Class A 25W power amplifier based on 25/25 and 50 similar items

This is one piece of bare board of a class A power amplifier, based on internet information of Bedini 25/25 amplifier. Based on the internet schematic and component placement, we did our development, with the following variation from the original design : 1. The output transistors are changed from the out-dated 2N3055H to more modern TO-3P package , reduced the difficulty in heatsink installation. In our development, Toshiba 2SC5200 was used. Other similar package and power rating power transistors can be used. 2. We changed the input stage biasing from original's zener diodes, to constant current source, thus improved PSRR substantially. We have kept the original design's special way of current sampling of output transistors to stabilize the quiescent current by the same type of output transistor. This method requires a massive heatsink to keep the quiescent current in a thermal equilibrium but it is an effective method in protecting the transistors from thermal runaway. Board dimension : 150mm x 65mm Board thickness : 1.6mm. Copper thickness : 70um - 4 times of normal board copper thickness ! This is one piece of power amplifier board for one channel only. For stereo application two boards are needed. The assembled board is for reference. The listing is for one piece of bare board. We provide schematic, part list and a brief build note to buyers by EMAIL. We do air shipping worldwide at US$6.00. We welcome combine shipping.