John Curl's Blowtorch preamplifier part II - Page 151 - diyAudio
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Old 23rd September 2009, 07:19 PM   #1501
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Pavel, we are getting bogged down answering random concerns. Perhaps we can go forward, instead. What have you found that works pretty good for mosfets? Anything new out there? Is an all j-fet design really significantly better?
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Old 23rd September 2009, 07:33 PM   #1502
syn08 is offline syn08  Canada
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Quote:
Originally Posted by Wavebourn View Post
You forgot about non-linear input capacitances of output MOSFETs that cause signal rectification and dependence of their idle currents on frequency, hence dynamic distortions.
Yep. It's probably hard to find a better simple example of open loop gain generating large amounts of PIM.
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Old 23rd September 2009, 07:45 PM   #1503
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Originally Posted by syn08 View Post
Yep. It's probably hard to find a better simple example of open loop gain generating large amounts of PIM.
And it would be hard to measure because of symmetry that hides non-linearities from an observer. The best way to catch it up is to observe triangle shape changes on an oscilloscope gradually increasing frequency on a full swing.
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Old 23rd September 2009, 08:00 PM   #1504
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Of course, we should have the more standard Parasound JC-2 preamp sort of stage to compare to. I don't have a simplified schematic handy, does anyone?
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Old 23rd September 2009, 10:04 PM   #1505
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Quote:
Originally Posted by john curl View Post
Of course, we should have the more standard Parasound JC-2 preamp sort of stage to compare to. I don't have a simplified schematic handy, does anyone?

I can send you one by email, if you think its ok you can put it up yourself, or let me know.

Cheers
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Old 23rd September 2009, 10:25 PM   #1506
zinsula is offline zinsula  Switzerland
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Post Jc-2

Attached Images
File Type: gif jc2 Line Stage.gif (64.8 KB, 442 views)
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Old 23rd September 2009, 10:54 PM   #1507
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Hi Zinsula

John was talking about the Parasound JC-2
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Old 23rd September 2009, 11:12 PM   #1508
brianco is offline brianco  Ireland
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Originally Posted by stinius View Post
Hi Zinsula

John was talking about the Parasound JC-2

The above schematic IS of the JC-2 "output module". IF it is not, then there is one more error on the internet or Jc designed at least two JC-2 preamps....
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Old 23rd September 2009, 11:33 PM   #1509
kl is offline kl  Europe
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The above schematic IS of the JC-2 "output module". IF it is not, then there is one more error on the internet or Jc designed at least two JC-2 preamps....
It seems that there are at least two JC-2 designs:
http://www.marklev.com/JC2/index.html
http://www.parasound.com/halo/jc2.php
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Old 23rd September 2009, 11:57 PM   #1510
brianco is offline brianco  Ireland
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It seems that there are at least two JC-2 designs:
http://www.marklev.com/JC2/index.html
http://www.parasound.com/halo/jc2.php
Apologies Stinius

This thread can be so confusing!!
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