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petrus bitbyter's picture

Interesting subject and design. Are you planning a PCB-design? Let me know if I can do something on that.

You mentioned the expensive audio transformers. Do you have any idea of the costs of this design (so including supply and enclosure) compared to the cost of that transformers?

Drawbacks of the solution may be the need for power, the cubic measure and the adjustments. I ever "solved" the latter by going digital using delta modem. The quality was pour due to the low sample rate and other restrictions but good enough for speech like for telephone. 

petrus bitbyter

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petrus bitbyter's picture

Submitted by petrus bitbyter on 27 August 2014 - 11:25pm.

So I did a stereo PCB-design. Tried to keep it single sided but could had to accept four wire bridges. The design is more or less optimized for DIY etching so the pads are little enlarged and all holes are set to 0.8mm. The design has not been tested yet so you'd better check it out before starting the etch proces. I've done it three times. If there is any error left I'll not see it the nest 999 times (I suppose).

petrus bitbyter

Messtechniker's picture

Submitted by Messtechniker on 15 August 2014 - 4:36pm.

A good audio line level audio transformer will set you back 50 to 75 EUR a piece.
The idea behind this project was to use as many off the shelf components as possible. This was forced by the fact that we needed a isolating amplifier immediately on a Sunday with no shops open. So components straight out of the junk box were the only option at that time.
Since my immediate needs were fulfilled, I am not planning a pcb. although I have investigated to some extent a fully balanced IN/OUT circuit. But I have left this at the breadboard stage.

Optically Isolated Unbalanced Audio Line Level Amplifier

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