Phono preamps from $5,000 to $10,000 are reference components built to be completely transparent to the cartridge signal. Dual-mono architectures, exotic tube or hybrid gain stages, and power supplies that would be overkill in a power amplifier ensure that nothing gets added or subtracted in the amplification chain. Swap cartridges at this level and the entire sonic presentation changes, because the phono stage isn't imposing its own signature. It's a straight wire with gain, exactly as the ideal demands. That's harder to achieve than it sounds.
