XERXES - DIY Audio Projects


Hypex UCD700HG mono amplifiers

A pair of 350wpc class D mono amplifiers based on modules supplied by Hypex.nl.

Hypex UCD700HG mono amplifiers

The components for a single mono amplifier.


Hypex UCD700HG mono amplifiers

The beginnings of the casework.


Hypex UCD700HG mono amplifiers

An assembled amplifier with the original 600VA transformer. The amplifier board is at the rear of the case, keeping the input signal cables and the speaker output cables as short as possible. The soft start module, transformer and the power supply board are towards the front of the case, separated from the amp board by an aluminum plate. A fairly large heatsink is sandwiched between the rear of the case and the aluminium plate and the amp board is hung beneath this with some thermal paste between the heatsink and the heatsink on the amp board itself.

Having assembled the amp, I was eager to try it out, so having double checked everything and connected a source, pre-amp and speaker I fired it up . Everything came on as it should, the lamp on the power switch lit and I could see that the LEDs on the voltage regulator boards on the amp modules were illuminated, but there was no sound from the speaker. I double checked everything, but to no avail.

I contacted Hypex to ask if they had any suggestions. I tried all the suggestions that Hypex made, but nothing made any difference. Finally Hypex suggested that I returned the completed amps to them for testing. The amps are heavy, about 12Kg a piece, so I was reluctant to do this, but having tried everything else, I packed the amps and shipped them to Hypex.


Hypex UCD700HG mono amplifiers

When the amps arrived at Hypex, in Holland, they worked. However, the engineer, Jorrit, had an idea that the problem might be with the transformers, or more accurately the mains voltage. Jorrit thought that the mains voltage where I live may be on the high side which was causing the over-voltage protection to kick in on the amp modules. so the transformers were changed for some with a slightly lower secondary output.

A week later the amps arrived back. When I removed the amps from the case I noticed that they had put on a bit of weight, so I opened them up to take a look. The replacement transformers are enormous! There's no indication on the transformers as to their VA rating, but they seem to have done the trick, I connected up the amps and we have music, many thanks to Hypex for taking the trouble to investigate.
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Hypex UCD700HG mono amplifiers

Another shot of the assembled amp.


Hypex UCD700HG mono amplifiers

The rear of the amp.


Hypex UCD700HG mono amplifiers

And the front.


I've had the amps up and running for some time now and I'm really pleased with them; they sound absolutely fantastic. :-D