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Old 15th November 2011, 04:33 PM   #3101
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Thumbs up I know a curcuit that looks like this.

Hi Joachim,

A circuit like this has been build before by a good friend of mine (Ronald) but in single supply from plus 24 volt to gnd.
This is an other kind of beast, working from plus to minus. I got to give it a try too. Thanks for your input

You'll hear from me

atb,


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Old 15th November 2011, 04:41 PM   #3102
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Yes, it works single supply too but then an output cap is needed. I got tired to listen to caps.
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Old 15th November 2011, 04:47 PM   #3103
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Talking Cap's

Joachim,

I second that !
Cap's gives the sound a sound that is typical to the caps brand and Ider you like it or you don't .

I admire your creativity it's fun and very wise at the same time. Danke Thanks !

atb,

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Old 15th November 2011, 04:47 PM   #3104
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Here, a single ended version.
Attached Images
File Type: gif clamped cascode.gif (39.6 KB, 282 views)
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Old 15th November 2011, 04:52 PM   #3105
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Thumbs up Yep !

Joachim,

I think that you both (Ronald and you) went to the same school

From memory this is the one I was talking about.

Sounds Good !


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Old 15th November 2011, 04:54 PM   #3106
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I hope so. The idea is simple.
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Old 15th November 2011, 11:43 PM   #3107
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With some few additions the folded driven cascode can be arranged as a phono stage.
This circuit here is very basic but it shows the principle.
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Old 16th November 2011, 12:32 AM   #3108
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Default R11

Hi Joachim,

Looks gooooood

I would like to see a j-fet instead of R11.

I need to study the circuit better, but it looks nice.

I'll be back in a few minutes.


Cheers,

Josť
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Old 16th November 2011, 12:46 AM   #3109
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To be honest Jose`, that constant current source is not that good with one pair of Fets at the input. The resistors R3, R8 are only 0,65V / 0.008A = 81,25 Ohm. That is a bit too low for optimum noise suppression. With two red Leds instead of the second transistor it would be 2 x 1,4V - 0,65V = 2,15V / 0,008A = 268,75 Ohm. That is better and does not add noise from the current source. That Led current source has a somewhat lower output impedance though because you loose the feedback action of the two transistors.
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Old 16th November 2011, 12:55 AM   #3110
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Adding a Led, a transdiode or a diode into the emitters of T6, T8, you can raise the value of R3, R8 too. There are other ways. I think Elviee had a thread about constant current sources. He compared so many circuits that even i lost oversight. As far as i remember, a
simple Fet with resistor was hard to beat in output resistance. If this is the best solution for this circuit concerning noise injection i can not tell. I never tried it.
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