mV output from cartridge, please explain

If the cartridge were a Shure product very detailed specs are available on the Shure website. I don't know what your cartridge is so I don't know how they spec it.

Shure specs output as millivolts RMS, with sinusoidal groove modulation at 1000 Hz having a PEAK velocity of 5 cm/sec. Other manufacturers probably follow Shure's example.

Twl speaks of having the volume "wide open" as if this were a bad thing. Actually, the amplification circuits are always wide open, and the volume control cuts the ouput voltage down to the level you want. Ideally you would have just enough gain to fully drive the power amplifier with the volume control maxed out (which really means it is having minimum effect). Most rigs end up with the volume control between 12 and 2 o'clock when playing loud, which means that there is unnecessary gain in the system.

Ok, I found this in a book I bought a few years ago called "The LP is Back!" It contains a reprint of an article from Stereophile vol. 1 no. 8 by J. Gordon Holt.

It says that the maximum recording level is a peak recorded velocity of about 20 cm/sec. At this level it has reached the velocity at which the sylus travels through the inner grooves, where this linear motion is the slowest. Beyond this the groove swings become so sharp that the stylus tends to ride over them rather following them.

The inner grooves are about 40 cm in circumfrence, times 33 1/3 rpm divided by 60 seconds is about 20 cm/sec.

If a cartridge puts out 1 mV at 5 cm/sec then it follows that it probably puts out 4 mV at 20cm/sec. I say probably because I don't know if this is a linear relationship, but I assume that it is.

Now I'm going out on a limb as I haven't found anything to back me up on this. If I also assume that that the record cutter is going to cut it at a maximum level that will leave some headroom, say at 3/4 of maximum, then at 15 cm/sec I should get somewhere around 3 mV during loud passages. I'm going with that until I hear from somebody other than me who actually knows what's going on.

BTW the book was put out in 1999 by Audio Amateur/ Old Colony Sound Lab and has a bunch of good stuff in it.

Shure put out a test record that had grooves cut at the full range of cm/sec. The purpose was to evaluate "trackability" of a phono pickup, a test which Shure pickups are good at. Few pickups will track the fastest grooves without audible breakup.

If you could get a hold of one of these records you could actually measure your preamp output voltage at the maximum groove velocity that your pickup can handle.