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Old 8th June 2007, 05:14 PM   #91
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Quote:
Originally posted by Babowana


Too simple . . . too simple . . .
What do you need more . . . ?

Someting to lower output impedance?

Maxpou idea?

Not more than 600 Ohms is a nice target.
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Old 8th June 2007, 05:16 PM   #92
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by apassgear



Someting to lower output impedance?

Maxpou idea?

SRPP...........



hehe

that's going in direction to some already made preamp
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Old 8th June 2007, 05:42 PM   #93
lineup is offline lineup  Sweden
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Smile Lineup Audio, 2SK170GR jfet-boz version 1.0

Quote:
Originally posted by Nelson Pass
Maybe you would like to try this first.
Attachment: jfet boz small.pdf
This has been
downloaded 338 time(s).

People hevent got anything else to do, than download Nelson Pass PDF.
... Well, for myself speaking: I do not do much anything else

----------------------------------------------------------------------------------


Comment to my attached SCHEMATIC
Lineup 2SK170GR Jfet BOZ - beta version 1.0a


Eventhough there are a coupe of things I would do different
and change, compared to Nelson's Qucikly posted simple circuit,
I have used same values as Nelson, in this version.
As far as I could .....

From several reasons, including:
1. Make it easy for those already having Nelson's original in mind.
2. By having similar conditions,
we can make as fair a comparison, as possible.
3. I trust Nelson Pass much. He has got experience and knows.
... you wouldnt like to change a winning setup
- not in football teams - not in amplifiers


just about the only being different in my version:

... is adding a current handling 2N5401 PNP, to 'help the jfet'
(I tried a BC640 type here fisrt, but trying like 6-7 different
the 2N5401 as 'the best'
Because this tranasistor works better at 9mA,
which is bit too high for best operation in BC560C / BC640-16.

... as 2SK170GR
is the variant I can buy up here, I use this ( IDSS max = 4.80mA, in my test circuit )

... Input Cap is optional - most cases you will NOT need it.
But just in case, you may keep it. It doesnt do no harm.


Supply Voltage is 30VDC, well regulated**.
The DC operation voltage at Ouput node is: ~10.5 VDC.

** I recommend the use of one
cheap & good TL431 adjustable zenerdiode ( 2.5V - 36V max)
plus a simple follower NPN Transisitor.
One that can deliver 10mA = total supply current



Regards
Lineup Audio Labs, the design division
/lineup
Attached Images
File Type: png lineup_2sk170-jfetboz-1.0a.png (11.4 KB, 3729 views)
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Old 8th June 2007, 06:24 PM   #94
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Yes, the minute you are willing to bias the input at other than
ground you can make for great improvement.

As to the question about cascoding, yes you can, but you no
longer have the load-line cancellation discussed earlier, and
you will have to alter other parts of the circuit.

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Old 8th June 2007, 07:55 PM   #95
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Quote:
Originally posted by Nelson Pass
Yes, the minute you are willing to bias the input at other than
ground you can make for great improvement.

That would be a simple trade off, but which great improvements?

Could you elaborate please?
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Old 9th June 2007, 01:44 AM   #96
F1 FAN is offline F1 FAN  Canada
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How would this simple circuit stack up against the DIY opamp in fig 16 in the 1/99 issue of Audio Electronics?Also what would the mininum load impedance be for both circuits?
Thanks
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Old 9th June 2007, 02:06 AM   #97
lineup is offline lineup  Sweden
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Arrow Lineup Audio Lab improved 2SK170 Jfet BOZ version 2.0a

Quote:
Originally posted by Nelson Pass
Yes, the minute you are willing to bias the input at other than
ground you can make for great improvement.
As to the question about cascoding, yes you can, but you no
longer have the load-line cancellation discussed earlier, and
you will have to alter other parts of the circuit.
hmmm,
I guess this was not a comment to my posted circuit.
Because I have still, for simplicity, bias at ground without cascode.
I have told this before:
I am not a man 'who cascode anything I see'

I guess Nelson Pass missed my post.
I have no comment to this.
He is often in A Great Hurry (not to miss train to heaven?),
I would imagine
------------------------------------------------



Lineup Audio Lab improved 2SK170 Jfet BOZ version 2.0a
-------------------------------

- Attached is the SquareWave at 10 KHz, with 4Vpeak / 10 kOhm output
- For my basic circuit, see previous post schematic.


Following criteria setup was used, for trimming for optimal performance:
1. Input bandwidth restricted to 3-300000 Hertz, -3dB (no junk outside this will even enter into 2SK170GR
2. LOAD was changed, temporarily to 4k7 = heavier, worst case, load
3. Test frequency input was set to 10000 sinus ( 10KHz)
( on the borderline of what most mature people can hear )


Was found that with these criteria, 2SK170 / 2N5401 combination
works best at slighly higher Voltage, 12-13 Volt, and a bit lower bias, ~7.5mA
(compared to 10.5 Volt / 9mA in my Version 1.0a)


Regards
lineup


----------------------------------------------------------------------------
Below is result for trimmed Version 2.0a
Shows the following Simulated Squarewave, at 4 Volt Peak output:
The frequency is 10 kHz Square
Attached Images
File Type: png lineup_2sk170-jfetboz-2.0a_10khz-square.png (6.6 KB, 3048 views)
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Old 9th June 2007, 03:50 AM   #98
Blues is offline Blues  United States
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Quote:
Originally posted by Nelson Pass
As to the question about cascoding, yes you can, but you no
longer have the load-line cancellation discussed earlier, and
you will have to alter other parts of the circuit.

Mr. Pass, can we not cascode it in tune with the load line ala Zv9?
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Old 9th June 2007, 05:01 AM   #99
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Quote:
Originally posted by Blues
can we not cascode it in tune with the load line ala Zv9?
Of course, but my previous comment still applies.

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Old 9th June 2007, 04:13 PM   #100
Blues is offline Blues  United States
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Quote:
Originally posted by Nelson Pass


Of course, but my previous comment still applies.


Ok. On 2nd thought, if we can tune it to the load line without a cascode and we have enough voltage swing with a single jfet...let's keep it simple!

Battery PS would make it a killer...we won't worry on rectified PS noise.
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