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TPA6120A2: Is it possible to safely combine the left and right outputs from my ASUS Xonar Essence STX Sound Card into a single mono output.

Part Number: TPA6120A2

In response to the kind reply to my earlier query by Ivan Salazar, today the Sennheiser headphone cable arrived and thus I have been able to connect up my test rig.

It works just fine, but I am wondering; as I am only able to take the output from either the left or the right channel, is it possible to safely combine these from my ASUS Xonar Essence STX Sound Card into a single mono output, please?

There are numerous videos on YouTube demonstrating the use of fairly lower powered transistors used to combine the + output from both sources into a single mono plug, but they generally are being deployed from low power ouputs such as an iPhone.

Is the procedure acceptable bearing in mind my aim is not for listening but purely as a driver, and if so should I use say two a 2-gang rotary potentiometer?

If this would seem to be acceptable bearing in mind the power output of the Zonar Sound Card, what value potentiometer might you suggest please?

Thank you so very much.

Christopher

ASUS Xonar Essence STX Sound Card.

  • · Output Signal-to-Noise Ratio (A-Weighted):
    124dB for Front-out,117dB for Headphone-out (600ohms) dB
    Input Signal-to-Noise Ratio (A-Weighted):
    118 dB
    Output THD+N at 1kHz:
    0.0003% (-110dB) for Front-out, 0.001% (-100dB) for Headphone-out
    Input THD+N at 1kHz:
    0.0002% (-113dB) for Line-in
    Frequency Response (-3dB, 24-bit/192kHz input):
    <10Hz to 90KHz
    Output/Input Full-Scale Voltage
    2 Vrms (5.65 Vp-p)
  • · Bus Compatibility

PCI Express:
-PCI Express Rev. specification compatible
-Compatible with X1, X4, X8, X16 PCI Express slots

  • · Main Chipset

Audio Processor:
ASUS AV100 High-Definition Sound Processor (Max. 192KHz/24bit)
24-bit D-A Converter of Digital Sources:
Texas Instruments PCM1792A*1 for Front-Out (127dB SNR, Max. 192kHz/24bit)
24-bit A-D Converter for Analog Inputs:
Cirrus-Logic CS5381* 1 (120dB SNR, Max. 192kHz/24bit)
High Fidelity Headphone Amplifier:
Texas Instruments 6120A2*1 (120dB SNR, 100dB THD+N @ Vcc±12V, RL=600Ω, f=1kHz)

  • Hi, Christopher,

    Our team will take a look at this and will reply as soon as possible.

    Best regards,
    Luis Fernando Rodríguez S. 

  • Dear Luis,

    I would be most grateful,

    Thank you.

    Christopher J James

  • Hi Christopher,

    If you can send your original signal on one channel, and an inverted version of the same signal on the other channel. This would allow you to connect the load in "pseudo-differential" way.

    What I mean is send original signal on right channel and the same signal but shifted 180deg on the left channel.

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

  • Dear Ivan,

    I am sorry but my technical knowledge on the subject is very limited.

    Can you please give me a fuller explanation, please?

    And if a small circuit is required, can you please supply a sketch.

    Thank you so much.

    Christopher

  • Christopher,

    Please refer to the below diagram. Please let me know if you have further questions.

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

  • Dear Ivan.

    I am sorry that my technical expertise is so limited, but by what means do I shift the second channel through 180 deg?

    And by using just one channel in effect twice, will I actually benefit from a greater output?

    Thank you so very much.

    Christopher J James

  • Chrisopher,

    What is your signal source? Is it a wav file or something similar? If you're using files there are some audio software that can be used to shift the phase of the content.

    Can you please elaborate on your second question? I think I didn't understand. In my proposal, you would have a differential signal on the load, this means the resulting signal is subtracting right channel signal from left channel signal. eg. at peak voltage lets say you have 2V peak, at the load you would have 2V-(-2V)=4V

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

  • Dear Ivan,

    My signal source is from an online tone generator creating a sine-wave at sub 50Hz frequency. 

    This is a screenshot of the settings on the output on my sound-card.

    Thank you so much, including for the explanation on the output level..

    Christopher

  • Hi Christopher,

    I'm not sure if the sound-card driver could invert the signal, but as mentioned before you could use files.

    Attached is an example with 500Hz tone, as you can see in the capture below the signals are opposite to each other on each channel. I use Audacity software to generate these signals.

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

  • Dear Ivan,


    I am extremely grateful to you for the trouble you have gone to, on my behalf, thank you!


    Alas, it would seem that the Audacity software cannot achieve the accuracy that I need, which is at least to two decimal places.
    The closest it would seem to be able to achieve is 40Hz which sadly is not accurate enough. I have not had a chance to read the manual yet, so I do not know how you actually achieved the out of phase signals?


    In an ideal world I would much prefer to create a circuit, initially generating a square-wave signal and converting this into sine-wave before outputting through an amplifier, rather than be tied to my cumbersome PC. Is it within your field of knowledge to advise whether such a circuit could likely match the volume presently generated via the Asus Sound Card attached to my PC?


    Thank you so very much.


    Christopher

  • Hi Christopher,

    I'll follow up on your new thread as it seems you're adding more circuitry to your system now.

    I'm closing this thread for now.

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