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RE: the idea is borrowed from BH Foreplay ver.1 ...

I have two outputs per channel on my DIY preamp.

One feeds the input of my SE 300b amp and the other feeds the input to a Opamp based low pass filter that feeds the SS amp driving my woofers.

I don't have isolating resistors and see no need for them.

I use a cap at the input of the 300b amp to create a 6db per octave high pass filter but even if I wasn't using a cap and the signal was just seeing the grid resistor of the input tube I see no need to isolate.

The Opamp low pass filter input is a Opamp followed by the filter parts followed by an opamp. The first opamp isolates the input from the filter so there is no need to further isolate the preamp output.

I asked the question about your application thinking that the isolation resistors might really be needed.

If you are just "doing it because BH did it" without knowing why you might want to re-think.

If there is a reason that those resistors need to be there then by all means use them, if there is no reason then I say get rid of them as they are serving no useful purpose.


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