What should a preamp do?
First, it should have pure resistive 47K ohm input impedanced on all line level inputs independent of the active stage feedback to provide an easy load for all sources.
Second, it should have a low output impedance, high slew rate, and high output drive current capability to allow driving any load or cables downstream without stressing the preamp line circuits, or making the sources have to attempt driving those loads directly.
Third, it should intercept and not pass on out of band garbage (digital switching sidebands, cartridge mistracking shatter, out of band resonances, etc) because your amplifier and speakers will not like that garbage.
Fourth, it should have ultra transparent and dynamic internal active circuits (don't screw up the source material). It should present you with sonic quality that exceeds your expectations and have long term durability.
Fifth, it should have the all of the control flexabily that you need, executed well (precision tracking controls, trouble-free switches, etc.).
Sixth, it should protect your amplifier and speakers from on or off transients from the preamp and from any equipment switched on or off by the preamp.
Seven, if you use the preamplifier for making recordings, the preamp should have buffered tape driver circuits available to isolate your sources from the really nasty loads recording devices often present, especially when they are connected to the tape outputs and turned off.
Note that none of these requirements require really expensive prices, just good careful engineering done by a company that actually knows what is needed to do right to make a useful product.
Frank Van Alstine
