Brazil had ordered 3 scout cruisers as part of their rearmament package of 1904. The ships were sourced in Britain. The design was taken from the equivalent Royal Navy Adventure class cruisers. The 4" of the Adventures were replaced with 4.7" and when completed these ships were the fastest cruisers in the world at 26.5 knots, they were the first of the type to have steam turbines. Like all of the pre-war ships these 3 were assessed as to whether serious money should be spent on them to upgrade the ships to more useful units.
All three ships proved to be in excellent condition and were sent off to British shipyards for refurbishment. The rebuilding was to turn the ships into anti-aircraft cruisers that could also act as escorts to the older capital ships. This included replacing the engines and boilers with new units. The Royal Navy was converting the 'C' class ships at the same time, so that was the template used for these three ships. The smaller dimensions, compared to the 'C' class, meant the fitting of the armament was tighter and the chance of future upgrades would mean the removal of top weight (including armament) if the Brazilian Navy wanted to be serious about adding electronics to the ships.
The refit fitted the Mk XVI twin 4" as the main armament. These dual purpose weapons were controlled by the HACS unit on the bridge. Further AA weapons were the single 2 pounder guns which were local control. While the 8x4" seemed a much lesser armament than the original 10x4.7", the much later Mk XVI twin 4" fired twice as fast (or more) than the older guns.
