McIntosh C40 Audio Control Center

Thank You & Introduction

Your decision to own this piece of McIntosh Stereo Equipment ranks you at the very top among discriminating music listeners. You now have "The Best". The McIntosh dedication to "Quality", is assurance that you will receive thousands of hours of musical enjoyment from this unit. Please take a short time to read the information in this manual. We want you to be as familiar as possible with all the features and functions of your new piece of McIntosh. This will ensure that you receive all the performance benefits this instrument can offer you, and that it will become a highly valued part of your home music system. The serial number and purchase date are important to you for possible insurance claim or future service. Record this information here.

McIntosh Laboratory has earned a world wide reputation for the technical superiority of its contributions to high quality sound reproduction. The advanced level of McIntosh technical innovations has integrity proven by time. The legendary reliability of McIntosh products is a matter of record since 1949. The "Classic McIntosh" design is acknowledged as the most outstanding in the audio industry. McIntosh products are designed to be maximum "User Friendly", so anyone can enjoy using them. Ease of maintenance is another McIntosh design philosophy that contributes to the long useful operating life of all McIntosh products. The McIntosh Model C40 is the most sophisticated and finest performing Audio Control Center that has ever been created. For example, the distortion limit of less than 0.002% is so low, it requires special test equipment to make accurate measurements. This distortion limit is 100 times better than the same specification on the first Mcintosh stereo preamplifier built in 1959. Noise levels are so low, they cease to be of any concern to the listener. The wide range of performance features of the C40 allows the serious music listener to realize maximum performance and enjoyment from virtually any audio music source. These features are available without any compromise in sonic accuracy.

The C40 "Classic McIntosh" all glass front panel has all control, switch and pushbutton nomenclature illuminated.

Important Safety Instructions

These instructions are to protect you and the McIntosh instrument. Be sure to familiarize yourself with them.

1. Read all instructions - Read the safety and operating instructions before operating the instrument.

2. Retain Instructions - Retain the safety and operating instructions for future reference.

3. Heed warnings - Adhere to warnings and operating instructions.

4. Follow Instructions - Follow all operating and use instructions.

WARNING: TO REDUCE RISK OF FIRE OR ELECTRICAL SHOCK, DO NOT EXPOSE THIS INSTRUMENT TO RAIN OR MOISTURE.

5. Power Sources - Connect the power supply only to the type described in the operating instructions or as marked on the unit.

6. Power Cord Protection - Route power supply cords so that they are not likely to be walked on or pinched by items placed upon or against them, paying particular attention to cords at plugs, convenience receptacles, and the point where they exit from the instrument.

7. Ventilation - Locate the instrument for proper ventilation. For example, the instrument should not be placed on a bed, sofa, rug, or similar surface that may block ventilation openings; or, placed in a built-in installation, such as a bookcase or cabinet, that may impede the flow of air through the ventilation openings.

8. Heat - Locate the instrument away from heat sources such as radiators, heat registers, stoves, or other appliance (including amplifiers) that produce heat.

9. Wall or Cabinet Mounting - Mount the instrument in a wall or cabinet only as described in the owner's manual.

10. Water and Moisture - Do not use the instrument near water for example, near a bathtub, washbowl, kitchen sink, laundry tub, in a wet basement or near a swimming pool, etc.

11. Cleaning - Clean the instrument by dusting with a dry cloth. Clean the panel with a cloth moistened with a window cleaner.

12. Object and Liquid Entry - Do not permit objects to fall and liquids to spill into the instrument through enclosure openings.

13. Nonuse Periods - Unplug the power cord from the AC power outlet when left unused for a long period of time.

14. Damage Requiring Service - Service must be performed by qualified service personnel when:

• A. The power supply cord or the plug has been damaged, or
• B. Objects have fallen, or liquid has been spilled into the instrument; or
• C. The instrument has been exposed to rain; or
• D. The instrument does not appear to operate normally or exhibits a marked change in performance or
• E. The instrument has been dropped, or the enclosure damaged.

15. Servicing - Do not attempt to service beyond that described in the operating instructions. All other service should be referred to qualified service personnel.

16. Grounding or Polarization - Do not defeat the inherent design features of the polarized plug. Non-polarized line cord adapters will defeat the safety provided by the polarized AC plug.

17. CAUTION: TO PREVENT ELECTRICAL SHOCK DO NOT USE THIS (POLARIZED) PLUG WITH AN EXTENSION CORD, RECEPTACLE OR OTHER OUTLET UNLESS THE BLADES CAN BE FULLY INSERTED TO PREVENT BLADE EXPOSURE.

ATTENTION: POUR PEVENIR LES CHOCS ELECRIQUES PAS UTILISER CETTE FICHE POLARISEE AVEC UN PROLONGATEUR, UNE PRISE DE COURANT OU UNE AUTRE SORTIE DE COURANT, SAUF SI LES LAMES PEUVENT ETRE INSEREES A FOND SANS EN LAISSER AUCUNE PARTIE A DECOUVERT.

[Warning: High Voltage Symbol] The lightning flash with arrowhead, within an equilateral triangle, is intended to alert the user to the presence of uninsulated "dangerous voltage" within the product's enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons.

CAUTION: TO PREVENT THE RISK OF ELECTRIC SHOCK, DO NOT REMOVE COVER (OR BACK). NO USER-SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL.

[Important Information Symbol] The exclamation point within an equilateral triangle is intended to alert the user to the presence of important operating and maintenance (servicing) instructions in the literature accompanying the appliance.

WARNING: THIS UNIT IS CAPABLE OF PRODUCING HIGH SOUND PRESSURE LEVELS. CONTINUED EXPOSURE TO HIGH SOUND PRESSURE LEVELS CAN CAUSE PERMANENT HEARING IMPAIRMENT OR LOSS. USER CAUTION IS ADVISED AND EAR PROTECTION IS RECOMMENDED WHEN PLAYING AT HIGH VOLUMES.

LIGHTNING: For added protection for this product during a lightning storm, or when it is left unattended and unused for long periods of time, unplug it from the wall outlet and disconnect the antenna or cable system. This will prevent damage to the product due to lightning or power line surges.

OVERLOADING: Do not overload wall outlets, extension cords or integral convenience receptacles as this can result in a risk of fire or electric shock.

Product Features

The McIntosh C40 Audio Control Center offers a wide range of performance features designed for the serious music listener, ensuring maximum enjoyment without compromise in sonic accuracy. Key features include:

• Balanced Output Connectors: Provide greater reduction of noise and interference.
• Multiple Input Options: Three pairs of unbalanced output jacks (one main, two switched), eight pairs of high-level inputs, and dedicated PHONO inputs for moving magnet cartridges. A pair of high-level Balanced Inputs is also included.
• Signal Processor Loops: For both Listen and Record circuits, with a front panel pushbutton to engage the processor.
• Five Band Frequency Equalizer: Allows modification of the frequency balance of program material with +/- 12dB boost or cut at 30Hz, 150Hz, 500Hz, 1500Hz, and 10,000Hz. Can be switched into Listen or Record circuits.
• Active Variable Loudness Control: Contours frequency response to compensate for human ear behavior at softer listening levels.
• McIntosh MODE Switch: Offers seven combinations of stereo and mono signal routing.
• Compandor: Can expand or compress the dynamic range of audio signals, useful for vintage recordings or specific listening environments. Features EXPAND and COMPRESS modes, adjustable RATIO, SPEED, and LEVEL MATCH controls.
• Logic Driven Electromagnetic Switches: Ensure low distortion, low noise, and reliable signal switching.
• Built-in Monitor Amplifier: A 20-watt per channel amplifier with McIntosh Power Guard circuit, feeding the front panel HEADPHONES jack and rear panel SPEAKER terminals.
• Illuminated Glass Front Panel: Features a classic McIntosh aesthetic with illuminated nomenclature.

Front Panel Controls, Switches, and Pushbuttons

The front panel of the C40 is equipped with numerous controls for comprehensive audio management. These include:

• MODE Switch: Selects signal routing (e.g., STEREO, MONO, STEREO REV).
• RECORD Selector: Selects program signal for tape outputs.
• LISTEN Selector: Selects program signal for main listening outputs.
• VOLUME Control: Adjusts the overall listening level.
• COMPANDOR Controls (Outer Knob: EXPAND/OFF/COMPRESS, Inner Knob: RATIO): Manages dynamic range.
• EQUALIZER FREQUENCY CONTROLS: Five knobs to adjust frequency response (+/- 12dB).
• REC COMP Pushbutton: Engages the Compandor for recording.
• REC EQ Pushbutton: Engages the Equalizer for recording.
• REC MON Pushbutton: Monitors signal going to tape recorder inputs.
• PROCESSOR Pushbutton: Switches an external processor into the LISTEN circuit.
• HEADPHONES Jack: For connecting headphones.
• MUTE Pushbutton: Silences main listening outputs.
• SPEAKERS 1 and 2 Pushbuttons: Switches switched outputs on/off.
• POWER Pushbutton: Turns the unit ON/OFF.
• LOUD (LOUDNESS) Control: Adjusts loudness compensation.
• BALANCE Control: Adjusts left/right channel balance.

How to Make Connections on the Rear Panel

High quality shielded cables are recommended for optimal performance. The rear panel provides various input and output connections:

LISTEN FUNCTIONS:

• BALANCED OUTPUTS: XLR connectors for connecting to balanced inputs of a power amplifier.
• SWITCHED 1 and 2 OUTPUTS: For connecting additional power amplifiers or accessory components, activated by the front panel SPEAKERS 1 and 2 pushbuttons.
• MAIN OUTPUTS (Unbalanced): Connect to the inputs of a stereo amplifier.
• (LISTEN) PROCESSOR FROM AND TO: Jacks for connecting an external signal processor to the LISTEN circuit.

RECORD OUTPUT FUNCTIONS:

• TAPE OUTPUTS 1, 2 AND 3: Provide signals to feed up to three separate tape recorders.
• (RECORD) PROCESSOR FROM AND TO: Jacks for connecting an external signal processor to the RECORD circuit.

AUDIO INPUTS:

• TAPE 1, 2, AND 3: Connect outputs from tape recorders.
• TUNER: Connect outputs from a tuner.
• CD1, CD2: Connect outputs from CD players.
• PH/AUX (PHono/AUXiliary): For connecting either a phono player or an auxiliary component.
• GND (Ground): Terminal for phono player ground lead.
• LINE INPUTS (Balanced): XLR connectors for balanced outputs of accessory components.

AC OUTLETS:

One UNSWITCHED AC outlet and four SWITCHED AC outlets are available for powering accessory components. Total current capacity for C40 rear panel AC outlets is 1400 Watts.

SCR (Optional Speaker Control Relay):

The McIntosh SCR-3 SPEAKER CONTROL RELAY can be connected to switch two pairs of speakers and provides two high current AC outlets (1800 watts total) for accessories.

Monitor Amplifier Functions

The C40 features a built-in Monitor Amplifier rated at 20 watts per channel for 8 ohm loudspeakers, incorporating the McIntosh Power Guard circuit. It feeds the front panel HEADPHONES jack and rear panel speaker terminals. Program sources can be selected from LISTEN, RECORD, or EXTERNAL INPUT jacks.

• SPEAKERS, LEFT AND RIGHT: Connect 8 ohm loudspeakers to the terminals.
• EXT, L AND R: Adjusts the volume level of each channel of the MONITOR amplifier.
• RECord LISTEN EXTernal INPUT (Switch): Selects MONITOR AMPLIFIER INPUT signals from RECORD, LISTEN, or EXTERNAL INPUT sources.
• EXTernal INPUT: Connect a pair of cables from any external high-level program source.

Compandor Operation

The COMPANDOR can expand or compress the dynamic range of program signals. The front panel COMPANDOR switch selects EXPAND, OFF, or COMPRESS modes. The RATIO control adjusts the degree of expansion or compression.

• EXPAND: Increases dynamic range, making soft passages softer and loud passages louder. Useful for vintage recordings or FM broadcasts.
• COMPRESS: Decreases dynamic range, making loud passages softer and soft passages louder. Useful for tape recording in noisy environments (e.g., car stereo) or for background music.
• SPEED Switch (FAST-NORMAL-SLOW): Determines how quickly the COMPANDOR circuit reacts to musical information. FAST is for percussion, NORMAL for general music, and SLOW for voice.
• LEVEL MATCH: Used to match volume levels after engaging the COMPANDOR for consistent listening.

Installation Diagram

The C40 can be placed upright on a table or shelf, or custom-installed in furniture. Proper ventilation is essential for optimal performance and longevity. Recommended clearances include:

• At least 1-1/2" (3.8cm) above the unit for airflow.
• 17" (43.2cm) depth behind the mounting panel to accommodate connectors.
• 1-1/8" (2.9cm) in front of the mounting panel for knob clearance.

A ventilation cutout in the mounting shelf is recommended. Refer to the detailed diagrams for precise dimensions and placement of the unit and any necessary cutouts.

Specifications

Preamplifier Section:

• FREQUENCY RESPONSE: +0, -0.5dB from 20Hz to 20,000Hz
• RATED OUTPUT: 2.5V at MAIN, SWITCHED 1 and 2, and BALANCED Outputs
• OUTPUT IMPEDANCE: 600 ohms
• MAXIMUM OUTPUT VOLTAGE: 8V from 20Hz to 20,000Hz
• TOTAL HARMONIC DISTORTION: 0.002% maximum from 20Hz to 20,000Hz
• SENSITIVITY: Phono: 2.5mV for 2.5V rated output; High Level: 250mV for 2.5V rated output
• SIGNAL-TO-NOISE RATIO, A-WEIGHTED: Phono: 90dB below 10mV input; High Level: 105dB below rated output
• MAXIMUM INPUT SIGNAL: Phono: 90mV; High Level: 10V
• INPUT IMPEDANCE: Phono: 47K ohms and 65pF capacitance; High Level: 22K ohms
• VOLTAGE GAIN: Phono to Tape: 40dB; Phono to Main: 60dB; High Level to Tape: 0dB; High Level to Main: 20dB

Equalizer Controls:

Variable, 12dB boost or cut, at 30Hz, 150Hz, 500Hz, 1500Hz and 10,000Hz

Monitor Amplifier Section:

• POWER OUTPUT: 20 watts into 8 ohm loads minimum sine wave continuous average power output per channel
• RATED POWER BAND: 20Hz to 20,000Hz
• TOTAL HARMONIC DISTORTION: 0.005% maximum harmonic distortion
• FREQUENCY RESPONSE: +0, -0.5dB from 20Hz to 20,000Hz
• INPUT SENSITIVITY AND IMPEDANCE: 750mV (170mV IHF) for rated output at 27K ohms
• SIGNAL-TO-NOISE RATIO, A-WEIGHTED: 100dB below rated output (87dB IHF)
• AC POWER OUTLETS: 1 Unswitched and 4 Switched for accessories
• POWER REQUIREMENTS: 120 volts, 50/60Hz, 25 to 85 watts

Mechanical:

• SIZE: Front Panel: 17 1/2 inches (44.5cm) wide, by 5 3/8 inches (13.7cm) high
• DEPTH: Depth behind mounting panel including clearance for connectors is 17 inches (43.2cm).
• FINISH: Front Panel is glass, with gold/teal nomenclature illumination. Chassis is black.
• WEIGHT: 26 1/2 pounds (12Kg) net, 38 1/2 pounds (17.5Kg) shipping

Technical Description

Logic Driven Electro-Magnetic Switching:

All signal switching in the C40 is performed using electro-magnetic methods. Each switch utilizes sealed glass tubes filled with an inert oxygen-free atmosphere. Tiny leads within the tube overlap and contact each other when a magnetic field is applied to a coil surrounding the tube. This system ensures low resistance and distortion-free switching.

Phono Preamplifier:

The phono preamplifier uses a high-technology integrated circuit operational amplifier optimized for low noise and distortion. It features high open-loop gain, extensive negative feedback for reduced noise and distortion, and precision RIAA equalization. The circuit provides a wide dynamic range, accepting up to 90 millivolts of input signal without overload. The sensitivity is 2.5 millivolts for 2.5 volts at the main output, with a gain of 40dB at 1000Hz.

Loudness Amplifier:

High-level signals pass through the volume control and into the loudness amplifier. This unit employs an active loudness control circuit with two feedback loops: one for flat frequency response and another for loudness compensation. A potentiometer allows selection of any degree of frequency response from flat to full loudness compensation.

Listen Program Path:

Program signals selected by the LISTEN input switch go through the COMPANDOR, LISTEN PROCESSOR jacks, VOLUME control, BALANCE control, Loudness Amplifier, and then the Equalizer. The Equalizer uses four operational amplifiers for tuned circuits at 30Hz, 150Hz, 500Hz, and 1500Hz, with a passive circuit for 10,000Hz. The output feeds to the MAIN, SWITCHED 1 and 2, and BALANCED outputs.

Record Program Path:

Program signals selected by the RECORD switch feed into a unity gain amplifier, then to the COMPANDOR, RECORD PROCESSOR jacks, and optionally through the five-band Equalizer. The output feeds to the tape recorder inputs.

Compandor:

The COMPANDOR expands or compresses dynamic range using a voltage-controlled amplifier (VCA). Electronic signal processing includes band shaping, logarithmic conversion, and level setting to control gain for expansion or compression.

Monitor Power Amplifier:

The C40's Monitor Amplifier produces 20 watts per channel with less than 0.005% distortion. It uses a push-pull complementary AB design with a differential input and includes the McIntosh Power Guard clipping protection circuit. Power Guard prevents amplifier overdrive and distortion by instantly activating an electronic level attenuator at the amplifier input.