OK I'll do the math once.
Let's take Lundahl LL9206 as example.
Primary DC resistance of that SUT is 10 ohm.
Secondary DC resistance in 1:10 mode is 790 ohm.
Now we can calculate the extra load (actually the copper loss), which is the (square of the step up ratio x primary DC resistance) + secondary DC resistance.
In our example the extra load is (10² x 10) + 790 = 1790 ohm.
Now, to calculate a real 100 ohm load resistance, these 1790 ohm must be added to the (simplistic) 10k (10k is 100 (load impedance) x 10² (square of step up ratio).
So we must present the cartridge through the SUT with a load of 10k + 1790 ohm = 11790 ohm.
To get this resistance the standard 47k input resistor of the phono preamp must be parallelled with a 15k7 ohm resistor (this gives 11769 ohm but the 15k7 resistor is the nearest standard value).
The 12k7 resistor of the simplistic calculation would present the cartridge with a real load of 82 ohm.
Let's take Lundahl LL9206 as example.
Primary DC resistance of that SUT is 10 ohm.
Secondary DC resistance in 1:10 mode is 790 ohm.
Now we can calculate the extra load (actually the copper loss), which is the (square of the step up ratio x primary DC resistance) + secondary DC resistance.
In our example the extra load is (10² x 10) + 790 = 1790 ohm.
Now, to calculate a real 100 ohm load resistance, these 1790 ohm must be added to the (simplistic) 10k (10k is 100 (load impedance) x 10² (square of step up ratio).
So we must present the cartridge through the SUT with a load of 10k + 1790 ohm = 11790 ohm.
To get this resistance the standard 47k input resistor of the phono preamp must be parallelled with a 15k7 ohm resistor (this gives 11769 ohm but the 15k7 resistor is the nearest standard value).
The 12k7 resistor of the simplistic calculation would present the cartridge with a real load of 82 ohm.
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Thanks for teaching us master.
The last phrase is only valid for Lundhal LL9206😀
BTW 15K7 is not and standard resistor value😀
N.B. Silk Thailand (the manufacturer) load measurements with 12K, value nearest to my calculated value, I guess the manufacture know more is product like you😀
Yes, the example if for a Lundahl LL9206 🙄
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Right; take 15k8.
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My English might not be great, but the last part of this sentence sounds like players in an orchestra each playing a different piece of music 😡
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Pieter's method is the correct way, and exactly the way I do my calculations, you cannot ignore the DCR of either the primary or secondary windings of the SUT in your calculations or you end up with a wildly incorrect result.
That said the manufacturer's stated load may or may not be optimum with any given cartridge due to sample to sample variations in the cartridge. (i.e. It may pay to experiment over some range - for me 50% to 200% or more typically). In the case of my muscovite phono stage, LL1941s (configured for 16x) and Ortofon Windfeld LOMC I actually prefer just a standard 47K load on the secondary.
That said the manufacturer's stated load may or may not be optimum with any given cartridge due to sample to sample variations in the cartridge. (i.e. It may pay to experiment over some range - for me 50% to 200% or more typically). In the case of my muscovite phono stage, LL1941s (configured for 16x) and Ortofon Windfeld LOMC I actually prefer just a standard 47K load on the secondary.
For updates, strangely I haven´t got reply from SacThailand yet about the DC resistance.
Pieter asked, why I don´t just measure the resistance..... hmmm.
I don´t know if this is valid, but was warned some time ago NOT to DC measure, ´cause it would pemanently magnetize the permalloy core, which would be irreversible. Anybody on weather this is true or not?
Pieter asked, why I don´t just measure the resistance..... hmmm.
I don´t know if this is valid, but was warned some time ago NOT to DC measure, ´cause it would pemanently magnetize the permalloy core, which would be irreversible. Anybody on weather this is true or not?
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