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6N1 preamplifier with phono
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<blockquote data-quote="handsome" data-source="post: 710472" data-attributes="member: 772"><p>Hi Mars, 1.2V over 100R is 12mA not 7mA? </p><p></p><p>You cannot measure the anode voltage of the first triode as it is DC coupled to the second's grid. This is a very high impedance point and any multimeter will give you an incorrect reading. You will have to estimate the first triode's anode voltage by measuring the current and voltage across the cathode resistor. Then use this current to calculate the voltage drop across the anode resistor and then subtract that voltage from the HT. </p><p></p><p>Digital has a nice fixed output maximum of 2V RMS. Vinyl unfortunately does not. Plus with records you have scratches and dust which can cause very high transients way above program material. Because of these factors you should try and bias the first triode to -2V or better to ensure no clipping. All tubes experience grid current as they approach zero grid volts so i always try to bias (if possible of course depending on the tube) a 0.5 - 1V margin - in your case -3V.</p></blockquote><p></p>
[QUOTE="handsome, post: 710472, member: 772"] Hi Mars, 1.2V over 100R is 12mA not 7mA? You cannot measure the anode voltage of the first triode as it is DC coupled to the second's grid. This is a very high impedance point and any multimeter will give you an incorrect reading. You will have to estimate the first triode's anode voltage by measuring the current and voltage across the cathode resistor. Then use this current to calculate the voltage drop across the anode resistor and then subtract that voltage from the HT. Digital has a nice fixed output maximum of 2V RMS. Vinyl unfortunately does not. Plus with records you have scratches and dust which can cause very high transients way above program material. Because of these factors you should try and bias the first triode to -2V or better to ensure no clipping. All tubes experience grid current as they approach zero grid volts so i always try to bias (if possible of course depending on the tube) a 0.5 - 1V margin - in your case -3V. [/QUOTE]
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Commercial Members
Commercial Members - News & Discussion
6N1 preamplifier with phono
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