ADAU1701 BIG PROBLEM

Another detail the thermal noise output is high even with the audio inputs on-120dBattenuated really means that the problem is in the DAC

Cleber, how much noise are you seeing? The DACs are specified to operate at around -104 dB SNR (including A-weighting filter). Given the 0.9 Vrms full-scale output level, this means that the noise level should be around 6 μV.

If you need to scale up the output level, then use some low-noise audio op-amps in the output signal path. If the op amp has very low noise and distortion, like the AD8597, the system's SNR will be maintained even when the level is scaled up.

So, if you maintain the -104 dB SNR for the 5 Vrms system, your noise level should be something like 30 to 40 μV.

Brett,

Thanks for answering,
Turns out my reach Full Power Amplifiers at 150mV,
and to connect the ADC noise increases even more, I'm using 2k2 RIN and the ADC res18k
Operational Amplifiers are my NE5532 and they are using the filter proposed in thedatasheet
Supply Voltage + /-15Vdc
Plan of Land in all the circuit.

How much gain is provided by the power amplifier?

Can you measure the noise directly at the DAC pin?

Did you try muting the DSP core to measure the noise floor?

On the evaluation board, you'll see very low noise levels at the DAC outputs - less than 10 μV, typically.

The ADC has worse SNR than the DAC, so if you use the ADC and run it through the DSP to the DAC, your noise floor will increase.

Then the power amp will apply gain to the noise floor and increase it significantly.

Also, the power amp will have its own noise characteristic that it imparts on the signal.

To rule out the ADAU1701 as the source of the problem, try doing this:

Mute the ADAU1701 core (or download a program to it from SigmaStudio that simply does not use the outputs)

Check the signal at the ADAU1701's DAC pins.

Brett,

Mute the Core DSP noise continues in the same way that keeping at-120dB ADC

the patterns of our equipment are these 150mV Full Power

we're talking about 150mV = 300Wrms output in speakers

I believe that to be the order of mV level comm the cause of these noises.

AC RMS level in the output of the proposed filter on my plate with the mute on this circuitin 12mVrms

This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

Thank you,
EZ Admin