Beast with 1000 JFETs redux?

[woofertester]

Schematic of both stages. The schematic is hierarchical. 8 instances of stage 1 and 72 instances of stage 2.

 

[woofertester]

Gerber view of top of PCB.

 

[twitchie]

Wow! 6-layer board

I cannot imagine what this has cost you to get to this point. This is a super interesting project for the hardcore greedy boy. Thank you for sharing your journey with the rest of us.

 

[woofertester]

Wow! 6-layer board

I cannot imagine what this has cost you to get to this point. This is a super interesting project for the hardcore greedy boy. Thank you for sharing your journey with the rest of us.

The engineering fee is more than the PCBs by quite a lot. It is a learning exercise for me. Adding to the skill stack. Having a one-of-a-kind NP inspired JFET power amp is the largest attraction.

 

[woofertester]

Cascode Single Ended B1 9 cells

This one is intended to be either a preamp or a headphone amp. 9 cells.

2-sided. It was more difficult to lay out but will cost less per area.

 

[avtech]

Looks good! What is the board size for that one?

 

[woofertester]

Looks good! What is the board size for that one?

100 mm x 100 mm

 

[gary s]

You should get some interest for the small buffer.

 

[avtech]

This one is intended to be either a preamp or a headphone amp. 9 cells.

2-sided. It was more difficult to lay out but will cost less per area.

Any progress lately?

 

[twitchie]

Hi Woofertester, did you end up completing these for headphone use? Any listening impressions to share?

Happy New Year to All!

 

[mkc]

Don't know if this is the appropriate thread.

Came across this last night while youtube surfing on the ipad.

@Nelson Pass Is this a piece with J113?

 

[Zen Mod]

yup

Jon Ver Halen's Mini Beast

 

[Jon Ver Halen]

Needs a photograph. Here is one.

Papa sent me the boards, j-fets, and resistors. There are 4 boards with 512 j-fets per board. It was a soldering exercise. Was done Tuesday about midnight, burned in on Wednesday, and off to Axpona on Thursday.

For those of you who are curious as to what it sounds like - it is lovely, precise, and very, very fast. Flat to 500 kHz.

At Axpona Kent English of Pass Labs and I played a game with the listeners called "Identify the Power Amp". Amazing how many audiophiles and every reviewer got it wrong. Common guesses as to what it was were pagoda, bee hive, and trash can. I guess I need to work on my artistic skills.

Jon

 

[Zen Mod]

1024/channel

not bad

relieving to see that I'm not sole slave of The Singing Bush

 

[Dennis Hui]

Jon, thanks for the details. I really like the look. (And no heatsinks!)

 

[Zen Mod]

one thing is sure - I'm not going to Babelfish that one

 

[mkc]

Hi Jon,

Thank you for the picture now that the video has been blocked.

It seems that it's a nice mailing list you are subscribing to

I wonder how many jfets it takes in order to get enough for building 2 channels. How much power does it deliver? ZM refer to it as the Mini-Beast.

 

[EUVL]

1024 pairs of Toshiba JFETs, now selling at 20USD a pair.
That is 20,000 USD for a pair of power buffers (not even amplifying).

And with 512 pairs per channel, at say 7mA per FET, that makes 3.5A bias at say +/-20V rails (already exceeding the max rating of 2SJ74 by 2x at full swing).
So 50Wrms Class A into 4R, or 400USD per watt.
Makes Semisouth look cheap.




Patrick

 

[Nelson Pass]

Muuuuhahahahahaaaaaa....

 

[EUVL]

I have on my drawing board a solution that cost much less, and uses devices still in production.
Whenever it goes to the top of my to list. Won't be 2022 though.




Patrick