Build This MoFo!

[Dennis Hui]

How was your mosfet attached to the heatsink? What thermal interface was used?

Do you have a photo of the board attached to the heatsink?

 

[Michael Rothacher]

Tape definitely won't work. The MOSFET needs to be firmly attached with a screw and washer or an aluminum bar such as the ones I use. Let me know if you need some close-up pics.

 

[MEPER]

What about heatsink.....does it get hot?
Or is MOSFET "dead" before heatsink gets hot?

Maybe a picture with heatsink attached would be good?

 

[cxk210]

Thanks guys. I'll bolt it right onto that block and see what happens.

"A lot of beginner projects run into trouble because of heatsinking..."

yep...face in palm

 

[Michael Rothacher]

You're almost there.

Don't forget your thermal pad, or mica and goop.

 

[marconi118]

does the DCR of the choke influence negatively to the output impedance of the MoFo?

 

[PRR]

> does the DCR of the choke influence negatively to the output impedance of the MoFo?

No.

 

[andyjevans]

Just came across this thread. I have some chokes which are 280mA, 2.7A, 3.4DCR.

Do they sound good for this?

 

[Eric]

My first guess is these chokes will not be compatible with this design. The chokes need to be able to handle 2A or 3A. Given ~20vDC rails, 3.4DCR will generate a TON of heat and they will cook.

I think you want something that can handle closer to 5-10A with 0.5 or less DCR.

 

[Ben Mah]

Just came across this thread. I have some chokes which are 280mA, 2.7A, 3.4DCR.

Do they sound good for this?

Is that 280mH and not 280mA, since you also noted 2.7A?

If it is 280mH, 2.7A, and 3.4DCR, then it is probably worth a go. There is a 1.7A version and a 2.5A version of the MoFo.

 

[andyjevans]

Sorry, correction. Yes 280mH. They could get hot. I could use 2 in parallel. How does that sound? I have several. I haven't read all the instructions - 1.7A sounds easier on the parts. Looks a very simple design.

 

[Eric]

Ah... This sounds better! The nice part of the design is that you set the bias with the trim pot. If your chokes get too warm for comfort, you can dial back the bias a bit. You really don't need much above 2A for an 8-ohm load.

Two chokes in parallel will reduce both inductance and DCR. May solve the heat problem, but will also reduce the impact of the chokes on the design...

 

[6L6]

Use a 19v brick and give it a try.

 

[andyjevans]

This is looking like a plan - I have some heat sinks. I usually build with DHTs so I'd be looking to use one as a driver, like 01A, 26, 10Y.

 

[6L6]

24V with Hammond 193V. Prasi boards.

Absolutely stunning chassis by member j_thomas. Ill take some better photos soon but this is just too good to wait.

 

[zman01]

6L6,

That is one sweet MOFO!

 

[Vunce]

Super Cool MoFo chassis!! I love it!

 

[mbrennwa]

Wow, FUGLY!

 

[Michael Rothacher]

Wow, those are really spectacular!

 

[mgb1965]

Those chassis are really cool!