TAS5825M: Optical Input

Sadanori Kato

Part Number: TAS5825M
Other Parts Discussed in Thread: TLV320AIC3262,

Hi,

The output signal is attenuated by approximately 3.9dB for the input signal with the level meter if selecting the optical input as the audio source.
Is my understanding correct that TLV320AIC3262 in the signal path on the PPCMB attenuates the input audio signal ?

Best regards,
Kato

over 6 years ago

0 Akio Ito over 6 years ago

Genius 3595 points

Kato-san,

I think that 3.9dB loss is caused by detection method of the Level meter, not by TLV320AIC3262.

This insertion loss of DRC Threshold settings already seems to have been considered in PPC3/TAS5825M App..

Best regards,

Akio Ito

0 Sadanori Kato over 6 years ago in reply to Akio Ito

Guru 36540 points

Hi Ito-san,

Thank you for the explanation.

It is difficult to persuade our customer, so please let me know if there is application notes which you mentioned.

Best regards,
Kato

0 Alix Wan over 6 years ago in reply to Sadanori Kato

TI__Genius 9995 points

Hi Kato-san,

As you known, both AP or other player like footbar, when they set input level to be -10dB sinwave, which means the peak value. The level meter measure the level of input signl with average value (average value of postive period of a sinwave). The relationship bwtween average value and peak value is: Vav=(2/pi)*Vpeak.
Hence, you can see a -3.9dB attenuation.

Regards,
Alix Wan.

0 Sadanori Kato over 6 years ago in reply to Alix Wan

Guru 36540 points

Hi Alix-san,

Thank you for the information.

As Ito-san mentioned above, the relationship between average value(Vav) and peak value(Vpeak) is "Vpeak = 0.5 * PI * Vav".
* The above formula "Vav=0.5*pi*Vpeak" is typo.

The above infomation isn't mentioned in the application note, so I will inform our customer that the level meter detects the average value, not the peak value.

Best regards,
Kato

0 Sadanori Kato over 6 years ago in reply to Sadanori Kato

Guru 36540 points

Hi Ito-san,

Thank you for your support.

For Vav value, it seems that 0.63662 is correct, not 0.63362.

Best regards,
Kato

0 Akio Ito over 6 years ago in reply to Sadanori Kato

Genius 3595 points

Kato-san,

Your indication is correct.
>> 2/pi
ans = 0.63662
0.63362 was a typo. And TLV320AIC3262 was too, TAS5825M is correct.

Best regards,

Akio Ito

0 Sadanori Kato over 6 years ago in reply to Akio Ito

Guru 36540 points

Hi Ito-san,

I greatly appreciate your cooperation.

Best regards,
Kato

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TAS5825M: Optical Input