[MrFixr55]

Hi Rich,
The tap has to do with "loudness contour" and should not affect AVC. Loudness contour has to do with the effect of the tone control circuits at lower volumes. The concept is that people, even with normal hearing have a peak sensitivity at the middle range of the hearing spectrum, therefore low and high frequencies may be attenuated. How important this is in a radio with a simple tone control and receiving the current AM programming is certainly up for discussion. If one was listening to classical music on FM, records, tape or a digital source, through a true high fidelity amplifier with a flat response and very low distortion, through a very clean set of speakers with a flat frequency response throughout the spectrum, then loudness contour becomes more important.

The AVC and detected AF signal come from 2 different sources in this radio. The AVC is rectified IF, like the detected signal but a different path. Even when AVC and audio come from the same diode, there are different paths, both isolated by RC networks. Looking at the volume control, one notices a capacitor coupling the detected signal to the volume control, passing only audio frequencies. A resistor separates the AVC from the detected signals when they come from the same diode. Both AVC and detected signals before the coupling capacitor can be considered to be pulsating DC, negative in reference to the chassis. A much larger capacitor between the AVC line and ground "filters" the AVC signal to flat DC at a negative potential to the chassis. The stronger the received signal, the more negative AVC, the more negative the bias on the IF and antenna stage, the less gain in these stages. This is one reason that the AVC cap has to be good, otherwise, there will be motorboating.