Conrad Johnson MV52 Tube Amplifier - Factory Upgraded

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The MV50 is one of our most beloved and versatile tube amplifiers from CJ. The MV52 takes it to the next leveI.

Our in-house tube expert went through this amplifier carefully to ensure it meets full and original factory performance.

PLUS this example was factory upgraded from an MV50 to MV52 in August 1993.

Tube Notes:
(4) Matched Quad New Svetlana EL34
(2) Philips ECG 6CG7
(2) GR 5751

Cosmetic Notes:
• Right channel terminal block has some slight damage
• Left handle slightly bent but barely noticeable.

Link to manual
https://conradjohnson.com/owners-manuals/mv52man.pdf

Click below to add our recommended matching cables from Kimber Kable, all brand new as SkyFi is an official Kimber dealer.

Kimber Kable - RCA Interconnects

Kimber Kable - Speaker Cables

Great bit of info from CJ:
CIRCUIT DESIGN
It has been our experience that simple designs with few active stages when executed with care and great attention to detail will be both more musical and more reliable than overcomplicated alternatives.

Accordingly, the audio circuit of the MV52 is remarkably straightforward.

A triode input amplifier comprised of paralleled sections of a 5751 is direct
coupled to a cathode coupled differential phase inverter using high current triodes to provide balanced, low impedance drive to the pushpull output stage.

The output stage features ultralinear operation which permits high power levels while greatly reducing the source impedance of the stage.

As a result, the amplifier is capable of supplying the large current demands of high amplitude musical transients driven into reactive speaker loads.

A substantial main power supply of massive polypropylene capacitors enables the MV52 to easily meet these extraordinary current demands.

Voltage regulators for the voltage amplifiers and phase inverters provide nearly absolute isolation of these sensitive stages from the output stages.

SPECIFICATIONS:
Power: 45 watts per channel RMS both channels driven into 8 ohms from 30Hz to 15KHz at no more than 1% total harmonic distortion or intermodulation distortion.
Sensitivity: 750 mv to full power.
Small Signal Distortion: Less than .1% at midband
Phase: Phase correct (non-inverting)
Frequency response: 20Hz to 20KHz +0, -.5dB
Hum and noise: 90dB below full power output.
Input impedance: 100K ohms.
Dimensions: 11.5D x 19W x 9H inches.
Weight: 39 lbs.

The SkyFi Testing Process for Tube Amplifiers:
We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and tubes are inspected for signs of stress overheating or cracking.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If it all looks clean we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier the remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will also be tested.

We also test all tubes for output gain and leakage on our modern and professional tester against the original manufacturers specifications. If needed, the tubes will be replaced from our vast NOS (New Old Stock) vintage or modern inventory.

Final testing involves pushing actual music thorough the amplifier. We've learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage KEF speakers that we're very familiar with which quickly reveal any discrepancies. Some amplifiers will then move into our listening room where they are tested with our in-house reference speakers of choice.