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Beast with a Thousand JFETs
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Old 4th September 2009, 09:59 AM   #91
jan.didden is offline jan.didden  Europe
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Quote:
Originally Posted by Nelson Pass View Post
I bet you would.

Does anyone have problems opening Nelson's graph from this post? On my PC it keeps saying "loading..." indefinitely.

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Old 4th September 2009, 10:44 AM   #92
zhoufang is offline zhoufang  Singapore
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Does it read 0.0024% THD at 1W without any NFB?
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Old 4th September 2009, 10:54 AM   #93
Spooky Electric is offline Spooky Electric  Germany
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Converted it to jpg.
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File Type: jpg temp.jpg (57.1 KB, 1438 views)
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Old 4th September 2009, 11:34 AM   #94
Atilla is offline Atilla  Norway
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Quote:
Originally Posted by zhoufang View Post
Does it read 0.0024% THD at 1W without any NFB?
Yes, I believe it does
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Old 4th September 2009, 11:53 AM   #95
soekris is offline soekris  Denmark
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Beast with a Thousand JFETs
What about using smt jfets, in sot23 ? Linear are supposed to launch their LSJ74 soon, you could mount them on a thin PCB that you glue directly on a big heatsink.... Any thermal problem solved.

I know that Nelson don't like stuff he can't see, but it much easier to have a machine mount 1000's of smt parts....
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Old 4th September 2009, 12:25 PM   #96
zhoufang is offline zhoufang  Singapore
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Quote:
Originally Posted by Atilla View Post
Yes, I believe it does
If we assume that the 588 jfets is for one channel in push-pull setup and unbalanced mode, driving into 8ohm load, then at 1W RMS each jfet will be driving a +/- 0.85mA (1.7mA pp) of load.

And it will be at 8Vpp.

Comparing with THD measurement of B1 buffer, this thousand JFET amp's performance seems to be too good.

The only explaination that I can think of is that the symmetrical output stage help to significantly cancel of the distortion.
Or else there could be some intellegent design in it, which I can't wait to see more details.
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Old 4th September 2009, 12:42 PM   #97
soekris is offline soekris  Denmark
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Beast with a Thousand JFETs
Distortion sounds not too far off, Borbeley's paper claims 0.0078% THD at 3V into 1Kohm with a single pair. 1W into 8 ohm is 2.8V, and 500 pairs into 8 ohm is like single pair into 4Kohm....

Sĝren
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Old 4th September 2009, 01:16 PM   #98
oliverniekamp is offline oliverniekamp  Germany
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There might be an X hidden in between 1000 Jfets?
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Old 4th September 2009, 01:19 PM   #99
Diomedian is offline Diomedian  Canada
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I'm not sure if the AP machine measures THD+N or not, but I'd imagine that most noise would be averaged out over so many pairs.
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Old 4th September 2009, 01:25 PM   #100
jan.didden is offline jan.didden  Europe
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Quote:
Originally Posted by Floyd42Flake View Post
Converted it to jpg.
Works. Muchos gracias!

jd
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