McIntosh C31V AV preamplifier
McIntosh audio components enjoy a worldwide reputation that few others can claim. It has been said that once you become a McIntosh customer, you will remain one for life. Detractors, on the other hand, have suggested that McIntosh is often slow to come up with new designs and that when they do, the designs are often behind the times. Judging by their latest A/V control center, the C31V, those accusations are totally unjustified. Furthermore, judging by the internal construction, I would guess that it will continue to provide unimpaired service long after many other currently popular or highly publicized preamplifier/control units have been relegated to the trash heap. I know several audio enthusiasts who still own and swear by McIntosh products which they purchased in the early 1960s, and there's every reason to believe that owners of the C31V will enjoy its performance well into the next century.
The C31V has enough inputs (six high-level pairs, two tape monitor loops, two loops for external processors, and a low-level phono input pair) to accommodate numerous audio program sources as well as the audio signals from VCRs, TV monitors, and videodisc players. A low-noise, electronic source-selection system uses cascaded FETs at the input jacks to switch between sources. This keeps input leads short to provide better source-to-source isolation; lower distortion, hum, and noise, and more freedom from external r.f. interference. The two tape monitors, whose switching is also electronic, can be used for audio tape decks or for the audio from VCRs; also available is an optional video selector, the MVS-1, which automatically switches video signals along with the audio.
Overall volume level is adjusted by an electronically switched ladder attenuator, with left/right tracking accuracy controlled to a fraction of a decibel. In fact, in my tests I could detect no difference in output level between channels at any volume setting from maximum to 70 dB below maximum! Of course, one of the best things about this type of volume control is that, with no moving parts, it will not become noisy or intermittent after extended use.
The loudness-compensation control is independent of the volume control. In any audio system, correct compensation depends on many variables besides volume-control setting, including recorded level, output level of the signal sources, amplifier sensitivity, speaker efficiency, and room acoustics.
The C31V's design allows you to dial in the precise degree of compensation needed for low listening levels in your particular system.
Instead of tone controls, the C31V is equipped with a five-band equalizer. A built-in headphone amplifier feeds a front-panel headphone jack, and all controls are effective when listening to headphones. The C31V employs electronically regulated power supplies.
Rear-panel jacks provide output and input facilities for signal-processing equipment, and such signal processors can be used independently to modify a tape recording or the program that you are listening to.
The C31V can be equipped with various useful options that extend its versatility. For example, by adding McIntosh's SCR-3 speaker control relay, you can control two sets of loudspeakers from the front panel of the C31V and switch two husky amplifiers on and off through 20-ampere power relays in the accessory unit. Another option is the MVS-1 video selector referred to earlier, which links video signal selection to the audio selectors built into the C31V. Most of the front-panel switches and pushbuttons of the C31V are duplicated on a supplied wireless remote unit. Remote control can be extended to two additional listening areas by installing McIntosh remote sensors that are easily connected using RG-59/U coaxial cable. Even more widespread remote operation is possible by adding McIntosh's accessory Area Controller, which allows remote control in up to six listening areas, with independent volume adjustment and source selection for each.
Like most other McIntosh components, the C31V can be custom installed or mounted in a special cabinet that uses McIntosh's "Panloc" installation system. This system allows the unit to be locked in place, supported on a pair of supplied brackets. A simple twist of a pair of front-panel "Panloc" buttons permits you to slide the unit out, should you want to remove it from the cabinet at any time.
Control Layout
The upper half of the front panel is a display which shows what source, volume setting, operating mode, and tape facilities are in use, along with the settings of the speaker switches. The volume indicator is a vertical row of LEDs at the right side of the display.
The lower left half of the black-anodized aluminum panel contains pushbuttons for program-source selection, muting, audio and video tape monitoring, tape dubbing, stereo/ mono selection, and speaker selection, as well as the a.c. power switch. The "Speaker" buttons not only operate the SCR-3 speaker control relay, but also turn two extra line outputs on and off. A stereo headphone jack is near the center of the panel; to its right are five rotary knobs to adjust boost or cut of the five equalizer bands. Concentrically mounted balance and loudness-contour controls and a pair of volume-control pushbuttons complete the front-panel layout. When rotated fully counterclockwise, the loudness control provides flat response; when rotated fully clockwise, it offers maximum loudness compensation.
On the rear panel are nine pairs of input jacks (including those for the two tape/VCR loops), the tape/VCR outputs, two external-processor loops, and three pairs of output jacks (the "Main" jacks plus the two pairs controlled by the front-panel "Speaker" switches). One processor loop affects signals going to the tape outputs, and the other affects main output signals. With an encode/decode noise-reduction unit, the encoding connections are made to the "Tape" processor loop and the decoding connections are made to the "Main" loop. The processor-loop jacks are the switching type; they automatically bypass the loop inputs if there is no cable connected to them. As a result, the C31V needs no front-panel switches to select the processed signals; the processors' own switches would be used instead.
A total of eight convenience a.c. receptacles are also found on the rear panel; only one of them is unswitched. A chassis ground terminal is located next to the phono inputs. Multi-pin connectors identified as "SCR," "Tuner," and "Video Selector" are intended for connection of cables from the optional McIntosh accessories mentioned earlier and to link McIntosh's MR7082 tuner (which has no remote control of its own) to the infrared and multi-room remote-control systems of the C31V. A DIN jack provides similar control connection for McIntosh's MCD7000 and MCD7005 CD players. Another DIN jack allows hookup of the McIntosh Area Controller described above. Finally, two coaxial connectors are provided on the rear panel for use with remote sensors that enable the remote control of the C31V to be used in listening areas where a direct line of sight to the main front panel does not exist.
Use and Listening Tests
There's no denying that the McIntosh C31V is expensive. Still, dozens of control preamplifiers from other manufacturers cost as much as or more than this one.
After hooking up the C31V to my reference power amplifier and loudspeakers, I was impressed by the total absence of any switching noise, the inaudible background noise and hum level-even when no program material was present to mask it-and the accurate and totally transparent musical qualities of this preamp. I listened to a variety of program sources, but frankly, the majority of my listening was done using some of my newer CDs, such as The Symphonic Sound Stage (Delos D/CD 3502), which features selections from recordings engineered by my good friend John Eargle. To be sure, both hardware designers and software producers have had to relearn some tricks of their trade. If there is anyone who understands how a CD should be recorded and mastered, it is Mr. Eargle, who learned quickly and effectively how best to handle the digital medium. McIntosh, too, has adapted itself perfectly to the requirements of the new, digital program sources. Even a brief listening session with the C31V will convince you, as it did me, that there's nothing behind the times about the good folks who turn out those magnificent McIntosh components, year after year, for all of us to enjoy.
