McIntosh C22 Stereo Preamplifier Owner's Manual

Introduction

The C22 Commemorative issue preamplifier and owner's manual are faithful reproductions of the original, produced from 1963 through 1968. A few changes were made to the original preamplifier design to reflect technology advances and contemporary system requirements.

Signal switching has been updated to Electromagnetic switches. Close tolerance film resistors and polypropylene capacitors add precision to equalizer, filter, and tone control circuits. The tube complement retains the reliable 12AX7A for the amplifying stages. The cathode follower output stages are changed to 12AT7's to allow more current output to drive lower impedance loads. Balanced audio outputs are added to take advantage of the greater noise reduction capabilities of Balanced cables. A built-in headphone amplifier provides headphone listening.

This preamplifier is dedicated in remembrance of the late Frank H. McIntosh, founder of McIntosh Laboratory and co-inventor of the McIntosh Unity Coupled output circuit, which provided the foundation for the forming of the company. Mr. McIntosh was president of McIntosh Laboratory, Inc. from its inception in 1949 until his retirement in 1977.

General Description

The McIntosh C22 Stereophonic Preamplifier is a control center for any stereophonic sound system. It performs four key functions with great precision to enhance your stereo music enjoyment:

1. Amplification: It amplifies weak electrical impulses. Phono signals are amplified 1000 times, while high-level signals are amplified 10 times. This is crucial for preserving the subtle details from a record's groove.
2. Tone Control: It compensates for variations in listening environments and individual preferences, allowing for precise tone balance adjustments.
3. Equalization: It accurately compensates for the specific frequency equalization introduced during the recording process for all stereophonic and monophonic phono records.
4. Source Selection: It allows selection and switching between various program sources such as tuners, records, tape recorders, and CD players, individually or in combination.

The C22 is renowned for its outstanding performance, upholding McIntosh's reputation as "THE BEST." It is designed to provide years of exceptional performance and become a valued part of your home music system.

Technical Description

The C22 Stereophonic Preamplifier offers excellent performance with ease of operation. It features large diameter control knobs and new rocker switches for simple on-off functions. The front panel is illuminated for convenient reading in low light conditions, with illuminated positions for the Mode and Input Selector switches.

The circuit comprises three amplifier sections (duplicate for left and right stereo channels) powered by a common supply. The first section is the Phono Preamplifier, designed for moving magnet cartridges, utilizing low-noise tubes, high-resistivity circuit boards, and metal film resistors for minimal noise.

The second amplifier section follows the main volume control, preventing overload of high-level input circuits. It incorporates feedback-type tone controls (Bass and Treble) with multi-position switches offering approximately 4dB change per step for precise frequency response contouring.

The third section is the cathode follower output, featuring sharp cutoff RUMBLE (18dB/octave) and HF (High Frequency) filters. These drive the Unbalanced Main Outputs and positive (+) Balanced Outputs, while unity gain phase inverters drive the negative (-) Balanced Outputs.

The power supply uses a power transformer with grain-oriented laminations and magnetic shielding for low hum. Long-life rectifiers, filter capacitors, and careful grounding contribute to its hum-free operation.

Mechanically, the C22 is designed for versatile installation in furniture cabinets, custom installations, or McIntosh cabinets.

Front Panel Facilities

The front panel features several controls for operating the C22:

• BALANCE: Adjusts the volume balance between left and right channels.
• INPUT SELECTOR: A rotary switch to select one of eight program sources (TUNER, TAPE 1, TAPE 2, CD, PHONO 1, PHONO 2, AUX 1, AUX 2).
• MODE SELECTOR: A rotary switch to select listening modes such as STEREO, STEREO REV, MONO (L+R), L TO L&R, R TO L&R, L+R TO L, L+R TO R.
• VOLUME: A rotary knob to control the overall volume level.
• BASS CONTROLS: Left and Right rotary knobs to adjust bass loudness.
• TREBLE CONTROLS: Left and Right rotary knobs to adjust treble loudness.
• POWER: A switch to turn the unit and four switched AC receptacles on/off.
• SPEAKERS: A switch to select SPEAKERS 1, SPEAKERS 2, or both, for output.
• TAPE MONITOR: Two switches to select between NORMAL (program source) and MONITOR (tape playback).
• RUMBLE Filter: A switch to reduce low-frequency rumble noise. Positions are FLAT (filter disconnected) and FILTER.
• HF (HIGH FREQUENCY) FILTER: A switch to minimize surface noise on worn recordings. Positions are FLAT (filter disconnected) and FILTER (rolls off response sharply at 7kHz).
• LOUDNESS: A switch with NORMAL and COMPENSATED positions to boost bass at low volumes.
• Front Panel AUX 2 Input: A 1/4" stereo phone jack for temporary connection of high-level output components.
• Front Panel HEADPHONES Jack: For private listening.

Connecting

AC Power Connections

The C22 has five AC outlets on the rear panel: four switched and one unswitched. The switched outlets are controlled by the front panel POWER switch. The unswitched outlet remains active as long as the unit is plugged in, suitable for a turntable or record changer to allow it to complete its cycle after the C22 is turned off. The unit requires 120V, 50/60Hz power and draws 37 watts.

Input Connections

The C22 offers eight input connections, selectable via the INPUT SELECTOR switch. TAPE inputs can also be controlled by TAPE MONITOR switches.

Phono Cartridge Load Impedance: For phono cartridges requiring less than 47,000 ohms load impedance, a resistor can be added across the cartridge terminals. A guide for desired impedance and corresponding resistors is provided.

Balanced Jack Pin Configurations:

• Pin 1: System Ground
• Pin 2: +Output
• Pin 3: -Output

Output Connections

There are five pairs of Unbalanced outputs (SWITCHED 1, SWITCHED 2, MAIN, TAPE 1, TAPE 2) and one pair of BALANCED Outputs on the rear panel.

• MAIN OUTPUTS: Connect to a power amplifier's inputs. Function when the C22 is on.
• SWITCHED OUTPUTS (1 & 2): Connect to power amplifier inputs. Activated by the front panel SPEAKERS switch. Can be controlled independently or together, especially with the optional SCR3 SPEAKER CONTROL RELAY.
• TAPE OUTPUTS: Connect to high-level inputs of a tape recorder. These outputs are not affected by volume, balance, mode, tone, filter, or loudness controls; they reflect the INPUT SELECTOR setting.
• BALANCED OUTPUTS: Use XLR connectors for connection to balanced inputs of a power amplifier. This can significantly reduce noise and interference, especially over long cable runs.

The input impedance of power amplifiers used with the C22 should be 10,000 ohms or greater.

Ground Connection

A single ground post is provided for chassis ground connections from turntables, tape decks, etc. Avoid duplicating ground circuits to prevent hum. Twist signal cables and their ground wires together, ensuring the ground wire only connects to the designated ground post.

Operating Instructions

Balancing a Stereo System

Proper system balance enhances stereo enjoyment. This involves two aspects:

1. Program Loudness Balance: Use the BALANCE control on the C22 to adjust for unequal loudness between left and right channels of a program source.
2. System Balance: Affected by room acoustics, speaker placement, etc. Adjustments are typically made on the power amplifier. If the power amplifier lacks input level controls, the C22's BALANCE control can be used.

Steps for System Balancing (Example with McIntosh MC275):

1. Set amplifier input switch to STEREO and input level controls to 2.5V.
2. Play a familiar program source (CD, record, FM).
3. Set BASS and TREBLE CONTROLS indicators to the center (L and R marks).
4. Set BALANCE control to center (12 o'clock).
5. Set LOUDNESS switch to NORMAL.
6. Set TAPE switches to NORMAL.
7. Set RUMBLE filter switch to FLAT.
8. Set HF cutoff filter switch to FLAT.
9. Set MODE SELECTOR to L + R TO L.
10. Alternate MODE SELECTOR between L + R TO R and L + R TO L. Adjust the power amplifier's gain control until left and right loudspeakers produce equal loudness. The system is now balanced.

Adjusting the Balance Control After System Balancing

Minor channel imbalances may occur between different recordings. Use the C22's BALANCE control to correct these on-the-fly.

Adjusting for Special Effects

• HF CUTOFF FILTER: Use the FILTER position to minimize surface noise on old or worn records.
• RUMBLE FILTER: Use the FILTER position to reduce low-frequency rumble noise from turntables or record changers.
• BASS CONTROLS AND TREBLE CONTROLS: Adjust these to achieve desired tone balance, compensating for recording, acoustics, and personal preference. Start with indicators centered and adjust as needed.
• LOUDNESS: Use the COMPENSATED position at low listening volumes to restore perceived bass response, compensating for the ear's reduced sensitivity to low frequencies at low levels.

Listening Modes:

• Listening to a Stereo Tuner: Set INPUT SELECTOR to TUNER, MODE SELECTOR to STEREO, filters to FLAT, LOUDNESS to NORMAL, TAPE switches to NORMAL, and adjust VOLUME. Tune the desired station.
• Listening to a Stereo Record: Set INPUT SELECTOR to PHONO 1 or 2, MODE SELECTOR to STEREO, filters to FLAT, LOUDNESS to NORMAL, TAPE switches to NORMAL, and adjust VOLUME.
• Listening to Monophonic Records: Set INPUT SELECTOR to PHONO 1 or 2, MODE SELECTOR to MONO (L + R), filters to FLAT, LOUDNESS to FLAT, TAPE switches to NORMAL, and adjust VOLUME.
• Listening to a Stereo Tape Recording: Plug tape recorder into TAPE 1 or 2 input. Set INPUT SELECTOR to TAPE, MODE SELECTOR to MONO (L+R) or STEREO, filters to FLAT, LOUDNESS to NORMAL, TAPE switches to NORMAL, and adjust VOLUME.
• Listening to Auxiliary Input Signals: Set INPUT SELECTOR to AUX 1 or 2 and proceed as for TAPE input.

Front Panel AUX 2 Input:

A 1/4" stereo phone jack on the front panel for convenient temporary connection of high-level output components like tape recorders or CD players.

Front Panel HEADPHONES Jack:

Connect dynamic headphones for private listening. The main speakers can be turned off via the SPEAKERS switch or by connecting the power amplifier to the switched outputs.

Installation

The C22 can be placed upright on a shelf or table, or mounted in a McIntosh equipment cabinet or custom furniture. Ensure adequate ventilation for cooling, even though the unit produces little heat.

Cabinet Installation:

• Slide the unit into the cabinet from the front.
• Secure with two 10-32 screws and washers (not supplied) through cabinet shelf holes into the unit's bottom panel receptacles.
• Recommended Spacing for Cool Operation:
• At least 1-1/2" (3.8cm) above the unit for airflow.
• 14" (35.6cm) depth behind the mounting panel for connectors.
• 1-1/8" (2.9cm) in front of the mounting panel for knob clearance.
• Remove the unit's plastic feet for cabinet installation.
• A ventilation hole in the mounting shelf below the preamplifier is recommended.
• Refer to Custom Mounting drawings (page 10) for details.

Important Considerations:

• Do not install directly above a heat-generating component like a high-power amplifier; the power amplifier should be at the top in a system stack.
• A quiet ventilation fan can be beneficial for maintaining optimal operating temperature for all components in a single cabinet.

Custom Mounting Details

Diagrams illustrate custom mounting requirements:

• Front Panel Outline: 16" (406mm) width, 5-5/16" (135mm) height.
• Cutout Dimensions: 15" (381mm) width, 4-7/8" (124mm) height.
• Mounting: Two 1/4" (6.5mm) diameter mounting holes in the support shelf. Bottom of cutout and top of support shelf must coincide.
• Clearance: Allow 14" (356mm) total depth for connecting cables. Allow 3" (76mm) clearance in front of the unit.
• Cooling: A 6" x 10" (152 x 254mm) suggested cutout area for cooling on the support shelf.
• Securing: Use two 10-32 screws and washers (not supplied), ensuring they do not penetrate the unit by more than 1/2" (13mm).

C22 Preamplifier Specifications

Operating Curves

The following graphs illustrate the performance characteristics of the C22:

• Phono Equalization: Shows the frequency response curve for phono input, typically representing RIAA equalization.
• Rumble and HF Filters: Depicts the frequency response with and without the Rumble and High-Frequency filters engaged, showing their effect on low and high-frequency noise.
• Bass and Treble Controls: Illustrates the range of bass and treble boost and cut adjustments available, shown as multiple curves against frequency.
• Loudness Control: Shows the frequency response with the Loudness switch in NORMAL and COMPENSATED positions, demonstrating the bass boost at lower volumes.

Service Contract Information

McIntosh offers a 3-Year Service Contract for the C22 Stereophonic Preamplifier. If the instrument becomes defective, McIntosh will provide parts, materials, and labor free of charge to restore original performance limits. Shipping costs are not covered.

Key Terms:

• Service must be performed by an authorized McIntosh service agency. Unauthorized repairs will void the contract.
• Damage from improper use or mishandling is not covered.
• The contract is issued to the original purchaser and is non-transferable.
• Units operating outside the United States and Canada are not covered by the McIntosh Factory Service Contract; consult local dealers for available service or warranty.
• Vacuum tubes are guaranteed for 90 days only.

For questions or to fill out the application, contact:

McIntosh Laboratory, Inc.
2 Chambers Street
Binghamton, New York 13903-2699
Phone: 607-723-3512