Circuit detail
Two input jacks provide the same functionality as found on the F-2B preamplifier. The input
is buffered by a cathode follower tube circuit, which is a unity-gain impedance matching
amplifier to feed the guitar level effects loop. This gives minimum loading on the output
signal from the guitar while driving the effects loop gear with the same signal voltage
level as the guitar but at a lower impedance, to isolate cable and other loading effects
from the guitar pickups.
 The other half of the 12AX7 tube provides the preamp's gain. This gain comes before the
volume control and the 300 volt supply assures that even large transients are handled
without overload or distortion. The tone controls are the interacting Fender circuit. The
bright switch shunts high frequencies around the volume control. The deep switch changes a
capacitor value in the bass control to change the frequency response (and a second section
on the deep switch changes the gain of the following amplifier to compensate for the
resulting change in signal level).
A solid state circuit restores the signal level after the volume control and provides
impedance matching to drive the full range output jack on the rear panel. Additionally, it
drives the crossover network. The active crossover network provides 12 dB/Oct slopes to
divide the output for bi-amping. The crossover points occurr at 6 dB down so that the
acoustic signals from the loudspeakers add seamlessly. A front panel control trims the
high-frequency signal component to match the level of the low frequency output.
A transformer-isolated balanced output to an XLR type connector provides auxiliary
Recording or PA feed. A switch selects the source to be the effects return (Pre) or the
full range output (Post). The transformer is large enough to handle the low-frequencies
without distortion to give good clear lows and a resistive pad isolates the transformer
from loading effects of long cables to give clear highs.
The heater of the 12AX7 tube is supplied by a regulated direct current supply to assure low
hum. The AC Line (Mains) connection is an IEC (computer-type) detachable cord. The supply
voltage can be changed by moving jumpers inside the unit to operate from 100, 120, 220,
and 240 volts for operation anywhere in the world. The F-1X is housed in a sturdy, road
worthy, steel enclosure.
| 
The F-1X gives
you a unity-gain impedance matching amplifier to
feed guitar-level effects units. The effects return goes thru the tube gain
stage and then to the tone controls. The signal from the tone controls is
amplified and sent to the full-range output jack on the rear panel. This same signal is
also fed to the crossover network. A transformer-isolated output feeds a 3-pin Cannon
jack.