same sort of design.  You may want more or less control.

To get a visual or demo what will happen on paper, the Duncan tool won't help you much here.  You probably need spice, though if you have it and art familiar, it would be easy to plug in values and 'see what you're hearing' so to speak.  Otherwise, this calc is more useful than Duncans in this application: http://www.muzique.com/schem/filter.htm.  

Otherwise, trial and error by isolating one variable along the a range of options (such as cap size) via your  breadboard (breadboard!) may be quicker, and more direct.   But if you want an explanation of how the values affect the range of the tone control while you expiriment by ear, that too can be explained, as a helpful starting point for choosing values, though the above linked calc is pretty straightforward.