Abbingdon Music Research Reference Class Proffessional Monitor LS-77 - Manual (Page 36)

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Appendix D – The AMR Active System
For maximum performance AMR's active system allows AMR's LS-77 speakers to be driven in active mode by
AMR's amplifiers. Separating the frequency ranges before the amplifiers avoids the destructive intermodulation
between the low and high frequency signals being passed through the same amplifier and increases the available
power and SPL.
AMR uses custom designed high quality passive filters instead of large numbers of Op-Amp's and other active
components, as a result avoiding many shortfalls (e.g. signal distortion) commonly associated with other active
systems. Hence, AMR's active system combines all the benefits of fully active operation with a much simplified
handling and physical setup.
D.1 - The AM-77 Control Center Edition (CCE)
The corner stone of AMR's active system is the AM-77 CCE Amplifier. The AM-77 CCE acts as a (i)
preamplifier, (ii) active crossover and (iii) high frequency amplifier. Thus it combines three separate devices into
one without loss of performance but with the added benefit of eliminating several interconnects.
The amplifier boards are optimised for high frequency reproduction including the use of non-magnetic Silver Foil
& Mica dielectric coupling capacitors, which have been found most ideal for detailed, resolved and non-fatiguing
high frequency reproduction. Hence the high frequency outputs from the active crossover are routed directly to
the internal power amplifier. The low frequency outputs of the active crossover are sent to additional AM-77s
configured as power amplifiers via the "Option" connector.
All control functions such as Input selection, volume control etc. are performed ONLY by the AM-77 CCE, in
effect the AM-77 CCE acts as the preamplifier with additional active crossover function and high frequency
amplification built-in.
Two or even four AM-77 CCE can in turn be operated as monoblock amplifiers with control functions to allow
very large systems to be assembled around AMR's core components. Any AM-77 can be converted into a CCE
Amplifier and visa versa by your AMR retailer at notional cost.