Replacing a Maplin MOSFET poweramp module

Over the years I have built various DIY Hi-Fi equipment, one such item is a power amplifier which I have been using since I built it over 20 years ago ! One channel started playing up and eventually stop producing sound all together.

The power amplifier consists of two Maplin Electronics 150 watt Mosfet amp modules , a hi-grade power supply with a toroidal transformer and a soft start / speaker protection module , all built from kits.

One of the Mosfet amp modules had blown and rather than try to fix it I thought it would be a good opportunity to update the amp modules to something more modern. The power supply and the soft start / speaker protection unit were all good quality so I wanted to keep them.

I started looking for DIY Hi-Fi kits , the ones at Maplin looked too low end so I searched the web.

There seems a great deal of interest in Class-D amplifiers which brought back memories for me as I built one for my college project years ago when they were not generally used for audio amplifiers. I found a very interesting range of Class-D amplifier kits at 41HZ however I did not fancy soldering surface mount devices and the kits that did not have surface mount devices did not  suit my power supply.

I eventually found some pre-built Mosfet power amp modules at Class-d designs who are in the UK and despite the name of the company the modules are not Class-d which is fine for me as efficiency is not a problem as I have a pretty beefy PSU.

The layout of the components in the module enabled me to re-use the L-bracket heat sink from the Maplin modules ( there are finned heat sinks on the outside of the case to carry away the heat ).

The picture below shows one of the new modules in place with one of the original Maplin modules on the left , the soft start /speaker protection unit at the bottom and the power supply at the right. As you can see the new modules are quite a bit smaller. The sound is as good or better than the Maplin ones – although I’m not a “golden ear” person !

Power Amplifier with one new module
Power Amplifier with one new module

I tend to rebuild things over the years but keep various bits like PSUs and cases so things can look a bit untidy.

Below is my pre-amplifier which I use with the above poweramp – it has been re-built a few times and I’m thinking of rebuilding it again.


One thought on “Replacing a Maplin MOSFET poweramp module”

  1. It is logical that the amplifier stopped working, since those amps need rather large heatsinks! Mounting them on the chassis is not enough at all. The other amp wil burn down quickly too! You van buy copies of the Maplinamp with the newer Hitachi mosfets in several stores.

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