Power Requirements
Each Shelford 5051 is fitted for use with a specialized stand alone, multi-unit power
supply modules. The power supplies feature a proprietary 4 pin polarized input for
+24 and -24V DC power input, and come in 5-way and 25-way options. The 5-way
is a brick & 25-way.
The Need for Dynamic Control
The dynamic range of sounds we hear around us in normal life greatly exceeds the
capability of our best recording and processing equipment - but even if this were
not so, the scale of dynamic range must be accommodated to the venue in which
it is to be reproduced. For example, actual volume levels of the dance hall would
be deafening in a students bedroom. In the same way, late night listening in a
quiet living room demands careful adjustment of dynamic range. In the constantly
changing background noise of a car, drama dialog does not work without constant
attention to the level control. In the field of communications, it is often necessary
to ensure that the best possible signal-to-noise ratio is obtained, in the interest of
intelligibility, within the limited performance of, say, a reporter’s recording device.
Digital recorders are unforgiving when overloaded. Overload can be avoided with
careful use of high ratio compression - on the verge of limiting - with careful choice
of time constants. A recording that still sounds “loud” can be produced without
non-musical harmonic distortion. A compressor-limiter is one of the most powerful,
yet subjective items in the sound engineer’s armory. Compression should never be
obvious to the listener and this needs intuitive and effective controls on the part of
the designer together with considerable skill on the part of the sound engineer.
A NOTE ON DISTORTION
The human hearing system is a remarkably complex mechanism and we seem to
be learning more details about its workings all the time. For example, Oohashi
demonstrated that arbitrarily filtering out ultrasonic information that is generally
5051:
Back Panel
5051: Block Diagram
Compressor S/C
Thresh
Attack
Release
Ratio
VCA
HPF
S/C Send/Return
Inpu t
Tran sformer
Ou tput
Tran sformer
Meter
Ou tput
Redu ction
Meter
EQ In
HPF In
G ain
Compressor In
EQ Pre/Post
FF/FB
Mid Band
Shelves
HPF
IP 1
IP 2
Input Select
Link