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Old 9th May 2011, 08:42 AM   #851
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Quote:
Originally Posted by Joachim Gerhard View Post
Thorsten, the measurements are from an Olympos in a Triplanar arm. I have now changed to a Titan i and will repeat the measurements with a bipolar phonostage i made. Sooner or later i will change the arm too. I have a Schröder Artemiz and wait for a Spiral Groove Centroid. To tame the main arm resonance at ca. 7 to 9Hz i will try a subsonic filter or i could fill more oil into the damper of the Triplanar or both.
QSerra, the measurement with the lowest noise is the residual of the measurement aparatus. Then from bottom to top comes the 2SK372V, BF862 and the 2SK170.
Units?
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Old 9th May 2011, 11:07 AM   #852
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I can really not remember. Scott made this measurements for EUVL and he knows.
Maybe he will kick in soon on this.
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Old 9th May 2011, 11:25 AM   #853
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OK, i found it.
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Old 9th May 2011, 12:47 PM   #854
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Hi,

Quote:
Originally Posted by Joachim Gerhard View Post
OK, i found it.
The testing of the K372 and BF862 at 1.2mA Id is impressively low noise.

Attempting to get low noise from a 2SK170 at 1,2mA Id is a fools errand though, just look at the Noise vs. Id curves in the datasheet.

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Old 9th May 2011, 01:03 PM   #855
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i did not do the measurements but found them interesting. I build may stages with 2SK170 and 2SJ74, usually near Idss and they are fine, noisewise.
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Old 9th May 2011, 01:07 PM   #856
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Joachim,

Quote:
Originally Posted by Joachim Gerhard View Post
i did not do the measurements but found them interesting. I build may stages with 2SK170 and 2SJ74, usually near Idss and they are fine, noisewise.
They are very interesting. If I ever make a 1980's Japanese Style compound RIAA circuit with Op-Amp and two J-Fets for RIAA clearly the BF862 is ideal, low current for low noise, very nice possibilities...

I agree at running at least > 50% Idss with the whole K170/J74/K147/J72 range, noise is lower based on my tests, though the rise at LF remains.

Ciao T
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Old 9th May 2011, 01:18 PM   #857
dimitri is offline dimitri  United States
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Here is input capacitance vs source resistor value for gainblock-simple circuit from post #741
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Old 9th May 2011, 01:24 PM   #858
MiiB is offline MiiB  Denmark
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Good with a low noise jfet that don't need a lot of current.. makes it possible to stick to smaller to 92 devices for the cascode, current mirror and also for the CCS.. that then again can be a higher current Jfet
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Old 9th May 2011, 01:57 PM   #859
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Quote:
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OK, i found it.
The 1kHz tone turned out to be the carrier(?) for some kind of HVAC control system that talks through the power lines. Nice of them, it now contaminates the entire building.
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Old 9th May 2011, 02:05 PM   #860
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Quote:
Originally Posted by ThorstenL View Post
Hi,



The testing of the K372 and BF862 at 1.2mA Id is impressively low noise.

Attempting to get low noise from a 2SK170 at 1,2mA Id is a fools errand though, just look at the Noise vs. Id curves in the datasheet.

Ciao T
These were for microphone circuits, but in general I don't go by noise vs. Id. For FET's that generally just tells you where the parasitic resistances kick in. Many of these FET's maintain <4nV @ 25uA of Id, opens up a bunch of neat battery powered circuits.

The massive paralleling of FET's at high Id to meet some stake in the ground spec on noise seems brutally obvious to me by now, I think it's done, yes?
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Last edited by scott wurcer; 9th May 2011 at 02:08 PM.
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