Limiting Functions, Limit LED Functions

user manual

QLight™ DP series

Limiting Functions

The amplifier modules are equipped with accurate limiters for both high frequency and low frequency sections. Because the HF and LF limiters work independently of each other, there is no possibility of either section compromising the performance of the other as is the case with a single broad-band limiter. Furthermore, each limiter has its attack and release time constants independently set and optimised according to the operating frequency range. These allow transient delivery whilst preventing overheating or over excursion of the transducers.

Limit LED Functions

At switch-on the power LED will illuminate and the red limit LED’s will flash in unison for approximately 5 seconds as the unit performs an initial diagnostic self-test. Audio will be automatically muted during this period.

After initialisation, the limit LED’s extinguish and the unit will now pass audio. During operation if either of the red limit LEDs flash this indicates that the DSP is taking corrective action by applying the limiter to that channel in order to avoid damage to the drive unit. You should reduce the signal accordingly so that the limit LED’s light only occasionally. Both LED’s flashing in unison under regular operating conditions indicates that the DSP is activating a protection feature, taking two possible courses of action: the input will either be attenuated to stop the unit being overdriven, or in extreme cases will be shut down.

Status	Condition	Action

Both Limit LED’s flashing	System initialisation

Both Limit LED’s flashing	Protection activated	Reduce input level

Limit high LED flashing	DSP applying limiting to the	Reduce input level
	high frequency channel

Limit low LED flashing	DSP applying limiting to the low	Reduce input level
	frequency channel

1 WARNING 1

The limiters are designed to allow short-term transients in program material in order to preserve sufficient dynamic headroom, while at the same time optimising component life by protecting against long-term heating effects. DO NOT allow the loudspeaker to constantly run into limiting; this will not only degrade your sound quality by reducing the available dynamic range, but also in extreme cases may increase the risk of damage to the drive units.

QLight DP series manual page 18