• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 30 subscribers
  • Views 894 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AIC3254 HP output impedance question

Nick Hsiao19
Intellectual 615 points

Hi,

I am looking into the AIC3254 HP output impedance. Below is my measurement by using Audio Precision and AIC3254 EVM-U (High performance playback preset, and HP output series 100uF). You can see there is a nature highpass filter which is fc=1/(2*pi*100uF*Rload).

To avoid the driving power issue, I make the output about 50mV. Starting with Rload=10k ohm, then 33 ohm, and 1 ohm in the end.

Set Vo as the voltage with 10k ohm load, and the equation Ro=Rload*(Vo-Vload)/Vload, I got AIC3254 impedance at 10kHz is around 2.3 ohm. Am I right?

V=54.3mV@10k ohm; 50.9mV@33 ohm; 16.2mV@1 ohm.

  • 0
    TI__Guru* 84915 points
    Hello, Nick,

    The HP driver impedance is 0.5 to 1-ohm when powered. In order to measure this impedance, we recommend to drive a 500-ohm resistor or so and calculating the resistance based on the observed voltage drop.

    Best regards,
    Luis Fernando Rodríguez S.
  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 615 points

    Hi Luis,

    it is assumed that the headphone amp output impedance is about 1 ohm, I just want to know if 500 ohm Rload is suitable for this measurement. Based on the equation, when using 500 ohm as target Rload, the drop voltage must be less than a certain level ( maybe 1mV), but any disturbance could make the voltage variance.

    Anyway, I have checked my cable connecting between AIC3254 HP output and Rload, it is about 1.2 ohm, so take cable impedance into account, the HP output impedance should be around 1 ohm.

    Thanks,

    Nick.

  • 0 in reply to Nick Hsiao19
    TI__Guru* 84915 points
    Hi, Nick,

    The 500 ohm Rload is used for this measurements in our codec devices. The headphone output supports 14.4ohm minimal. So, there won't be a problem if this load is used for measurement purposes.

    Best regards,
    Luis Fernando Rodríguez S.