My 2204 Mojotone clone has been experiencing some problems. It sounds great overall but it makes funny whines and clicks when the main power is switched on or when everything is shut down. It started life with an aluminum chassis but I recently upgraded to a steel chassis. The steel chassis has a different design and I had to update the voltage and ohm selector switches to Mojotone's proprietary switches. But i've had some noises with both types of switches. https://www.mojotone.com/amp-parts/Switches_1/Mojotone-Impedance-Selector-Switch Right now the problem is the whining that mainly comes on startup or shutdown. Although, when I first brought it into the house and plugged it in the whine was continuous but faint. I'm thinking that it may have something to do with the NFB. The presence control seems to have very little to no effect and the amp really shrieked when I accidentally turned the ohm selector to 4ohm and plugged in a 16ohm speaker. I did post questions about this problem on the Building the Classics thread but I'm not getting much response over there. http://www.marshallforum.com/threads/upgrading-a-2204-build.107838/ The NFB is hooked to the 4ohm output from the OT. The presence knob makes a slight static noise when it is turned. Also, the static noise can be heard even when the volume is completely off. I was initially thinking that the whine might be some type oscillation but I haven't reversed any of the usual (pin 3 or pin 5) wires at the power tubes. I'm trying to get some ideas of what may be going on and how to fix this before I start blindly switching things.