I see a lot about the Tone TwEQ being inserted into circuits but not so much the Sonic Tonic. After building a couple Sonic Tonics for myself and my father, I was impressed with its transparency. Settling on the Blues Buster, I decided to take the transparency a set further by pairing it with a Sonic Tonic and inserting it through the tone control on the former. Though simple, it is a blast to play.
Fit into a 125B, I figured out after populating I could have fit this into a 1590 by stacking the boards on top of on another and soldering the electrolytic caps from the bottom of one. Oh well!