In this new A-19 the input circuit consists of a symmetrical circuit. That part is controlled using constant current sources. The second stage of the voltage amplifier forms a current mirror with the input circuit. All semiconductors in the voltage amplifier are bipolar transistors. This way of configuring results in an extremely linear amplifier circuit.
The current amplifier holds four power fets configured as source followers. No source resistors are used.
The linearity of the entire amplifier avoids the need of an overall feed back in order to compensate for non-linearities.
Both channels each have their own power supply circuit. Per channel there's 40.000 µF of buffer capacity.
Also four integrated voltage regulators are used. The first pair isolating the voltage amplifier circuit from the power supply. So variations in the power supply caused by the varying (music) signal and the behaviour of the load are suppressed. The second pair regulates and stabilizes the supply of the current mirrors. These measures also brings the noise level down to over -100 dB.
Last year we converted the latest A-18 version into a A-19 version using SMD components. That version was never delivered to our customers because the supplier could not guarantee the quality of the components. The current A-19 is a (discrete) newer version of the A-18, i.c. the A-18 Mk III.
The heatsinks are an integral part of the cabinet, located at both sides.
Apart from the soldering 9 holes have to be drilled and 4 of these holes threaded M4.
