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In Reply to: RE: Perfectly Normal posted by Nickel Core on October 23, 2014 at 11:56:49
I think I agree but you can only get away with an unloaded transformer if the transformer is really good.
A poor transformer will ring so much, without a damping resistor, that the ringing will be so large that it will harm the audio signal.
Or at least that's how I understand this issue.
Tre'
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"Still Working the Problem"
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Ringing isn't the only concern. Basic theory says that as the load across the winding increases in resistance, upper frequency response will degrade. This is why OPTs aren't simply rated as a ratio.
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I wish I understood all this better.I understand that the primary winding only has the inductance that it has and if you increase the load on the secondary the low frequency -3db point will increase proportionally.
Does the HF suffer because of the winding capacitance or the leakage inductance?
The winding capacitance is shunt, in parallel with the reflected impedance, and the leakage inductance is in series with the reflected impedance.
That would mean that as you increase the load on the secondary, increasing the reflected impedance at the primary, the effects of both the winding capacitance and the leakage inductance would be minimized. That is, the -3db point of the HF roll off would go up? No?
Edit, I have the effects, when increasing the R, of the winding capacitance backwards don't I?
Thanks
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 10/24/14 10/24/14 10/24/14
Right, as R across the secondary increases, interwinding capacitance becomes a larger percentage of the load and eventually dominates. This degrades high frequency response. An increase in R can also cause power to be lost in the windings if their inductance is insufficient for the operating impedance of the circuit.
When R is decreased, leakage inductance and core flux increase, potentially degrading low frequency response. Decreased R can also cause transformer heating due to both I2R winding losses and increased core loss. That aside, I generally consider it acceptable to use an audio transformer at a lower impedance, as long as it's not operating near its power rating.
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Buy Chinese. Bury freedom.
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Have Fun and Enjoy the Music
"Still Working the Problem"
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