Friday, March 15, 2013

 Dada proudly announces the new 405 v2 High End boards

We used a double sided board with fully metalized holes. We had to do this to fix all the layout issues in the original Quad design. Also we where able to increase the distance between the input and output circuit. The collector current of the pre drivers was through a nut and bolt in the original design. This is a pretty awkward way to conduct current! So in the new design we use the centre pin of the transistor to do this. Also the TO-3 output transistors have their collector current now guided trough two nuts and bolts instead of the single one in the original design. All the tracks are widened and shortened where possible. It is possible now to split the power supply tracks to prevent the dumpers to pollute the tracks of the class A stage. So from a mechanical point of  view; this is the best 405 PCB ever produced. 

We also made some changes to the circuit itself. The Op Amp circuit is now a non inverting configuration. This reduces the noise to the excellent 606 level. We use a transistor to stabilize the power supply voltage of the op amp, this strongly reduces the switch off noise. The current source to drive Tr2 is also improved using a transistor instead of the capacitor in the original design. We also introduced extra power supply rail decoupling by means of electrolyte capacitors. All the electrolytes are decoupled with small film capacitors. For the critical capacitors we use polystyrene audio grade capacitors. The current limiters are optional. But the layout faults in the current limiting circuit concerning the position of the class A stage are solved. So the Class A stage Psu rails are not modulated by the dumper currents anymore. The current dumping bridge is rearranged and has the same layout as in the excellent 606 designs.

The new v2 High-end boards are now officially launched and available in the Webshop.