In Reply to: Larger Swing posted by Triode_Kingdom on October 21, 2014 at 08:04:45:
First, let's clear up that the suggestions I made went somewhat further than a minor change to the operating point in the existing driver circuit. I also eliminated the coupling cap but as I pointed out this compromises OP power, which would ideally be rectified by increasing HT for the best of both worlds. The bonus is a considerable improvement in headroom afforded by A2 transition. Or, one could choose to sacrifice it by taking drive from the plate of the bottom tube, a better sounding option IMO and that of others I respect.
For clarity, I've done what you suggested earlier and concentrated on the driver differences. I've re-Simmed both circuits and went as far as optimising for the best output swing and even tweaked the operating points to be close enough to identical for fairness.
Then I set identical output swing, to the max in the case of your circuit, which yielded 240V PP. My circuit comfortably goes to 300V PP swing but I've shown the OP waveforms and ffts at 240V PP. The non-linearity in your circuit becomes visible at this OP whereas the waveform still looks very clean in mine. The ffts magnify the differences and even if they aren't completely accurate they serve to provide a compelling comparison.
First your circuit. Note that it requires a high 5.5V input signal to drive it to maximum output. Then look at the distortion level, particularly the damaging high order harmonics.
Now, my circuit. Only 2.5V input is required for the equivalent output. More importantly harmonic distortion beyond the 4thH is insignificant by comparison.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- One last try at convincing you ... - Naz 06:13:54 10/23/14 (5)
- RE: One last try at convincing you ... - Triode_Kingdom 13:21:35 10/23/14 (4)
- RE: One last try at convincing you ... - Naz 14:47:52 10/23/14 (3)
- SPICE Results - Triode_Kingdom 19:47:41 10/23/14 (2)
- The ASC Files here for anyone to verify! - Naz 22:36:52 10/23/14 (1)
- RE: The ASC Files here for anyone to verify! - Triode_Kingdom 08:53:13 10/24/14 (0)