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Top ten ways to better a Pearl ?
Top ten ways to better a Pearl ?
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Old 6th December 2005, 06:10 PM   #31
MRupp is offline MRupp  Germany
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"Try lowering the voltage over the FETs ..."

I found te following information in an article from Klaus Boehning detailing his phono pre design, at http://www.klaus-boening.de/html/lab_page.html - check the chapter Determining the lower limit of UDS . Some other references tend to also prefer a higher VDS for the common source transistor but I cannot really say what is better.

Btw., where can I find the Hiraga article, please?
Martin Rupp
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Old 6th December 2005, 08:14 PM   #32
thorstenlarsen is offline thorstenlarsen  Denmark
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The article was about a hybrid amplifier called " le Passific ". Two stages with j-fet/bjt cascode input differential driving two el84 push-pull outputs. I read a photo-copy of the article around 12 years ago. I think it was from "l`Audiophile".
The decision to lower the fet-voltage was made on subjective grounds. The lower gate leakage current was mentioned as a possible explanation for the better sound quality.
I tried it out on a "Monster amp" together with a friend, and we came to the same conclusion as Jean Hiraga.
To Buhl: On the Pearl schematics at passdiy.com, you can see two voltage-dividers each with two 10 kOhm resistors. The middle points connected to bases of bjt´s of the cascodes. To decrease the voltage over the fet, you just have to decrease the value of the lower resistor. For listening tests, just solder another over the existing one. Remember that a new solder-joint takes around 15 minutes of playing to burn in.
Just try it out. But let us know what you think.

( another one )
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Old 7th December 2005, 08:53 PM   #33
steenoe is offline steenoe  Denmark
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Now this thread has come out of the sauerkraut and back to the technical.
Hans, I am sorry to have caused disruption on your thread! I see now that my post didnt have the impact, it was supposed to, at all! I did read my first post again, and didnt find it expressed, what I meant it to! The tone was too harsh, no matter how I try to turn it I am sorry for that The sauerkraut is all mine, Hans I will try to contribute in a more polite and hopefully enlightening manner for the future

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