< Picture: Prototype Linear Supply

Thermal management

An important issue with any linear supply is thermal management. There is a good reason why Behringer uses switched-mode power supplies: they run very efficient and therefore very cool. Stuff that is used for PA duty gets stacked up, placed in full sunlight and can be used in places that are very hot to begin with. Any additional watt increases the thermal load. But there is a disadvantage that is critical to hi-fi home use: switching residues remain on the supply lines, get into the circuits and lead to noise and intermodulation products. Other things being equal, linear supplies provide much cleaner supply voltages for lower noise, better imaging and clearer sound.

With a linear supply for the voltages and currents required by the DCX you can be looking at up to 10W dissipation you need to get rid of. The usual solution of using heat sinks is good if you can use heat sinks on the outside of the case. I didn't want to do a lot of mechanical mods to the DCX case, and internal heat sinks are out of the question. You'd only move the heat problem from the regulators to the rest of the DCX electronics. I had to find a way to get that heat out of the case.

The way I solved it was by using the existing mounting holes for that smps to thermally connect the regulators to the case bottom. The regs themselves still get warm (especially the +5VDC reg which goes up till 50 degrees Celsius at room temp), but the internal temperature does hardly rise. The case temperature does rise, but because of the large surface, also only a little.