This is my own custom BA3 version (BLUE PCB), Using a Cascode which enables more than double the Rail Voltage. I have tested it on 50Vdc and achieved 33Vac RMS signal on the output.
Very High Gain can be achieved. 
The rest of the circuit is the same as the classic BA3 board, Using Zero Negative global feedback.

The Circuit uses J74/K170 Jfets for the front end.
MJE15028/15029 or equivalents for the cascode.
And FQP3N30/FQP3P20 or equivalents for the output section.
 
This Board is 100x100mm in size

I will provide a schematic, parts list and a how to start this amp up power wise  info sheet.
I will also provide help and answer questions as needed.
Happy to have a chat.
Find me on Facebook for detailed build photos and personalized help.
@DIYAudiophile

This listing is for 2 blank PCB boards. 

There will be listings for 6 different colour boards.

I will have a few spare PSU Boards to suit listed separately.

I do combine shipping for multiple Board sets/listings which are purchased.