03-11-2016, 11:35 AM
Andy wrote "I'm reluctant to to use a bigger ECC82 anode R as this will lower the load line, which will put it through the curved part of the g1 line. AFAIK, this will make the OP non linear and introduce distortion."
So far as I understand these things a lower value of Ra will produce more distortion than a higher value of Ra, are you confusing mutual characteristic curves with anode characteristic curves? (I stand to be corrected)
I've done a couple of load line plots below for the ECC82, one for a 12k anode load and one for a 50k anode load to show the difference in anode voltage swing either side of the operating point, for convenience, an operating point of -4v is chosen, the distortion figures are approx only and are based on a formula in RDH4 (Langford Smith).
You'll notice that the anode voltage swing either side of the operating point also includes a distance measurement in millimeters...! I find it an easier and more a precise method of working out the voltage differences on those types of data sheets.
Lawrence.
So far as I understand these things a lower value of Ra will produce more distortion than a higher value of Ra, are you confusing mutual characteristic curves with anode characteristic curves? (I stand to be corrected)
I've done a couple of load line plots below for the ECC82, one for a 12k anode load and one for a 50k anode load to show the difference in anode voltage swing either side of the operating point, for convenience, an operating point of -4v is chosen, the distortion figures are approx only and are based on a formula in RDH4 (Langford Smith).
You'll notice that the anode voltage swing either side of the operating point also includes a distance measurement in millimeters...! I find it an easier and more a precise method of working out the voltage differences on those types of data sheets.
Lawrence.
