Build This MoFo!

[dimkasta]

I am currently building a Mofo to drive an efficient 100db 8ohm speaker. In my estimation, one or two watts RMS should be enough to have comfy or even loud volumes. For now I am building it according to the article with a 12V smps and IRFP250 biased at 1.7A. Does it make sense to look for a smaller mosfet that would bias with a smaller current and a smaller heasink? Any suggestions for parts to try?

 

[Zen Mod]

IRF510

 

[dimkasta]

IRF510

Thanks. Any suggestions for min voltage and bias currents for it?

I had a deep dive in my stash but could not find any 510s. I'll get some on my next order.

I got lots of 610s and FQP3N30s though, so I'll probably start there

 

[Zen Mod]

610 is good too

see Papa's ACA Mini for rails and Iq

say 15Vdc and no less than 200mA

more if you need more oomph!

 

[dimkasta]

610 is good too

see Papa's ACA Mini for rails and Iq

say 15Vdc and no less than 200mA

more if you need more oomph!

I'll check the mini. Thanks again

 

[PRR]

100db 8ohm speaker. {snip} one or two watts RMS should be enough {snip} 12V smps and IRFP250 biased at 1.7A. Does it make sense to look for a smaller mosfet that would bias with a smaller current and a smaller heasink?

2 Watts works out something less than 7V and 1A. A third of the heat. I don't think you need to down-size the FET for such a small shift. I don't know that the energy savings justifies odd power supplies; 12V seems fine to me. You rarely regret having a little more power thna you think you need. (And it is easy to mis-estimate.)

 

[e_fortier]

I believe Dimkasta meant to write 19V at 1.7A, not 12V

 

[dimkasta]

I checked the ACA mini article again, and something like a 510 at 0.4A sounds really promising and will not require a huge heatsink. I will build both though and see how things work and sound

 

[Zen Mod]

2 Watts works out something less than 7V and 1A. A third of the heat. I don't think you need to down-size the FET for such a small shift. I don't know that the energy savings justifies odd power supplies; 12V seems fine to me. You rarely regret having a little more power thna you think you need. (And it is easy to mis-estimate.)

there is some minimal DS voltage, to keep intrinsic mosfet capacitances at least somewhat linear

lower than that, that cap goes wild

 

[andyjevans]

I haven't read the whole thread yet (I will), but can anyone recommend a production output transformer that could replace the capacitor on the output? What would the specifications for it be?

 

[nicoch58]

I haven't read the whole thread yet (I will), but can anyone recommend a production output transformer that could replace the capacitor on the output? What would the specifications for it be?

tango made ones https://www.passdiy.com/project/articles/arch-nemesis

 

[pinholer]

J&K Audio Design can build output transformers for solid state amps. I have a pair which I will be using for a SIT amp.

 

[andyjevans]

J&K Audio Design can build output transformers for solid state amps. I have a pair which I will be using for a SIT amp.

Where are they located - no mention of this anywhere?

 

[pinholer]

They are in Malaysia. Their website is https://jandkaudiodesign.blogspot.com/.

 

[Vix]

I haven't read the whole thread yet (I will), but can anyone recommend a production output transformer that could replace the capacitor on the output? What would the specifications for it be?

What about a "balanced" Mofo? Yes, double everything, but no output cap...

 

[Zen Mod]

everything doable ( and most likely already done)

that one even easier than Wooden Stove



I mean - if F1 was commercial product, in all its simplicity, why not - just make it, properly

 

[Ben Mah]

I suggest giving the capacitor output a try.

"The proof of the pudding is in the eating."

An audio grade electrolytic capacitor is perhaps $10 whereas an output transformer is hundreds of dollars. It's easier on the wallet to start with the capacitor.

 

[pinholer]

I agree, Ben.

Extra points for getting the saying right.

 

[Zen Mod]

don't forget Porridge saying

 

[andyjevans]

Of course the circuit will be built with a capacitor out in the first instance and may stay that way. 6,800uf is far beyond DC Link caps so has to be electrolytic, but I guess some have experimented with smaller bypasses.