John Curl's Blowtorch preamplifier part II

[john curl]

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?

[syn08]

Originally Posted by Wavebourn

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.

[Wavebourn]

Originally Posted by syn08

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.

[john curl]

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?

[stinius]

Originally Posted by john curl

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

[zinsula]

[stinius]

Hi Zinsula

John was talking about the Parasound JC-2

[brianco]

Originally Posted by stinius

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....

[kl]

Originally Posted by brianco

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

[brianco]

Originally Posted by kl

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!!