Usually, zero feedback refers to zero global negative feedback, so there's typically local or nested feedback networks in a ZNF amplifier. Use of negative feedback in a preamp is far less problematic, because the preamp will have its output impedance fixed by a resistor, and thus will never be exposed to a load impedance that creates hf stability problems. That said, use of op-amp based filter networks really isn't desirable in a high-end system, so a passive filter is probably the best choice.
Last edited by Art Vandelay; 04-03-2019 at 07:27 AM.
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