Citation MF12 Equivalent Components

[kramskee]

Hi all,

I've decided to build the Citation Mosfet 12. I just have a couple of component related questions

I can get IRFP264's at a really good price so I'm thinking of going with these.

In terms of drivers:

I can get 2n5401 for the P types. I can get 2SA970's but they cost around 30x more than the 5401's ( is it worth the extra cost? )

I want to use 2n5550 for the N types since these are complementary to the 5401. I can't get a complementary 2sc for the 970's!

Any Thoughts?


I designed my own set of boards to fit a standard 40mm square aluminium tubing that is readily available here. The other great thing about this is I can press fit a small 40mm DC fan for forced cooling!

Mark

 

[Zen Mod]

drivers , go for cheaper ones

 

[kramskee]

Cheap Drivers

great 2n5550 and 2N5401 it is then they're about 10 U.S. cents a piece 😉

 

[kramskee]

Mica Cap Alternatives

Ok,

So what do you guys recommend as an alternative to the Mica Caps specified in the Citation MF12 Schematic?

Thanks

Mark

 

[Zen Mod]

either mica ........... or whatever you can find instead

😉

 

[kramskee]

I can get Mica but only from RS components here and it's a little pricy! is it worth the expense?

 

[Zen Mod]

if you are just playin' , no

if you are making definitive version of amp ...... planning to use it several years ..... yes

 

[woody]

You could have a problem using the IRFP264. The IRF100 has a Ciss ( this is the input capacitence ) of 600pf but your IRFP264 has a Ciss of 5400pf ! That is likely to high for that front end to drive.

 

[kramskee]

Ok I'll use IRFP240's these seem to have the lowest input capacitance of what I can find here.

thanks for pointing that out 🙂

As for the Silver Mica caps, turns out they're not easy to come by here, I've found the general replacement for these is class1 multilayer ceramics. These however are all Surface mount and only rated at 50V

 

[Zen Mod]

good enough

 

[kramskee]

Ok, thanks .............. anyone ever tried some Sanyo 2SK Devices in place of the IRF's?

 

[Zen Mod]

why not , but you need to compensate for lower Ugs

 

[woody]

Sort of funny this old project being brought up but I may actually have 4 of the IRF100 devices that went obsolete when Nelsom was doing the article. I just spent 10 min. looking
and found 2 of them but where the other 2 are hiding is a mystery.

 

[kramskee]

I've made boards for it, will upload pics as soon as I'm no longer moderated. Sounds like quite an incredible Amp. I want to replace my current amp which is a crib of the Maplin mosfet guitar amp. It uses the 2SK and 2SJ complementary pair. They're very expensive, only come in pairs, it's always the one that pops ( can't remember which one, it's been a while! ) so you land up with a pile of the other. Also I found them to be quite prone to oscillation. In comparison I built the IR Hexfet amp from the datasheet and it just worked right on the bench with long wires everywhere not a stitch of oscillation. So I thought this would be a nice amp to build a little beefier than the IR reference design, quasi complementary with two N-channel fets, they're cheap and if you buy them at the same time they're more than likely from the same batch. Pretty much a winner all round I'd say!

 

[kramskee]

Ok,

So here it is, my completed MF12 board. Designed with separate output and removable driver PCB Complete with PSU smoothing caps 4 x 3300ufd 50v. Size is 160mm long by 38mm wide. PCB mounts to the the heatsink through the mosfets which are soldered to the underside of the output board.

I designed this to fit a common 40mm square aluminium tube extrusion that we get here. will attach more pics of a completed amp module with heatsink when ready

Thanks to all for your guidance