How many amplifiers can be connected to with the audio processor at the same time?

How many amplifiers can be connected to with the audio processor at the same time?

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Update time : 2022-07-21 15:04:06
How many amplifiers can be connected to one output channel of a mixer or digital audio processor at the same time?
Some people say that you can connect one; some say that you can connect up to three, and some say that as long as there are no more than 10, there is no problem.
So how many can you take?
To understand this, you need to understand the matching relationship between the output impedance and input impedance of audio electronics.
Audio electronic equipment before the power amplifier, such as mixers, digital audio processors, KTV pre-effectors, and various peripherals have input impedance and output impedance, and the power amplifier itself also has input impedance and load impedance.
Take PA 2 digital audio processor as an example:

In the parameter table, there are indicators of input impedance (Input Impedance) and output impedance (Output Impedance).

Number of Inputs 2 line inputs, 1 RTA mic input
Connectors 2 female XLR line inputs, 1 female XLR RTA mic input
Type Electronically balanced/RF filtered
Impedance > 50 kΩ
Max Input Level (line inputs) > +20 dBu
CMRR > 45 dB
  RTA Mic Preamp Phantom Power   +15 VDC
Number of Outputs 6 line outputs
Connectors Male XLR
Type Electronically balanced, RF filtered
Impedance 120 Ω
Max Output Level +20 dBu
Alignment Delay Up to 10ms per output channel pair
A/D Converter 24-bit with dbx Type IV™ Conversion System
A/D Dynamic Range 112 dB A-weighted, 110 dB unweighted
Type IV Dynamic Range 123 dB with transient material, A-weighted, 22kHz BW;
121 dB with transient material, unweighted, 22kHz BW;
  115 dB typical with program material, A-weighted, 22kHz BW  
D/A Converter 24-bit
D/A Dynamic Range 112 dB A-weighted, 110 dB unweighted
Internal Processing Wordlength 32-bit floating point
Sample Rate 48 kHz
Dynamic Range 110 dB A-weighted
107 dB unweighted
THD+Noise 0.003% typical at +4 dBu, 1 kHz, 0 dB input gain
Frequency Response 20 Hz - 20 kHz, +0 /- 0.5 dB
Interchannel Crosstalk < -110 dB, -120 dB typical (input-to-output: < -100 dB)
Latency Input to output: 1.847 ms
Operating Voltage 100-120 VAC 50/60 Hz or 220-240 VAC 50/60 Hz
Power Consumption 22 Watts

Among them, its output impedance (Output Impedance) is 120Ω
Impedance: It is an indicator that describes the resistance of a certain circuit or line to the current, and the unit is ohm (Ohm/Ω).
The higher the impedance (the larger the value), the greater the resistance to current flow, the lower the impedance the opposite.
Use a common example to briefly explain the influence of impedance on current. It is like water flowing in a water pipe. The thicker the inner diameter of the water pipe, the smaller the obstruction to the water flow, which is equivalent to the lower the impedance; and the thinner the water pipe, the less the water flow. The greater the hindering effect, the higher the impedance.
We imagine the connection between the front-level equipment and the rear-level equipment as the water supply system of a residential building. Each building has a relatively thick water inlet main pipe, which is regarded as a front-level output channel. Each household has a relatively thin household water pipe, and the water pipe of each household is equivalent to a post-stage input channel.
If there are more occupants in a building, you need to use a thicker inlet main for water supply. If the inlet main is too thin, the water pressure will be insufficient. On the other hand, if the inlet mains are thicker, it means that more households can be supplied with normal water.
When the inner diameter of the household water pipes is constant, for example, there are 4 pipes, the thicker the main water inlet pipe, the more households can ensure normal water supply.
Looking back at the sound, the lower the output impedance of the front-end equipment, the thicker the inner diameter of the water supply main pipe; and the higher the input impedance of the latter-stage equipment, the thinner the inner diameter of the household water pipe.
Under the premise that the input impedance of the post-stage equipment is certain, the lower the output impedance of the pre-stage equipment used, it means that the pre-stage equipment can bear more post-stage equipment at the same time.
Of course, from the point of view of only being able to respond, it is no problem to connect a pre-stage output channel to many power amplifiers. As long as there is a signal entering the power amplifier, the speakers connected to the power amplifier can produce sound.
However, under the premise of ensuring that there is no obvious impact on the effect, one output channel of the pre-stage device can be connected to several post-stage devices at the same time? The empirical formula can be calculated as follows:
The maximum number of channels that can be connected = the input impedance value of the post-stage device / (20x the output impedance value of the pre-stage device)
For example: the output impedance of the digital audio processor mentioned above is 120Ω; the power amplifier adopts balanced input, and the input impedance is 20KΩ
Then the maximum number of power amplifier channels that can be connected to one output channel of this digital audio processor at the same time is: number of channels = 20000/(20x120) = 8.3333
That is, one output channel of this processor can connect up to 8 power amplifier input channels in parallel at the same time without affecting the effect, that is, one for eight.

If you are using another brand of digital processor,like 4 input 8 output audio processor AD48:
Item Specifications
Max Input Level 18dBu
Max Output Level 18dBu
Default Output Level 0dBu
THD+N <0.003%;1kHz@+4dBu
Frequency Response 20Hz-20kHz, +/-0.2dB
In To Out dynamic range 110dB (Unrecorded right)
S/N -110dB (Unrecorded right)
ADC Dynamic Range CS5361 114dB
DAC Dynamic Range CS4382A 114dB
DSP 400Mhzfloating - point SHARC ADSP-21488
Sampling Frequency 48K
QE 24Bit
Storage 32
Control Mode 100M Ethernet
Language English
Noise Gate Yes
Feedback Yes
Signal Generator Yes
Pressure Limiter Independent 12 channel
Delay Output 1-4 218ms
Output 5-8 148ms
Low Shelf
High Shelf
Independent 16-band
High Pass/Low Pass 
Independent 12 channel
The source impedance (output impedance) displayed on the output channel is less than 110Ω.
Then if this processor is connected to the above power amplifier, one output channel can load at most:
The number of channels = 20000/(20x110) = 9.09, which is almost 9.
It can be seen that the lower the output impedance of the pre-stage device, that is, the stronger the load capacity, the more post-stage devices that can be connected.
Note: If an unbalanced connection is used, since the input impedance of the amplifier is twice as low as unbalanced than balanced, the number of connected power-end devices will be doubled.

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