In Reply to: Not necessarily posted by Triode_Kingdom on December 9, 2023 at 15:52:36:
A dozen years ago or so, we (Bottlehead) changed from a 12AT7 driver to a 5670 driver in our 300B amp. We found virtually no difference in the distortion spectrum, though the data sheet plate curves for the 5670 look much better than the 12AT7 curves.
FWIW, the operating points were
300B: 350v / 70mA / 3000 ohms (EH, if I recall correctly)
driver: 200v / 4mA / current source plate load + 300B grid resistor 250K
I concluded from this that the CS plate load kept both drivers in a very linear region, so the distortion must have come from the 300B.
Subjectively we thought there was a small improvement, but this was not a blind test and involved only 2 or 3 sets of ears so I don't have much confidence in that conclusion.
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Follow Ups
- RE: Not necessarily - Paul Joppa 21:40:36 12/09/23 (3)
- Never got too excited about the sound of the Paramour... - Ivan303 05:54:04 12/10/23 (2)
- RE: Never got too excited about the sound of the Paramour... - Paul Joppa 22:24:32 12/10/23 (1)
- As I have over 100 NOS 6SN7 and... - Ivan303 05:41:47 12/11/23 (0)