8
8. Voltage clipping/Peak LED
The Peak LED will illuminate when the voltage is clipping, i.e. there is insufficient voltage to
maintain a constant current.
Momentary short term voltage clipping is unlikely to be audible in hearing aids, but if
clipping occurs for any length of time (the Clip LED (8) remains on), the audio quality will
suffer and remedial action should be taken to reduce or eliminate the problem.
Voltage clipping will occur at higher frequencies first. It causes distortion of the audio
signal. Situations that require higher voltages from the loop driver and where voltage
clipping may occur are typically where:
• The loop has a high impedance. The impedance of the cable is determined by its length
and cross sectional area. The longer and thinner the cable, the higher its impedance.
The feed cable must also be considered when calculating the loop impedance. A 2-turn
loop will have an impedance more than double that of a single turn loop of the same
length and cross-section due to mutual inductance.
• Strong compensation from the parametric MLC control is applied
Note
In some cases metal reinforcement can actually reduce the voltage requirement.
9. Loop monitor/headphones socket
Univox
®
PLS-X series has a powerful speaker amplifier and a 3.5mm headphone socket
built-in. The headphone socket is on the front panel, the speaker connectors (13) and
volume control (17) are placed in the rear panel. Both are fed directly from the loop
providing an accurate reproduction of the loop signal. A distorted, poor quality signal or
lack of audio input is easily identified by use of this feature.
Note 1
The volume control is located in the rear panel and controls the volume level of both the
external speaker, if attached, and the headphones output.
Note 2
Excessive output to speaker may reduce the overall loop output power.
10. Power LED (On)
The blue Power LED is illuminated at all times when the unit is connected to a working
power supply.