Low Volume Level at output of BF537

I have compiled and executed the C_Talkthrough_I2S.dpj example in the ADSP-BF537 EZ-Kit Lite folder included with the BF537 evaluation board and I don't get the same level as I'm putting in.

Using a D-scope I am measuring a 1.4dB loss at the output.

Can anyone explain why this is happening?

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  • I'm using the analogue output on the dScope to generate a 0dBu sinewave. This is being fed into one channel of the BF537 via the AD1854. I'm then using the simple C_Talkthrough_I2S.dpj to pass the encoded signal straight back into the DAC(AD1854) without, as far as I can tell, any modification to the input. I'm then using the dScope to look at the output of the DAC. This is where I measure -1.4dBu at the output. 0.1% THD+N at the output under these conditions.

    If I generate a 0dBFS sinewave I measure -4.2dBFS at the output. I'm measuring 18.1% THD+N at the output under these conditions.

    I am not able to access the digital data between the ADC and DAC. I have attached a guide to the BF537 with schematics. Page 78 shows the ADC while page 79 shows DAC serial interface pins shorted to ground.

    Thanks for your assistance with this.

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