What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

McIntosh MC 500 (1994)

The Mclntosh MC500 is a 500 watt per channel stereo power amplifier created in a stunning new contemporary industrial design. Two 5½ inch True Power Output meters are mounted behind the ½ inch thick glass front panel. The high efficiency of the MC500 circuits together with oversize heatsinks utilizing convection cooling eliminates the need for internal cooling fans. Typical Mclntosh attention to detail includes the use of 1% metal film resistors and polypropylene capacitors throughout. Internal heatsink module connectors use gold plated contacts to ensure reliable operation. Gold plated Balanced as well as Unbalanced Input connectors ensure reliable signal transfer.

A rear panel MODE switch is also provided to change the MC500 output configuration from a 500 watt per channel STEREO amplifier to a 1000 watt bridged mono amplifier The patented Mclntosh Power Guard circuit in each channel eliminates the possibility of overdriving the MC500 amplifier into clipping distortion. Mclntosh Sentry Monitor Output protection circuits are also included. You ensure maximum amplifier reliability and long operating life with absolutely no sonic limitations or compromises.

Each channel is coupled to the loudspeaker loads by a Mclntosh Output Autoformer with matched impedances of 2, 4 and 8 ohms. Each channel of the MC500 can produce a peak current output of more than 112 amperes, the highest ever for a Mclntosh stereo power amplifier. The MC500 can successfully drive any type of loudspeaker. With a distortion limit of less than 0.005%, the MC500 power amplifier is absolutely transparent, ensuring total sonic accuracy.


Two 5 inch illuminated output wattmeters read the True Power Output by measuring output voltage and current simultaneously.

Includes two McIntosh Output Autoformers

2, 4 and 8 ohms output impedances

Bridge Mono capability

Gold plated, multi-way output.

1% metal film resistors and polypropylene capacitors used throughout

Balanced and Unbalanced inputs

Exclusive McIntosh Power Guard non clipping circuit

Peak output current of 112 amperes


In BRIDGED Mono configuration the outputs of the two channels of the MC500 will combine to produce 1000 watts. All performance specifications for the stereo configuration will be exactly the same in BRIDGED Mono configuration, but with double the power. In BRIDGED Mono Configuration, only the BRIDGED Output terminals marked +4, +8, +16, -4, -8, and -16 are used. The COM (Common) terminals are not used.


The design philosophy incorporated in the MC500 involved many different techniques, all based on sound scientific logic. Every stage of voltage or current amplification is designed to be as linear as possible. Negative feedback is then utilized to enhance the performance.

Mclntosh engineers know how to properly design negative feedback circuits so they contribute to the extremely low distortion performance expected from a Mclntosh amplifier. The typical Mclntosh owner would never accept the approximately 100 times higher distortion

of many so called non-feedback designs. All transistors are selected to have nearly constant current gain (Beta) over the entire current range they must cover. Output transistors in particular, must have matched uniform current gain, high current-bandwidth product and large active region safe operating area. Resistors and capacitors in the signal path are carefully selected to have exceedingly low voltage coefficients, (change of resistance or reactance with applied voltage). Precision metal film resistors, low dielectric absorption film capacitors and premium audio grade electrolytics are used in all critical circuit locations.


Some power amplifier manufacturers claim that their products do not need or do not use protection circuits and that such circuits compromise performance. Mclntosh feels that protection circuits are desirable and necessary to prevent amplifier or loudspeaker damage due to abnormal circumstances. The genius of Mclntosh engineering has resulted in protection circuits which do not effect or compromise the normal performance of a power amplifier. Six different types of protection circuits are incorporated in the MC500 to insure it a long, safe and trouble free operating life. This is just one of the characteristics of Mclntosh power amplifiers that have made them world famous. The SENTRY MONITOR circuit is a good example


All power transistors have limits for the maximum amount of power they can handle. The MC500 output transistors and power supply have been designed to allow very high current flow into properly matched load impedances. However, if a short circuit or very low load impedance were connected to the MC500 outputs, destructive current levels could be reached if it was not controlled by the Mclntosh SENTRY MONITOR circuit. This circuit senses the dynamic operating time, voltage and current of the output stage, and controls it to safe operating limits. The SENTRY MONITOR circuit does not limit the power output available from the amplifier.

There is absolutely no compromise in sonic performance and it ensures safe operation of the amplifier under even the most extreme operating conditions.


All power transistors have limits to the maximum amount of heat they can safely tolerate. The MC500 uses a highly efficient amplifying circuit which produces relatively little heat from the power transistors for the output power produced. The amplifier uses large area heat sinks with an area of more than 2800 square inches to efficiently dissipate the transistor heat. Natural convection air flow is sufficient for safe cool operation. Cooling fans are not required. If the cooling air is blocked, or the amplifier operating temperature is forced too high, thermal cutout switches will turn off the AC power to the amplifier. When the problem is corrected and the amplifier cools to its normal operating temperature, the AC power will turn back on.


The MC500 includes the unique patented Mclntosh POWER GUARD circuit on each channel. POWER GUARD eliminates the possibility of ever overdriving the amplifier into clipping. Clipping occurs when an amplifier is overdriven past its output design capabilities. An overdriven amplifier can produce both audible and ultrasonic distortion levels approaching 40%. The audible distortion is certainly unpleasant, but the ultrasonic distortion is also undesirable, since it can damage tweeter loudspeakers.

The Mclntosh POWER GUARD circuit acts as a waveform comparator, monitoring both the input and output signal waveforms. Under normal operating conditions there are no differences between these waveforms. When an amplifier is overdriven beyond its maximum distortion free output, there will be a difference between the two signal waveforms. If the difference exceeds 0.3% (equivalent to 0.3% harmonic distortion), the amber POWER GUARD indicator will light. If the difference continues to increase, the POWER GUARD circuit controls an electronic attenuator at the input of the amplifier to reduce the gain just enough to prevent any further increase in distortion. Distortion will not exceed 2% with as much as 14 dB overdrive.

Without POWER GUARD, the distortion could easily reach 40% for the same operating conditions. A Mclntosh power amplifier with POWER GUARD will always deliver its maximum distortionfree output. This power is always well above the rated power due to the Mclntosh philosophy of conservative design. You will never experience the harsh and damaging distortion due to clipping when using a Mclntosh MC500 amplifier with POWER GUARD


Two illuminated 5½ inch WATT meters are provided on the MC500 front panel. The meters are peak responding and their circuits are constantly reading both voltage and current delivered to the loudspeaker loads. The load impedance of a loudspeaker may differ at various parts of the audio frequency range, resulting in a change of output current requirements. The MC500 meters react to these changing current and voltage conditions and indicate the true amplifier power output of each channel at all times.

in the METER WATTS position, the meters respond to the musical information and read the amplifier output of each channel on a continuous basis. In the METER HOLD position the meters will lock to the highest power peak in a sequence of peaks. If no higher power peaks are reached the meter pointers will slowly return to the lower power level. If the music stops, the meter pointers will return to the rest position. The meter pointer decay rate is approximately 6dB per minute. The MC500 output meters are extremely accurate, and will respond to 9 5% of full scale, with only a single cycle of a 2,000 Hz tone burst. In MONO operation, the two meters will read identical power levels. The total mono power output of the amplifier will be the sum of these readings.


All transistor power output circuits work best into what is called an optimum load. Depending on the number and configuration of transistors used, this optimum load may vary considerably from what a loudspeaker requires. In the case of more than one loudspeaker connected in parallel, the impedance load reflected to the power amplifier may drop to two ohms or even less.

A power amplifier connected to a load that is lower than optimum causes extra current to flow and extra heating of the power transistors. This means the amplifier will run much hotter, with a corresponding reduction in operating life.

The output signals from the two channels in the MC500 are coupled into the autoforrner at the point on the windings that is an optimum impedance match for the transistors in the output circuit. The MC500 amplifier output circuits are always operating at their highest possible efficiency.

The MC500 autoformers include output impedance taps for exact loudspeaker matches of 2 ohms. 4 ohms and 8 ohms. Loudspeaker performance will always be at its best Any Mclntosh power amplifier with an autoformer is especially well suited for stereo installations that require multiple speakers, since it is possible to have a very close impedance match.

The frequency response of a Mclntosh autoformer exceeds that of the output circuit itself, and extends well beyond the audio range. Its distortion level is so low it is virtually impossible to measure. The Mclntosh Autoformer is quite simply a significant engineering advance in power amplifier performance and reliability. The unequaled expertise of Mclntosh in the design and manufacturing of autoformers is legendary in the high fidelity industry. In the rare event of output circuit failure, the Mclntosh autoformer will conduct any speaker damaging DC (direct current), directly to circuit ground. This will protect your valuable loudspeakers from possible damage.


Heavy duty high current gold plated output terminals will accept speaker cables up to 0.204 inches (5.18 mm) in diameter. It is easy to connect speakers using any of the currently popular speaker cables

Both Balanced as well as an Unbalanced input jacks are provided for complete flexibility in any installation.


Power Output:

500 watts per channel into an 8, 4 or 2 Ω load is the minimum sine wave continuous average power output

1000 watts Mono into a 16, 8 or 4 Ω load is the minimum sine wave continuous average power output

Rated Power Band: 20 to 20,000 Hz

Total Harmonic Distortion:

0.005% maximum harmonic distortion at any level from 250 milliwatts to rated power output

Dynamic Headroom: 2.1 dB

Frequency Response:

+ 0, -0.25 dB from 20 to 20,000 Hz

+ 0, - 3.0 dB from 10 to 100.000 Hz

Input Sensitivity:

2.2 volts, Stereo Balanced and Unbalanced

2.2 volts, Mono Balanced

3.2 volts, Mono Unbalanced

A-weighted Signal-to-Noise Ratio: 85 dB (115 dB below rated output)

Intermodulation Distortion, SMPTE: 0.005% maximum if instantaneous peak power output does not exceed twice the output rating

Wide Band Damping Factor: 200 at 8 Ω output

Input Impedance: 10,000 Ω

Power Guard: Clipping is prevented and THD does not exceed 2% with up to 14 dB overdrive at 1000 Hz

Power Requirements: 120 volts. 50/60 Hz, 12 amperes UL/CSA

Dimension including front handles (W x H x D): 438 x 264 x 511 mm (17¼ x 10 x 20 inches)

Weight: 51,7 kg (114 pounds)

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