The phono equalization curve needs about +20db equalization in the bass frequencies, compared to the median part of the curve at 1kHz.
When applying this equalization, it is easier to do it early in the signal chain when the signal is in millivolts, with little current. The demands on the power supply are far less than doing it at the main amplifier.
You could do it at the main amplifier, but the demands on the amp and power supply would be enormous, considering that it would require many watts of amplifier power, just to bring the bass frequencies in-line with the midrange frequencies at 1 watt. Then you could start amplifying the music to the volume that you wanted to listen at. Assuming a 90db efficient speaker, to achieve the normal live-listening volume that audiophiles normally use, of 105db, you would need a couple thousand watts per channel of amplifier power available for the bass frequencies, due to the logarithmic nature of the db scale. However, doing it at the phono stage where the signal is in milliwatts, would require only maybe a watt or so of power to handle the task.
As far as us vinyl audiophiles eschewing tone controls and graphic equalizers, we don't like them because they have several or even numerous rotary or sliding potentiometers which have bad effects on sonics. It has nothing to do with proper equalization being used. I can offer the Merlin BAMM as an example of equalization that is well accepted by the audiophile community. Many other speakers use equalization to extend bass frequencies, as well. However, they do it on the scale of a few db, and not on a huge scale that would sap nearly any amplifier available today.
Regarding the tweeter never "seeing" the bass frequencies, the tweeter has to "see" at least a portion of the bass frequencies, in order for the crossover slopes to work. If you want to use ultra-steep crossover slopes, you had better have perfectly matched drivers at the crossover point.
When applying this equalization, it is easier to do it early in the signal chain when the signal is in millivolts, with little current. The demands on the power supply are far less than doing it at the main amplifier.
You could do it at the main amplifier, but the demands on the amp and power supply would be enormous, considering that it would require many watts of amplifier power, just to bring the bass frequencies in-line with the midrange frequencies at 1 watt. Then you could start amplifying the music to the volume that you wanted to listen at. Assuming a 90db efficient speaker, to achieve the normal live-listening volume that audiophiles normally use, of 105db, you would need a couple thousand watts per channel of amplifier power available for the bass frequencies, due to the logarithmic nature of the db scale. However, doing it at the phono stage where the signal is in milliwatts, would require only maybe a watt or so of power to handle the task.
As far as us vinyl audiophiles eschewing tone controls and graphic equalizers, we don't like them because they have several or even numerous rotary or sliding potentiometers which have bad effects on sonics. It has nothing to do with proper equalization being used. I can offer the Merlin BAMM as an example of equalization that is well accepted by the audiophile community. Many other speakers use equalization to extend bass frequencies, as well. However, they do it on the scale of a few db, and not on a huge scale that would sap nearly any amplifier available today.
Regarding the tweeter never "seeing" the bass frequencies, the tweeter has to "see" at least a portion of the bass frequencies, in order for the crossover slopes to work. If you want to use ultra-steep crossover slopes, you had better have perfectly matched drivers at the crossover point.