A friend of mine gave me some vintage Russian NOS 1uF paper-in-oil caps for bypasses on my Crack's output caps, and a third for bypassing the last cap in the power supply (which I've replaced with a 100uF film cap). To my ears, there is better impact/slam but otherwise I don't hear much. I'm not complaining since I got them free but it's not something I'd spend my own money on.