VS1003 + TPA3128D2 (Class D)

Designing hardware that uses VLSI Solution's devices as slave codecs such as an external MP3 decoder chip for a host microcontroller.
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VS1003 + TPA3128D2 (Class D)

Post by tin » Sat 2019-04-13 14:01

in my application I would like to connect the TPA3128D2 amplifier with VS1003 controlled with VNC1-L (FTDI).
I tried single-ended connections without using GBUF.
Unfortunately, the output signal from VS1003 is a bit too low (around 260mV Vpp) and I need about 330mV (Vpp) to fully drive the amplifier.
How could I amplify the output signal from the system?

The differential connection with the use of GBUF gives even smaller input signal for the TPA3128D2 amplifier.
Or maybe I should use a simple non-inverting amplifier, eg LM358?

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Re: VS1003 + TPA3128D2 (Class D)

Post by Panu » Mon 2019-04-15 12:35


Wouldn't it be easier to adjust the gain of the TPA3128? You can adjust the gain from 20 to 36 dB with resistors connected to the GAIN/SLV pin of that amplifier. The difference of 330 mVpp to 260 mVpp is about 2.1 decibels, so you could just increase your gain by 2 dB to get the same effect.

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Re: VS1003 + TPA3128D2 (Class D)

Post by Henrik » Wed 2019-04-17 11:59


The single-ended full-scale sine output from VS1003 at full output volume (register SCI_VOL = 0x0000) is around 1500 mVpp so your value of 260 mVpp seems very low.

When connecting to a differential amplifier you can connect Left output to one terminal and Right output to the other terminal, and then activate VS1003 differential output by setting bit SCI_MODE register bit SM_DIFF. This will double your output to 3000 mVpp. If you don't set SM_DIFF, you will get almost no output.

Whatever you do, make sure you follow Panu's Line In and Line Out guidelines, as presented in the signature part of his message. Failing to do so may result in excessive noise.

Kind regards,
- Henrik
Good signatures never die. They just fade away.

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