Blacktop Fuzz – Vintage Silicon Muscle. This Keeley machine is a relatively straight-ahead fuzz. The circuit features a battery sag switch. The magic is in the transistors.The voltage sag makes a difference. It makes it spongy, softer, more pleasant on the ear. So Keeley sag the heck out of the supply voltage and give you a nice Yin/Yang thang. You chose, saggy or tight. Soft or bold. For Fuzz fans, this is where Eric Johnson meets Joe Bonamassa. Tuned in-between the two. You never have to worry about it going dead on you when it hits about 90 degrees. Toss it in your gig bag and know that you have that sound, just right, any time. That border between germanium and modern silicon, the Vintage Fairchild 2N3565. The Keeley Blacktop Fuzz – Vintage Silicon Muscle.