The Ortofon measurement test set-up is a PC-based test system
Prior to testing, the cartridge is mounted on a special headshell, that has been optimized for repeatable and reproducible use.
The cartridge is connected to an amplifier, that is adjusted for an input impedance of either 100ohm, 200ohm or 47kohm/220pF (cable capacitance incl.) depending on two following elements:
- The impedance characteristics of the cartridge
- The type of cartridge, i.e. Moving Magnet or Moving Coil
Then the signal is amplified with a gain of +40dB for MM and +60dB for the MC types.The amplifier has a switch for measurements with/without RIAA-equalization. For lower frequencies below 1kHz the test is being performed with the RIAA equalization curve set on the ON/automatic switch. For high frequency tests the switch is set on OFF allowing maximum bandwidth since the records have been cut linear and non-equalized.
Subsequently the signal is converted through an AD-converter and filtered for optimal use of the PC capacity. Finally, the data is stored on a hard disk.
For each MM/MC model a set of limits, reflecting the performance of the cartridges, is being used.
After the system has been hooked up, a calibration sequence is initiated and the data stored. The sequence compensates for changes in the temperature, humidity etc. The calibration sequence also compensates all cables, impedances, gain etc in the measurement chain from the headshell to the PC