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Old 17th August 2012, 11:15 PM   #231
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Quote:
Originally Posted by smms73 View Post
Dirkwright it works but not with the very low distortion that my circuit is capable. Joachim wants to achieve my distortion levels with the simplicity of the
cen topology
Well, it's just a matter of a tweek here and a tweek over there. I just wanted to show that it wasn't an oscillator. I'm just trying to help out.
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Old 17th August 2012, 11:15 PM   #232
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At the cost of some complexity it could be a voltgae in - current out mirror but then we come closer to component count of the original design.
Yes. And start to make no sense.
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Old 17th August 2012, 11:18 PM   #233
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I would be happy with -100dB, but anyway. It all feels so familiar to me. Malkolm told me in the old days that I/U converters and MC inputs can have a lot in common.
I have virtually no experience with I/U converters for digital though.
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Old 17th August 2012, 11:20 PM   #234
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Originally Posted by dirkwright View Post
Well, it's just a matter of a tweek here and a tweek over there. I just wanted to show that it wasn't an oscillator. I'm just trying to help out.
It seems a stable circuit . Its strange to give problems to Joachim.
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Old 17th August 2012, 11:24 PM   #235
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Quote:
Originally Posted by Joachim Gerhard View Post
I would be happy with -100dB, but anyway. It all feels so familiar to me. Malkolm told me in the old days that I/U converters and MC inputs can have a lot in common.
I have virtually no experience with I/U converters for digital though.
How much current a MC produce ? What is the gain you need?
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Old 17th August 2012, 11:33 PM   #236
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Optimal is a gain of 20x to 30x ( 26dB ), the cartridge i have has a DC impedance of 6 Ohm and puts out 0.5mV nominal. Because some records are cut hot ( plus 20dB ) and there is dirt and cracks on the record it can put out more then 10mV pulses, especially at higher frequencies.
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Old 17th August 2012, 11:52 PM   #237
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that is very low. you shold be fine with the simple circuit that you construct. its stranje to have problems. if possible post the shema that you use. just to better visualization.
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Old 18th August 2012, 12:03 AM   #238
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Sure, it should work, I will make some experiments over the weekend and post the schematic.
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Old 18th August 2012, 06:30 AM   #239
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One possible solution to make it low distortion is use a cacode with mosfet or jfet for the bias bjt, like the picture below. (this is only a test not a functional circuit)
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File Type: jpg cen.jpg (57.4 KB, 277 views)
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Old 18th August 2012, 06:42 AM   #240
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another idea
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