Broskie tilt control

[stephenl]

http://www.tubecad.com/2013/06/blog0266.htm

I wonder how this would sound in a guitar amp application?

[VacuumVoodoo]

I have implemented this in my Tubewonder amp as tone control on reverb return signal.
The cathode follower as low impedance drive for the feedback network isn't really needed. You can skip it and connect what was CF output coupling cap directly to the anode of the 1st stage. Put that CF at the front of the circuit, it works better with low impedance input drive.
Mr Broskie's circuit tilts the frequency response around 500Hz pivot point, it's the first parameter to tweak.
Also, +-2.5db control range is fine for tuning your listening room depending on whether you have wall to wall carpeting or not. I opted for +-8db for the reverb return. All of it using a 12AX7 220k plate and 2.7k/22uF cathode, 350V supply.
...and that's the amp Nashville producer Ric Web uses most often for recording reverberated guitar.