Large Power supply for the modular high end audio amplifier

Project presentation

Abstract

The power supply presented here fits my high power amplifier module and is also part of my modular audio amplifier system. For lower supply voltage and lower power designs, I would recommend a smaller power supply.

Design considerations

The form factor of this power supply fits my modular audio amplifier system. Actually it is physically too large to fit the enclosure together with all other modules and it is also electrically way over-sized for the modular amplifier system. It was designed for the high power amplifier module and is sized accordingly. Focus is on versatility and all the small details that improve performance compared to the most basic and commonly seen power supplies.

Schematic

Assembly

PCB Design

The PCB is designed using two layers. This is the lowest layer count that makes any sense. Some DIYers enjoy etching their own PCBs. I've done that 25 years ago and I'm done with it. The performance improvement of good PCB design is significant and for such a high cost assembly, it does not make any sense to save on one of the least expensive components and in turn accept performance degradation.

The placement and routing is pretty straightforward. The only thing that stands out is the fancy meandering between the storage capacitors. The idea behind is that the current is forced to pass the capacitors in a defined sequence. Also, the resistance of the copper between the capacitors forms a low-pass circuit. As little as 3*10-3 Ω prior to a 10000µF capacitor forms a low-pass filter with roughly 5kHz corner frequency. Standard copper thickness is perfectly adequate as a bit of resistance is welcomed.

The routing to the output terminals follows the "T" approach, which forms a kind of star point. Actually two of them - one for the positive supply and one for the negative. The sequence of connection should be that more noisy grounds and supplies are connected more central within the terminal array.

Cost

Here is the cost breakdown of the large power supply module:

Part Quantity Cost p.p. [€] Cost total [€]
Storage capacitors 8 13.00 104.00
Rectifier diodes 8 2.00 16.00
Heat sinks 8 2.50 20.00
Cage clamp terminals 36 0.25 9.00
Small capacitors 14 0.50 7.00
Resistors 14 0.15 2.00
PCB 1 10.00 10.00
168€ incl. VAT

In case the rectifiers are mounted to the chassis, 20€ could be saved without compromising performance. A stripped down module could be roughly 10€ cheaper, but with some impact on performance. For me the point of DIY is not to design something that just covers the bare basics, but to include all the small details omitted in many commercial designs for profit maximization.

Summary

This is a massive power supply targeted towards high power applications in the range of 800W to 1kW. For lower power applications, the medium size power supply for the modular audio amplifier would be more suitable.