How it relates to real life is related to the output voltage times the amount of gain that it is subjected to all along the signal path. It starts out at, say 1mv, and then goes into a phono section. It then goes thru the gain stages of amplification and the voltage is increased by whatever value of gain those amplification stages have.
That's where the rubber hits the road. You have to have enough gain to bring the voltage up to the point where you can drive the input of the amplifier to full volume. This spec is called the input sensitivity of the amp. If the input sensitivity of the amp is 2v, then the maximum output of the preamp must be at least 2v in order to drive the amp to maximum output. If the gain in the phono stage and linestage added together do not generate the full 2v, then the preamp will not be able to drive the amp to max level. This could happen when the cartridge output is lower than the gain stages can increase to the 2v level. So you have to have enough cartridge output to supply to the preamp to allow it to amplify it enough to drive the amp to max. If it is too low, then you have to crank the volume wide open to get decent listening levels. If it is too high, then you can barely crack the volume controls and it gets real loud. Also, if it is really too high, then you can overload the phono section inputs and cause distortion.
The reasons that it is hard to just give a flat figure for this, is that all phono stages and linestages have different gain specs. Some are high, and some are low. In addition, many amps have different input sensitivities, so a front end that may work perfectly on an amp with 2v input sensitivity would be way to hot for an amp with 0.3v input sensitivity.
The best way to calculate this is to take your cartridge output voltage, and figure out what gain amount is needed to provide the necessary output voltage to match, or slightly exceed the input sensitivity voltage of your amp. This way you will know that you will be capable of driving your amp to full volume with the voltage that comes from your preamp output. Then compare this gain figure with the specs for gain in your phono stage and linestage combined.
That's where the rubber hits the road. You have to have enough gain to bring the voltage up to the point where you can drive the input of the amplifier to full volume. This spec is called the input sensitivity of the amp. If the input sensitivity of the amp is 2v, then the maximum output of the preamp must be at least 2v in order to drive the amp to maximum output. If the gain in the phono stage and linestage added together do not generate the full 2v, then the preamp will not be able to drive the amp to max level. This could happen when the cartridge output is lower than the gain stages can increase to the 2v level. So you have to have enough cartridge output to supply to the preamp to allow it to amplify it enough to drive the amp to max. If it is too low, then you have to crank the volume wide open to get decent listening levels. If it is too high, then you can barely crack the volume controls and it gets real loud. Also, if it is really too high, then you can overload the phono section inputs and cause distortion.
The reasons that it is hard to just give a flat figure for this, is that all phono stages and linestages have different gain specs. Some are high, and some are low. In addition, many amps have different input sensitivities, so a front end that may work perfectly on an amp with 2v input sensitivity would be way to hot for an amp with 0.3v input sensitivity.
The best way to calculate this is to take your cartridge output voltage, and figure out what gain amount is needed to provide the necessary output voltage to match, or slightly exceed the input sensitivity voltage of your amp. This way you will know that you will be capable of driving your amp to full volume with the voltage that comes from your preamp output. Then compare this gain figure with the specs for gain in your phono stage and linestage combined.