Thanks for the explanation. It's helped me understand what I need to change with my existing DIY attenuator/loadbox. In my case, I'm already using a 4 pole 3 position rotary to switch in different values, but only 3 of the 4 poles, which may give me some options. Noted regarding the line out. How hot does your unit run? I've messed around with adding a speaker driven fan using the powerbrake implementation as below. But I didn't much like what it did to the sound - mind you, I was connecting it across the lugs on the input jack, perhaps this isn't the right way to do it - If I look at the 2nd schematic the fan comes after a 56R resistor - (2nd schematic has an error in the bridge rectifier wiring) The one I used to build the fan supply. More detailed schematic, but with error in bridge rectifier wiring Has anyone else added a fan in this manner - any suggestions?