This simple design has very low noise, close to the theoretical minimum, high hum rejection and variable gain with a single rotary pot. It is similar to that used in many professional grade mixing desks and can form the basis of a no compromise recording mixer for live work.
http://sound.westhost.com/project66.htm
Uses special Amplifier module from Op-Amp Labs
http://www.opamplabs.com/2wrmic.htm
No description
http://www.jensen-transformers.com/as/as016.pdf
This circuit is is a simple converter to convert line level signal (0..1 V) to phono input levels (0..5 mV)
http://www.epanorama.net/circuits/phono.html
Uses Jensen Twin Servo topology
http://www.jensen-transformers.com/as/as082.pdf
For the Mackie 1604 Mixer Eliminates RFI Problems
http://www.jensen-transformers.com/as/as074.pdf