Conversion of mV to dB

Jeffreybehr, as far as I know, it has to do with which test record the cartridge was measured on, JVC (3.54 cm/s) or CBS (5.0 cm/s). I don't know about the mono versus stereo numbers. I do know that you can translate between the two numbers by using basic math.

As I mentioned, the KAB calculator assumes the 5 cm/s standard, so if your cartridge is measured using the CBS standard 5 cm/s then you can just plug that value in. However, if your cartridge's output was measured using the JVC standard (3.54 cm/s) you can divide 5 by 3.54 and multply the outcome (1.4) by the output to translate the output voltage into the CBS standard of 5 cm/s.

So a cartridge that has a rated output of 0.24 mV @ 3.54 cm/s will put out the same amount of voltage as a cartridge with a rated output of 0.34 mV @ 5 cm/s.

Note when using the KAB calculator that the output is based @ 5 cm/s. If your cartridge is rated @ 3.54 cm/s, you will need to multiply it by 1.41 to equate to 5 cm/s.
Just to make sure you are comparing apples to apples.

As for your phono preamp, it would help to know what speed was run to determine the mV values. For example, if running at 5 cm/s, then 0.3 mV will equate to 61 db of gain on the KAB scale. However, if using the 3.54 cm/s speed rating, then you 0.3 mV would equate to 58 db of gain. I would think it best if you ask the manufacturer this question, since we don't know what recording speed they based their numbers on.

Thanks for chiming in here Al, I was waiting for you to help us out. I don't really understand it that much myself, but Mehran, of Sorasound, who distributes ZYX cartridges which are rated at 3.54 cm/s is the one who explained to me about the output voltage conversion to 5 cm/s rating. It seemed to make sense to me....but I'm not an EE, though I did stay at a Holiday Inn Expres last night. :)