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Old 13th September 2012, 03:42 AM   #91
bcarso is offline bcarso  United States
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Quote:
Originally Posted by bkdog View Post
Dunno what you're talking about - we're at the top, see here:

The Upsidedown Map Page - World Maps with South at the Top


My friend DHC wanted to know where the earth was --- above or below the Galactic Plane.

WTF? Who defines the up and down of that to begin with??
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Old 13th September 2012, 04:01 AM   #92
qusp is offline qusp  Australia
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Quote:
Originally Posted by bcarso View Post


My friend DHC wanted to know where the earth was --- above or below the Galactic Plane.

WTF? Who defines the up and down of that to begin with??
someone who wants to map it I guess
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Old 13th September 2012, 09:12 AM   #93
bcarso is offline bcarso  United States
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Originally Posted by qusp View Post
someone who wants to map it I guess
I guess it has to do with the "handedness" of things defining a rotation axis. That reminds me of a professor I know who said he went through an E&M final as a student writing with his right hand and using his left hand for vector cross-product guidance (the so-called "right-hand rule"), thus getting a bunch of signs wrong.
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Old 13th September 2012, 09:14 AM   #94
EUVL is offline EUVL  Europe
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Should I open a thread call XEN Lounge for such interesting topics ?




Cheers,
Patrick
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Old 13th September 2012, 09:18 AM   #95
bcarso is offline bcarso  United States
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Will it be above or below the current thread?
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Old 13th September 2012, 10:08 AM   #96
EUVL is offline EUVL  Europe
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You have to ask the moderators.



Serious. Let's go back to circuits.


Patrick
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Old 13th September 2012, 11:59 AM   #97
Calvin is offline Calvin  Germany
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Hi,

bcarso, You are right. The gate resistors of the cascode JFETs are not needed in the combination of LSK389C and MMBF/SST4391. The pin layout of the LSK389 SOIC-8 and the SOT-23 allows for tight direct connections. You wonīt even need a 0-Ohm resistor to bridge a trace. Gate stoppers might be required with other transistor combinations though.

Patrick, the DAO sure is the most powerful, but it is the most complex and is it unconditionally stable? I had already oscillation problems with the much simpler Borbely buffer (CCS, modulated via a upper drainīs resistor and a RC-Gate-Network to the lower JFET). I assume the DAO could be even more prone to instability.
The third Buffer of my post -btw. would īcascoded Sziklay pairī be a correct naming(?)- is compensated for by only the small caps C1 and C2.
It may have been overlooked, but all parts of all three buffers are SMDs, allowing for small, compact footprints and all three may be DC-coupled.
The first two circuits are best used with load impedances >10kOhm and Zload should not drop below 1kOhm. The third circuit is best between 10kOhm and 300Ohms. Either with MOSFETs or bipolars, running on ~50mA bias current, it can drive 300Ohms to 3Vrms, which is sufficient for home and studio line level circuits.

Joachim, the probs I had were with a simple ccs loaded Source-follower (like the first in my post). It used BF244C or BF246A and input AC-coupling of the stage with a Gate resistor of >1MOhm. It eventually suffered from serious dc-offset (input and output were driven into one of the supply lines) and fatal destruction.
In our correspondence You assumed heavy oscillations as reason and suggested the use of Gate stoppers. I later found out that the JFETs didnīt oscillate, but latched-up, due to rising Gate leakage, which itself was affected by temperature, Vds and the high valued Gate resistor (a self amplifying effect). Reducing the value of Rgate and changing to different JFETs solved the prob.

jauu
Calvin

Last edited by Calvin; 13th September 2012 at 12:03 PM.
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Old 13th September 2012, 12:36 PM   #98
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Calvin, good that you solved the problem.
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Old 13th September 2012, 04:04 PM   #99
EUVL is offline EUVL  Europe
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The DAO is in essence a MOSFET cascoded JFET source follower.




Patrick
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Old 20th October 2012, 05:04 AM   #100
EUVL is offline EUVL  Europe
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Another update, showing THD measurements.

We are not totally happy with the PSRR and DC drift, even if they are quite OK.
So we are currently working on an improved version to solve both of these problems.
As soon as we have test results, we shall let you know.

The bad news for the new version is, you would need 5 pairs of matched 2SK246/2SJ103 and 1 pair of 2SK170.




Patrick
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