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I'm building a prototype, checking the potential for a project.

I want to be able to sample a sine wave from a power amplifier using a Teensy4 ADC.

I have a Teensy 4.0 powering an Evisun isolated DC-DC module to generate +/-15v I have a full wave precision rectifier to eliminate any negative voltage on the output and increase digital range on the ADC (I don't need to recreate the sound, just need to capture the half cycles)

My missing part is a differential input stage, where I can connect either a single ended output or a differential output amplifier, then feed the unbalanced output into the precision rectifier >> ADC and sample the half cycles.

I need to have a voltage divider connected on each input to reduce up to 200v peak-peak down to 6v peak-peak.

I'm looking for suggestions on a balanced to unbalanced circuit that is capable of handling frequencies of 10Hz to 20kHz.

Also, can I connect the input ground of the dc-dc converter to the com output? I don't really need an isolated supply and used it just for low component count, and I need a ground reference for the ADC anyways.

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Looking for suggestions on a balanced to unbalanced circuit that is capable of handling frequencies of 10 Hz to 20 kHz

I could easily suggest a differential amplifier but, given that the power output might have considerable common-mode signals associated with it, I would favour an audio transformer from people like Hammond.

Also, can I connect the input ground of the dc-dc converter to the com output?

You won't need an isolating DC-DC converter with this method.

If you insist on using op-amps, this is a decent mixer input for a balanced signal from Rane. The following is an image of the specific section (microphone amplifier with an added 30 dB attenuator):

enter image description here

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  • \$\begingroup\$ Id rather go for an op amp based converter, and stay away from transformers. I have enough spare NE5532s to quickly prototype with. \$\endgroup\$
    – David R
    Commented Jan 28 at 14:49
  • \$\begingroup\$ Also as I mentioned I used the isolated converter as its a quick way to get a dual rail supply for the op amps. So I'm sticking with it, just need to know if the input ground and output common ground can be connected \$\endgroup\$
    – David R
    Commented Jan 28 at 14:51
  • \$\begingroup\$ @DavidR yes they can. Because they are isolated the device doesn't care if they are connected. It's a common trick to employ. If you want to use op-amps you are going to have to establish what the common mode signals are on a typical speaker output that you might use. Then, it still may not be feasible to use op-amps. \$\endgroup\$
    – Andy aka
    Commented Jan 28 at 14:58
  • \$\begingroup\$ @chester thanks for helping with the image. Dunno what's going wrong. \$\endgroup\$
    – Andy aka
    Commented Jan 28 at 15:26

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