Alcorn Mcbride Digital Binloop HD, User Manual

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Alcorn McBride Binloop User’s Manual Page 93
Installation Guidelines
Grounding and System Performance
The connection of the Binloop into the audio system completes a
gain stage that may pass through equalizers (EQs), mixers, and
other low level processing gear before reaching the amplifiers.
Once this connection is complete, any sources of noise in the
system will be unmasked, and must be resolved in order to
achieve optimum performance.
The Binloop itself has a muted signal to noise ratio of 120 dB.
There should, therefore, be no audible hiss in the system once
the connection is made and approximate amplification levels
have been set. If any hiss is present, it is likely due to excessive
gain at the low level end of the circuit. Since the Binloop is
capable of generating very high audio output levels (up to +4
dBm into 600 ohms), it should be possible to restructure the gain
stages to eliminate any boost prior to the inputs to the amplifiers.
The use of the balanced outputs, rather than the unbalanced
outputs provides twice the signal amplitude for any given
material, and also isolates the signal from any common mode
noise that may be present. Any hiss present only during
playback, of course, must be a part of the recording itself.
Hum is a far more common problem than hiss, and is
unfortunately a far more difficult problem to correct. Hum is
fundamentally caused because the audio signal becomes
contaminated or, more often, referenced to noise from the 60 Hz
AC line. Improper grounding almost always causes this, but the
question is: where? Hum may be caused by grounding errors
present anywhere throughout the audio chain right up to the
amplifiers, or even in the building wiring external to the audio
system. A systematic approach is required to eliminate any
ground loops and reference the entire audio system to a single,
clean ground reference point.
All audio lines should be run as balanced signals, beginning with
the Binloop and ending at the amplifiers. Neither the positive nor
the negative side of any of these balanced signals should be tied
to ground at any point along their journey. Additionally, it is
essential that each of these signal runs be shielded cable, with
the shield connected at only one end. This shield connection will
normally be to the chassis of the connected audio equipment.
The shielding scheme should be consistent throughout, for
example with the receiving equipment providing the shield
connection for each cable: The shield of the cable between the
Binloop and the EQs tied
at the EQs, the shield of the cable between the EQs and the
Amps tied at the Amps.