| Yes, you are right, the voltage divider from 6.3V across 47K and 10K resistors shall give not 0.9V but 1.1V. However, the numbers that are in circuit are not something that I saw in my dreams but the actual numbers that I measured. I might presume that at the time I measured it I did not run the phonostage from my AC stable PP2000 but from wall and the voltage was lower and I did not have 6.3V but perhaps 6.1V or something like this. All those numbers are perfectly acceptable and with 1V basis the 12AX7 is not near to be closed up. I do not know what curves you looked at but 1V is fine bias for this tube and with 140-150V on plate it is perfectly fine operational point. Thanks for spotting the .2 difference but I think it is in given case negligible. |
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