Audio amplifier APEX A40

Dear Privalov, It may not be a good idea to place the buffer capacitors on the amplifier circuit board. If you are not using a dual-mono setup, you can create a ground loop very easily. Also, from a high-frequency point of view, even in the case of dual-mono construction, you will have a ground loop through the primary-secondary coils of the transformers. Sensitivity to radio frequency interference may increase and transient behavior of the amplifier may deteriorate. It is a better idea to use a central buffer bank and a star point grounding. It is important that as little AC current flows on the ground wire between the buffer bank and the amplifiers as possible. It is advisable to filter the low-signal supply voltages inside the amplifier through resistors, separately on the amplifiers' circuit boards. Of course, if you use a dual-mono structure, with low primary-secondary capacity main transformers, then it is perfect as it is. I wrote all my comments with good intentions, in order to meet the technical audio parameters as accurately as possible :) -- Kind regards, Milan Zarka