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Old 30th June 2012, 08:53 AM   #1061
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by keantoken View Post
Furthermore, the increase in distortion could be compensated by doubling R4 and R12 in your schematic.
It is indeed a possibility, but of course as there are no free lunches, the negative swing would be further reduced.
And if you try to reduce the current in R4/R12 in the same proportion, the transconductance of the input pair would be reduced by the same amount, canceling the gain benefit
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Old 30th June 2012, 12:47 PM   #1062
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Again, bases of Q5Q6 (LP) should be -20 rail.
To allow the full negative output swing.
Cascode supply then providing -22.5.

But why some bizarre voltage like 2.5?
3.3V or 5V warts are more easily scavenged.

The original pair there also had a short tail R5
(OP) that Elvee said necessary for stability.
Somehow in the rush we forgot that?

Last edited by kenpeter; 30th June 2012 at 01:01 PM.
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Old 30th June 2012, 12:59 PM   #1063
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Then it'll just be weird and everyone will immediately look for something else to build.

Although it is a good idea.
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Old 30th June 2012, 02:41 PM   #1064
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Quote:
Originally Posted by kenpeter View Post
The output cannot swing very low with that cascode in the way. Have you considered the existing negative rail for cascode base? You would have to provide an extra negative rail for circlophony. But it needn't be anything elaborate since the common mode is strongly controlled by quadrature anyway, a 5v wart might do.
I've no idea what that means, due to lack of a schematic. The idea sounds interesting yet vague. Connect where?
Quote:
Originally Posted by kenpeter View Post
Again, bases of Q5Q6 (LP) should be -20 rail. To allow the full negative output swing. Cascode supply then providing -22.5. But why some bizarre voltage like 2.5? 3.3V or 5V warts are more easily scavenged.
Again, could you show your idea on schematic? Even a sketch would do fine. Please, something to see instead of confuse.
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Originally Posted by kenpeter View Post
The original pair there also had a short tail R5 (OP) that Elvee said necessary for stability. Somehow in the rush we forgot that?
Well, I looked up the "OP" (post #1) Original Post's R5 and I didn't omit that resistor on any schematic posted. Therefore, what???
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Old 30th June 2012, 02:58 PM   #1065
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Quote:
Originally Posted by keantoken View Post
Then it'll just be weird and everyone will immediately look for something else to build.

Although it is a good idea.
HEAR HEAR!!!!!
How would a printed circuit board look like. I did design 40 years ago but then stopped and now my knowledge is not even there any more. Daniel sorry but I misread the number of your output devices when I did ask if those output devices were able to stand this abuse!
Krokkenoster is a DNA mixture of all species! Before I got injured I worked on all kinds of lift truck sort of "Jack of all trades"
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Old 30th June 2012, 04:55 PM   #1066
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Originally Posted by danielwritesbac View Post
Well, I looked up the "OP" (post #1) Original Post's R5 and I didn't omit that resistor on any schematic posted. Therefore, what???
Cease your panic. LP was 1059, no reference intended to any of yours.
Keantoken's LP schematic appears to omit equivalent function of R5 (OP).

Read 1062 again, I was specific which reference designators were LP and OP.
1062 also answered your question regarding proper use of the extra rail.
I will draw for you when I get around to it, Patience...

Last edited by kenpeter; 30th June 2012 at 05:23 PM.
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Old 30th June 2012, 07:28 PM   #1067
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Quote:
Originally Posted by krokkenoster View Post
HEAR HEAR!!!!!
How would a printed circuit board look like. I did design 40 years ago but then stopped and now my knowledge is not even there any more. Daniel sorry but I misread the number of your output devices when I did ask if those output devices were able to stand this abuse!
Krokkenoster is a DNA mixture of all species! Before I got injured I worked on all kinds of lift truck sort of "Jack of all trades"
Daniel, Thank you for the info sent to me I appreciate it.
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Old 1st July 2012, 07:14 PM   #1068
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Before anyone develops a drawing withdrawal anurism...
Here we can swing an output within 1.4V of either rail.
Because this cascode's reference drop isn't in the way.

No other point was intended, so ignore everything else
that might be weird about this circuit. Its not finished.
Attached Images
File Type: gif RailCascode.gif (31.0 KB, 275 views)
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Old 1st July 2012, 07:21 PM   #1069
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We could do the Mimesis thing and add a voltage doubler to the trafo secondary; that would require the least extra hardware.
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Old 1st July 2012, 07:37 PM   #1070
Elvee is offline Elvee  Belgium
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Basically, I hate anything resembling multiple supplies.
I have designed amplifiers or variable lab supplies amongst other things, but I always managed to get decent performances without this kind of prop, even high voltage supplies with full I/V control down to zero.
The plain vanilla Circlophone swings to within 1.5V of either rail without any artifice, and I think it would be a pity to depart from that philosophy.
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