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This lesson is about the circuit related to the speaker

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Take the Changxiang 20 Pro model as an exampled

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Because its speaker circuit is quite special, it also uses the MediaTek platform

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Let's take a look at the components in this circuit

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The one on the right is the seat J3601 connected to the speaker

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Here are two small audio chips

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Changxiang 20 Pro was a machine that was focused on louder sound at the time,

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so it used two audio power amplifiers to drive a speaker at the same time,

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making the power of the speaker higher, so the sound would be louder

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The two small audio models are basically the same

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Look at the power supply here, the power chip contains a main audio chip

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This is the main CPU

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The main CPU sends the sound signal to the main audio for encoding and decoding through these two lines

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The main power supply processes the sound signal, and after processing,

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the sound signal is passed to the small audio through the AU_LOLN line

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The small audio amplifies the power of this audio signal,

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and then outputs the amplified signal from the corresponding pin,

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and sends it to the seat, and then to the speaker, so as to push the speaker to emit sound

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It has a similar structure to HiSilicon, the main audio is included in the power chip

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Let's take a look at the codename here

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AU and AUD refer to audio, which belong to audio signal circuit

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This is Changxiang 20Pro, which is an older model

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Let's look at another older model, Changxiang 9

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This phone is very similar to the Redmi K50, with a very simple structure

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Look at the right side first, this is the seat of the speaker, we regard it as a speaker

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The middle one is the power IC, which contains an audio power amplifier

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On the left is the CPU

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Its bus is different from the above models

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Its bus uses the PDM transmitting line and receiving line to transmit the sound signal

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The CPU transmits the sound signal to the audio power amplifier inside the power supply through the PDM bus

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The audio power amplifier processes the signal, amplifies it finally,

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and then outputs it to the speaker, which drives the speaker to emit sound

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This is an early Qualcomm solution

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Through the above models, we found that their buses are different,

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and some of them contain the main audio in the power supply.

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Some are 2 small audio to push the speaker, most are a small audio to push the speaker

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In some cases, the small audio is connected to the large audio first, and then connected to the CPU

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In some cases, the small audio is directly connected to the CPU

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This is the relevant circuit of the speaker of the Android phone

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That's all for this lesson