[mix4fix]

Some of the higher-end passive pre-amps have options that require electricity to operate (remote volume control, LED display, etc.) but is still passive in function.

But, isn't a passive pre-amp supposed to be basic in nature?

[glynnw]

Why basic, if more complex yields better sound?  Passive's appeal is that there are fewer devices in the signal path.  Passive does not necessarily mean cheaper.  I love my Tortuga passive, but it has a lot of options which require power while not mucking up the signal.

[FullRangeMan]

I understand passive pre-amps as those that no add gain to the signal, usually just a volume pot, some have a tube buffer.

[jonbee]

Purely passive preamps (volume control only) often have poor bass response and dynamics due to impedance mismatches, which a buffer is designed to correct. My advice is to not get one without a buffer. Tortuga sells an add on tube buffer for theirs.

[ssglx]

My Tortuga LDR preamp does not have a buffer, and excellent bass and warmth of tone and sound are not issues with my system.

I have also tried a TVC (very transparent and clean sounding) and a pot in a box. Neither ultimately had enough flesh on the bone for me.

[richidoo]

But, isn't a passive pre-amp supposed to be basic in nature?

Passive or active only refers to presence of electrically powered amplifiers in the signal path.

It does not refer to the presence of electrically powered accessories to make operation of the preamp easier. It's still passive if it has remote control, powered VC and source switching, LED level readout, etc.

As long as the signal never touches a tube, transistor, amplifier IC, then it's passive. Even if it uses magnetics to boost voltage or current.