Manley Labs 50/50 owner manual Bias Procedures

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BIAS PROCEDURES

The Manley DIRECT INPUT 50/50 uses a fixed bias system that requires very little attention. If you wish to adjust or check the bias, follow the following steps.

For this procedure you will need a voltmeter (a hand held autoranging DMM digital multimeter is the easiest) and a small flat screwdriver.

1.On page 8, which shows the FRONT panel of the amplifier, you can see 1 black tip jack and 4 red tip jacks. To measure the current draw of each output tube place the POSITIVE meter probe into the first red tip jack and place the negative meter probe into the BLACK tip jack.

Set the meter to read 'millivolts' DC (direct current).

2.Each of the four output tubes can have its own bias adjusted by adjusting its own bias adjust pot. On the top view picture on page 6, you can see the numbering sequence for the 4 output tubes and each tube's bias adjust pot. You'll need to remove the top cover by unscrewing the screws found on the top and sides of the cover. Do not touch any components inside the amplifier. Do not adjust any other pots except for the ones pictured on page 6. High voltages are present even after the amplifier has been turned off!

3.The first step to setting the bias is to turn on the amplifier and ensure that there is zero signal input, either leave the preamplifier muted, source signal turned off, volume control down, etc. In other words, you want to measure the quiescent current of the amplifier: NO input signal. Also, leave your loudspeakers connected as these provide an ideal load on the output. (DO NOT EVER OPERATE YOUR AMPLIFIER WITHOUT SPEAKERS CONNECTED!) It is recommended that you leave the amplifier on long enough to ensure that the tubes have reached their stable current draw, at least 1/2 hour is recommended.

5.Place the red positive meter probe in the first red tip jack . Adjust the first bias trim pot slowly until you measure 275mV to 300 mVDC (0.275V to 0.300VDC). Since you are measuring across a 10 ohm cathode resistor, this would correspond to a 27 to 30 mA current draw for each tube by Ohm's law.

6.If you are unable to bring the bias voltage down to 300 mV on any tube then we recommend that the tube be carefully watched or replaced.

7.Follow step five with the remaining tubes, switching to the next tube measurement point and adjusting the next trim pot each time. After you have adjusted all the output tubes, recheck and repeat the procedure as they will drift a little bit during adjustment. Once they are all set, your amplifier should be in perfect operation.

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50/50 specifications

Manley Labs has long been synonymous with high-quality audio equipment, and the Manley Labs 50/50 power amplifier is no exception. This remarkable amplifier is designed to deliver exceptional sound quality with a range of features and technologies that set it apart in the world of audio amplification.

At its core, the Manley 50/50 is a vacuum tube power amplifier, which means it utilizes vacuum tubes to amplify audio signals. This technology is beloved by audiophiles for its warm, rich sound reproduction. The 50/50 employs a unique combination of 6L6GC power tubes, providing an output of 50 watts per channel. This power output is ample for driving a wide variety of speakers, making it suitable for both home use and professional studio applications.

One of the standout features of the Manley 50/50 is its all-tube design, which ensures that the amplifier delivers a natural, musical sound that many believe cannot be matched by solid-state amplifiers. The 50/50 incorporates a push-pull configuration that results in low distortion and a wide frequency response. This means that listeners can experience a full spectrum of sound with incredible clarity.

The amplifier also boasts an impressive frequency response that ranges from 20 Hz to 20 kHz, allowing it to reproduce low bass tones and high frequencies with exceptional fidelity. This range is critical for achieving an accurate soundstage, making it a favorite among sound engineers and music enthusiasts alike.

Another notable aspect of the 50/50 is its user-friendly design. The front panel features a simple, yet elegant layout with power switches, LED indicators, and a robust set of speaker binding posts. This allows for easy connectivity and operation, making it accessible to both seasoned audiophiles and newcomers to high-end audio.

The build quality of the Manley 50/50 is equally impressive. Constructed in the United States, the amplifier features a sturdy chassis and a meticulous hand-wired design. This attention to detail ensures longevity and durability, making the amplifier a worthwhile investment for any serious audio enthusiast.

In conclusion, the Manley Labs 50/50 power amplifier stands out in the realm of audio amplification due to its all-tube design, impressive power output, and remarkable sound quality. With its combination of modern engineering and classic design, the 50/50 continues to be a favored choice for those seeking a high-fidelity listening experience.