Cartridge
This tool works out a starting turns ratio and load for a moving-coil cartridge feeding a step-up transformer (SUT), then checks the result against your transformer and phono-stage figures. It is a physics-checked starting point, not a substitute for listening.
No minimum load figure to hand
When a cartridge’s spec sheet does not give a minimum recommended load, a working floor is about ten times its internal impedance. Leave the field blank to use that rule automatically; it is a starting point, not a published spec.
Phono (MM) input stage
These describe the phono stage the SUT feeds: its own voltage gain, and the input impedance the transformer secondary sees. 40 dB and 47 kΩ are typical MM-stage figures; change them to match your own equipment. The recommended ratio depends on this gain, so enter your actual stage figure. Very low-output cartridges (the “G” at 0.1 mV, for example) need a high total gain, about 70–78 dB: into a standard ~40 dB stage they call for a high ratio, but with a capable higher-gain stage (about 46–50 dB) a 1:16–1:20 transformer is ideal.
Turns ratio & gain
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Ratio comparison
Turns ratio (N): how many times the transformer steps up the cartridge’s voltage. Presented: the voltage reaching the phono stage’s own input, shown for reference. Output: the voltage at the phono stage’s output once its own gain is added; this is the figure that decides the gain verdict, against the 0.25–0.7 V line-level window. Reflected load: the impedance the cartridge sees, equal to the phono stage’s input impedance divided by N². Total gain: the cumulative voltage step-up from cartridge to the phono stage output, in decibels, shown for reference. Load: Too low (under the cartridge’s minimum), Acceptable (above the minimum but under ten times its internal impedance), or Optimal (at or above ten times internal impedance). The highlighted row is the ratio shown above.
Secondary loading (advanced)
A resistor across the SUT secondary can bring the reflected load down to a specific target, useful when the bare phono-stage input alone reflects more than you want the cartridge to see. Calculated for the ratio shown above.
Ultrasonic damping (advanced)
An SUT’s secondary leakage inductance and the cable-plus-input capacitance after it form a resonant circuit, usually well above the audio band. A resistor across the secondary flattens that peak. Both figures come from the SUT datasheet and your cable; leave either blank to skip this section.