Locomotive Audio 286A, User Manual, Page: 8 / 12

FRONT PANEL
The front panel of the 286A features two identical sets of channel controls.
1. Power Switch: Switches unit on. Illumination of the power lamp and VU
meter will result.
2. +48 Switch: Supplies 48-volt phantom power to the xlr input of channel.
Use only with condenser microphones that require phantom power. Some
microphones can be damaged if exposed to 48-volt phantom power, so it is
a good idea to switch phantom power off after each session.
3 . Gain:
This controls the amount of signal that passes from the first gain
stage (EF806 Tube) to the second gain stage (12AY7-1)
4 . Level:
This controls the amount of signal that passes from the second
gain stage (12AY7-1) to the final gain stage (12AY7-2) and through the
output transformer, followed by the next device in your signal chain.
5. -20dB Switch: When in the up position, a resistive pad is switched in
between the xlr input and the input audio transformer. This setting does
not affect a DI source. The pad sets a 1500Ω load impedance for the mic
to work into. The output impedance of the pad is 150Ω and should be used
in conjunction with the 1800Ω setting for a flat frequency response.
6 . Polarity Switch:
Also placed before the input transformer, this switch
controls the polarity of the microphone signal and will not affect a DI source.
7 . Impedance Switch:
This switch allows the user to select between a
500Ω and 1800Ω transformer load impedance on the microphone. Typically,
users will choose a transformer load impedance that is around 10x the out-
put impedance of their microphone for best frequency response. There are
no rules, so please experiment with the tonal changes associated with this
switch. This setting does not affect a DI source.
8 . Low Cut Switch:
If switched to the up position, a 100Hz low frequency
roll-off filter is placed on the signal for either the xlr mic input or DI. Use
this control to filter our low frequency rumble or to combat proximity effect
from a microphone.
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