Is anyone familiar with the transformers on ebay listed as Finemet? They say they were sold through Noguchi in the past. JELabs mentions the Noguchi ones on his blog. But I haven't seen anything else on them and the ebay ones seem like more recent arrivals.
On the data sheet what do the different frequencies next to the primary resistance mean? does that mean it bottoms out at 60Hz on the 5K taps?
On the data sheet what do the different frequencies next to the primary resistance mean? does that mean it bottoms out at 60Hz on the 5K taps?
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It means the lowest frequency they can develop full power (20W) is 60Hz. At lower DC current they would perform better. At lower power they would also perform better.
A lot of manufacturers don't even mention full power performance, so don't sweat it.
I have used their PP outputs and interstages but never SE.
It is possible to change the Raa depending on how you use the secondaries from 2K5 native to higher values . Different frequencies next to the primary resistance mean that lower Raa tubes will perform better ... which is perfectly normal , higher Raa tubes need higher inductance for the same power at low frequency .
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For higher power at low frequencies, you not only need higher inductance,
You need more Un-Saturated Laminations.
What causes laminations to saturate? . . .
Too many DC Amp x Turns (and we have to have more turns to get more inductance)
Too much power at to low of a frequency (the combination of power and 1/frequency)
Too little amount of laminations (volume of material)
A lamination material that saturates easier (material science) Sometimes a lamination material that works really good at high frequencies, will saturate early at low frequencies.
Global Negative Feedback taken from the output transformer secondary, will not reduce low frequency saturation that occurs, it will only make it worse.
There is no free lunch here.
When you find free lunches, you can sell them, and you will be rich.
You need more Un-Saturated Laminations.
What causes laminations to saturate? . . .
Too many DC Amp x Turns (and we have to have more turns to get more inductance)
Too much power at to low of a frequency (the combination of power and 1/frequency)
Too little amount of laminations (volume of material)
A lamination material that saturates easier (material science) Sometimes a lamination material that works really good at high frequencies, will saturate early at low frequencies.
Global Negative Feedback taken from the output transformer secondary, will not reduce low frequency saturation that occurs, it will only make it worse.
There is no free lunch here.
When you find free lunches, you can sell them, and you will be rich.
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