MM load resistance
The resistance a phono input presents to a moving-magnet (MM) cartridge, measured in ohms (Ω).
You may see this listed as MM input impedance. Values are usually given in kilohms (kΩ): 1 kΩ equals 1,000 Ω, so 47 kΩ means 47,000 Ω.
In a phono preamp
Match the preamp’s fixed input value or available setting to the cartridge maker’s recommendation. For a cartridge specifying 47 kΩ, use a 47 kΩ input or setting. That value is common, but check your cartridge rather than assuming it applies to every MM model.
Load resistance helps shape the cartridge’s frequency response—the balance of bass, midrange and treble. A higher resistance is not automatically better.
Load capacitance, measured in picofarads (pF), is a separate matching value. The cartridge’s internal coil resistance is also a different specification: it describes the cartridge, not the external load from the preamp.
Sources
- 2M Red: load and internal resistance specifications — Ortofon
- Phono Box RS2 manual, p. 4: MM input specifications — Pro-Ject Audio Systems
Sources
- AN-346, p. 2: cartridge loading — Texas Instruments