Manley LANGEVIN ALL-DISCRETE PULTEC EQP1-A TYPE EQUALIZER - Manual (Page 6)

The Langevin products are very easy to connect in most studio situations. There are both
XLR balanced inputs and outputs as well as 1/4 inch jacks for unbalanced inputs and outputs. Please
read this section because there is some special considerations and notes.
The XLR Inputs and Outputs are transformerless. The Pin Out is as follows:
PIN 1 = GROUND
PIN 2 = HOT (positive going phase)
PIN 3 = LOW (negative going phase)
The inputs are designed to be used with the professional standard of +4 dBm nominal levels
and will handle +26 dBm peaks. The input impedance is 20 Kohms. There is a 3 position PHASE
SWITCH (polarity) on the back panel. The normal setting is 0˚. Changing it to 180˚ reverses the
phase. The middle position is DIR IN and is meant for the 1/4" input and disconnects the XLR. You
could lose signal here.
The XLR outputs must only be used to drive balanced inputs. This excludes many project
console insert points where a 1/4" stereo jack shares both send and return functions. Use the
unbalanced output instead. The signal on pin 3 is derived from pin 2. If pin 3 is shorted to ground
(typical unbalanced hook-up) then a 6 dB loss occurs. If pin 2 is shorted to ground (typical mis-
wired studio) then all signal is lost except for some low level distortion. If you have either of these
symtoms using the balanced output, you should just try the unbalanced output. A 6 dB loss could
also be caused by a bad cable that is not connecting either pin 2 or 3 ("open") all the way back to the
console.
The 1/4 inch jacks are meant to be used with unbalanced or "single-ended" sends and
returns. The Phase Switch should be set to DIR IN which disconnects the XLR input. Note that the
unbalanced input is always on and that you should not use both inputs and "select" with this switch.
The 1/4 inch unbalanced output is designed to mate only with mono (tip-sleeve) plugs. If
one uses stereo (tip - ring - sleeve) plugs then most likely the output will be down 6 dB. The only
way around this is to connect the sleeve to the ring - if you must use a stereo plug.
The UNBALANCED Pin Out is as follows:
SLEEVE = GROUND
TIP = SIGNAL
There are also two ground terminals on the back panel. CIRCUIT GROUND and CHASSIS
GROUND. Normally these are connected together with a a small piece of metal called a ground
strap. These terminals are used to find and fix hum problems. CIRCUIT GROUND is the ground of
the audio electronics. Chassis ground is like the third pin mains ground but also includes the chassis
that is often grounded in a rack. If you are hunting hum problems first try separating these terminals.
You can also try running a wire between the console to either of the terminals. You might also try
cutting the shields at the cables to the unit to break ground loops. The general idea is that every piece
of gear should have one and only one ground point - all these extra grounds can cause a ground loop
and hum is the usual result. Another possible cause of hum is that some gear radiates a strong hum
field. You might try moving it or the Langevin away from each other. Don't panic - experiment a bit.
CONNECTIONS
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