w99: It's more like a nominal value, but it may happen to represent the 0 dB reference value for certain measurement standards. For example, 5 cm/s peak velocity in lateral/mono modulation at 1 kHz would be JIS standard.
Ideally the output spec should cover, whether it's peak or effective, and then the test frequency as well as the reference velocity (and whether that's peak or effective and in lateral or 45° modulation) - or alternatively name the particular measurement standard/test record. So in the worst case that could cause a difference of factor (2^0.5)^3 or respectively (1/(2^0.5))^3 at the same test frequency.
For some more info you might want to check Yosh's page on record specifications (
http://www7a.biglobe.ne.jp/~yosh/recspecs.htm).
Tom: Well, actually you could still compare. However, you'd have to do a little conversion for that purpose. Formula for the velocity for sine-shaped signals would be: peak velocity = amplitude of modulation (0 to peak) x 2 x pi x frequency. So velocity is directly proportional to frequency.
But then one might additionally have to consider the RIAA curve, depending on whether that was applied or not. Considering that output level would usually rather appear to be intended to be measured directly from the cartridge outputs, not applied could be the more likely case - but I don't think that's really a problem in practice, as test records would seem unlikely to contain a non-1-kHz test tone for that purpose.
Anyway: So for example a 2 kHz sine instead of a 1 kHz sine would only require half the modulation for the same (peak) velocity. But to produce the same output level after RIAA (re-)equalisation we'd need an additional boost of +2.6 dB = ca. factor 1,35. So together the modulation would have to be ca. 0.5 x 1.35 = 0.675 times as high.
Greetings from Munich!
Manfred / lini
P.S.: Seems like Tom has removed his reply regarding the test freqency, while I wrote my reply, so that part of my reply now has lost its reference...
