Thursday, January 8, 2009

Fender Champion 600 Cathode Bypass Mod Pt 3



Here's the response curve for the switched cathode bypass caps in part 2 of this post. The first graph is for the stock tone stack:



From top to bottom the curves show:

6V6, 1st stage (12AU7) and 2nd stage (12AX7) engaged (stock).
6V6 and 1st stage (12AU7) engaged.
6V6 bypass cap engaged.
All bypass caps disconnected.



The curves in the next graph follow the same pattern but this time the Tone Stack Bypass is engaged. There is a great deal more gain with the tone stack bypassed. If you click to enlarge the graphs and look at the right hand scale you'll see that the peak response in the modified amp is about 10dB higher than in the stock one.



This amp has the 12DW7 mod installed so the 1st stage has less gain and correspondingly less increase in gain with the cap engaged. In a stock amp the jump from the aqua curve to the green curve would be increased to about the same as the jump between the green curve and the dark purple curve on top.


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