Many people have had great success using passive linestages. But, you have to be very careful to get good results. Ralph Karsten offered the following thoughts about the role served by a preamp (linestage), and some thoughts about passive linestages, in an earlier thread:
What some active buffering circuitry in the linestage can provide is greater flexibility, greater isolation of component interactions, buffering of mis-matched impedances among various other components and among interconnect cables themselves, use of longer interconnects where this may be a need, sometimes improved dynamics, sometimes improved tonal balance (because of control over all of these other interactions). This is all HIGHLY system dependent. While a good passive linestage can be a great solution, the bar is raised for excellent execution within a given system implementation. If you are prepared to pay attention to these things, a passive might be the right solution. If not, a good quality active linestage takes care of these issues for you, but adds the challenge of some active circuitry that will have some sonic signature of it's own to contribute.
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A line stage should perform the following functions:
1) control the effects of the interconnect cables in the system. In general, transistor units do this rather well and tube units do this rather poorly, passive units do it the worst.
2) provide a proper volume control system. This means that the position of the volume control should have no impact on the quality of the sound (a big problem with passive setups and digital volume control systems, a very noticable issue with the vast majority of remote volume control systems).
3) Gain is helpful, but not manditory- a lot depending on the amplifier being used and the efficiency of the loudspeakers being used. Generally moderate and lower efficiency speakers (92db or less) will have some benefit from a little gain in the line section, unless the amplifier has a very sensitive input. If the unit does have gain, that gain must be wide bandwidth (+100KHz) and low distortion.
4) provide an input signal switching capability. This again is not mandatory, for those who only have one source. However input switching can greatly add to ease of use (and if the stereo is hard to use, it will gradually get listened to less often). If input switcing is present, it should be sonically transparent.
Given thes things, ultimately the goal of reproduced music is to sound identical- indistinguishable- from the real thing. To this end the line stage is critical, and this is not about taste, it is about accuracy. Most transistor units tend to impart a stilted quality that is instantly recognizable to the trained ear. This raises the bar on transistor units, leaving tubes to be the main contendors. The possible exception might be a buffered unit with an extremely high quality volume control, but the higher resolution systems usually have no trouble revealing even the relatively transparent buffer circuitry.
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1086678948&openusid&zzAtmasphere&4&5#Atmasphere
What some active buffering circuitry in the linestage can provide is greater flexibility, greater isolation of component interactions, buffering of mis-matched impedances among various other components and among interconnect cables themselves, use of longer interconnects where this may be a need, sometimes improved dynamics, sometimes improved tonal balance (because of control over all of these other interactions). This is all HIGHLY system dependent. While a good passive linestage can be a great solution, the bar is raised for excellent execution within a given system implementation. If you are prepared to pay attention to these things, a passive might be the right solution. If not, a good quality active linestage takes care of these issues for you, but adds the challenge of some active circuitry that will have some sonic signature of it's own to contribute.
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