Altec Lansing 1662A manual Troubleshooting Tips

Page 7

Operating Manual -1662A Mic/Line Mixer

the use of mic inputs on channels five or six, but only one level controls both the mic and RCA inputs. The RCA sum inputs have a nominal operating level of -10dBu to match most consumer audio sources.

6.5 Outputs

The Euroblock "A" and "B" outputs are controlled by the output level master controls. They are active servo-balanced with a nominal operating level of +4dBu into any load, and are capable of driving long lines. Outputs can be used balanced or unbalanced. For unbalanced output, connect the shield to both (-) and (G).

6.6 +48V Phantom Power Switch

This switch applies +48VDC to all six mic inputs for condenser microphones. Phantom power will not affect most dynamic mics, which may be used along with condenser mics.

7. TROUBLESHOOTING TIPS

7.1 No Sound

Check the AC power. Is the power switch on? Check the level meters. If they are operating, the problem is between the mixer and the later components in the system. If there is no meter activity, check to see that you really have an input signal and that it is on the desired channel.

7.2 Distorted Sound

Something is being overdriven in the signal path. If the clip indicators are active, reduce the

channel gain and/or press in the pad switch on the rear panel. There are many gain adjustments in the mixer itself and probably several others in other system components which makes it possible to overdrive an input section and then incorrectly try to reduce the gain of the output section. The best way to approach setting gains is to establish the operating level of input stages first by setting their gain as high as possible but leaving about 20dB of headroom for loud peaks, then move on to set the master gain to produce a good meter reading. Proceed to set the gain of equalizers, limiters, crossovers, and amplifiers following the mixer in the same manner, always working toward the later stages of the system.

7.3 Excessive Noise

If the noise is in the form of hiss, the problem is usually due to an input stage set for insufficient gain and then compensating for it by increasing the level. Try increasing gain and reducing level. Also, check that the -20dB rear panel pad switch is not unnecessarily enabled.

7.4 Excessive hum

This is usually caused by "ground loops" in the system wiring. A complex sound system with many sources separated by significant distance and using several power outlets has many opportunities for this problem to occur. If possible, every component in the system should be plugged into the same AC circuit with a common ground. Use balanced input and output connections between widely separated components.

7

Image 7
Contents 1662A Table of Contents Introduction AC Power RequirementsUnpacking Front Panel Controls Connectors and Cables Phantom Power LEDChannel TRS Insert Rear Panel FeaturesMicrophone Input Input PadTroubleshooting Tips Typical Application DimensionsWarranty Information SpecificationsBlock Diagram Operating Manual -1662A Mic/Line Mixer 1662A-0