SPARE TUBE
There is a spare 12AU7
tube mounted inside your Convertible amp. This is a stock
replacement tube for the Cascode module.
We also discovered an interesting sound when replacing the standard 12AX7 tube in the
Classic module with a 12AU7
tube. If you use a Classic module in the input stage (first
position), try using the 1 2AU7
tube there. You'll notice a little less output volume, but it
will also allow you to get a louder, clearer rhythm. Try this setup:
Classic with 12AU71
Classic Normal Hi-Gain Presence
If you play a guitar with a high output humbucker pickup and you're having problems with
a loud, clean rhythm, this could easily provide the sound you're after.
POWER AMP TUBES
Convertible amps are designed for use with EL-34 power tubes. These tubes will give
you the sweetest tone and are generally more "musical".
The EL-34 tubes installed in your amp are specially matched for cathode current. This
reduces hum and noice -especially noticeable when playing quiet passages and in the
recording studio. You'll notice a little label attached to the base of each tube that shows
current draw. When you replace your output tubes, make sure to ask for matched sets to
keep your amp sounding like new.
If you're transporting your amp often and subjecting it to rough handling, there are other
power tubes that will better withstand the abuse.
The 6CA7 is an industrial version of the EL-34. While the tone is not as sweet as
EL-34's, it is better suited to handle bumps and bangs. You can plug 6CA7 tubes directly
into the power tube sockets because the pin matchups are identical and the amp bias
will not have to be changed.
The 6L6 and 6550 tubes will also stand up to road knocks. Like the 6CA7 tubes, they are
not as musical as EL34's. You'll notice a harder sound. Although the pin matchups allow
you to directly plug 6L6 and 6550 tubes into the power tube sockets, you'll need to have
a service technician replace a bias resistor with one that's value matches the 6L6's or
6550's. See your authorized service center for cost
