This is a master volume control module. Designed to fit fender Blues Deluxe / Deville /Hot rod Deluxe/ Deville amp when you find it hard to set a low volume for home use. Will work with any amp lacking a MASTER VOLUME CONTROL. 
This is a Plug-in module which adds a master volume control to amps like the Fender Hot Rod Deluxe and The Fender Blues Deluxe. No modifications to the amp are necessary, the module simply plugs into the top of the amp as shown in the picture. 
Main Functions 
Volume Control for High-Output Amps: The Lion Tamer is particularly useful for amplifiers without a master volume, allowing you to crank the preamp for better tone without disturbing the peace. The lion tamer is mainly for amps with no master volume. It allows you to increase the volume of your preamp section while keeping speaker volumes reasonable. 
Pedal Platform: It works well for those using their amp as a clean pedal platform, ensuring the preamp is pushed without the power amp being too loud. "If you use it mainly as a pedal platform, then you use the amp clean only, never pushing the power amp into breakup." 
Practical Applications 
Home Use: Many users appreciate the Lion Tamer for home practice, allowing them to enjoy their tube amps at lower volumes. "I have one plugged into my Hot Rod Deluxe. Works perfect. 
Live Settings: It can be used in live settings to control stage volume while keeping the desired tone. You can use it to crank the regular volume knob to get natural overdrive, and the Lion Tamer brings down the speaker volume without losing the overdrive or overall tone." 

Bought a few months ago and ended up selling my amp. Works well