Direct Conversion Receiver help

what is the best gain for the audio amp in a Direct Conversion Receiver
so that it will not be too large so that the amp osc and amp noise
and will not be small that it will not amp the received signal:D

Hi;
Can you, please, say me about Direct Conversion Receiver?
Can you advise me any book?

you can't find abook only about DCR
you find it as a one page in any communication theory book