Actually the answer is simple, if one keep in mind, that several integrated amplifiers like the good known Luxman L210 don't use an active line stage (preamp section consists only of an input selector and attenuator for volume control):
only unity gain for the pre-amplifier (i. e. only a buffer to transform the impedance to drive all kinds of signal leads) and factor 30-50 for the power amplifier.
In real life I note at nearly all commercial tube and solid state pre-amps gain factors around 10.
As a result, the total gain factor is around 300-500 with the problem that the maximum undistorted level is reached shortly after the zero position (under certainly conditions speakers blown away).
Under
https://www.tubecad.com/2009/03/blog0161.htm
and
https://web.archive.org/web/2007010...m/tubecircuits/Tube_Line_Stage_Amplifier.html
I read this (concerning only line stages):
Just how much gain is needed for a line amplifier? Let's begin the answer with the observation that most line amplifiers have too much gain.
Working on the assumption that even the world's most inefficient power amplifier needs only 3 volts of drive signal to be driven to full output and even the weakest tape deck or CD player puts out at least 0.5V of signal, the greatest amount of gain needed would be 6:1 or 15 dB of gain.
Yet most tube line stages have between 20 to 30 dB of gain (10:1 to 32:1).
While this extra gain impresses the audio neophyte who marvels at the power implicit in the distorted thunder that a mere one quarter twist of the volume knob provokes, it ultimately only subtracts from the useful range of turning on the volume control and usually only worsens the signal-to-noise ratio of the line stage. (Remember, many audio systems don't use any active gain line stage—zero gain—and rely on only passive attenuators and switches to connect line level components to the power amplifier.) If 20 to 30 dB of gain is too much, how much then is best? The answer will depend on each system. (This is the answer most hated by dogmatic audiophiles who seek absolute answers to relative questions...) A safe guess, however, would be 10 to 20 dB of gain, which translates into 3 to 10 times the input signal.
This means, due to the lack of clear guidelines regarding the distribution of the gain factors, everyone of the manufacturers does what they think is right.
Because the overall gain was too high, I often had to intervene in the devices (mostly in the pre-amplifier line stages) in order to reduce them when I was a hi-fi dealer in the 90s.
Always on Moth' active preamp - go to
http://www.stancurtis.com/downloads.htm
this was absolutely necessary in order to use the volume control usefully.
It was very unpleasant to have to modify new devices in order to sell them to an interested audiophile guy.
But what actually is the best gain distribution in order to get best sonic performance ?
Some people think, power amp should be only unity gain character and the pre-amplifier should have the wanted resp. necessary voltage gain.
In real live this is the absolute exception - the only unity gain power amp I now are Andrea Ciuffoli's Power Follower DIY projects - go to this URL's:
https://www.diyaudio.com/community/threads/quality-in-a-cool-follower-99.12542/
https://www.diyaudio.com/community/threads/andrea-ciuffolis-power-follower.3471/
and similar projects mentioned in post #11
only unity gain for the pre-amplifier (i. e. only a buffer to transform the impedance to drive all kinds of signal leads) and factor 30-50 for the power amplifier.
In real life I note at nearly all commercial tube and solid state pre-amps gain factors around 10.
As a result, the total gain factor is around 300-500 with the problem that the maximum undistorted level is reached shortly after the zero position (under certainly conditions speakers blown away).
Under
https://www.tubecad.com/2009/03/blog0161.htm
and
https://web.archive.org/web/2007010...m/tubecircuits/Tube_Line_Stage_Amplifier.html
I read this (concerning only line stages):
Just how much gain is needed for a line amplifier? Let's begin the answer with the observation that most line amplifiers have too much gain.
Working on the assumption that even the world's most inefficient power amplifier needs only 3 volts of drive signal to be driven to full output and even the weakest tape deck or CD player puts out at least 0.5V of signal, the greatest amount of gain needed would be 6:1 or 15 dB of gain.
Yet most tube line stages have between 20 to 30 dB of gain (10:1 to 32:1).
While this extra gain impresses the audio neophyte who marvels at the power implicit in the distorted thunder that a mere one quarter twist of the volume knob provokes, it ultimately only subtracts from the useful range of turning on the volume control and usually only worsens the signal-to-noise ratio of the line stage. (Remember, many audio systems don't use any active gain line stage—zero gain—and rely on only passive attenuators and switches to connect line level components to the power amplifier.) If 20 to 30 dB of gain is too much, how much then is best? The answer will depend on each system. (This is the answer most hated by dogmatic audiophiles who seek absolute answers to relative questions...) A safe guess, however, would be 10 to 20 dB of gain, which translates into 3 to 10 times the input signal.
This means, due to the lack of clear guidelines regarding the distribution of the gain factors, everyone of the manufacturers does what they think is right.
Because the overall gain was too high, I often had to intervene in the devices (mostly in the pre-amplifier line stages) in order to reduce them when I was a hi-fi dealer in the 90s.
Always on Moth' active preamp - go to
http://www.stancurtis.com/downloads.htm
this was absolutely necessary in order to use the volume control usefully.
It was very unpleasant to have to modify new devices in order to sell them to an interested audiophile guy.
But what actually is the best gain distribution in order to get best sonic performance ?
Some people think, power amp should be only unity gain character and the pre-amplifier should have the wanted resp. necessary voltage gain.
In real live this is the absolute exception - the only unity gain power amp I now are Andrea Ciuffoli's Power Follower DIY projects - go to this URL's:
https://www.diyaudio.com/community/threads/quality-in-a-cool-follower-99.12542/
https://www.diyaudio.com/community/threads/andrea-ciuffolis-power-follower.3471/
and similar projects mentioned in post #11