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In Reply to: Same Set Up...Same Results! posted by amandarae on October 3, 2006 at 20:01:51:
Hey Garth! Of course, the transformer does not care. At ideal conditions(lossless), the electrical equivalent of both locations are the same.But here is my reasoning behind it and please tell me if it has merit.
With the loading resistor close to the SUT, let's assume that a 5 mV output was coming out of the transformer secondary. If we load the the cart with its specified resistance, the voltage will be half for example. Then this signal will travel the, say 1 meter ,interconnect. It is possible that it will be reduce further and S/N will be less if the transmitted signal was less to begin with than the opposite scenario when the whole 5mv signal will travel across the 1m interconnect first before it was halve.
Does it make sense? I do not know. Besides, I should have posted "try loading the SUT near the preamp side and see if there's a difference" instead.
regards
Follow Ups:
The cartridge "produces" half the voltage of the unloaded condition. It is not a case of the "full voltage" hitting a "resistor brick wall" and being reduced.The secondary "sees" the load impedance and reflects it to the cartridge through the transformer primary. The load on/at the coils of the cartridge is X or 1/2X or whatever the transformer presents it.
There may be some good reasons (that I don't know) to put the additional parallel resistor at the preamp but that is not one of them.
Sorry. :-)
At least I got straighten out. I was assuming maximum power transfer since a 14 ohm impedance source driving a 14 ohm load. So now I know that it is not really the case. How do you compute the resulting voltage depending on the load values?thanks
Hi Abe! (it's earlier than I thought in SoCal)here's the formula:
Va = (Vi / Is+Il) * Il
Va = voltage actual
Vi = voltage initial
Is = Impedance source
Il = Impedance loadSo you can see for instance 2 / 28 * 14 = 1
As you point out that is max power but not max voltage. But who cares about voltage? Voltage is only loudness.
I really appreciate it.
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