BIAS PROCEDURES

The Manley 120 Watt Amplfier uses a variable "fixed bias" system that requires very little attention. If you wish to adjust or check the bias, complete the following steps. For this procedure you will need a multimeter to read millivolts (less than 2 volt range) and a small flat screwdriver.

1.Looking at the front section of the top plate of the amplifier, you can see 2 red tip jacks and 1 black tip jack. To measure the current draw of each output tube place the positive probe (red) into the red tip jack for the tube you wish to measure and the negative probe (black) in the black (GROUND) tip jack and set the meter to read 'millivolts'.

2.Each of the two (2) output tubes can have its own bias adjusted by altering its own bias adjust pot. The numbering sequence for the 2 output tubes runs from left to right, as do the corresponding tip jacks (measurement points). The bias adjust pots are located on the top side of the amplifier, therefore it will be NOT be necessary to remove the bottom cover to changing the bias. They also read left to right.

3.The first step to setting the bias is to turn on the amplifier and insure that there is zero signal input. Mute your preamplifier. Don't play tunes. Also, you MUST leave your loadspeakers connected as these provide an ideal load on the output. Never operate your amplifiers without a suitable load or speakers attatched. It is recommended that you leave the amplifier on long enough to ensure that the tubes have reached their stable current draw.

5.Set your meter to read VOLTS DC. You will be measuring less than 1 volt so set your meter for a low range if it is not an autoranging meter. Place the probes in the first red tip jack (negative probes remains in the black tip jack for whole biasing procedure) and adjust the first bias trim pot located on the left side top deck of the amplifier until you measure approx. 300 mVDC (0.300 VDC). Since you are measuring across a 10 ohm cathode resistor, this would correspond to a 30 mA bias current. Settings between 275 mV and 300 mV are perfectly OK but try to have each tube the same.

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 other tube. Then go back and recheck again. Check and set the bias on your amplifiers every day for the first week or any time you retube. Then check every week, then every month. A red glowing area on the side of the tube usually indicates it is drawing way too much current. If you see a red spot on the side of the tube, check and reset your bias immediately.

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Manley Labs 120 Watt Monoblock Amplifier owner manual Bias Procedures
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120 Watt Monoblock Amplifier specifications

Manley Labs has long been revered in the audiophile community for its commitment to producing high-quality audio equipment, and the 120 Watt Monoblock Amplifier is no exception. This powerhouse amplifier exemplifies the brand's dedication to a superior listening experience, offering a blend of premium sound quality and robust functionality that caters to the needs of discerning music lovers.

At the heart of the 120 Watt Monoblock Amplifier is its stunning power output, capable of delivering 120 watts per channel into an 8-ohm load. This ample power ensures that the amplifier can drive even the most demanding speakers with ease, maintaining clarity and detail across all volume levels. The use of high-quality transformers and carefully selected components further enhances the amplifier's efficiency and performance.

One of the standout features of the Manley Labs amplifier is its tube-driven design, utilizing high-performance vacuum tubes to enrich the audio signal. This not only adds a warm, natural character to the sound but also produces a harmonic richness that solid-state amplifiers often struggle to replicate. The amplifier employs 6550 power tubes, known for their linearity and high output capability, providing a dynamic range that breathes life into any musical genre.

In terms of technology, the Manley 120 Watt Monoblock Amp features a fully balanced design. By minimizing the potential for noise and distortion, this balanced architecture contributes to an overall cleaner audio output. The amp also incorporates high-quality capacitors and resistors, ensuring that signal integrity is preserved throughout the listening experience.

The build quality of this amplifier is exceptional, with a rugged chassis that includes top-notch connectors and a solid finish, which not only enhances its durability but also adds an aesthetic touch to any audio system. Additionally, the monoblock design provides flexibility for bi-amping configurations, allowing audiophiles to tailor their system for optimal performance.

Another impressive characteristic of the Manley Labs 120 Watt Monoblock Amplifier is its thermal management system. The amp is designed to run cool, which increases its longevity and ensures consistent performance even during extended listening sessions.

In summary, the Manley Labs 120 Watt Monoblock Amplifier stands out as a premium audio solution that combines power, elegance, and cutting-edge technology. Its tube-driven design, exceptional build quality, and advanced engineering make it a worthy addition to any serious audio setup, promising a listening experience that is both immersive and true to the artist's vision. With Manley Labs, every note comes to life, making each listening session a memorable one.
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