My AF signal generator would drive the amp to hard with the output set to minimum even with the 20db attenuator switched in. After adding the bypass caps I can adjust the pot from min to max without it breaking into oscillations with an antenna and ground connected.
EDIT: R11 is a 2K pot used to adjust the J112 bias. It will pinch off the Jfet at about 1K. You could use a lower value.