I have a sine source in my schematic. I edit the A parameter in its model statement, but it has no effect on my AC analysis. It always runs at 1V.
The sine source and pulse source each default to AC small signal sources of magnitude 1. The model statements only have an effect in transient analysis and in the operating point calculation for AC analysis. The small signal sources that may vary are the 'Voltage Source' and 'Current Source' sources in the Waveform Sources section of the Analog Primitives. The AC source is defined for these two components in its VALUE attribute as in the following statement:
This would force the 'Voltage Source' component to be a 2V small signal source and the 'Current Source' component to be a 2A small signal source. Alternatively, just enter the desired AC magnitude value into the AC magnitude field and the above statement will be placed into the VALUE attribute automatically.