Fender 6G3 Schematic

6G3 Brownface Deluxe 1961-63

Bias wiggle single triode tremolo, 7025 (premium 12AX7) preamp, 12AX7 long tail pair phase inverter, Negative Feedback, GZ34 rectifier, 2 6V6GT power tubes
using non-adjustable fixed bias putting out about 20 watts. The amp is called "brown face" due to its control panel color.

6G3 Brown Face Deluxe Signal Path

Tremolo circuit at bottom left. Note both channels have a 500pF "bright cap" across the volume control but the Bright channel's tone cap is twice the Normal
channel's size at .02uF. The Normal channel also has a .002uF plate load resistor bypass cap which darkens the Normal channel's tone. Click image for clean

schematic.

The 6G3 marks a big break from the previous Deluxe designs. The separated tone and volume controls with the addition of 220k mixing resistors remove most
of the control interaction the previous 5E3 is famous for. Input channels are officially changed to "Normal" and "Bright." The phase inverter was upgraded to a
modern long tail pair which has much more voltage swing than the 5E3's no-gain cathodyne phase inverter so the long tail pair phase inverter can drive the

power tubes harder and generate more power tube distortion. The long tail pair phase inverter upper triode passes the guitar signal to its lower triode through
their connected cathodes. The LTP phase inverter is the most common phase inverter in guitar amps and is known for keeping its composure during overdrive
and the resulting sweet overdrive tone. The first stage preamp goes from 100k to 220k plate load resistors and the cathodes share a 1.5k resistor (equivalent
to 3k for each triode) for higher gain.

Note the 100k-15k voltage divider between the second gain stage and phase inverter. This divider dumps 87% of the guitar signal to ground. Replacing the
divider with a 100KA pot to form a master volume would be a good mod for the 6G3.

Negative feedback was added back into the circuit for good to reduce distortion and add headroom. Moving from the 5Y3GT to GZ34 rectifier tube increased
"A" or B+1 voltage to 375v which along with fixed bias increases output from 14 to 20 watts. The phase inverter gets it's own "C" or B+3 power node with
higher voltage than the preamp tubes which increases headroom, voltage swing and drive. 6.3v heater filament circuit is balanced with a center tap--both
wires are hot with 3.15v AC. Balanced AC on the heater lines takes advantage of twisted pair hum cancellation to reduce heater induced hum.

Bias wiggle tremolo (bottom left) is added along with non-adjustable fixed bias power tubes. Bias is non-adjustable because adjusting the bias will change the

intensity of the tremolo which is the major weakness of bias wiggle tremolo. Bias wiggle creates the tremolo (volume modulation) effect by modulating the
power tube bias.

The voltage dropping resistors are changed from 5k + 22k to 1k + 10k + 27k. The drop from 5k to 1k would raise screen (B+2) voltage which would increase
power output. The 10k resistor gives the phase inverter it's own, higher voltage node. The preamp's voltage drops through 38k of resistance (1k+10k+27k) which