17
SIGNAL INPUT
The MPA is totally balanced. A High quality balanced input stage is a perfectly straightforward
development, and it offers better isolation from noise than an unbalanced input. This is
especially true when the input source is not located close to the amplifier and therefore the
cables on the inputs are long, and when in presence of a ground loop with the associated
current circulation.
This situation naturally causes concern for those who have never come across such an input
on an amplifier, questions such as “How do I connect my Preamplifier?” arise.
There are principally two different possibilities: the first is to simply make a short circuit
connection between pins 1 and 3 inside the three pin XLR connector which plugs into the
MPA, and the signal is then placed on pin 2 and the screen to the bridged 1+3. Adapters
which do this are readily available on the market (Neutrik for example) and such connectors
have a female RCA connector on one end and a male XLR on the other end.
or
Neutrik Adapter
If hum difficulties arise, please refer to the manual of the PL-P for instructions on AC Mains
supply wiring possibilities.
If hum still persists on the loudspeakers when the PL-P is connected to the MPA, then one of
the following possible connections could be used. Each of the possibilities exploit the
balanced input facilities of the amplifier. In this case we would get better electrostatic and
magnetic cancellation, and we will break the eventual current loop.
Remember that conventionally a balanced XLR connector is wired as:
Pin 1 = Ground
Pin 2 = High (or signal positive)
Pin 3 = Low (or signal negative)
Solution 1:
Connect an RCA connector for use in a balanced environment
Solution 2:
Floating ground
