MoFo Amplifier DIY project.

[pre65]

I had heard very good reports about this DIY amplifier, so decided to have a go.

MoFo = Mosfet Follower, and uses a single IRFP250 Mosfet, so definitely class A and single ended.

For anyone remotely interested, here is the article that got me started.

https://6moons.com/audioreviews2/mofo/mofo.pdf

Now I was fortunate, because breaking up my 50W Mosfet amp (Pass design) gave me a great deal of the hardware I needed, particularly the heatsinks. And I already had two 22v toroids in the spares box, so a 24v version was a given.

On DIY audio, some had been using MOTs (microwave oven transformers) as the choke, and I was lucky to get a pair from a friend whose own MoFo project has stalled, and he also provided a pair of the PCBs, which made construction a doddle.

They (monoblocks) are up and running (as of late Friday night) and are, I think, the best sounding amplifiers I've ever built. I'm still running them in and experiencing my favourite music allover again.

[pre65]

I'm using Imgur to host my photos, and for some reason, on this forum, they come out BIG.

[bob orbell]

Your first post has followed the picture Philip, to the right some words are missing, they disappear off screen . Bob

[A Stuart]

Bob, I was able to scroll along using a slide-bar which came up at the bottom of the page.

[bob orbell]

Thanks, I did not see that . Bob

[Chris]

Phillip that's a great build, glad your enjoying it lots, I looked at the pdf link, those are some big heatsinks..

Chris

[Mark]

Phillip,

Impressive. I love the whole Pass/Burning Amp/minimalist Class A/SE thing but I have been put off having a go in the past by the cost of the heat sinks. Can you give an estimated/budget/indicative cost breakdown even though some of the bits came from another project and others from a friend ? Did the pcbs come from the DIYAudio store ? Did you have to drill and tap the heat sink ?

Thanks

Mark

[pre65]

Originally Posted by Mark

Phillip,

Impressive. I love the whole Pass/Burning Amp/minimalist Class A/SE thing but I have been put off having a go in the past by the cost of the heat sinks. Can you give an estimated/budget/indicative cost breakdown even though some of the bits came from another project and others from a friend ? Did the pcbs come from the DIYAudio store ? Did you have to drill and tap the heat sink ?

Thanks

Mark

The heatsinks were on Ebay years ago, and were stripped from a computer UPS (uninterruptible power supply), to buy something that size new would be muchos wonga.

Having said that, a smaller heatsink and a quiet fan would do just as well.

Yes, tapping M3 (for the mosfet) may be needed, depends on the heatsink.

I have the time, and patience, to spend hours searching Ebay for things like heatsinks, and there are bargains to be had.

Something like this would probably be Ok, It's the right degree rating.

https://www.ebay.co.uk/itm/Heatsink-...EAAOSwr05eF1yF

I got the PCBs from a friend, but I believe they are available from DIY audio.



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[bikerhifinut]

That's a really interesting pair of amps Phil.
And to be able to build them mostly from reclaimed and otherwise economically sourced parts is a real joy.
I have to say my initial reaction was "Why?" And then the obvious reply, "Why not?"
That's the fun of the DIY hobby, you can experiment with designs that are non mainstream and usually keep it in the affordability zone.
Nice work Phil.

Andy.

[Mark]

Phillip,

Thanks for the information. It's very helpful.

Mark