Manley Labs MM/MC GRAMOPHONE CARTRIDGE PREAMPLIFIER - Manual (Page 8)

7. LINE INPUT SELECT BUTTON
The LINE switch routes external line level signals to the top of the feature switch stack, and through the
VOLUME control. In this way, an external signal source may be manipulated by the SUM, DIM and MUTE
switches, along with the volume control, before transmission to any downstream power amplifiers. Notice here
that the Steelhead’s VARIable internal line driver does not have any voltage gain, but does have power gain by
virtue of its low output impedance. Since most line level gear these days has plent of output level, the last thing
you probably need in your system is more gain. Thus, this LINE input allows you to run a CD player (for instance)
into the Steelhead, control the volume and let the Steelhead's Variable Outputs go drive your amplifiers. Or if you
have many LINE level sources, you can run the output of another preamplifier or passive switching device(such as
a Manley SKIPJACK) into the Steeelhead's LINE input. It's novel. Try it.
In addition, when the LINE function is invoked, the phono stage remains active, and any cartridge signals present
will appear in amplified form at the Steelhead’s FIXED outputs. Thus, the preamplifier’s dual signal paths may be
applied simultaneously, i.e.; listening to the LINE input signal while, for example, recording material from the
phono stages.
When the LINE feature is not engaged, the phono signals travel through the complete path normally, as described
for the line signal above. Notice that the line signal is subject to a fairly demanding 500 ohm termination resistance
(not a short-circuit) when the LINE feature is not engaged. This helps cut down on crosstalk between the line and
phono signals inside the STEELHEAD enclosure.
8. BUFFERED VOLUME CONTROL
The STEELHEAD is equipped to drive external power amplifiers directly via low output impedance VARIable
line drivers. Purists may easily bypass other outboard preamplifier circuitry by connecting power amplifier inputs
directly to the STEELHEAD’s VARIable output jacks.
9. SEPARATE BUFFERED FIXED AND VARIABLE OUTPUTS.
Choice of constant-level source for interconnection to a line-level-only pre-amp or recorder, and variable outputs
for direct connection to power amplifiers.
9. TWO-STAGE RF INTERFERENCE SHUNTS.
One set of dual dip switches per channel for selective shunting of annoying radiofrequency energy to the
STEELHEAD chassis, or earth ground. These switches are located on the rear apron, nested within each channel’s
cluster of RCA jacks. These switchable shunts effectively connect the signal ground to the chassis ground at high
frequencies only. Switch the shunt switches on as needed if RFI is encountered. Notice that the shunts are made
switchable for those installations where having a permanent shunt connection would, due to innumerable saftey
and signal grounding arrangements, provoke unacceptably audible “buzz current” ground loops for some users.
Notice that these shunts are not part of the signal path.
10. DISCRETE SYSTEM COMMON AND EARTH GROUND POINTS.
Breakable link between electronics common “zero volts” point and chassis ground allows great flexibility in
grounding arrangements.
11. REMOTE HIGH PERFORMANCE POWER SUPPLY.
Multiple channel power supply in separate enclosure eliminates supply proximity-based noise intrusions into the
signal path. Robust and regulated ultra quiet high-voltage rail maintains electrical quiet of sensitive input stage
amps. Each voltage channel is conveyed to the preamplifier via separate source and sink lines; no common supply
points except at the star-grounding point on the amplifier boards. Multi-core interconnect cable is screened via
tinned overall shield braid.
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