to compensate for hostile conditions on the AC mains:
•suppresses high voltage transients up to several kilovolts
•filters EMI (radio frequencies and noise present on the AC line)
•sustains operation during low-voltage periods, which minimizes audio discontinuity
•provides soft-start power-up, which eliminates high inrush current
The UM-P can withstand continuous voltages up to 264V and allows any combination of voltage to GND (i.e. Neutral-Hot-GND, Hot-Hot-GND). Continuous voltages higher than 264V may damage the unit.
Voltage Requirements
The UM-P operates safely and without audio disconti- nuity if the AC voltage stays within the range 88–264V, 47–63 Hz. After applying AC power, the system is muted while the circuitry charges up and stabilizes. After two seconds, the On/Temp. LED on the user panel illumi- nates green, the system unmutes and is ready to pass audio signals. If the On/Temp. LED does not illuminate or the system does not respond to audio input after ten seconds, consult the Troubleshooting section.
The UM-P’s power supply uses stored energy to continue functioning for about 10 AC cycles if the voltage decreases below 88V (a condition known as brownout). The precise length of time the unit functions during brownout depends on the operating level and how low the voltage drops. The unit turns off if the voltage does not increase above 88V before the storage circuits are depleted. If the UM-P shuts down due to brownout, the power supply automatically turns on after three seconds if the voltage returns to the normal operating range. If the UM-P does not turn back on after ten seconds, consult the Troubleshooting section.
NOTE: We recommend that the supply be operated at least a few volts away from the upper and lower bounds of the operating range to avoid possible shutdown.
Current Requirements
Each UM-P requires approximately 3Arms @115V (1.5Arms@230V) for proper operation, allowing up to five UM-Ps to be powered from one 15A circuit. How- ever, we recommend powering no more than three UM-Ps per 15A branch to allow a 30% margin for peak voltages. The UM-P presents a dynamic load to the AC mains which causes the amount of current to fluctuate be- tween quiet and loud operating levels. This affects the number of UM-Ps that can be used for a given breaker type. Since different types of cables and circuit breakers heat up and trip at varying rates, it is essential to understand the types of current ratings and how they correspond to circuit breaker and cable specifica- tions.
The maximum continuous RMS current is the maximum RMS current over a duration of at least 10 seconds. It is used to calculate the temperature increase in cables, which is used to select cables that conform to electrical code standards. It is also used to select the rating for slow-reacting thermal breakers.
The maximum burst RMS current is the maximum RMS current over a one second duration. It is used to select the rating for most magnetic breakers.
The maximum instantaneous peak current during burst is used to select the rating for fast-reacting magnetic breakers and to calculate the peak voltage drop in long AC cables according to the formula
Vpkdrop = Ipk x Rtotal cable
Use the table below as a guide to select cables and circuit breakers with appropriate ratings for your operating voltage.
UM-P Current Ratings
| 115 V | 230 V | 100 V |
| | | | |
Idle RMS | 0.25 ARMS | 0.13 ARMS | 0.3 | ARMS |
Max. Continuous RMS | 2.8 | ARMS | 1.4 | ARMS | 3.2 | ARMS |
Max. Burst RMS | 3.2 | ARMS | 1.6 | ARMS | 3.7 | ARMS |
Max. Peak During Burst | 5.0 | APEAK | 2.5 | APEAK | 5.8 | APEAK |
To determine the minimum total service power re- quired by a system of UM-P, or other Meyer self-pow- ered speakers, add their maximum continuous RMS currents together. We recommend allowing an addi- tional 30% above the minimum amperage to prevent peak voltage drops at the service entry and nuisance tripping.
