Manley LANGEVIN DUAL MONO MICROPHONE PREAMPLIFIER WITH EQ - Manual (Page 10)

TECH NOTES
10
PHANTOM POWER FUSE
In earlier sections we explained most of the possible small disasters that can happen when phantom
power is used. The big one is damage to other gear not designed for phantom. This includes old
ribbon mics, non-pro battery powered mics and possibly other things we have yet to hear about.
FOUR reasonable rules: 1) Most modern mics with 3 pin XLR connectors will be safe and there is
no need to worry unless you own some exotic or real cheap mics. 2) ONLY FET condensor mics
need phantom power and some direct boxes can either use it or use batteries. 3) Because usually
phantom power is not needed, leave it off to prevent excessive noise from poor connections & cables
and because some mics that don't need phantom sound slightly better with it off. 4) ALWAYS turn
the monitors down when you turn phantom power on or change a mic or mic cable or mic patch.
How can I tell when I need phantom? There will be no signal at all from the mic. However this might
be caused by any number of reasons (cables).
If you have lost phantom power in this mic pre (the phantom LED won't light) it is very likely because
somebody broke one of the above rules. It happens. There is a fuse inside the unit for these situations
and it has blown. Unplug the AC then, replace the fuse with another
AGC 4/10 A (fast blow) and you are back in business.
INTERNAL TRIMS
The drawing below shows the location of the LINE VOLTAGE SELECT for you international
engineers (110 or 220). It also shows the locations of the phantom fuse, channel gain trims and power
supply trims and test points. These are all factory set and it is very unlikely that they will ever need
to be adjusted or changed.
CHAN A
GAIN
POWER SUPPLY
48 VDC ADJUST
C202
GROUND
+48 VDC
LINE
VOLTAGE
SELECT
CHAN B GAIN
(FACTORY SET
FOR 45 DB)
PHANTOM
FUSE AGC
4/10 AMP
FAST BLOW
TRIM1
TRIM201
TRIM01