Millennia M-2B Transformerless Vacuum Tube Stereo Microphone Preamplifier - Manual (Page 4)

M-2b

M-2b REAR PANEL
(1) CONVENTIONAL (+48V) INPUTS "In 1 (Left), In 2 (Right)"
Conventional 3-pin female XLR input jacks for all balanced microphones. Pin 1 is chassis
ground, pin 2 is positive phase audio signal, pin 3 is negative phase audio signal. Input imped-
ance is 3,800 ohms.
(2) DPA (B&K) HIGH VOLTAGE (+130V) INPUTS — optional
Conventional 4-pin female XLR input jacks for use only with B&K 4000-series high voltage
audio microphones. Pin 1 is chassis ground, pin 2 is unused, pin 3 is +130VDC, pin 4 is audio
signal. Input impedance is 9,000 ohms.
(3) OUTPUTS "Out 1 (Left), Out 2 (Right)"
Conventional 3-pin male XLR unbalanced outputs. Pin 1 is chassis ground, pin 2 is positive
phase audio signal, and pin 3 is audio ground. Output impedance is 120 ohms.
(4) EARTH/AUDIO GROUND JUMPER
A barrier terminal which ties earth ground to audio ground. If ground "hum" loops are expe-
rienced when using the M-2b, removing this jumper may help. Removing this jumper will not
compromise chassis/earth ground integrity.
(5) AC VOLTAGE MAINS SELECTION "100-120" or "200-240"
A power entry module with a removable fuse holder block. This fuse holder block is selectable
for 100 to 120 Volt or 200 to 240 Volt worldwide mains powering. The fuse block contains
two fuses — one fuse is in series with the hot power line while the other fuse is in series with
the neutral power line. Both fuses must be installed. To change the mains voltage selection,
remove IEC power connector and assure that the M-2b is not connected to mains power. With a
non-conductive tool, gently pry the fuse block away from the power entry module. Remove the
two fuses and replace both with type as shown below. Slide out the internal PC Board assy, turn
it over, and reinsert the PCB assy so that the desired AC mains voltage appears in the viewing
window. Double check that the fuses installed correspond to the AC mains voltage range which
appears in the viewing window. Gently push the fuse block back until flush and snug.
FUSES:
For 100-120 VAC mains, use 5x20mm, 1A, slow blow, 250V, Littelfuse 218 or equivalent.
For 200-240 VAC mains, use 5x20mm, 500mA, slow blow, 250V, Littelfuse 218 or equivalent.
(6) POWER ENTRY "IEC Power Receptacle"
An IEC-type AC line-power receptacle for use with removable cords. Use only the power cord
provided with the M-2b unit or equivalent U/L approved type SV, SVT, SJ, or SJT AC power
supply cord. Do not defeat the third pin earth ground! If ground lifting is desired, remove the
Earth/Audio Ground Jumper strap (3).