eq cap switch idea.

[TimWaldvogel]

i am curious about my idea to use a 3 way guitar-like switch to switch in two different caps for tone. one for bass boost. one for bright. and the middle being balanced. any idea how i could make this happen cap value wise? for use with a ROG tube reamer.

[GibsonGM]

Sure, that's not too hard, Tim.  Sort of like the Varitone tone circuit some older guitars had, but they used inductors.

For the Tube Reamer, you'd have to make some choices.   Switch input cap? Output cap? Both?  If you do this, I'd play with output cap first, and let the input remain the same, cutting bass so you don't get a muddy signal...

Or add a real tone control?  <Probably the easiest, IMO.  Something like the original tone control from the Tube Screamer.     .22u is the stock value....you could try switching in parallel, series, or both if you like.  Remember that the frequency you'll end up working with is 1/2piRC.     
Not a bad idea, I may explore this a little more!   

[Mark Hammer]

I would suggest something a little different.  The midscoop filter found on devices like the Shin-Ei FY-2, the Univox Superfuzz, and its many variants (including the Z-Vex Octane), produces the illusion of big bottom and sizzling top by simply attenuating the mids with a 4-component (2 caps, 2 resistors) filter.  Such filtering tends to eat up a bit of signal, but that is easily compensated for by increasing the value of the 51k feedback resistor in the final gain stage of the Reamer.  Here it is.

Lets call the 10k resistor R1, the 15k resistor R2, the .001uf cap C1, and the .1uf cap to ground C2.

The extent of bass boost, or rather bass heard, is going to be a function of R2.  R1 and C2 make up a lowpass filter, and R2 effectively sets the balance between top and bottom paths.  Insert a resistance between C1, and its normal junction with R2 on the bass path, and you shift the treble/bass balance so that the treble recedes.  Leave C1 as is and increase the value of R2, and now the bass recedes.  That can be easily done with a SPDT 3-position on-off-on toggle.  I would recommend using that in tandem with the variable midscoop produced by a variable 2k-5k resistance between C2 and ground.  Lotta flexibility between those two controls.

[TimWaldvogel]

Thank you mark !! I appreciate it. Looks like the photo you put in didn't work though. Can you post a link for me?  Much thanks !!

[PRR]

Looks like the FortuneCity host does not like its files called from other pages.

You can sometimes right-click the placeholder image, get "Properties", grab the URL, and open it directly.

Here's the image, hi-jacked onto another less-fussy server:

[Pakaloabob]

Do I understand this correctly?
The midscoop filter replaces the output cap (100n) on the tube reamer. The center (off) position of the switch would be the circuit as is, with one throw adding a resistor in series with C1, attentuating treble,  and the other throw adding a resistor in series with R2, attentuating bass. In addtion, a 2k-5k pot between C2 and ground would vary the midscoop level, in essence making the bass or treble sound louder, depending on the position of the switch.
n'est-ce pas?