Amplifier power output uses vacuum tube

Whether or not phase is inverted. Just swap speaker leads black for red if permanently inverted

Balanced architecture internally

A post to connect grounding wire to, often helpful for troublesome turntable setups

Number of seperate chassis to form a stereo 2-channel preamp

Note that some inputs may be either RCA or XLR, not both, so the total count of inputs is often less than just adding the RCA inputs to the number of XLR inputs

number of phono XLR inputs of any kind (mm or mc)

number of phono RCA inputs of any kind (mm or mc)

Output allows recording or equalization of source before it gets to the volumn control

Output allows recording or equalization of source before it gets to the volumn control

number of headphone jacks of any kind

Wall power consumed when playing at rated output

Has a built-in DAC (digital to analog converter)

Switchable or permanent low gain. Useful for horn speaker systems, for example. Normal gain preamps make these systems very loud even when the volume is turned to 1.

Total weight of all boxes required to make a stereo preamplifier

Also known as Unity Gain or processor bypass. Input allows home theater preamp to send front 2 channel signal through audio preamp, bypassing the audio preamp volume control, to the main speakers. This way only the HT volume control controls the volume of the entire HT system as well as preserving the quality of the HT signal by not having it have to go through the audio preamp's gain stage

Also known as a tape in/out loop. A combination output and input that allows a processor, like an equalizer, to processes the signal between the source, like a CD player, and the volume control.

Output impedance for single-ended output. Double this for balanced output

Maximum output voltage for single-ended output. Double this for balanced output.

Weight of all pieces and packaging