jderimig,
to put it roughly, for physical reasons, the PP amps do not produce any even order harmonics.
Is this circumstance considered as low distortion or high distortion?
to put it roughly, for physical reasons, the PP amps do not produce any even order harmonics.
Is this circumstance considered as low distortion or high distortion?
No, I want lower distortion acoustic output. Low distortion amp makes higher distortion acoustic output compared to properly phased SE amp to single driver.
Perhaps. I do know what the graph looks like:
The dotted line passing thru zero plagues every PP amp with an OPT.
Ideally it should be straight, it can be made very small.
dave
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Rod - we had this discussion a few years ago on this forum and there is no need to repeat the same arguments. As I posted then, the data you provide are not convincing. With all due respect, your explanation of how AC filaments modulate signal in a differential stage is not convincing as well. AC filaments cannot modulate anything because the AC signal is common mode, and in a properly designed differential stage, it is practically zero. Your idea of shorting music signal across the filament may hold true if you short it with a capacitor, but battery-powered filaments are shorted too, and this golden standard filament powering does not have sonic drawbacks.
Dave - you can look at it like this. Hysteresis is caused by re-orientation of magnetic domains. With DC magnetization, some proportion of domains do not change their orientation while constant magnetization is present, so they can be excluded from the picture. The remaining domains do change their orientation, so they behave according to the same B-H curve as in a transformer without DC magnetization.
A simple filter with feed-through capacitors and series chokes does the trick. Also, use power transformers that have enough primary inductance to stay safely away from saturation, tube rectification, and choke input power supply.
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If you are saying there is actual signal loss, I would be interested to understand the mechanism if someone can explain it to me.
Lost in the “mush”. I believe you and Chris described at least part of that as IMD? IMD is not a wide enuff metric IMO.
dave
dave
It's not like that at all. Transformers of any kind and DC voltage is a poisonous combination. Even a small DC voltage has a huge impact on the AC magnetization of transformer core, leading to core loss, core saturation, hysteresis, unsymmetrical magnetisation, production of harmonic voltages, overheating and a bunch of other problems. You have much left to investigate.
I don't know enough about transformers, I've been reading about hysteresis loss which causes distortion, I suppose the question is, what kind of distortion?
Now I see the root of the misunderstanding.
The AC heating waveform is not common mode.
The differential AC waveform is set to a nominal balance (for lowest hum) by centre tap or hum pot. The AC heat generates intermodulation because it sweeps through different parts of the triode curves when there is a large grid signal, compared to the idle condition. If the triode curves were perfectly symmetrical, the cancellation would hold good with any grid swing... But the symmetry is not at all perfect, and intermodulation follows. Having two triodes in opposition does not lead to cancellation either - this is the exact point proved by the measurement.
The measurement was not in this instance taken by me: follow the link and see the original appearance of it. If this measurement does not satisfy you, please supply your own.
Battery heating is not a gold standard for sound or anything else - complete isolation of the two filaments is the gold standard.
From the sound viewpoint - the orchestra is huge, and the composer's use of instrumentation is often deliberately shrill, percussive, loud and dramatic. It is not easy listening by any means, and amplifiers that don't have a grip make it a painful experience!
But the rewards are great when it sounds right...