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Old 8th April 2011, 05:36 PM   #2171
MiiB is offline MiiB  Denmark
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Clever You....Looks really good...With the last version...Is there not a risk of frying the coils in case of drift..???

NO MAC...I HAVE.....

Last edited by MiiB; 8th April 2011 at 05:39 PM.
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Old 8th April 2011, 05:40 PM   #2172
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I never fryed a coil. Even my most badly offsetted transimpedance BJT stages where not able to destroy my rather expensive Titan i. For the faint at heart there is the Transconductance version.
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Old 8th April 2011, 05:44 PM   #2173
MiiB is offline MiiB  Denmark
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For sure offset with Jfets will be low....but anyway....

Talking of Lyra...Anyone in the fora heard from Jonathan Car...He has though my visits grown to be a friend, but...seen or hear nothing since the tragedy in Japan...
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Old 8th April 2011, 05:59 PM   #2174
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Jonathan is in design mood. That has the consequence that he is even hiding for Stig. I skype with Stig regulary and he said "Tokio is nearly back to normal". I whould leave the country but that is against the japaneese culture of "Insisting, Resisting, Persisting". An amasing, admirable but somewhat ancient society.
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Old 8th April 2011, 09:24 PM   #2175
Salas is offline Salas  Greece
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Quote:
Originally Posted by Joachim Gerhard View Post
Lets get serious. Here is a high PSSR version of the input stage. No Leds, no elcaps, no conventional RC filtering. Bias is done with an adjustable micropower voltage reference. It has an extremely low dynamic impedance of 1 Ohm, runs on less then 0.1mA, has a tempco of 150PPM. The way i have connected it gives even lower noise. The 100kOhm resistor gives enough exess current to run the bases of the cascodes.
Is stabilizing the cascode's base voltage enough to give the full PSRR? What lurks on R2, R6 from the rails, is not affecting any more?
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Old 8th April 2011, 09:54 PM   #2176
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Well, the cascode has some stabilizing purpose because the voltage at the Fets is constant. R2, R6 can be substituted with current sources. Yes, if the PSU has a flaw, the resistors can not supress this. It will simply downmodulate. Popa has shown in Linear Audio Volume 1 that a current source improves PSSR ( humm ) but does not reduce the noise ( hiss ). How a cascode can be made that is referenced to ground and has no seperate voltage reference i have shown in my FPS in Linear Audio Volume 0 cleaning the baby and not throwing it out of the water the same time. This little workaround did not stir any interest though as far as i can tell from the comunication i got. My PSU that i have not shown so far solves that problem to a certain degree too. I could go on and on. This is all managable with ever increasing complexity. The question is what we want this time. It started out with minimum complexity plus no use of obsolete components and now we are back into state of the art, high tech solutions plus some NOS thrown in for good measure. If an fine with that as long as do not bore the contributors and readers.
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Old 8th April 2011, 10:41 PM   #2177
Salas is offline Salas  Greece
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We want clean supply for no extra complexity. Since there is a clean rail, and good cascode base supply is established, we are OK short of folded cascode. Its good we discuss why and how non the less IMHO.
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Old 8th April 2011, 11:04 PM   #2178
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I think now that the circuit is fine. Not too expensive, not too complex and stiil performs well at least in simulation. This micropower references are not expensive at all despite the exotic name. The 10uF to ground can be made from 2 x 4.7uF Wima MKT-2. They are inexpensive too and measured under 10mOhm ESR at 100kHz. I build the 12V battery supply version and was happy with the measurement so it works in praxis and the latest changes will make it only better. Lets look at an equally simple and good PSU. I think that could be fun.
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Old 9th April 2011, 03:35 AM   #2179
Salas is offline Salas  Greece
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You may like what juma liked for his BF862 preamp. juma's BF862 pre. You also see how it mirrors there.

I attach the non Zener one.
Attached Images
File Type: gif SalasMirrorTwist.gif (6.1 KB, 304 views)
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Old 9th April 2011, 07:15 AM   #2180
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So this one uses a current mirror.
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