The World Wide Leader In State Of The Art High Fidelity Technology Engineered and Manufactured in the United States of America Mclntosh Laboratory Inc.
YOU SHOULD OWN McIntosh BECAUSE • Mclntosh instruments are designed and manufactured for long life. • Mclntosh instruments have always been designed for long life with low maintenance costs and high quality performance. Mclntosh instruments have been and are the LABORATORY STANDARD for the world.
THE NEW MCINTOSH AMPLIFIERS Mclntosh leadership in research and bipolar epitaxial transistor technology has produced startling new advances in safe, cool, superior performance and protection. Mclntosh engineering continues to advance power amplifier technology and protected performance. Experience and knowledge are the foundation on which the engineering superstructure is built that supports the Mclntosh recognized reputation as Laboratory Standard for the world.
YOU ARE PROTECTED FROM LISTENING TO AMPLIFIER PRODUCED DISTORTION WITH MCINTOSH POWER GUARD Plus: • Mclntosh Output Autotransformer delivers full power output.
THE MCINTOSH POWER GUARD THE MCINTOSH POWER METERS The Power Guard waveform comparison circuit detects minute amounts of waveform difference between the output signal and the input signal. A sampling of the program material at the output of the amplifier is constantly compared with the program material at the amplifier input. Should the differences reach 1%, Power Guard goes to work. Mclntosh developed output monitoring meters add to your operating flexibility.
The meters have extremely fast rise time, about 500 microseconds for 90% accuracy. A tone burst of 500 microseconds is almost inaudible even at full power. The meters are protected from damage in the event of overloading in the wrong meter range. AUTOMATIC TEST SYSTEM The Automatic Test System provides positive protection and extends the long trouble free life of an amplifier.
test reports "Reprinted with permission from the June 1982 issue of STEREO REVIEW magazine. Copyright © 1982 Ziff-Davis Publishing Company. All rights reserved." Mclntosh MC 2255 Power Amplifier • • • • • Mclntosh MC 2255 Power Amplifier Power Rating: 250 watts per channel Size: 16¼ x 14¾ x 7¼ inches Weight: 82 pounds Price: $2,750 HE Mclntosh MC 2255 basic power amplifier is rated to deliver its output into loads of 1, 2, 4, or 8 ohms, from 20 to 20,000 Hz, with no more than 0.
test reports to the two input phono jacks is a switch that sets the i n p u t sensitivity to either 0.75 or 2.5 volts for f u l l output depending upon the associated e q u i p m e n t . (The l a t t e r is the normally preferred setting for most setups.) The MC 2255 is a handsome and rugged amplifier, following a long-standing McIntosh t r a d i t i o n in its styling and construction.
Output Transformers in Transistor Power Amplifiers by Sidney Corderman* Output transformers can make transistor power amplifiers more reliable, more flexible, and more powerful. At the same time output transformers offer the best continuous protection to loudspeakers against the hazards of avalanche failure of output transistor devices. Time has shown that o u t p u t transformers make transistor amplifiers operate cool and safe.
The impedance ratio required between primary and secondary has been reduced by a factor of four-to-one compared with the conventional arrangement. It is now 125 to 1 (1000/8). The turns ratio is therefore only half of w h a t it was before. Leakage inductance is therefore much lower, and so is the shunt capacitance across the windings. The use of a bifilar winding technique completely eliminates the leakage inductance problem of coupling between the sections of the primary windings.
Fig. 5 - McIntosh MC 2205 o u t p u t stage and transformer dred to one. With transistor output stages, a ratio of only about 4 to 1 is required. In tube amplifiers, extremely good balance in the push-pull primary was required if notch distortion was to be avoided. Now, using a single ended push-pull transistor output stage the transformer can be driven in a single ended fashion. One end of the winding Is returned to ground potential.
be mated to a specific amplifier circuit. We went through dozens of developmental samples in the case of our new MC 2205 amplifier. What we ended up with it shown schematically in the diagram of Fig. 9. The transformer is trifilar wound to provide coupling between sections. It takes 23 individual windings to make this output transformer. There are five different winding sections, all five of which are connected in parallel.
provided for reactive loads. Collector volts Fig. 11 - Current versus voltage limitation epibase type output transistor fiers. In Fig. 10 we have combined the safe operating diagram of Fig. 10 with load and limiting characteristics at the 8-ohm tap of our MC 2205. As you can see, even when the load is totally reactive, every possible voltage and current condition falls within the safe operating area of the o u t p u t devices used. Compare this diagram with Fig.
You are Mclntosh protected six ways with the new Mclntosh amplifiers. PROTECTION 1. The patented Mclntosh Sentry Monitoring circuit constantly monitors the output signal. At signal levels up to rated output this circuit has high impedance and has no effect upon the output. If the power output exceeds design maximum, the Sentry Monitoring circuit operates to limit the signal to the output transistors.
POWER AMPLI MC 2500 POWER OUTPUT STEREO Minimum Watts, Both Channels Operating 500 Watts Per Channel POWER OUTPUT MONO Minimum Watts 1000 Watts POWER BAND WIDTH 20 Hz to 20 kHz TOTAL HARMONIC DISTORTION Maximum, 250 mW to Rated Power, 20 Hz to 20 kHz 0.02% OUTPUT LOAD IMPEDANCE Stereo Mono 1/2, 1, 2, 4, 8, 16 W INTERMODULATION DISTORTION Maximum, 250 mW to Rated Power 0.
FIER PERFORMANCE LIMITS MC 2255 MC 2250 MC 2155 MC 2120 MC 502 250 Watts Per Channel 250 Watts Per Channel 150 Watts Per Channel 120 Watts Per Channel 75 W/Chan. 2.7 to 4 W 50W/Chan. 8 W 500 Watts 500 Watts 300 Watts 240 Watts 150 Watts into 8 Ohms 20 Hz to 20 kHz 20 Hz to 20 kHz 20 Hz to 20 kHz 20 Hz to 20 kHz 20 Hz to 20 kHz 0.02% 0.02% 0.02% 0.1% 0.
THE McINTOSH C 27 STEREO PREAMPLIFIER STATE-OF-THE-ART PERFORMANCE WITH FLEXIBILITY PERFORMANCE LIMITS and RATINGS FREQUENCY RESPONSE: + 0, -0.5 dB 20 Hz to 20,000 Hz. DISTORTION: Will not exceed 0.05% at rated output level, 20 Hz to 20,000 Hz. INPUT SENSITIVITY AND IMPEDANCE: Auxiliary 1 and 2, Tuner, Tape 1 and 2: 250 millivolts at 100,000 ohms. Phono 1 and 2: 2 millivolts at 47,000 ohms and 100 pF. HUM AND NOISE: Auxiliary 1 and 2, Tuner, Tape 1 and 2: IHFA 90 dB; unweighted 85 dB below rated output.
Electronic Laboratories' PRODUCT ANALYSIS THE McINTOSH C 27 STEREO PREAMPLIFIER Fig.1 - Front view MANUFACTURER'S PUBLISHED LIMITS (SPECIFICATIONS): PERFORMANCE Rated Outputs: Main, 2.5 volts (Maximum greater than 10 volts) into 22k ohm load or greater; Tape, 0.25 volts (Maximum greater than 1 0 voltsl into 22k ohm load or greater; Center Channel (L+ R ) , 2.5 volts into 22k ohm load or greater.
works a bit differently from that contained in the C 32. The user is instructed to set the volume control for maximum ( l i f e l i k e ) listening levels while the loudness knob is set to its "flat" (counterclockwise) position. Then, for lower listening levels, the loudness control is rotated (rather than the volume control) and proper Fletcher-Munson compensation is introduced as listening levels are lowered. Completing the panel layout is a group of pushbuttons and a headphone jack at the lower left.
back curve measured via the phono inputs and shown as photographed from the face of our spectrum analyzer's CRT tube. Mclntosh has wisely elected to adopt the new IEC standards for playback which call for an additional roll-off time constant of 7960 microseconds in addition to the three time constants normally prescribed for R1AA equalization.
92 dB with an "A" weighting network inserted, both figures exceeding published limits of Mclntosh. Volume control tracking was found to be accurate from left to right channels within 0.
McINTOSH c 29 SOLID STATE STEREO PREAMPLIFIER PERFORMANCE LIMITS and RATINGS FREQUENCY RESPONSE: + 0 -0.5 dB 20 Hz to 20,000 Hz. DISTORTION: .02% maximum at rated output level. 20 Hz to 20,000 Hz. INPUT SENSITIVITY AND IMPEDANCE: Auxiliary, Tuner, Tape 1, Tape 2, 0.25 volts at 250,000 ohms: Phono 1 and Phono 2, 2 millivolts (1,000 Hz) at 47,000 ohms and 65 pF; Microphone, 2.5 millivolts at 500,000 ohms. HUM AND NOISE: Auxiliary, Tuner, Tape 1, Tape 2, IHFA 100 dB; unweighted 90 dB below rated output.
IF YOU DESIGNED A PREAMPLIFIER THAT HAD THE FLEXIBILITY YOU WANT WITH THE PERFORMANCE YOU NEED IT WOULD LOOK LIKE THIS... C 33 shown in optional walnut veneer cabinet. Separate LISTEN and RECORD program circuits Record on up to 3 tape recorders from any connected source or copy from one tape recorder to another with complete independence from the program being listened to. The RECORD and LISTEN input selector switches operate without any interaction.
• Signal Processor input and output for both LISTEN and RECORD circuits External signal processors can be connected to modify the program when recording or when listening. • Low Frequency and High Frequency Filters The low frequency (LF) filter attenuates the. program material at 12 dB per octave below, 50 Hz to help eliminate rumble, acoustic feedback and other similar unwanted noises. Above 7,000 Hz the high frequency (HF) filter attenuates hiss, scratch and such unwanted noise at 12 dB per octave.
PERFORMANCE LIMITS and RATINGS PREAMPLIFIER SECTION FREQUENCY RESPONSE + 0, -0.5dBfrom20Hzto20,000Hz MAXIMUM VOLTAGE OUTPUT 10 volts from 20Hz to 20,000Hz TOTAL HARMONIC DISTORTION 0.01% maximum from 20Hz to 20,000Hz at rated output SENSITIVITY Phono- 2mV for 2.5V rated output (0.4mV IHF) High Level- 250mV for 2.
McINTOSH MR 75 AM-FM STEREO TUNER The Mclntosh MR 75 AM-FM Stereo Tuner is a superb tuner using the latest high technology circuits. This fine tuner will discover more FM stations with good quality than ever before. FM AUTOMATIC FREQUENCY LOCK The Automatic Frequency Lock (AFL) is a patented Mclntosh circuit that activates when you tune to the center frequency of an FM station.
15 YEARS OF BASIC CIRCUIT AND CONCEPT RESEARCH HAS DEVELOPED THE TECHNOLOGY NECESSARY FOR A TRULY LOW DISTORTION FM TUNER WITH VARIABLE SELECTIVITY . . . THE MCINTOSH MR 78! A FORTRAN computer program using an algorithm that took six years to develop was used in its design. The mathematical complexity of the filter design procedure is almost beyond belief. Using a process called "numerical integration in the complex S-plane," a high speed IBM computer was used on the design of the IF filter.
The MR 78 tuner uses linear phase filters at the NORMAL and the NARROW positions of the SELECTIVITY switch settings. LINEAR PHASE BRIDGE DISCRIMINATOR The excellence of the IF filter would be useless if it had to work into an ordinary FM detector. Thus a new detector with suitably low distortion had to be developed.
Electronic Laboratories' PRODUCT ANALYSIS THE McINTOSH MR78 FM/FM STEREO TUNER Fig. 1 — Front view MANUFACTURER'S PUBLISHED LIMITS (SPECIFICATIONS): PERFORMANCE Tuning Range: 88 to 108 MHz. Antenna Inputs: 300 ohms balanced; 75 ohms unbalanced. Intermediate Frequency (IF): 10.7 MHz Sensitivity: 2 mV for 35 dB of quieting; 2.5 mV at 100% modulation (± 75 kHz deviation) for 3% total noise and harmonic distortion. Signal to Noise Ratio: 75 dB below 100% modulation. Harmonic Distortion: 0.
illuminated over a portion of its length. Also located within the dial opening are symmetrically positioned center-ofchannel and signal-strength meters. To the left of the dial area are two rectangular areas denoted as "function" and "selectivity". Illuminated words "stereo", "filter", and "muting" appear (when selected) in the upper area, while the lower area is illuminated with either the notation "-7 dB", "-22 dB" or "-55 dB".
variable output jacks. The power supply section consists of a 24-volt regulated supply which uses electronic filtering and supplies power to all signal stages, while a second, halfwave rectifier supply also equipped with electronic filter circuits feeds the necessary DC voltages to the multiplex decoder section.
if he could have heard FM the way we heard it over the Mac MR 78. F R E Q U E N C Y - HZ Mono: (1) Total Harmonic Distortion (THD) Stereo (2) Total Harmonic Distortion (THD) Fig.
THE MOST FLEXIBLE CONTROL SYSTEM EVER FOR A DIGITAL DISPLAY PROFESSIONAL FM TUNER The Mclntosh MR 80 Engineering direction dictated a tuner design governed by insistence on great flexibility and ease of use. This had to be done while designing for great sensitivity and the world's best selectivity in keeping with the needs of low distortion. These values were achieved. They retain the Mclntosh reputation for outstanding performance, long life and reliability.
as the detector coupled with a broadband limiter to produce unmeasurable noise and distortion. The heart of the multiplex section is a new third generation phase locked loop (PLL) stereo decoder integrated circuit (IC).
Electronic Laboratories' PRODUCT ANALYSIS THE McINTOSH MR 80 DIGITAL FM/FM STEREO TUNER Fig. 1 - Front panel view of Mclntosh MR 80 Tuner MANUFACTURER'S PERFORMANCE LIMITS: Sensitivity: 9.3 dBf (1.6 uV) for 35 dB of quieting; 14.7 dBf (3 uV) for 50 dB of quieting; 13.2 dBf ( 2 . 5 uV) for 3% total noise and harmonic distortion (IHF Usable Sensitivity). Signal-to-Noise Ratio: 75 dB (mono). Harmonic Distortion: 0.2%, 20 Hz to 15 kHz, mono or stereo; typically 0.08% at 1 kHz. IM Distortion: 0.
separate closely spaced signals in our listening area. We have been told by some of our friends and colleagues, however, that there are some areas of the country in which high adjacent selectivity is a must if listeners are to be able to tune to distant weak signals without being swamped by local strong station signals separated in frequency from the remote desired signal by only one channel width, or 200 kHz.
the de-emphasis switches, an electronically switched filter circuit is used to reduce out-of-phase noise when receiving weak signal stereo. The filter is actually a twin-T bandpass that blends high and low frequencies, but leaves separation unaffected at mid-frequencies for improved stereo imaging when the filter is required. LC notch filters further reject any residual 19 kHz or 38 kHz sub-carrier output products.
The spectrum analyzer plots of Fig. 4 illustrates frequency response and separation characteristics of the tuner measured with selectivity set to the "narrow" or normal position. We measured a separation of 50.5 dB at 1 kHz, 48 dB at 100 Hz and 35 dB at 1 0 kHz. The lower trace in the 'scope photo shows the cross-talk in the unmodulated channel. The center trace shows what happens when the multiplex filter circuit is introduced.
COMPACT, FLEXIBLE - MASTER CONTROL WITH SUPERIOR AM/FM TUNING THE MCINTOSH MX 117 AM-FM STEREO TUNER-PREAMPLIFIER Match the Mclntosh Stereo Tuner-Preamplifier with the Mclntosh power amplifier that satisfies your room and musical requirements. Advanced cir- cuits and performance features make the Mclntosh MX 117 ideal and especially convenient solution for discriminating stereo listeners. FM AFL AUTOMATIC FREQUENCY LOCK and 10 kHz, ± 12 dB of control capability.
separation—noise reduction control circuit. When listening to weak or distant FM stations, optimum stereo separation and signal to noise ratio is automatically provided. UNIQUE AM TUNER SECTION The AM circuit in the MX 117 is unique in design for a superheterodyne tuner. The AM RF amplifier circuit has constant selectivity, constant sensitivity and high image rejection across the complete AM band. In addition there is no loss of audio frequency response at the low end of the band.
Electronic Laboratories' PRODUCT ANALYSIS THE MCINTOSH MX 117 AM/FM TUNER-PREAMPLIFIER Fig. 1 —Front panel view of Mclntosh MX 1 1 7 Tuner-Preamplifier MANUFACTURER'S PUBLISHED SPECIFICATIONS: FM Tuner Section: Usable Sensitivity: 1 1 .2 dBf ( 2 . 0 uV/300 ohms) 50 dB Quieting Sensitivity: 19.1 dBf, mono; 39.5 dBf, stereo. Signal-to-Noise Ratio: 70 dB minimum, both mono and stereo. Harmonic Distortion: 0.18% mono, 0.38% stereo, maximum. Alternate Channel Selectivity: 78 dB minimum.
Rear Panel Controls Stereo pairs of input jacks and a chassis ground terminal are located at the extreme right of the rear panel of the MX 1 1 7.
phone jack. A turn-on delay circuit using a lightemitting diode/light dependent resistor network that transmits no signal for two seconds after power is applied also operates to turn off signals almost instantly when power is turned off. This arrangement serves to keep turn-on and turn-offs of the tuner-preamplifier transient-free. The power transformer of the MX 1 1 7 is triple shielded (copper strap, silicon steel strap and steel outer shell) for minimum hum and radiation.
division in this and all other 'scope photos. At 1 kHz, separation measured an impressively high 55 dB fas opposed to Mclntosh's conservatively guaranteed 45 dB) while at the frequency extremes of 100 Hz and 10 kHz we measured 37 dB and 35 dB respectively. In Fig. 7, the sweep mode was changed, so Fig. 7 —Crosstalk components, 5 kHz, Mclntosh MX 117 Tuner-Preamp that this time the sweep was linear, from 0 Hz to 50 kHz, with the lightly visible scale corresponding to 5 kHz per horizontal division.
reference 0.5 volts output, and this too corresponds exactly to the 250 mV spec called for by Mclntosh for their referenced output level of 2.5 volts. Figure 9 illustrates the range of control of each of the three equalizer controls provided on the MX 117. The frequencies at which the three equalizer controls are centered make for an extremely versatile range of control.
105 mV at 1 kHz. Overall frequency response was down by - 1 dB at 1 4 Hz and 41 kHz, while the -3 dB points were observed as 1 0 Hz and 78 kHz. Summary and Listening Tests Fig. 14 —Phono signal-to-noise plot, referred to 5 mV input, 0.5 volts output tained. Spectral distribution of the noise, in one-third octave bands, is plotted in the frequency/amplitude grid of Fig. 14.
THE MAC 4100 A HIGH QUALITY, HIGH POWER AM/FM STEREO RECEIVER AUTOMATIC POWER TURN ON/TURN OFF Power to the entire stereo system can be controlled from either the front panel power switch or the turntable's power switch. A current sensing relay connected to the turntable AC power outlets is controlled by the turntable power switch. The relay, in turn controls the AC power to the remainder of the system. Sensitivity of the circuit is adjustable to match the current consumption of your turntable.
loudness compensation accuracy is dependent on many variables such as speaker efficiency, amplifier gain and differences in input level. The loudness control is continuously variable, operates independently of the volume control, and its contour is accurately modeled after the Fletcher Munson family of "Equal Loudness" curves. • HIGH ACCURACY TRACKING VOLUME CONTROL The volume control, is a step attenuator which has tracking accuracy within 1 dB throughout its entire range.
New Equipment Reports A CONSUMER'S GUIDE Preparation supervised by Robert Long, Harold A Rodgers. and Edward J. Foster Laboratory data (unless otherwise noted) supplied by CBS Technology Center Mclntosh's New Receiver: Breeding Tells Mac 4100 stereo FM/AM receiver, in case with simulated wood-grain finish. Dimensions: 18-5/8 by 5-3/4 inches (front), 14 inches deep plus clearance for controls and connections.
Very little of the receiver's special quality is immediately apparent from the outside, though in hooking it up you get a clue from the convenience outlets. In addition to the conventional switched (black) and unswitched (red) ones, there are two green ones marked TURNTABLE, plus an AUTO/MANUAL switch.
range of the signal-strength meter is well chosen as an aid in antenna orientation for best reception of problem stations. The amplifier section, loo, exemplifies the extra care that sets the receiver apart. Whether the option that enables switching in three speaker pairs simultaneously requires them or not, it has three distinct protection systems. The most conventional is triggered by a heat sensor and shuts down the output until the heat sink has cooled to within safe operating limits.
HERE IS PERFORMANCE ONCE ONLY OBTAINED WITH SEPARATE PREAMPLIFIERS AND POWER AMPLIFIERS THE McINTOSH MA 6200 STEREO PREAMP-AMPLIFIER Here's Mclntosh performance and quality in a combination solid state preamplifier and solid state power amplifier. It reproduces music accurately with real life definition. Here is the quality power and outstanding flexibility you need to give you the sound of live music in your home.
THE MCINTOSH CUSTOM EQUALIZER ELIMINATES THE LAST MAJOR SOURCE OF DISTORTION IN YOUR STEREO---YOUR ROOM A Mclntosh Environmental Equalizer: • Adjusts for musical balance in your listening room tailored to your personal needs • • Restores musical balance when you move your speakers• • Restores musical balance if you move to a new room • • Reduces distortion caused by room construction, materials and dimensions • Mclntosh equalizers are two stereo equalizers in one: the first, programmable filters that correc
The continuous improvement of its products is the policy of Mclntosh Laboratory Incorporated, who reserves the right to improve design without notice. Printed in U.S.A.
