Classe Audio C-151 User manual

CLASSÉ AUDIO
C-151
REMOTE CONTROL
BALANCED PREAMPLIFIER
C-151
OWNER'S MANUAL

CLASSÉ DESIGN PHILOSOPHY
1. REPEATED LISTENING DESIGN SESSIONS:
Fine tuning of sound by exchanging and mixing of parts (transistors, capacitors, wiring, PCB boards
etc.), and adjusting many specific operating voltages within proper engineering ranges, producing an
overall sonic recipe giving the most natural harmonic realism of music typical of instruments in a
live performance.
2. UPGRADABLE SINGLE CIRCUIT DESIGNS:
All Classé products (all preamps and all amps) share exactly the same circuit design philosophy
(excluding moving coil and moving magnet phono circuits). This means all amplifiers and all high
level circuits of the preamps benefit from the same design goals. Similar circuits are then tailored to
different power levels etc. Differences between less expensive models and more expensive models
are parts quality and compliment, power supply extravagance and the amount of filtering etc., as
well as features and packaging.
This means that for years Classé has been constantly sonically fine tuning and technically upgrading
this circuit design and its application, thus reaching a very high level of natural musical enjoyment,
as well as excellent reliability which benefits all models - least expensive, most expensive, preamps
and amplifiers alike.
3. EXTREME LONG LIFE IN REAL WORLD CONDITIONS:
Choosing the best attainable quality parts and materials combined with the advantages of the two
above-mentioned areas provides Classé owners with years of proven trouble free reliability and
musical enjoyment.

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C-151
OWNER'S MANUAL
TABLE OF CONTENTS
UNPACKING & SET-UP......................................................... 4
A.C. LINE POWER................................................................... 5
INPUTS...................................................................................... 6
JUMPER SETTING DIAGRAMS (MC/MM,) ...................... 10
OUTPUTS ................................................................................. 12
FRONT PANEL CONTROLS.................................................. 13
FEATURES AND SPECIFICATIONS ................................... 16

UNPACKING & SET-UP
Your CLASSÉ C-151 preamplifier has been carefully wrapped in heavy gauge plastic, packed in
semi-rigid foam and contained in a special box. To remove the unit, open and spread the top flaps of the
box. By its sides, lift out the entire unit with foam pieces intact. Remove each foam side by pulling
straight out. Remove the plastic wrap and inspect the unit for any concealed damage. Apart from this
owner's manual, please ensure the following has also been included:
1) DETACHABLE LINECORD.
2) ALLEN KEY FOR TOP COVER.
3) REMOTE CONTROL UNIT (Allen key and Batteries: AAA X 2 included).
4) RESISTOR KIT FOR MOVING COIL GAIN ADJUSTMENT. (with optional phono only)
Please report any damage or missing parts to your dealer promptly.
This preamplifier, being capable of very high gain, must be located in a position free of any
hum-inducing magnetic fields. (This also applies to turntables and interconnect cables.) Positions
adjacent to power amplifiers, A.C line filters, or regulation devices should be avoided. Ideally, a few feet
should separate the preamplifier from the power amplifier. As well, keep low-level interconnect cables
away from the power amp and separate from A.C. linecords.
Heat generated by the preamplifier is negligible. Air space around the unit need not be a
concern.
Check the Serial Number sticker on the back of the unit for the correct operating voltage.
Regardless of voltage, the internal fuse rating should be 1 AMP SLO-BLO.
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A.C. LINE POWER
The Classé C-151 preamplifier has no power switch. Its low power consumption and improved
sonics from always being ON led to the omission of an ON/OFF switch. In fact, while thoroughly
musical shortly after turn-on, the preamplifier will exhibit "sonic growth" during its first 300 hours of
use.
For optimum sonic performance, you should consider the use of the optional CLASSÉ REFERENCE
A.C. LINECORD. Consult your dealer regarding this accessory.
SAFETY FEATURE:
The C-151 preamplifier is designed with an auto-muting circuit which engages and is indicated
by a FLASHING GREEN LED when the unit is first connected, or after an AC power failure. After 15
seconds the STEADY GREEN LED signals that the unit is in STANDBY mode (Note: MUTE is ON
during STANDBY mode).
This feature will prevent any turn-on surges or unstable output from reaching the power
amplifier and possibly the loudspeakers. Similarly, make sure the MUTE is ON (STEADY GREEN)
again when removing A.C. line power.
CAUTION:
DISCONNECT AC LINE CABLE WHILE MAKING ALL CONNECTIONS. "FLOATING THE GROUND” OR
DEFEATING THE GROUND ON A 3-PRONG LINECORD MAY CREATE A SHOCK HAZARD. CONNECT ALL
INTERCONNECT CABLES BETWEEN THE ELECTRONICS BEFORE CONNECTING THE A.C. LINECORDS
TO THE WALL OUTLETS. THIS WILL REDUCE THE POTENTIAL SHOCK HAZARD. SEE ALSO THE
WARRANTY SECTION OF THIS OWNER'S MANUAL.
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INPUTS:
The input jacks are clearly marked on the back of the C-151. The following inputs are
provided: PHONO/AUX, VIDEO, CD, TUNER, BALANCED, and TAPE.
PHONO/AUX
The C-151 preamplifier can be configured as a PHONO unit by installing the optional
internal phono board onto the main board. The PHONO and AUX inputs share the same pair of RCA
input jacks. The GND screw is located next to PHONO/AUX input jacks. The following steps
should be performed to remove or install the phono board.
1) Make sure MUTE is ON (Steady GREEN)
2) Disconnect A.C. linecord from the wall outlet.
3) Remove the top cover with the Allen key supplied.
PHONO CONFIGURATON: (installation of phono board)
4) Locate and replace mounting screws 1, 2, 3 with the stand-offs supplied.
5) Remove jumpers J1, J2 (see fig.1, Page 9)
6) Install and secure the phono board using screws in step 4, make sure all connectors are
properly aligned. Set MC/MM jumpers if required (see fig-2a, 2b page 10). Replace the top
cover.
AUX CONFIGURATION: (removal of phono board)
7) Reverse steps 4, 5, and 6, make sure jumpers J1 and J2 are reinstalled for AUX
operation. (see fig.1a, page 9)
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PHONO INPUT:
When switched to PHONO the input can accommodate both magnetic and moving coil
cartridges of various outputs. In the MC position, gain of the Moving Coil stage is factory preset at
16dB which matches perfectly with most typical MC cartridges. With the resistor kit included, the
gain can be adjusted to 18dB, 23dB, or 28dB, in order to optimize system gain, and lower noise
while using other less typical MC cartridges. (Note: The MC gain is in addition to the standard MM
gain of 42dB). To change the MC gain, proceed as follows:
1) Perform steps 1, 2, and 3 as mentioned above.
2) Locate R104 and R204 (see fig.2, Page 10), which are the MC gain setting resistors for the
LEFT and RIGHT channels respectively. Remove the resistors and replace them with newly selected
ones, according to the following chart:
GAIN COLOR CODED RESISTOR (or) NUMERICAL RESISTOR
Standard 13 dB (Brown,White,Blue,Brown) 1961
18 dB (Orange,Grey,Orange,Brown) 3831
23 dB (Purple,Green,Black,Brown) 7501
28 dB (Brown,Red,Purple,Red) 1272
5) Having completed the resistor changes, replace the top cover.
AUX INPUT:
When selected (see AUX configuration) the AUX input serves as an additional high level
input, accommodating additional sources such as VIDEO, CD, TUNER, etc...
VIDEO, CD, TUNER:
These are all high level inputs sharing exactly the same characteristics, and may be
interchanged if so desired.

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BALANCED The BALANCED INPUT is a true differential high level input, wired as follows:
PIN 1: GROUND
PIN 2: POSITIVE (NON-INVERTED) SIGNAL
PIN 3: NEGATIVE (INVERTED) SIGNAL
It may be used with CD players that have a balanced output, or any other high level balanced
sources.
TAPE IN
The TAPE IN of the C-151 preamplifier should be connected to the LINE OUT or TAPE
OUT of the tape deck. The TAPE input does not appear on the selector switch. It is activated by the
TAPE switch. (See FRONT PANEL CONTROLS: TAPE SWITCH.)

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