Small but crucial | Power supply sequencer, power safety steward of audio-video system

When building an audio and video system, people always pay attention to the mixer, power amplifier and speaker, and often ignore the power sequencer in the cabinet. Many people equate it with high-power plug-in. In fact, it is the power guardian for the stable operation of the whole system, avoiding sonic boom and surge impact and prolonging the service life of the equipment.

When building audio, conference and public address systems, we often focus on the core signal equipment such as mixer, power amplifier and audio processor, but it is easy to ignore an unremarkable equipment in the cabinet-power sequencer.

Many practitioners have a misunderstanding: the power sequencer is only a multi-channel high-power plug-in, which can be replaced at will. However, in the professional engineering scene, standardized and orderly sequential power supply is the first line of defense to prevent the impact on sonic boom, reduce the equipment failure rate and ensure the long-term stable operation of the system.

1. What is a power sequencer?
Power supply sequencer, also known as sequential power supply, relies on built-in control circuit and multi-way relay to turn on power in turn according to preset time intervals, and turns off power in reverse order when it is turned off. The conventional channel has a delay of 1 ~ 3 seconds, and the mainstream is 1U rack structure, which is common in 8-channel, 10-channel, 12-channel and 16-channel specifications and can be directly installed in the standard equipment cabinet.

To put it simply: control the equipment to power on in batches to avoid all equipment starting at the same time to compete for power.

Second, the sound system, why must comply with the start-stop order?
Standard operating logic startup sequence: first turn on the front stage, then turn on the power amplifier audio source equipment, wireless microphone host → audio processor, feedback suppressor → mixer, video matrix → power amplifier.

Shutdown sequence: turn off the power amplifier first, then turn off the previous equipment to cut off the power supply of the power amplifier first, and then turn off the signal equipment such as the mixer and player in turn.

Once the huge hidden danger of manual operation is reversed, the amplifier will suddenly cut off the pre-stage signal when it continues to work, which will have a huge impact on sonic boom in an instant. Continuous high-voltage impact will accelerate the aging of the speaker unit, and directly burn the speaker unit and the power amplifier output module in serious cases.

In addition, multiple high-power devices are powered on synchronously, which will generate superimposed surge current:

Instantaneous current is too high, which is easy to trigger air-to-air trip;
Power grid voltage fluctuates violently, which interferes with digital audio equipment and induces current noise;
Accelerate the aging of the internal power capacitor of the equipment and shorten the service life of the whole machine.
The power sequencer can automatically execute the standardized start-stop process with one button, eliminating human error, and is widely used in conference rooms, lecture halls, campus broadcasting, theaters and mobile performance systems.

Third, the power supply sequencer not only supplies power sequentially, but also has full practicability of these functions.
1. Overload and short circuit protection
Automatically cut off the circuit when the load exceeds the standard and the line is short-circuited, so as to reduce the risk of line heating and fire.
2. Real-time monitoring of mains voltage
The model with digital display can display the input voltage in real time and quickly locate all kinds of system anomalies caused by unstable power supply.
3. Intelligent remote linkage
High-end models support RS232/485, TCP network, dry contact docking central control system, and realize integrated intelligent management and control of the whole set of equipment in the conference room.
4. Independent straight-through socket
Some models are equipped with through channels that are not controlled by time sequence, which can continuously supply power for routers, computers and monitoring equipment.

Important distinction: ordinary plug-in ≠ power sequencer

Ordinary power strips only realize power distribution, and there is no delay control and relay isolation protection, which can't solve the surge impact of power on and off, and professional audio systems can't directly replace sequential power supply with power strips.

Four, the system channel wiring reference (project landing directly apply)
Channel power-on sequence from first to last:

Channel 1: Player, wireless microphone host

Channel 2: Audio processor, feedback suppressor

Channel 3: Mixer, Video Matrix

Channel 4 and subsequent channels: all kinds of power amplifiers and active speakers.

Remember the formula: signal equipment comes first, power amplifier comes last.

Five, choose and buy power sequence key points to avoid pit
1. Accurately calculate the total load current
Summarize the maximum power consumption of all equipment and reserve 30% load margin. Don't just look at the number of channels and ignore the relay load specification.
2. Select the model as needed
Basic model: fixed time delay, manual control of panel, suitable for small conference room and simple background music system; Smart model: adjustable delay, supporting central control linkage, mostly used in multi-function halls and large venues.
3. Give priority to the models with voltage display and independent loop protection.
The protection circuit of low-cost simple model is shrunk, the relay contact is easy to ignite, and the stability of long-term continuous operation is insufficient.
4. For scenes with high sound quality and poor on-site commercial power environment, you can choose a model with power filter to purify commercial power clutter and improve the system noise floor.

6. Which scenarios suggest standard power sequencer?
Government-enterprise meeting room and multifunctional lecture hall

Campus public broadcasting and park background music system

Theater, fixed performing arts venues, KTV

Outdoor mobile stage performance system

Recording studio, professional audio-visual room

Small and simple system, and long-term standardized operation by professionals, can be simplified as appropriate; It is strongly recommended that the power sequencer should be standard in unattended places where many people take turns to operate.

Many audio and video system failures are rooted not in the equipment itself, but in the irregular power supply mode. The power supply sequencer is not the most eye-catching equipment in the whole system, but it is the invisible guardian to ensure the stability of the system, prolong the service life of the amplifier speaker and reduce the later maintenance cost. Standardizing sequential power supply is a standardized configuration that cannot be omitted in every professional audio and video project.