Knoll Systems service information
The MX1255 amplifier does not contain any user serviceable parts inside. If you suspect a problem that may require servicing, contact us at www.knollsystems.com/contact.html, or by phone at 800
Troubleshooting
If a problem is encountered with the MX1255, the most expedient procedure is to locate the problem and if possible repair it before requesting service. Be sure to carefully check other system components such as controllers, CD players, volume controls, wiring, speakers, etc. that may be at fault.
Problem | Action | |
Power LED does | 1. | Check that the MX1255 is plugged in. |
not light - no sound | 2. | Test the AC outlet with a lamp. |
| 3. | If remote on/off is used, check that |
|
| the trigger voltage is at 12 VDC. |
| 4. | Check MX1255 power button on (in). |
Sound cuts out | 1. | Verify speaker impedance is |
|
| Changing speakers may be required. |
| 2. | Check if the MX1255 feels hot. If it's |
|
| hot increase cooling - see Installation. |
Sound is distorted | 1. | Turn the volume down. |
| 2. | Check speakers for damage. |
| 3. | Check inputs for proper levels. |
|
| MX1255 gain and source output level |
|
| may, have to be adjusted. |
| 4. | Speakers may be less than 4 Ω. |
MX1255 does | 1. | Push MX1255 power switch off (out). |
not turn off | 2. | If trigger is being used, power switch |
|
| needs to be set to off (out) position |
|
| or amp is on all the time. |
| 3. | Try disconnecting trigger jack. |
Trigger does not | 1. | Measure the trigger voltage with a volt |
work |
| meter. It needs to be |
|
| to work (current is about 35mA total |
|
| per amp). See page 5 for details. |
Speaker pops when | 1. | Speaker may need resistor placed |
amp turned on or off |
| across terminal. Suggest 2k0 1/4 w. |
|
| Discharges speaker internal capacitor. |
Installation
Installing the MX1255 should be relatively easy. With a bit of planning, it will give trouble free service for years.
1.The most important consideration when installing the MX1255 is cooling. The MX1255 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
2.Amplifiers should always be the top components in the system.
3.If MX1255 channels frequently shutdown due to overheating, install a fan directed up from the MX1255 bottom center.
4.Never operate the MX1255 on its side, as the cooling potential drops significantly when operated this way.
5.Connect the MX1255 inputs to the source component outputs with good quality, short as possible RCA jack cables. Connect each channel individually.
6.Connect the MX1255 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 MX1255 likes
7.Individually adjust the channel gains as required. Ideally, all gains are fully on (fully clockwise).
8.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.
9.Connect trigger if being used to a 12 VDC source (about 35mA) using a 3.5mm mono jack. 5 VDC triggers will not work.
10.Connect the AC power into an outlet that supplies at least EIGHT amps (1000 watts) dedicated to each MX1255.
11.If more power is needed, channel 6 can be mono bridged to give 180 watts into an 8 Ω load. Minimum impedance for channel 6 in the bridged mode is 8 Ω. The bridged switch needs to be in the out position. The bridged input is 6L and the 6L gain pot adjusts the bridged gain. The speaker is connected to the 6L+ and 6R+ in the bridged mode.
