6 moons primer
https://6moons.com/audioreviews/stepup/primer.html
think about future changes now:
separate control of gain and impedance is most flexible,
to leave your cables alone:
pass for MM bypass is a nice feature, leave SUT in-line bypassing it's transformer
multiple front selectable inputs is good for multiple arms
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impedance guidance: coil impedance x 10 = _____?
that’s the ’guidance’ impedance you want ’shown’ to your MM phono input. (MM Phono input is typically 47,000, verify yours). then go up/dn from there, it’s just guidance. (nothing wrong, but, frequency response can be effected)
your choices: coil 12 x 10 = 120; coil 14 x 10 = 140, close, so: avg 130. ’guidance.
formula: 47,000 divided by x-factor squared = the impedance that will be shown to the MM Phono input (change 47,000 if yours is different)
now, working backwards to find a desired x factor: 47,000 divided by "what x factor squared?" will be close to 130. 47,000 divided by the goal of 130 = 361 for a desired x factor squared.
x factor 18 sq. = 324. x factor 19 sq. = 361.
Note: it’s inverse: up the x factor thus up the x factor squared, higher number yields LOWER impedance that will be ’shown’
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NOW, that x factor yields what signal strength? enough? overload?
one choice is .25mv x 19 = 4.75mv, allow some loss, say 4.5mv
other .4mv x 19 = 7.6mv, allow some loss, say 7mv.
So, if settings are NOT independant, look for a SUT setting withan x factor of 19 or just a bit lower.
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from an old chart I found:
Denon AU-320 offers too low, or too high xf 10 or xf 36
Denon AU300LC has only xf 10
Fidelity Research FRT-4, 3 inputs + PASS for MM Thruput; offers 4 optional x-factors, one is 18,27 (it’s 30 ohm setting), +25db; another is x factor 20.68 (it’s 10 ohm setting) +26db.
EAR MC4 one of 4 settings is xf 18.
EAR MC3, one of 3 settings is xf 20, +26db
Entre ET 100, 3 inputs + PASS for MM thruput; 3 optional loads
Input impedance: 3, 10 or 40 ohms select, you would use the 10 ohm setting.
Gain:
3 ohm -- 32dB
10 ohm -- 26dB
40 ohm -- 20dB
It’s Tricky.