Audio Transformer Isolation

[sled]

I plan to use my soundcard to do some signal processing, however I noticed that the ground of the sound card is quite noisy, so I had the idea to use an audio transformer to galvanically isolate the analog front-end from the sound card.

There's a lot of variety of audio isolation transformers, most common are 600Ohm:600Ohm and 10kOhm:10kOhm, what would be the best choice if I have the following source and load impedances:

[waltr]

I have connected circuits to PC sound card and know about the noise issue. A RigBlaster to connect Ham Radios to PC sound card has been the best noise free interface.

http://www.westmountainradio.com/rigblaster.php

A schematic is:
http://www.westmountainradio.com/pdf/Schematplus.pdf

The Sound Card transformers are 600:600 Ohm.

Good for you to actually experiment to find what works best.

[sled]

I worry a bit that the 600Ohm transformer might load the line-out too much? I attached some interesting PDFs about the topic:

"Using the Creative SoundBlaster X-Fi Surround 5.1 Pro USB sound interface asbaseband sampler for QSD based SDR receivers
"Audio galvanic isolatorFor soundcards and SDR receivers"

[waltr]

The x-formers recommended in those pdfs are 1:1 600 Ohm.

Remember that this is 600 Ohm IMPEDANCE not Resistive since Audio is AC not DC.

[sled]

Going to try this, I still have some old 56k modems with 1:1 600ohm line transformers in them

[waltr]

Those should work fine.
Post back on what you find.