F4 Beast Builders

[generg]

very nice!

 

[Soundhappy]

http://www.moremusic.nl/pass_labs/Manuals/Manual-XA25.pdf

 

[2 picoDumbs]

very nice!

I am very happy with that matching.
I'll start measuring the others to see how much variation there might be between devices.

 

[generg]

http://www.moremusic.nl/pass_labs/Manuals/Manual-XA25.pdf

Good that you revealed this soundhappy!

Now I can stay in this thread and must no more believe in teleportation....

:--))

 

[generg]

"We still use the same “New Old Stock” of small power JFETs and cascoded MOSFET, in the classic “CFA” voltage gain circuit."
Cascoded Mosfets in the front end, does this allow the no degeneratin in the second stage?

 

[2 picoDumbs]

"We still use the same “New Old Stock” of small power JFETs and cascoded MOSFET, in the classic “CFA” voltage gain circuit."
Cascoded Mosfets in the front end, does this allow the no degeneratin in the second stage?

I think that could be a potential error.
Most likely cascoded Jfet then regular 2sk2013 2sj313 in 2nd stage.
No need to change the recipe.

 

[2 picoDumbs]

Variation between 5 x IXTN40P50P devices

 

[lhquam]

Do you also have gm measurements for each of the 5 series?

 

[2 picoDumbs]

Do you also have gm measurements for each of the 5 series?

Yes but only at Id=2A, if you need a complete curve, I will need to perform more measurements.

 

[Zen Mod]

what I can see from graph , it's around 6.15A/V

do we need more precise measurement ?

 

[2 picoDumbs]

For all 5 devices it ranges between 6.1 and 7, but 4 out of the 5 devices range between 6.8 to 7.
I'll probably repeat the measurements one more time, but I am mostly interested to see whether they are a reasonable match to 48N60P when measured under identical conditions. KISS

Temperature of heatsink right next to mosfet was 52.7C

 

[generg]

Bah, really impressive Mr. Pass!

 

[2 picoDumbs]

Also based on the measurements performed at 22.1C and 52.7C it appears a difference of 0.1V between cold and hot is all that is required in the biasing circuit for 40P50P.
So maybe a 0.2V difference in the biasing circuit between cold and hot across the pair of 48N60P/40P50P will be adequate.

 

[2 picoDumbs]

Bah, really impressive Mr. Pass!

Yes that is what I am getting for both 4 and 8 Ohms.
That is why I won't be losing sleep over positive or negative phase harmonics. Maybe still worth playing with though, let your ears be the judge.

 

[lhquam]

Bah, really impressive Mr. Pass!

Where did that distortion plot come from?

 

[2 picoDumbs]

Where did that distortion plot come from?

The user manual

 

[2 picoDumbs]

Aaah stuff it, who needs sleep anyway. hahah
I'm gonna go measure the rest of IXFN48N60P

 

[generg]

Where did that distortion plot come from?

soundhappy was so nice to give the link a few postings above....

http://www.moremusic.nl/pass_labs/Manuals/Manual-XA25.pdf


while 2picodumbs tried to convince me of his teleportation abilities on his saloon table..... :--))

 

[generg]

Aaah stuff it, who needs sleep anyway. hahah
I'm gonna go measure the rest of IXFN48N60P

Well done, man!

 

[Dennis Hui]

soundhappy was so nice to give the link a few postings above....

http://www.moremusic.nl/pass_labs/Manuals/Manual-XA25.pdf


while 2picodumbs tried to convince me of his teleportation abilities on his saloon table..... :--))

I noticed the user manual doesn't say anything about 2 ohm load, unlike
the prelim info we saw earlier.

But dang, <0.01% distortion for 8 and 4 ohm load over the entire power
range is nothing to sneeze at.

And the dimensions are pretty room friendly; just put it where your FW
amp currently resides.

Dennis