Monday, April 15, 2019

Burning Amp BA-3b (Balanced)

Big, hot, heavy, and definitely a keeper. The discussion of the amplifier is on

The build is in a 4U/400 case from modushop; each side has two 200mm heatsinks, each holding six MOSFETs (three complementary pairs) and a biasing circuit.

The construction is dual mono, with separate transformers for each channel. Power supplies occupy most of the chassis, while the actual electronics is mounted on the sides.

The power supply was initially CRC filtered, with four 22,000uF Mundorf MLytic® HC High Current Power Caps per channel (pictured).

After successfully fitting my ZenV4-J with CLC filters, I learned how much can be gained by improving power supplies in no- and low-feedback amplifiers, which  have little or no control over output errors and thus poor PSRR. On this premise, I replaced the CRC filters in the power supply of my BA3B with CLCs, so instead of 22mF + (2 x 0.22ohm) + 22mF I now have 100mF + 10mH + 100mF per rail per channel.

The power supply provides +/- 18V rails, with quiescent current set at 3 amps per channel.