LuFo Amp - 39w SE Class A from 28v Rail

I'm in the same boat on the adaptor boards, dBel. Also need another MOT. I only ordered one just in case the measurements didn't pan out. ;) Oh! And we can all use some of those sweet JPS boards once Vunce is all done with his verification build. Thanks X, JPS, and Vunce, as always!

If it inspires even more confidence I measured three other crossover inductors I have laying around, ranging from 2.5mH to 20mH. All measured well within the printed spec. Really handy tool to have around. I have to leave it in sight on my shelf from now on. :D
 
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I use my DATS v2 as my go-to LCR meter also. It’s quite accurate. 75mH means a little more storage energy at the expense of higher DCR.

What do you guys estimate the number of turns in the primary? I estimate about 120 turns for 0.5ohms based on published impedance/ft of 14ga copper wire.

Vunce has most of the board built up. He also has the LU1014Ds with adapter boards already. So we should be a seeing a verification build progress pretty soon. :)
 
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A bit of progress this evening, I dismantled the Stratos chassis and cleaned the heatsinks. The LuFo pcb’s are positioned such that the MosFets and JFET are just south of the HS center line.

The Mosfet in the picture is just for show, it’s not the correct part ;)
 

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It will be interesting to see if we can configure and ACP+ for 50Vpp output. Mark Johnson suggested using the typical Edcor transformer used for voltage gain in the M2. I think the Wayne’s Burning Amp 2018 preamp can run at +/-30v rails just fine. The resistors settings could be reduced to decrease the bias current.
 
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I have used a 48v variant of this same type of supply. They have an annoying fan which can be swapped with a Noctua, problem solved. They are actually very quiet based on FFT’s that so have taken. They might suffer from startup hiccup mode if you have too much rail capacitance. I think up to 10,000uF should be ok. I used to drive my TPA3255 which had dual 4700uF and it worked fine. But when I tried driving 2x 22,000uF it did not work. But, there is a simple slow start circuit that I have that can fix that. I used it on my VFET amp.

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Yes, 6C45 could do.
You don't need the full mu; so no need for current source loading, even with resistive anode load you'd have a bit too much gain.
With a 3:1 interstage transformer you'd be perfectly there with enough gain and ample drive current for the mosfet.
One of multiple options...
It seems that if you lower the voltage the mu lowers to,thats a good thing.
Tube Tester Files - 6S45PE