External TDM DACs output quality question

[dmit2k]

Problem Description

Hello,

I have the following question regarding the DAC boards from the "External TDM DACs" WiKi page:

This chinese CS42448 boards use basic passive RC output filters with small SMD components. However, those components are physically too small to handle output levels above -20 dBFS without adding distortion (except between 500 and 1000 Hz).

Also, the CS42448 outputs are internally buffered and provide ~0.9 V RMS with a 1.5 V DC offset. So, without an active op-amp stage, the board must be connected to a high-impedance input, and you're stuck with a relatively low signal level and roughly half the potential dynamic range.

In theory, the CS42448 can drive a line input directly (via a DC-blocking capacitor), and the ~1.1 V RMS may be technically enough in terms of volume. But can we really talk about high-quality audio output under these conditions?

In summary, with such weak RC output stages, both boards effectively cripple the performance of the CS42448 DAC:
– significant distortion appears at levels above -20 dBFS due to undersized SMD components,
– the output voltage is too low, cutting the dynamic range in half,
– and overall sound quality suffers greatly as a result.

Can you confirm or debunk these concerns? I'd really appreciate any insights.

Device Description

ESP32C3 board with round screen and rotary encoder.

Sketch

not a code-related question

Other Steps to Reproduce

No response

What is your development environment (incl. core version info)

No response

I have checked existing issues, discussions and online documentation

• I confirm I have checked existing issues, discussions and online documentation

[pschatzmann]

So far I never had the time to test any TDM: Maybe somebody else might have some input on this ?