Help. I have a '64 Champ in mint condition that has a major tone problem: the treble has gone away, leaving only a dull and lifeless low to mid range tone. The tone is clean: there is no scratchiness, buzz or hum. There is just no top end. I have replaced both the 12AX7 and the 6V6 tubes, with no change in tone. I have switched out the original CTS speaker for a new Kendrick, with no change in tone. I have even played the Champ through the speakers in a '70 Vibrolux Reverb (a Ragin' Cajun and a Copper Head), with no change in tone. Does anyone have any ideas about what could cause the top end of the tone to go away? Thanks.