Hypex Power Amplifier

Published 24.11.2014 (built late-2014)

This design is to be connected to possibly lethal mains voltage. These are not detailed instructions, so do not try to build similar device without extensive understanding of electronics and electrical safety!

Power amplifier designed for 4-channel DIY audio system

  • 2x Hypex UcD180HG HxR audio amplifier modules delivering 2x 180 W @ 4 Ω or 2x 120 W @ 8 Ω
  • Hypex SMPS400A180 switched mode power supply designed for UcD180s with power rating of 400 W

This is not my own design but OEM/DIY modules from Hypex have been used to implement a stereo power amplifier. I haven’t designed power amplifiers yet, and to understand everything deeply enough to design a discrete power amplifier from scratch is another long project I didn’t have time for now. One idea was to build an amplifier around some AB-class chips, so called gainclone. However, I ended up ordering widely used D-class amplifier modules from Hypex (shop). My power amplifier consists of aluminium enclosure from eBay, Hypex SMPS400A180 400-watt switched-mode power supply and two Hypex UcD180HG HxR D-class amplifier modules with nominal power rating of 180 watts to 4 ohms and 120 watts to 8 ohms. I have mounted the modules inside the enclosure so that there is (barely) space for additional set of amplifiers and power supply.

It is (maybe) possible to mount two more UcD180 amplifier modules on the heatsinks and another SMPS400 on top of the existing one. At least there should be enough cooling capacity in the heatsinks for these small modules.

There is not much to tell about this project as it was just about putting things together following Hypex instructions. Although I have to say those instructions could be better. Documents are quite simple and short barely including all the necessary information, and obviously at least the power supply is designed to be used with various different modules making it more complex to figure out the necessary/possible connections. After all, all the information is there and it is all you need (and get). Hypex is selling specific cable sets which make things slightly easier although when powering two amplifiers from one power supply you need to divide the power cables. Besides mains voltage and dual DC-supply there are wires from amplifier outputs to a DC-protection circuit in the power supply, providing shutdown of the amplifiers in case of DC-voltage at any output. It is also possible to use standby functionality but I will power off the amplifier completely when not in use.

I have to mention one anomaly from Hypex application notes. They suggest the user not to connect mains safety earth to the enclosure when using unbalanced connections, to prevent ground hums, but instead make a so-called double-insulated design. Yes, ground loops can cause problems but I would never suggest DIYers to do that! Always connect safety earth unless you really know what you are doing. It is good to design double insulation in mind but still use safety earth. The best cure for possible ground loops is to use balanced interconnections. And even without, most probably there won’t even be any problems. Even if, solve the problem by other means than discarding safety.

Hypex modules have differential signal inputs so balanced inputs are natural choice. They also match nicely with Quad Preamp with balanced outputs.

I didn’t include power switch in the amp since there was ready-made hole for the mains connector without switch, and making rectangular holes in 3 mm aluminium with hand tools is quite frustrating. I am going to use mains switch for the whole system anyway. The power supply has mains sensing circuit so it mutes the amplifiers when the power is turned off. No loud thumbs can be heard from speakers even if I turn off all the devices at the same time.

These heavy heatsinks should be enough for efficient class D modules under all circumstances.

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