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Old 21st August 2012, 10:33 PM   #6921
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I have a theory what happens when we switch off one polarity of the PSU. Could be tested rather safe also by soldering in a 50 Ohm ballast resistor, cartridge NOT connected, switch off one polarity, then measure the input DC offset and get the offset current by DC Offset / 50.

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Old 21st August 2012, 10:39 PM   #6922
Salas is offline Salas  Greece
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Will 5mA flow through the offset trimmer to the other side?
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Old 21st August 2012, 10:43 PM   #6923
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Under what conditions ? Switching off one polarity of the PSU ?
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Old 21st August 2012, 10:51 PM   #6924
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Actually the offset trimmer is a differential shunt feedback loop. It should also lower distortion in the input stage.
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Old 21st August 2012, 10:57 PM   #6925
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Quote:
Originally Posted by Joachim Gerhard View Post
Under what conditions ? Switching off one polarity of the PSU ?
In any transient or failure scenario conditions worth looking at. But the offset trimming grid is high impedance and the current will go through the 33R I guess. So 150mV max input offset in any disaster case?
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Old 21st August 2012, 11:01 PM   #6926
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I hope so. I really have to test this to be certain. Could be also Ube plus 150mV, that was my first guess.
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Old 21st August 2012, 11:04 PM   #6927
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If you like it or not, for the faint at heart there is always the option to put a high value elcap on the input. I build a D.Self like pre-pre with bipolar Black Gates at the input that sounds much better then many think. The best substitute i found are bipolar Nichicon ES.
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Old 21st August 2012, 11:06 PM   #6928
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The "natural" input impedance of the Paradise is in the 10kOhm range so using a 10kOhm ballast resistor we can come away with a 10uF foil.
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Old 21st August 2012, 11:10 PM   #6929
Salas is offline Salas  Greece
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Yes, do try it at power on/off, especially at off cycle the lytics don't extinguish in perfect sync, and on (-) or (+) rail disaster case. Many people are going to be involved, some may use small boxes, push the regs CCS or deprive correct ventilation, whatever. So you can give them info about risks if any, and recommendations.
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Old 21st August 2012, 11:16 PM   #6930
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Sure good idea. The best start is of cause build the beast, then put on a ballast resistor in the range of the DC impedance of your cartridge, then measure the input , THEN put on the cart. This does of cause not prevent fatal failure that happens in the future.
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