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MC LOADING & STEP UP DEVICE

Hi;

After a great deal of research in this forum, vinyl engine's library of articles, and 6moons I have only utterly confused myself. I remain baffled as to how to properly match a step up device to a phono cart and MM stage. This is realy killing me as I am very eager to start experimenting with some moving coil designs. As a matter of fact I have 3 of them in my possession at present with no way to listen to them and I have been hesitant to purchase a step up without learning how to match it properly.

Is there a simple formula or rule of thumb I can follow?

What are the inputs that need to go into the equation?

What is primary and secondary impedence?

Please help me and I will forever be in your debt. Thanks guys, I really appreciate it.
dfelkai

Showing 2 responses by cincy_bob

cincy_bob
270 posts
 
Axel, thanks very much for the primer. I now understand these SUT impedance calculations. Using your formulae, I was able to recalculate the 3 Ohm input impedance for the Auditorium A23 Hommage T1 MC transformer that is referenced in Art Dudley's recent column based on the winding ratio (1:30) and the secondary coil impedance (2.8k ohms) specified in the column.

Very educational.
cincy_bob
270 posts
 
Here is the excerpt from Art Dudley's write-up:

Aschenbrenner's Hommage T1 measures somewhat differently, with a primary coil impedance of about 3 ohms and a secondary coil impedance of 2.8k ohms

I assumed that the secondary coil impedance was equivalent to a secondary trannie loading that is reflected back to primary as discussed in Axel's post above. The math seemed to confirm this:

47k*2.8k / 47k+2.8k = 2,643 / 933 = 2.83 ohms

Is it coincidence that the mathematical result agrees with the "primary coil impedance of about 3 ohms" that is cited in the write-up?
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