Hum and noise

In most cases, one of the following suggestions should help you solve a hum noise in your system. Please try these steps in the order shown, proceeding from one step to the next if the prior suggestion does not eliminate the problem.

Suggestion #1

To determine if a cable TV connection is responsible for the hum, first turn off all the components. Disconnect the cable TV feed to your system at the first place where it connects to your components. Alternatively, disconnect the cable TV wire where it is connected at the wall outlet. Turn your system back on, and listen if the hum has disappeared. If removing the cable TV feed has eliminated the hum, you will need to insert a Ground Loop Isolator (Knoll model GB634) before reconnecting the cable TV feed, or contact your cable TV operator to see if they can better isolate your cable feed.

Suggestion #2

Turn off all components in your system and then disconnect the input cables at the amplifier. Turn the amplifier back on to see if the hum is still present. If the hum disappears, the fault may be in the input cables used. Try replacing them with cables that have better shielding, and make certain that the input cables are not running on top of any AC power cords. Change the cables one at a time to determine if one or all cables are responsive. If the hum disappears when the input cables are disconnected but returns after the cables are changed and the system reconnected, your source device may be causing the problem.

Suggestion #3

Poor grounding of the electrical system in your home may also cause ground loop problems, particularly when there are multiple components with three prong, grounded, power cords. Unplug these components one at a time, and see if one or all of them is causing the problem. The ultimate solution to this type of problem is to rewire your house with an isolated, star type-grounding configuration. Knoll understands that this may be impractical and expensive. In some instances, the use of an approved AC Power Isolation Transformer (Knoll model PLB200) of sufficient capacity may solve this problem.

Warning: If you suspect that the grounding system in your home’s electrical wiring is causing the hum problem, it is important that you do not make any changes to the wiring. Only a licensed electrician should make any changes to household wiring and they must be made in full compliance with all local building, safety and electrical codes.

Installation

Installing the MA250 should be relatively easy. With a bit of planning, the MA250 will give trouble-free service for years.

1.The most important consideration when installing the MA250 is cooling. The MA250 has a lot of power packed into a small chassis size. When installing it in an equipment stack, it should be the top component. It needs at least 3"-5" of space above the amplifier to allow for adequate convection cooling.

2.When installing the MA250 in a rack, we suggest adding a

3-1/2" blank above and below the MA250. In multiple MA250 installations, plan for a 3-1/2" blank (double) between each MA250 and a 3-1/2" blank on the top and bottom. Amplifiers should always be the top components in a rack system.

3.If MA250 channels frequently shutdown due to overheating, install a fan directed up from the MA250 bottom center.

4.Never operate the MA250 on its side, as the cooling potential drops significantly when operated on the side.

5.Connect the MA250 inputs to the source component outputs with good quality, short as possible RCA jack cables. Connect each channel individually.

6.Connect the MA250 speaker outputs to speakers using good quality speaker wire. Minimum 16 gauge copper wire is recommended with 14 gauge minimum for runs over 30' (10m).

Note: Ideally the MA250 likes 6-8 ohm loads. Connecting

to 4 ohm loads won't hurt the MA250 but it may occasionally shutdown. Never connect a MA250 to less than 4 ohms.

Do not attempt to mono bridge the MA250.

7.Make sure the speakers in each room are connected in phase with the amplifier + going to the speaker + . Out of phase speakers give unstable imaging and poor bass response.

8.If connecting the MA250 to a whole house sound system or another amplifier make sure that the other amplifier is a common ground amplifier and that you use good quality speaker wire, minimum 16 gauge.

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Knoll MA250 specifications Hum and noise, Installation
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MA250 specifications

The Knoll MA250 is a notable addition to the world of office seating, combining style, comfort, and functionality in an elegant design. This chair is particularly designed for those who spend long hours working at a desk, catering to the needs of professionals who require both support and aesthetic appeal in their workspace.

One of the standout features of the MA250 is its ergonomic design. The chair offers a contoured backrest that provides essential lumbar support, promoting healthy posture during long periods of sitting. This feature is crucial for reducing fatigue and discomfort associated with prolonged desk work. Additionally, the seat height is adjustable, allowing users to tailor the chair to their specific preferences, ensuring optimal comfort.

The MA250 is built with high-quality materials, enhancing both its durability and visual appeal. The upholstery options available vary from premium fabrics to leather, allowing users to choose a finish that best fits their office decor. This versatility means that the MA250 can seamlessly integrate into various office environments, whether modern or traditional.

Another significant feature of the MA250 is its advanced mechanisms. The chair is equipped with a synchro-tilt mechanism that allows the backrest and seat to move in harmony. This feature supports users in a variety of seated positions, enabling comfortable transitions between tasks and promoting movement throughout the day. This adaptability makes the MA250 suitable for collaborative spaces where dynamic work habits are common.

In terms of sustainability, Knoll emphasizes eco-friendly practices in the production of the MA250. The materials utilized are sourced responsibly, and the design prioritizes longevity, aiming to reduce waste over time. The chair can be easily disassembled for recycling, reflecting a commitment to environmental stewardship.

With its combination of elegance, ergonomic design, and sustainable practices, the Knoll MA250 stands out as a premier choice for modern workspaces. Its thoughtful features cater to the demands of today’s professionals, ensuring that comfort and design go hand in hand. Whether in a private office, conference room, or shared workspace, the MA250 provides the balance needed for productivity and well-being in the workplace.
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