100W Ultimate Fidelity Amplifier

Years ago(1990?) in the Elektor cmos preamplifier used cmos and op amp in input and out, as source switches.
I will try to find the boards.
I found it!
 

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I used a cmos cd4016 and/ or cd4066 with great success. You can't hear them in the circuit at 18v and 47k 47pf loading. CD4052 4*2 makes a great analog selector.
newer chips provide better resistance but it's moot.
I still have the 1024 step attenuator I made for fading tape recordings in and out.
Their only practical limitation is the rail to rail maximum input signal