I just bougt second hand ATC-3 and there is a hum sound thar is also transmitter to the speakers.
I oppened the unid and found that the layout of the 3 valves is not marked. There are 2 12au7 and 1 12ax7.
I dont know where to place the 12ax7 !
This post is made possible by the generous support of people like you and our sponsors:
Topic - preamp Air Tight ATC-3 valves layout - Valvulator 05:57:29 07/07/12 (3)