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Old 20th May 2008, 12:39 AM   #801
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Quote:
Originally posted by Nelson Pass

Last question, what is your supply voltage?
It's +/- 24VDC

The DC offset is tweaked down to about 10mV which is nice, but this takes a bit of patience.

The DUT was the one without the thermal compensation, although that shouldn't make a difference.
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Old 20th May 2008, 01:19 AM   #802
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I asked because the design was optimize for 24V, and as you
go down, any peaking is exacerbated.


Your vocabulary word for the day-

Exacerbate: to make more harsh or severe.

usage: "This solid state amplifier exacerbates the peak in my tweeter"
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Old 20th May 2008, 01:26 AM   #803
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Nelson Pass
...........
Exacerbate: to make more harsh or severe.

usage: "This solid state amplifier exacerbates the peak in my tweeter"

cure :

just exactoknife that exacerbating tweeter .......

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clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
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Old 20th May 2008, 02:25 AM   #804
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Quote:
Originally posted by Nelson Pass

Exacerbate: to make more harsh or severe.

usage: "This solid state amplifier exacerbates the peak in my tweeter"
I'll use that with my wife this evening.
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Old 20th May 2008, 02:44 AM   #805
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Just a passing observation...but if all you've got is a tweeter, shouldn't you be trying one of those spam e-mail pills that claims to give you a long-throw woofer?

Grey

P.S.: I've always been partial to the word sesquipedalian, myself.
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Old 20th May 2008, 03:28 AM   #806
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Quote:
Originally posted by Nelson Pass

Your vocabulary word for the day-

Exacerbate: to make more harsh or severe.

usage: "This solid state amplifier exacerbates the peak in my tweeter"

Now, we are learning not only to make amps here.
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Old 20th May 2008, 03:45 AM   #807
fab is offline fab  Canada
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Angry PROFET Question

Quote:
Originally posted by Nelson Pass


Much of the difference is due to the high degeneration of their
input JFETs, the lower transconductance of Laterals and their relatively
high output gain. This means a lot less feedback, as seen by the
output impedance and distortion specs.

For Common Source topologies, damping factor = feedback.
Since I do not have complementary vertical mosfet in hands but lateral mosfet, I have tried the "Profet" version and I can not make it work on the bench when loading with 8 ohms. When I connect the 8 ohms load, the signal amplitude drops to about 70%. The open loop gain is way too low. I even used lower degeneration resistors for the jfet and less close loop gain than the original profet. I used only one output pair as the Profet. And the THD is quite high. It seems that laterals 2SJ49/2SK134 (or 2SJ162/2sk1058) have about 10 times lower transconductance than IRF244 for example. Has someone successfully built and heard an F5 or Profer with lateral outputs? I know that jackinnj has described a lateral F5 adaptation in one post somewhere... he had 3 output laterals but even that is a lot less transconductance than 2 output verticals...

Thanks
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Old 20th May 2008, 04:39 AM   #808
fab is offline fab  Canada
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Default Profet like schematics

Here is the schematics for the previous post.

M1 and M4 are laterals.
Bias current is about 0.6A

J1 and J2 are SK170/J74

Thanks in advance for your comments
Attached Images
File Type: gif profet_fab_rev_5d3.gif (8.3 KB, 2636 views)
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Old 20th May 2008, 04:44 AM   #809
jam is offline jam  United States
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Fab,

.................Nice! My thoughts exactly.........byt do you need the compensation capacitor (C21)?

Jam
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Old 20th May 2008, 05:06 AM   #810
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Default Re: PROFET Question

Quote:
Originally posted by fab
Since I do not have complementary vertical mosfet in hands but lateral mosfet, I have tried the "Profet" version and I can not make it work on the bench when loading with 8 ohms. When I connect the 8 ohms load, the signal amplitude drops to about 70%. The open loop gain is way too low. I even used lower degeneration resistors for the jfet and less close loop gain than the original profet. I used only one output pair as the Profet. And the THD is quite high. It seems that laterals 2SJ49/2SK134 (or 2SJ162/2sk1058) have about 10 times lower transconductance than IRF244 for example.
That appears to be consistent with "Chuck" Hansen's review of the
Profet in AX magazine, in which he measured a 6.8 ohm output
impedance. That doesn't mean that the amp sounds bad, but it
tends to limit its application.
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