Recommandation for 1:6 1:8 SUT under $5K?

@lewm 

What you need to know is the turns ratio (in your parlance, the ratio of

 

This most basic detail is the point I am trying to get across.    I agree the turns ratio is the key factor and what you need to use to compute impedances and gain.  Then you go on to mention  "voltage in to voltage out" which represents the gain and this number includes the effects of the source and load impedance and the gain is not used to calculate anything impedance related.  Turns ratio is a simple definable constant for a device.  Determining gain requires info unique to the specific situation.  

In the attempt to simplify things and make it easy for the end user, the process of specifying and labelling SUTs has made a simple topic clear as mud.  What is needed is the use of accepted math and known well defined terms.  The introduction of the yet to be defined X-factor simply makes no sense when proper well defined terms exist.

dave

One example from the AudioNote website: One option is

AN-S4/M - 27.5 Ohm input impedance - For cartridges with an impedance of 7 to 9 Ohms

I guessed that means the SUT has a turns ratio that results in the cartridge seeing a 27.5 ohm impedance when the secondaries are terminated in the standard 47K ohm resistance. So I started by calculating what number when squared and divided into 47K ohms will give you 27.5, or 47K/X^2 = 27.5. This gives a turns ratio of about 1:40, slightly higher in fact. That does not make sense; nearly no cartridge ever made needs that much boosting into an MM stage with the typical 40 to 50db gain. So I am stumped.

lewm

guidance for a cartridge of 7 ohms x 10 = 70 ohms or more

8 x 10 guidance is 80 or more

9 ohms x 10 is 90 ohms

Surely Audio Note knows that

THUS, I figured, their 27.5 input impedance was not/could not be what was shown to the cartridge.

It's another absurdoid number

Perhaps I'll write them, and see what they reply

repeat

AN-S4/L  - 3 Ohm input impedance - Primarily designed for use with the Audio Note (UK) IO range

note that 0.75 x 4 = 3

AN-S4/LM - 12 Ohm input impedance - For cartridges with an impedance of 3 to 4 Ohms

note that 3 x 4 = 12

AN-S4/M - 27.5 Ohm input impedance - For cartridges with an impedance of 7 to 9 Ohms

note that 7 x 4 = 28

AN-S4/H - 48 Ohm input impedance - For cartridges with an impedance of 12 to 16 Ohms

note 12 x 4 = 48

so, their input designations are 4x the lowest coil impedance, WTF?????

Like I said before, a transformer has no impedance by itself, except for the resistance of the primary. You need to know what it is hooked up to on the secondaries, which one might assume is 47K ohms for a SUT. The resistance of the primary with no load, so far as I know, would typically be in the one ohm-ish range.  I never measured a SUT, but I have measured the primary resistance of a few power transformers. Anyway, those numbers (3, 12, 27.5, and 48) are unlikely to represent the resistance across the primary.  Maybe Intact would comment.

That's why I calculated the turns ratio based on the idea of the SUT hooked up to 47K ohms so that the cartridge sees 27.5 ohms.  If you do the math, you get a turns ratio of 1:40-ish. I doubt that is correct. For vintage Japanese SUTs, I came to think that the ohms ratings are to guide the user to select a cartridge with internal resistance approximately the same as the ohm rating of the SUT. AudioNote seems to be using the numbers differently.