A Line or RIAA stage could be characterized as "good" if it complies with its primary objective: To amplify the music signal with enough gain to be listened comfortably at the proper volume level, and do it without introducing obvious anomalies not present in the original recording. I think many of today's products could fit in that description.
Do you want more than merely "good"? First, the device should be accurate, transmitting all aspects of the reproduction with completeness and neutrality. With accuracy I'm not implying a clinical, analytic or sterile sound. This is not accuracy, is just, well, sterility. It also should be able to process even the most dynamic signals without any trace of compression or congestion. Every nuance, every detail, every "emotion" should come out in the right proportions. Nothing should be added or removed. The device should be "transparent" in the sense that listening to it would give you the feeling of being closer to the original event, not processed through electronic circuits.
As for the circuit details, there are probably as many different opinions as there are designers out there, but some general desirable characteristics could be extracted. It should have as extended a bandwidth as possible, both ABOVE and BELOW the audio band (officially 20 Hz to 20 kHz). Low noise is absolutely fundamental. A low distortion is highly desirable, because a high amount of it can be easily discernable as an added "gloss" in the instruments. Feedback can improve the measured specs, but if not properly done it will also rob life from the music (causing that sterile sound). In the RIAA department, it should provide clean gain for your cartridge (some of them needing up to 70 dB), and be able to manage input signals of at least 10 times without overloading. It should decode the RIAA curve with the minimum error possible, or it will show up as a permanent color of your sound. Finally, the unit should be reliable, stable, and have a fast warm-up time.
We now have the technology to satisfy all of these requirements simultaneously. If a unit aptly does that, there is a good chance that you will experiment all that "emotion" trapped in your recordings.
Do you want more than merely "good"? First, the device should be accurate, transmitting all aspects of the reproduction with completeness and neutrality. With accuracy I'm not implying a clinical, analytic or sterile sound. This is not accuracy, is just, well, sterility. It also should be able to process even the most dynamic signals without any trace of compression or congestion. Every nuance, every detail, every "emotion" should come out in the right proportions. Nothing should be added or removed. The device should be "transparent" in the sense that listening to it would give you the feeling of being closer to the original event, not processed through electronic circuits.
As for the circuit details, there are probably as many different opinions as there are designers out there, but some general desirable characteristics could be extracted. It should have as extended a bandwidth as possible, both ABOVE and BELOW the audio band (officially 20 Hz to 20 kHz). Low noise is absolutely fundamental. A low distortion is highly desirable, because a high amount of it can be easily discernable as an added "gloss" in the instruments. Feedback can improve the measured specs, but if not properly done it will also rob life from the music (causing that sterile sound). In the RIAA department, it should provide clean gain for your cartridge (some of them needing up to 70 dB), and be able to manage input signals of at least 10 times without overloading. It should decode the RIAA curve with the minimum error possible, or it will show up as a permanent color of your sound. Finally, the unit should be reliable, stable, and have a fast warm-up time.
We now have the technology to satisfy all of these requirements simultaneously. If a unit aptly does that, there is a good chance that you will experiment all that "emotion" trapped in your recordings.
