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You're welcome

You might consider that you can do everything you want here except the protection relay with a single opamp like a TLO82, which is cheap and not really high performance, and yet still be effective and entirely inaudible.

First, I think you will find that you don't need all that much gain to do the job so you won't get into offset or stability issues with the opamp; a gain of 100 will be **plenty**! One opamp can sort out your correction bias voltage, the 2nd can be used to drive the LED.

I don't filter the LED signal as much; just a simple 6 db slope. In this way, at higher volumes the LED flashes with the music; it gives me an indication that I'm driving the preamp at a higher level. I use bi-directional LEDs.

You should be able to have no more offset then about 0.001 volts or so, which won't harm any amp made. It might even be lower than most cap-coupled preamps can do (unless they don't use feedback).

If you pull this all off, I think you will find this to be one of the most transparent preamp circuits you've ever heard. Its a big deal getting rid of that output coupling cap!


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  • You're welcome - Ralph 11:20:51 08/10/17 (1)

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