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TPA6120A2: TPA6120A2

Andreas Hanke Stern
Prodigy 30 points
Part Number: TPA6120A2

Tool/software:

Dears,  

I have a Headphone amplifier with (TPA6120A2 High Fidelity Headphone Amplifier) , +/- 12 VAC R-core transformer , Stereo analog inputs (L, R) from a DAC  and the quality output signal is fantastic, in my Sennheiser Headphones.

Questions : 01 - This chip (TPA6120A2 ) is all analog, linear or have some Class D PWM modulator inside ?

02- Why this Headphone amplifier (using TPA6120A2 TI chip) which has SNR 128 dB , THD 112 dB,  Slew rate - 1300 V/uS, that has a wonderful response, no background noise when connected to a passive Headphone (Sennheiser), NOT seems so wonderful when it is connected “as a preamplifier” before the power amplifier and speakers ?  Seems that you loose the dynamic range of sound ?

Many thanks for your explanations, considerations,

Andreas 

  • 0
    TI__Mastermind 21527 points

    Hello Andreas,

    The TPA6120A2 is a class-AB architecture current-feedback amplifier.  There is no Class D PWM modulator inside the device.

    The TPA6120A2 is designed to drive headphone impedances directly; could you share your circuit or block diagram of your system?  You may not need a dedicated power amplifier as the TPA6120A2 can drive 700mA output current per channel.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 30 points

    Alec, thanks for the prompt reply ! My idea was to use the TPA6120A2 in the place of traditional "audio preamplifier", because its THD, SNR, slew rate are very good numbers and sounds very good with Headphones! But in practice, when i connect the TPA6120A2 output at my power amplifier ( 200 + 200 W RMS/ 8 ohms), the "quality" of sound is NOT so good as when the TPA6120A2 was direct feeding the Headphones. Can be some impedance mismatch , my power amplifier input impedance is high, around 20,000 ohm, and normal use of TPA6120A2 is for feeding Headphones (16 to 300 ohms, low impedance) ?

    The audio diagram is just , instead of using preamplifier, power amplifier and Loudspeakers, you put the TPA6120A2 , power amplifier and Loudspeakers. (Normal household stereo equipments, nothing special !)

    P.S - the idea was to use TPA6120A2 to drive the power amplifier/Loudspeakers , NOT some Headphone !

    Have some idea why the quality of sound seems to be changed for what i hear when the headphones are connected directly ?

    Many Thanks, Andreas

  • 0 in reply to Andreas Hanke Stern
    TI__Mastermind 21527 points

    Hello Andreas,

    Thank you for the background information!  Could you share your circuit for the TPA6120A2 and power amplifier?  The gain of the TPA6120A2 would be important here, as well as knowing power amplifier device.  If in a lower gain, the SNR on the TPA6120A2 may not be as good as in specified higher gains, which would be affected by a less performant power amplifier.

    Best,

    Alec  

  • 0 in reply to Alec Saebeler
    Prodigy 30 points

    Dear Alec, i don´t have the diagram/circuit of the amplifier using the TPA6120A2, it came assembled (board assembled ) and i just recognized the main TPA6120A2 chip on it .  But i will do some tests and contact you later .  Many thanks for your time and explanations about AB class and no PWM modulator inside ... Andreas

  • 0 in reply to Andreas Hanke Stern
    TI__Mastermind 21527 points

    Hello Andreas,

    Absolutely, I am glad to help.  Let me know what you find.

    Best,

    Alec