mV output from cartridge, please explain


I understand that cartridges are rated by how much output voltage they generate when using certain standard test records. How does this relate to real life? If a cartridge is rated at 1 mV then is that the average level at an average volume? Or is it a maximum? Or what?

The reason I ask is I am looking at the overall dB gain of several phono preamp---line preamp---power amp combos and I'm trying to decide if I will have enough gain to drive my power amp to full power.
herman

Showing 2 responses by herman

Thanks guys. I understand all that but it still doesn't answer the question. It is impossible to do the math (peak output voltage of system = peak voltage from cartridge times total gain of system) unless you know the value of all three variables. To calculate the peak voltage out of the amp I need to know the peak voltage I can expect from the cartridge.

I know how much voltage my amp puts out at full power, or I can easily figure it's sensitivity if you want to go that route.

I can add together the gains of the different components I am interested in to get the total gain of the system.

What I don't know is the peak output of the cartridge. I know it is rated to put out a specific voltage (say 1 mV)when playing a certain test record. I know some records are cut hotter than others, but:

1. is this 1 mV the average it will normally put out when playing a typical record and the peaks are higher?

2. or is 1 mV the maximum voltage I can expect from that cartridge when playing a typical record?

3. or is it somewhere in between?
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.