TPA6133A2: No difference in the perceived output power level while increasing the voltage in the TPA6133A2 evm

Part Number: TPA6133A2

Hi,

We are evaluating TPA6133A2 evm module. We are testing ( testing setup fig. 2) the output power of the TPA6133A2 using two different voltage levels (3.3V and 5V). We are unable to find any significant difference in the perceived audio level between the two voltage levels while listening through earphones. In the datasheet pg 5, appended fig.1 (it is mentioned that output power varies with different voltages).

Why there is no increase in loudness while giving 5 V to the TAP6133A2.

Voltages given to evm:

a) 5 V input

b) 3.3 V input 

                                                                                                                              Fig. 1

                                                                                                                      Fig. 2 

Regards,

7 Replies

  • Hi Amey,

    Welcome to e2e.
    Have you verified that THD+N is set to 1% at both supply voltage levels? The spec table from data sheet suggest that output power measurement was taken at THD+N=1%.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • In reply to Ivan Salazar:

    Hi Ivan,

    We have used TPA6133 EVM module in the above experiment. Is there any procedure to set THD+N  to 1% and why it is important. I am unable to get the physics behind setting the THD+N to 1 % .

    I am sharing  the screenshot of the experiment, the voltage in the oscilloscope is that taken across 33 ohm resistor. According to the datasheet the 5V will have more power as mentioned in the previous thread.  

    Input signal: 200mV

    Outup signal: 322mV

    Fig a) 5V given to the TPA6133 EVM

    Fig b) 3V given to the TPA6133 EVM

    As you can see there is no difference in the voltage level between the two setup. 

    Fig. a

    Fig. b

    Regards,

    Tapas

  • In reply to Tapas Pandey39:

    Tapas,

    The output power will not immediately increase by increasing the supply voltage. Output power also depends on the input signal amplitude...
    THD+N = 1% is obtained when the signal is starting to clip so the distortion begins to raise at this point, some equipment like AP can measure THD+N.
    The reason I mention this spec is because, when you increase the supply voltage, the output of the device should be able to provide higher voltages as well, so the distortion on the output signal due to clipping should be reduced. So in order to obtain a THD+N = 1% across different supply voltages you should adjust (increase) the input signal as well.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • In reply to Ivan Salazar:

    Hi Ivan,

    You have mentioned that some equipment like AP can measure THD+N. Can you expand the abbreviation AP.

    According to the line levels  in the consumer audio space maximum voltage is 0.894 VPP. I think it should be dependent on load. We can only increase the input signal to the amplifier such that voltage across load should be around 0.89VPP. Is that correct.

    Regards,

    Tapas 

  • In reply to Tapas Pandey39:

    Tapas,

    AP means Audio Precision.
    Yes, output voltage would depend on load impedance. Usually Line applications use loads from around 600-ohm to 10-kohm.
    If you want to stay within the 0.894-Vpp range then yes, you would need to adjust input signal or the gain of the amp (although in the specific case of TPA6133A2, the gain is fixed) so that the output does not go over this voltage level.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • In reply to Ivan Salazar:

    Hi Ivan,

    The output from TPA6133A2 is meant to drive load of 16 ohm. I have one doubt regarding conventions in the field of audio, output from
    a) Mic ------------> mic level
    b) Pre-amp -----> line level
    c) Amplifier-----> speaker level

    Output from headphone amplifier is called ? What are attributes of this level.

    Regards,
    Tapas
  • In reply to Tapas Pandey39:

    Tapas,

    I think those names might be too subjective, perhaps a better way to identify them could be by voltage or power level. Mic and Line are usually specified in Volts:
    a) Mic - in the order of mili Volts
    b) Line - in the order of Volts, Vpp or Vrms

    While headphone or speaker amps are specified in Watts:
    c) Headphone - in the order of mili Watts up to around 1W
    d) Low Power - from 1W up to 10W
    e) Mid Power - from 10W up to around 50W
    f) High Power - higher than 50W

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators