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Old 5th September 2018, 09:32 AM   #1401
marconi118 is offline marconi118  Germany
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what is the best N Mosfet for MoFo?

The highest YFS for lowest input capacitance at the working conditions I=2A U=15V

Found the
FQP20N06
FQP30N06 16 / 900pF
FQP33N10

bur their YFS are measured at higher current (more than 10A)... at 2A they are lower
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Old 13th September 2018, 10:55 PM   #1402
flocchini is offline flocchini  United States
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A number of people have mentioned using MOFO as headphone amp.
Any changes necessary?
Thanks
Bob
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Old 13th September 2018, 11:09 PM   #1403
MEPER is online now MEPER  Denmark
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Quote:
Originally Posted by marconi118 View Post
what is the best N Mosfet for MoFo?

The highest YFS for lowest input capacitance at the working conditions I=2A U=15V

Found the
FQP20N06
FQP30N06 16 / 900pF
FQP33N10

bur their YFS are measured at higher current (more than 10A)... at 2A they are lower


In the paper from MR I think it was concluded that IRFP250 was the best choice….…..


"You could substitute other MOSFETs, the old favorite IRFP240 for example, but the IRFP250 is just about optimal here, and they’re dirt cheap. I know some of you might want to experiment with Q1. I tried lots of other parts. I tried fancy, expensive parts from Cree and they did not have lower distortion. I also tried obsolete parts from Semisouth and Fairchild and they had slightly better distortion performance, but they’re unobtanium and of dubious merit here anyway."
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Old 14th September 2018, 04:45 PM   #1404
Bangla H is offline Bangla H  Germany
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Marconi

if you like to experiment i would suggest the FQA Serie.
A robust, for my own little opinion, good playing one FQA40N25.
FQA40N25 ON Semiconductor | Diskrete Halbleiterprodukte | DigiKey
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Old 27th September 2018, 04:08 PM   #1405
marconi118 is offline marconi118  Germany
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is there a simple good sounding preamp for the MoFo?

ideally non cap coupled
I am thinking to a P JFET BOZ
Is this feasible?
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Old 27th September 2018, 04:42 PM   #1406
MEPER is online now MEPER  Denmark
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BA3 pre has a lot of gain so will be good for a power amp with no voltage gain. BA3 pre has an output cap but I guess it could be bypassed when used with MoFo as MoFo has an input cap? BA3 can be adjusted to there is very little DC at the output?
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Old 27th September 2018, 05:12 PM   #1407
marconi118 is offline marconi118  Germany
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BA3 uses unobtanium parts...

and I don't need high gain
6x is ok

Last edited by marconi118; 27th September 2018 at 05:16 PM.
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Old 27th September 2018, 11:49 PM   #1408
6L6 is offline 6L6  United States
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Quote:
Originally Posted by marconi118 View Post
BA3 uses unobtanium parts...

Obtanium - Linear Systems Matched LSJ74/LSK170 JFET pairs (Grade B) – diyAudio Store

Quote:
Originally Posted by MEPER View Post
BA3 pre has an output cap but I guess it could be bypassed when used with MoFo as MoFo has an input cap? BA3 can be adjusted to there is very little DC at the output?
No compelling reason to bypass the cap but I suppose you could. Particularly if you know its always going to be attached to an amp with an input cap.

Yes, the BA3 can be adjusted for very little DC at output, but only once it's to temperature and stable, hence the cap.
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Old 28th September 2018, 06:57 AM   #1409
MEPER is online now MEPER  Denmark
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i have all parts for my BA-3. I went for the Fairchild output transistors and 1k trimmers (got 2SK jfets from ebay). The idea with bypass of the output cap of BA-3 was to fulfil "Marconi118" requirement but also gave me an idea as I will use BA-3 for MoFo also…...and for ACA. Maybe a jumber or switch could be install so BA-3 can work with or without output cap.
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Old 1st October 2018, 09:44 AM   #1410
marconi118 is offline marconi118  Germany
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does the BA3 with Fairchild output devices sound the same as with Toshiba ones?

I am speaking about complete capless coupling:
remove the input cap and bias network from MoFo
tweak the preamp to have at the output a DC voltage to bias the mofo at desired current
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