OPERATIONAL NOTES

SWITCHING ON

The power switch is located on the right hand corner of the front panel. Flip the switch up to turn on the preamplifier and down to turn off the preamplifier.

RUNNING

It is not recommended that you leave your preamplifier permanently switched on. This only wastes electricity and tube life. Your preamplifier has both tube and solid state rectification and reaches peak operating condition in approximately 30 minutes.

TUBE LIFE

As with all tubes, their quality degrades with age. This is due to cathode emission, a natural process found in all tubes. We recommend that you have your preamplifier checked every 4-5 years, depending on usage. An excessive increase in noise level can indicate the need to replace a tube. A 300B is a long life tube.

REPLACING A TUBE OR LAMP. You may need a small Phillips screwdriver and a replacement tube or lamp. First be sure the unit is off and remove the IEC mains cable. Let it sit for 15 minutes to be sure all power supply capacitors are discharged otherwise one could still get a shock even though the unit is unplugged. If you are changing a tube or lamp, be sure that it the same number or is on the list of possible substutions. Gently wiggle the tube around while pulling it out of the socket. Avoid bending the printed circuit board. Before putting a new tube in, look at it. Check to see that the pins are straight and that they line up to the socket. You should be able to gently push the tube into the socket without excessive force. If it is the indicator lamp that needs replacing. Remove the bottom cover. Six screws near the sides hold it in place - when these are removed, the cover should lift off. You will see what looks like a fuse directly behind the black name panel. Gently pry the lamp out and replace it with another lamp and not a fuse. Replace the cover before powering up the unit.

HUM This unit is meant to use the third pin of the mains as the ground reference. Many power amps also use the third pin mains ground. Here we have a potential source of hum and what we call ground loops. The solution is to use one of those grounds and only ONE. Use an 3 pin to 2 pin adapter for other equipment rather than breaking off a pin. Typically one power amp will be grounded and all other 3 pin mains gear will have adapters. Sometimes the better option is to ground the preamp and "float" the amps.

Another source of hum can be equipment stacked on top of one another. This is not a good plan from the ventilation standpoint generally and it is likely to introduce hum, buzz or noise into the system. Certain gear radiates magnetic fields or high frequency noise around its chassis and other gear may be prone to receiving these fields. Distance helps greatly.

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Manley Labs 300B owner manual Operational Notes, Switching on
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300B specifications

Manley Labs 300B is a high-fidelity tube amplifier that has gained a reputation among audiophiles for its exceptional sound quality and craftsmanship. This amplifier is named after its use of the 300B vacuum tube, a component famous for producing a warm, rich sound that is both detailed and engaging. The Manley Labs 300B amplifier has become a reference point for those who appreciate the artistic qualities of sound reproduction.

One of the key features of the Manley Labs 300B is its fully balanced design, which helps to minimize noise and distortion. This design approach allows for greater dynamic range and clarity in the audio signal. The use of premium components throughout the circuit further enhances performance, ensuring that every note is rendered accurately and with depth.

In terms of power, the Manley Labs 300B delivers 8 watts per channel in a class A operation, which is a hallmark of high-end audio equipment. While this may seem modest by modern standards, the quality of sound produced is often more important than sheer wattage. The 300B’s output stage offers a creamy and dynamic sound, excelling particularly with vocal and instrumental music, where it conveys subtle details with remarkable fidelity.

Another significant aspect of this amplifier is its flexibility in terms of speaker compatibility. It is designed to drive a variety of speakers, making it a versatile choice for different listening environments. The Manley 300B supports both 4 and 8-ohm output impedance settings, allowing users to match it to their favorite loudspeakers for optimal performance.

Additionally, the amplifier's construction is noteworthy. It features a robust chassis that not only reduces resonance but also adds to the overall durability of the unit. The hand-built nature of the Manley Labs 300B ensures that each piece is crafted with meticulous attention to detail and quality.

The Manley Labs 300B also comes equipped with a rich array of features, including an input selector, volume control, and high-quality binding posts for speaker connections. These components are not just functional; they also reflect Manley’s commitment to providing a user-friendly and high-performance experience.

In summary, the Manley Labs 300B is a sophisticated and beautifully crafted tube amplifier that offers a level of sonic performance that is hard to match. Its combination of high-quality components, thoughtful design, and powerful performance make it a standout choice for audiophiles seeking a true musical experience. Whether used in a dedicated listening room or as part of a larger audio setup, the Manley Labs 300B delivers a sound that is both engaging and lifelike.
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