Here is a Stereo Tube Tone Control Kit that is easy to build, and is just fun!  The Tube Tone Control utilizes a 5670 triode.  TheTone Control is compatible with all "L" Series Amplifiers, it gets its B+ and filament voltage from the Amplifier board and can give a cut or boost of greater than 20 db. One control adjusts the bass for both channels and the other control adjusts the treble also for both channels

The TL Stereo Tube Tone Control comes in kit form (K-TL).  The kit comes complete with all the resistors, capacitors, tube, circuit board, and necessary hardware for mounting on a "bread board" provided (which is compatible with the amp you purchase or have previously purchased).

NOTE:  The Preamplifier and Tone Control kits cannot be used together as they both have gain.

Model TL Stereo Tube Tone Control

Model TL
    Page Updated August 2015

   Input Impedance = 100k ohms
   Frequency Response = 20 to 20,000 Hz
   Signal Input = From Jumpers to Amplifier PC Board
   Overall gain (pots at 50%) = 10 to 30 db - set by a resistor
   Two channel  

CautionThese amplifiers may be operated as supplied, however voltages in excess of 240 volts are present on the board and the tubes get very hot. It is advised that the amplifier be mounted in a well-ventilated metal enclosure to reduce the potential of  fire or shock.
"L" Series
8 Watt Stereo Amp with Tone Control
   If ordering separately specify which kit you already have, so we
   can furnish the correct mounting board.