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Cartridge tests - Output

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output-2mblack-3.54cms_sec

Output of 6.4mV at 3.54cms/sec peak of Ortofon 2M Black, on Shure TTR-109 test disc.


OUTPUT


WHAT IT TELLS US

Pickup cartridges produce a very weak signal. Moving Magnet (MM) types output a few thousandths of a volt when playing (i.e. a few millivolts) and Moving Coils around one-tenth as much, or a few hundred microvolts (millionths of a volt). The output from MCs is so low, hiss from preamplifiers is an issue, although this is not the case with MMs.


Measurement of output level tells us whether hiss will likely be an issue. For example, the Goldring Legacy MC produces a very low 0.26mV and hiss is audible with many preamplifiers. Only a low input Z transformer with a high turns ratio can cope with this, such as that of the Luxman E200 preamp (see our August 2010 issue). The Lyra Dorian produces 0.84mV, or 10dB more, and hiss is rarely an issue.


It also tell us whether preamps will have enough gain, and sufficient overload headroom. High output from a modern cartridge is delivered by the Ortofon 2M Red and Bronze, which deliver 7mV at 5cms/sec peak. Our tracking tests show they can clear 22 cms/sec peak so a very high 30mV is possible. This will give 3V from a x100 preamp and 6V from a x200 unit. As 6V-10V is the maximum output from a majority of (silicon chip) preamps a cartridge of this output needs no more gain than x200, and where gain is adjustable it should be set low to avoid the possibility of output overload.



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HOW WE MEASURE IT

We measure output using the Shure TTR-109 tests disc, which carries a 1kHz tone cut at 3.54cms/sec rms (5cms/sec peak). The output into 47k Ohms for MM and 100 Ohms for MC is measured direct by a spectrum analyser, through a screened feed from our special measurement preamplifier, to avoid hum and noise.





 

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