11
PHASE SHIFT
Pickup Signal
Microphone Signal
TIME
By using the phase control, you can increase the phase delay of
CH2 until it comes into phase alignment with the mic signal.
PHASE ALIGNED
Pickup Signal
Microphone Signal
TIME
This control is on the left hand side of the chassis. To use it you
need to first open up your FELiX and set internal jumper J31 to
“ON”.
Please see page 12 for directions on how to do this. It’s
easy!
Once the jumper has been set, then you turn this control
clockwise to begin adjusting the phase delay of CH2. This is
a small recessed trim pot, designed to be adjusted by a small
flathead screwdriver.
This control made with an “allpass” filter, which have flat
FREQUENCY response but have frequency dependent phase
shift. As the frequency of the input signal increases, the phase
delay of the output increases. From the plots shown below, you
can see that at the maximum setting (10 o’clock) there is about
-180 degrees of phase shift at 1000kHz. This is about 0.5ms of
delay.
Since sound travels at about a foot per millisecond, this is
equivalent to about 6”, so if your mic is mounted to your
instrument at about 6” from the strings, you would be time
aligned with this setting.
PHASE (deg)
Hz
20
1k
20k
2k
ALL PASS FILTER
-180
0
100
500
5k
10k
300
-90
Control locations
2 o’clock
4 o’clock
6 o’clock
8 o’clock
10 o’clock
48V
ch2
ch1
6
1
5
4
3
2
This control is set be ear! While playing (or better yet with a
band-mate playing) and the pot all the way counter-clockwise
(0
o
), slowly begin to turn the pot clockwise. If there is phase
shift between the two sources, you should hear them come
into phase. They will sound more focused and sturdy. Adjust
this control while listening under headphones or IEMs, which
allows you to isolate the effect of the control from the direct
sound of the instrument.
This contol may make a huge improvement or it may be barely
noticeable. Result can vary based on a wide array of variables
in your instrument, mic, pickups, and wiring. If it doesn’t make
a big change, then your system might be just fine the way it is
and you can set the jumper back to ‘OFF’ and fuhgeddaboudit.
10 Adjusting Internal Jumpers
A bunch of the preamp’s settings can be adjusted via internal
jumpers. If you are handy with a screwdriver and tweezers,
you’ll be able to make these changes without a problem.
However,
this is not something you should attempt to do
on a dark stage or in the back of the tour van.
Directions for
disassembling the chassis and accessing the jumpers is as
follows:
1.
IMPORTANT:
Before you do anything, disconnect
Felix 2 from the AC power, and disconnect
instrument and mic cables and place Felix 2 on a
flat stable surface with good lighting.
2. DOUBLE CHECK:
Did you completely disconnect the power
supply? Ok then.
3. With a #2 phillips screwdriver, remove the 4 chassis screws,
located on the outer edges of the front bottom and rear
bottom of the aluminum top chassis.
4. Orient the unit so the rearpanel is facing away from you.
Carefully pull up on the top chassis and flip it up towards
you. This will reveal the top and bottom circuit boards. Do
not pull them apart any further than the ribbon cables that
connects them will allow. The top should rest easily on the
work surface flipped over and in front the bottom chassis.
