McIntosh C11 Tube PreAmplifier *Original* (C20 & C22 era) AUDIOPHILE SERVICED

Description

McINTOSH C11 TUBE PREAMPLIFIER
OVERALL CONDITION: NEAR MINT
Excellent A+, Unit presents extremely well!
Fully serviced and bench tested. Scored 100%
*MESSAGE ME IF YOU PREFER THE LOOK OF ORIGINAL LAMPS INSTEAD OF GREEN LED’s.
PHOTOS
are considered part of the description. What you see in the photos is exactly what you get. Please view and zoom in on all pics for more details and a better understanding of the quality.
INCLUDED
Owners Manual
GENERAL DESCRIPTION
The McIntosh C11 Stereophonic Preamplifier is the control center for any Stereophonic Sound-system. To increase the enjoyment of Stereo, this control center does four jobs with precise control.
First, the control center amplifies week electrical impulses. As the record rotates on the turntable, undulations in the grooves move the pick-up stylus approximately 1000 of an inch, in any direction, from the rest position. From this slight mechanical movement, the pick-up stylus generates a weak electrical impulse on the order of a few thousands of a volt. To amplify and preserve the information in such an electrical impulse, the finest Amplifier performance is required.
Second, every sound system is used in a different acoustical environment. The tone balance of the music is affected by variations in this environment. Also, people listening to the music have varying ideas of correct tone balance. To compensate for these conditions a high-quality control center is needed.
Third, there is a great variety of stereo phonic and monophonic records manufactured today, both domestic and foreign. The control center must accurately compensate for the equalization introduced in the recording process.
Fourth, the programs originating from several sources such as tuners, records, tape machines, microphones, etc., a control center is needed to select and switch these sources separately or in combination.
All of these jobs are performed with excellence by the C11 and yet this instrument is simple to operate, easy to mount, and is the finest in appearance.
TECHNICAL DESCRIPTION
The C11 stereophonic preamplifier combines excellence and performance with ease of operation. The controls used the most have large diameter knobs. A new type of rocker switch indicates those controls with simple on/off functions. The C11 has an illuminated front panel with light intensity control to provide convenient reading under low level lighting conditions.
The C11 circuit consist of three amplifying sections in duplicate for the left and right stereo channels and a power supply. The first section is the input preamplifier used to amplify and equalize the input signals coming from the phonograph pickups, microphones, or tape heads. Skillful layout, grounding, and shielding for low hum pickups, metal film and wire wound resistors, terminal boards with a high specific resistivity, loan noise tubes and extreme care in manufacturing combine to achieve a new low in noise and hum.
The second amplifying section follows the volume control, and thus it is impossible to overload the circuit or any following circuits. The same techniques as were used in the preamplifier stage assures low hum and noise. The bass and treble tone controls or feedback type circuits and operate in connection with this section. Exceedingly low distortion and correct frequency response are assured using this arrangement.
The third section is the cathode follower output. The sharp cut-off (18dB per octave) rumble and high frequency filters are associated with this section. Output level set controls are located at the input of the cathode follower to allow simple balance of the entire amplifying and speaker system. These controls are conveniently accessible at each side of the front panel under the end caps.
The power supply deserves special mention. The power transformer is constructed with “core” type grain oriented laminations and magnetic shielding for low hum field. Long life rectifiers, for wave rectification, filter condenser sectionalization and careful grounding add to the hum free and long life characteristics of the C11.
Special attention has been given to the mechanical design also. The C11 may conveniently be installed in furniture cabinets, custom built installations, or professional relay racks. The tubes and the electrical connections are conveniently located on the back panel of the C11 for ready access.
A Word About Audio Equipment
I deal mostly in vintage HiFi audio equipment from the 60’s, 70’s, and early 80’s. To me (and many others), this was the golden era of HiFi audio, where much of it was built heavily, with a good design, great sound, and stunning appearance.
The audio equipment I sell is generally refurbished with a minimal amount of intrusion. This reflects my negative attitude towards the wholesale “recapping”, (replacing capacitors), of vintage audio gear.
In professional electronics circles, component replacement is determined by failure to function or to meet an element of the unit spec. That includes vintage audio, excluding of course those who see recapping as a profit center in their business. Yes, capacitors age and some brands are well into their wear-out period, but most of the quality vintage brands did not use those time-bombs and those who advocate wholesale recapping are usually unable to state what percentage of variation from nominal value was allowed for in the original design. Component failure as opposed to drift is a random process and the probability of any component failing tomorrow is much the same as it was when the unit was built 50 years ago. Exceptions exist of course, but the above are the facts from inside the profession with decades of experience in a world where electronic reliability was safety-critical.
LED Upgrades
In most cases, I replace incandescent dial lamps with an LED equivalent. LED lamps typically have a much longer lifespan and generate far less heat, which can damage to the unit.
COSMETICS
- Fully detailed and cleaned inside and out.
- The control panel is excellent with some wear to some lettering.
- The cabinet is near mint.
- From a non-smoking environment.
SERVICED
BENCH TESTED A+ / SCORED 100%.
FULLY FUNCTIONAL, EVERYTHING WORKS AS IT SHOULD.
- All dust has been carefully removed from the interior of the unit and all exterior surfaces have been meticulously cleaned.
- Dial lamps upgraded to LED’s.
- Control pots & switches have been cleaned & lubricated and operate flawlessly.
- All solder joints have been checked with a jewelers loupe for cold solder and reflowed where necessary.
- The faceplate was removed, thoroughly cleaned and polished.
- All knobs were removed and polished.
- New McIntosh Factory 1” feet installed.
SPECIFICATIONS
- Frequency response: 20Hz to 20kHz
- Total harmonic distortion: 0.2%
- Gain: 60dB (MM), 20dB (line)
- Input sensitivity: 2.5mV (mic), 2mV (MM), 250mV (line)
- Signal to noise ratio: 85dB (line)
- Output: 250mV (line), 2.5V (Pre out)
- Valve complement: 6 x 12AX7
- Dimensions: 15-3/4 x 5-1/8 x 12 inches
- Weight: 15lbs
- Year: 1961
EXPERT SHIPPING
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