Andy and others
The Irwell modules are interesting, thanks for sharing these.? I've been studying the Audio module.
It appears that all of the preamp gain is via U1 NE5534, which includes filtering. I am not smart enough to recognise what the textbook configuration is for this stage.? can someone enlighten and also provide indicative bandpass for these values?
I am also wondering why U1A and U1B (NE5532) are needed. U2A is configured as a voltage follower to give high input impedance and low output impedeance, but why follow it with a second op amp?? Are two better than one?? Was it a small gain for no extra parts, given one was available in the dual package?
Finally, can you explain the meaning of virtual ground? I'm guessing this is a grounding arrangement to avoid earth loops that could lead to hum.? I am not sure how to build it.?
73 Paul VK3HN.?
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Paul VK3HN