Conrad Johnson PV-12AL Line Stage Tube Preamplifier

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General:
Wonderfull smooth and uncolored vintage preamp from CJ made in the USA.

Fitted with a super cool set of East German made tubes.

This is a line stage preamp, meaning if you'd like to use a turntable you'll need an external phono preamp.

Cosmetic Notes:
• Light mark on faceplate above balance control.
• Light marks on top cover.
• Super clean and presentable with little signs of use.
• Excellent faceplate finished in light gold.

Tube Notes:
• Both tubes are strong testing RFT 12AU7 tubes marked E. Germany (East Germany).

More from Conrad Johnson:
Introduced:
PV-12: August, 1993
PV-12A and PV-12AL: January, 1997

The PV-12AL is a line stage version of the PV-12 without the phono section.

Like its predecessor, it featured zero feedback circuits, and passive equalization in the phono stage. For the PV12, critical plate resistors are a special laser-trimmed metal foil type chosen for their extremely low noise and low inductance. The balance control is an eleven-step switch incorporating discrete resistors.

Features:
Inputs/Outputs
• Phono
• Tuner
• Auxiliary
• Monitor and recording facilities for two tape decks
• One main output

Controls:
• Source Selector
• Record Out Selector
• Balance
• Volume
• Power 

Brand Background:
In the mid-1970s, two economists—friends and serious audiophiles—Dr. William Conrad and Dr. Lewis Johnson—were highly dissatisfied with the commercially available equipment of the time and were also perplexed and challenged by the readily apparent sonic differences among components in their own systems. What made these two classic tube systems sound so different? Could the virtues of each be somehow combined? Not content to merely speculate on such issues, Conrad and Johnson decided to systematically investigate by developing and refining a vacuum-tube preamplifier.

The resulting conrad-johnson preamplifier was immediately recognized as a state of the art contender and catapulted Conrad and Johnson into the audio industry.
The most important legacy of conrad-johnson design’s beginnings is the basic methodology which took shape in the course of the development of that first preamplifier.

This methodology has enabled conrad-johnson to develop new products which have routinely been ranked among the most musically satisfying. Few other manufacturers have so consistently received such high praise for their products.

Ownership:
Single Owner

Connections:
RCA inputs and outputs throughout, captive power cord.

General Sound:
Smooth, uncolored, undistorted natural and clean

Cosmetic Condition:
7/10 = Good. One or two minor scratches. Well Maintained. See our detailed rating description here.

Working Condition:
Working perfectly and tested in our lab and listening room.

Included:
Just the unit and power cord.

Packing:
Will be packed using our highly developed in-house process and custom packing materials.

Specs:
Gain:
Phono Stage: 47 dB (phono overload 200 mV at 1kHz)
Line Stage: 18 dB

Distortion:
less than 0.1% THD or IMD

Response:
bandpass 2Hz to more than 100kHz

RIAA Equalization:
+/- .25 dB (20 to 20 kHz)

S/N Ratio:
Phono Stage 78 dB below 10 mv input
Line Stage 92 dB below 2.5 volt output

Phase:
Line Stage is phase inverting
Phono Stage is phase correct

Dimensions:
19″ X 3.15″ x 12.5″

Weight:
16 lbs.

Approximate Age:
1997

Link to Manual:
Click Here

Recommended Cables:

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Testing Process:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCB’s for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface. The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope. We then switch to a 1KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment. Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.

We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected. If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.