Headphone amp output buffer stage help.

[diy didi]

Hi All.
I’m busy building the final output opamp buffer stage for my mono headphone amp.
I have managed to build the output stage using opamps configured as non inverting buffers and using 1ohm current sharing resistors to effectively parallel the two sections of a dual opamp.
I however only realized afterwards that I need to use an inverting buffer topology as my preceding mixer/ gain stage is inverting also.
This will give me absolute phase from input socket to output socket.
What are the drawbacks of using the inverting topology over the non inverting topology? If any.
I can see that the parts count is higher and that I would have to increase the input coupling cap value.
I have attached the two circuits. Sorry for the jpegs.
Thanks in advance.

 

[ronsimpson]

This will give me absolute phase from input socket to output socket.

While 0 phase is good, your ears will never know. It is likely the phase has been flipped 180 several times in the recording process. So the question is; was it flipped an even number of time or a odd number of times? Are you certain the vocals and the instruments are "in phase". Your ear will never now or care.

 

[RadioRon]

I don't think you will see any performance difference. If there is any, it will come down to the quirks of the particlar op-amp you have chosen, and perhaps how the op-amp behaves when the output saturates. I note that you can force the coupling cap value back to the same as the non-inverting configuration simply by doubling the resistance of the 39K resistors. So the difference is mainly the extra resistors.

 

[audioguru]

Absolute phase can be heard only if you are wearing microphones on the headphones and you want the leaked sound to haver the same phase as is produced by the headphones.

Your input coupling capacitor values are so big that they will pass earthquake frequencies that you cannot hear. Also then the capacitors must be electrolytic instead of film type. 2.2uF into 39k produces -3dB at 1.86Hz. 0.33uF into 100k ohms produces -3dB at 4.9Hz which is low enough.

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