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PLINIUS M12 PREAMPLIFIER
Thank you for buying a Plinius product. This Preamplifier has been carefully designed and
manufactured by hand and under normal circumstances will maintain its present high level of
performance for many years to come. Please read this manual fully before you attempt to use the
Model 12 as it does require some familiarisation before you add it to your music system.
Serial Number:
Date of Manufacture:
Final Test Certified by:
PLINIUS M12 Instruction Manual
Page 2
The M12 has been designed to operate with medium output cartridges ie 1.5mV and above. The
Volume Control should be set between 10 o'clock and 2 o'clock for normal listening. If required
there is a small jumper located on the Phono Board that can be moved to provide an extra 2db of
gain.
The Balance Control when rotated alters the relative gain between the left and right channels.
Rotating the control to the left shifts the image left and rotating it to the right shifts it right.
The Source Selector allows any of the inputs chosen to appear at the Main Outputs.
The Record Selector allows recording of any chosen source and will not interfere with any source
that is being listened to eg. it is possible to be listening to the CD Input and be masking a
recording from the Tuner. Two Tape decks can be fitted and dubbing in either direction is
possible.
The Phase Invert switch will change the absolute phase 180 degrees. Some recordings sound
better inverted than they do in the normal position due mainly to the recording technique used.
Usually this is 'felt' rather than heard and relates to the music being better focused and defined
than before. Not all recordings are made the same way and so some experimentation is necessary
to find out which is best for you.
As a note of caution, the Model 12 Phono stage is inverting and the switch should be in the
"Invert" position for you to hear the phono output in a 'non inverted' way. This switch also
changes the Balanced Outputs when operated. The high level inputs are all 'non inverting'.
The Mute Switch allows manual muting of the Model12 Outputs. This switch does not override
the automatic mute which is activated when the preamplifier is first switched on or when it is
switched off. The Mute Switch should be used when changing discs and provides an
instantaneous interruption to answer the 'phone etc. It is wise to leave the preamplifier in the
'Mute' position when not in use. This will prevent any unwanted signals reaching the amplifier.
Do not leave the Volume Control at a high level when the preamplifier is in the 'Mute' mode.
Someone may use the system not realising the level is set and a high volume of signal may be
sent to the amplifiers.
When the Model12 is in the 'Mute' position the LED on the front will be slightly less bright than
when operated.
PLINIUS M12 Instruction Manual
Page 4
INSTALLATION
The Plinius Model12 preamplifier should be left switched on at all times. We have purposely
fitted the Mains switch on the rear to discourage turning the unit off. If the Model12 is switched
off between listening sessions you will never hear just how good it really sounds. In our
experience a 48 hour warmup period is required during which the sound quality will change quite
dramatically. This change will continue for at least 72 hours after which the preamplifier will be
at its optimum. This warmup period is a nuisance but the results are very worth waiting for.
While the Model 12 does not dissipate an inordinate amount of heat, it does require a reasonable
amount of space to allow airflow. Do not place anything over the vent holes in the top panel and
if placed in a cabinet there should be at least 50mm of clearance above the Preamplifier.
The Model 12 should not be stacked with another amplifier as hum could be induced through the
Preamplifiers Phono circuits. If you detect any hum try moving the amplifier around. If the hum
level diminishes it has been induced from another source.
REAR PANEL CONNECTIONS
All input connections are clearly marked and apart from the Phono Input have a 50k Ohm
impedance.
If fitted with a Phono Board the Model 12 may be 'loaded' at the Phono Input with the supplied
Phono Loading Plugs. Without Plugs in place the loading is 47k Ohm and the Plugs supplied will
allow the following loading to the Phono Circuit : 10 Ohms, 47 Ohms, 100 Ohms, 470 Ohms, 1k
Ohms. The internal capacitance is set at 220pF which will provide immunity from stray RF fields.
TAPE CONNECTIONS AND DUBBING
If two tape decks are fitted to the Model 12 it is possible to dub in either direction. Selecting
either Tape Input with the Record Selector automatically sends the tape playback signal to the
other tape deck. eg. Select Tape 1 as a record source and its playback output will go to Tape 2.
Select Tape 2 as a record source and its output will go to Tape 1.
A 'Tape Lock' feature ensures that the machine playing back and selected as a record source does
not get a signal fed to its input sockets , so inadvertently switching it to record mode will not
cause feedback howl. While dubbing, the Source Selector allows easy monitoring of either tape
deck.
PLINIUS M12 Instruction Manual
Page 5
GROUND LIFT SWITCH
The M12 is fitted with a switch on the rear panel adjacent to the Earth Terminal. This is to allow
the Signal Ground to be either connected to the Chassis Ground or to 'float' above Chassis
Ground.
On some Amplifiers an earth loop or hum can develop if both Signal Grounds are connected to
Chassis Ground. Due to the unique Input Selector arrangement, Plinius SA series Amplifiers
require the driving preamplifier to have the Signal Ground at Chassis Ground for optimum
performance.
SERVICING.
If the Top or bottom covers of the Model 12 Preamplifier are taken off for any reason, remove the
mains Supply Plug first. The Voltages present on the circuit board could be harmful.
In the unlikely event that your Model 12 should require any service please take it firstly to your
Dealer in its original packaging. He will then determine if the unit should be returned to the
factory. Your Plinius Dealer has a good understanding of our Amplifiers and will be able to
advise on any further installation requirements.
CLEANING.
A damp cloth is all that is required to remove dust and finger marks from the Model 12's anodised
surface.
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