PAGE 7
HSP SERIES INSTALLATION AND OPERATION MANUAL
HSP Amplifier
HSP Amplifier
CONTROLS, CONNECTORS & INDICATORS
6
Input Signal Attenuation Pot
The fully clockwise position (when viewed from rear) of the input signal
attenuation pot provides no attenuation (ie 0 dB). Turning the pot counter
clockwise provides a logarithmic attenuation all the way to -128 dB.
7
Phoenix Balanced Input
A balanced male 3-pin (3.81mm) Phoenix type connector is provided
on each input channel.
Consult the Balanced Input Wiring section of this manual for further
detail of this control.
8
Ground Lift
Use the DIP switches to control the grounding of the audio inputs. The switch for the given channel is pushed down to connect the input signal ground with the mains
safety ground. The piano DIP switch is in the lift position (ie up) when the input ground needs to lifted from the mains safety ground to prevent circulating earth loops.
If at anytime a hum or unwanted noise is experienced then the input should be configured so that the input signal ground is lifted from the mains safety earth. This
minimises the circulating ground loop current by adding in an impedance which results in significantly less loop voltage drop being amplified by the amplifier.
Refer to diagram below which illustrates the above concept:
Audio Source
Mains Safety Earth
Mains Safety Earth
Ground Lift Switch in Ground Position
Signal In (‘+’ Hot)
Signal In (‘–’ Cold)
Signal Gnd
Pre amp
15 ohms
Circulating
Earth Loops
Amp
Audio Source
Mains Safety Earth
Mains Safety Earth
Ground Lift Switch in Lift Position
Signal In (‘+’ Hot)
Signal In (‘–’ Cold)
Signal Gnd
Pre amp
15 ohms
Amp