A "regular" receiver use digital volume control. It is the biggest difference comparing to a 2-channel integrated amp.
The signal path look like this: 2 Channel: CDP(digital) - DAC (D/A converter) - Amp (amplify analog signal) - Speakers.
Receiver with pure direct(signal direct): CDP(digital) - DAC (D/A converter) - Reciever (A/D for bass management and volumn control, D/A back and Amplify) - speakers.