Diode Efficiency
Diode efficiency might be defined the ratio between the loaded rectified power supply voltage over the potential voltage. It is expressed as a percentage. This not an easily explained aspect of a diode's performance, made up as it is from the diodes voltage drop, resistance's, and other non-linear losses.

Transformer Regulation
Transformer regulation is the ratio between the unloaded over the loaded secondary voltage expressed as a percentage. Usually, the larger the transformer the better the regulation. This is an often overlooked design consideration; dangerously so.

Voltage Output
The output voltage of a power supply is the whole point of a power supply. The stability of the output voltage and purity of the output voltage are the criteria by which the power supply is judged. In general, the higher the output voltage, the more difficult the task of maintaining voltage stability and low noise.

Current Output
The current drawn by the load. The demands made on the output current sourcing of a power supply often vary in most audio power amplifier and remain fairly constant preamplifiers, tuners, tape decks, CD players.

AC Input Minimum
The wall voltage varies from city to city, from hour to hour. At peak usage, the voltage can drop by 20%. During a brownout, the drop can be as great as 40%. For many designs, 100 vac is the specified lower limit of wall voltage needed to insure proper operation in the US.

AC Input Nominal
The nominal wall voltage in the US used to be around 115 vac; today it's closer to 117 to 120 vac.

AC Input Maximum
If a power line is hit by a car and unloads your feed line past your house, the wall voltage could increase by 100%. This is when your microwave says "Nevermore". Or, after the resumption of service following a blackout, the line voltage can increase by 40%.

Voltage Ripple
The peak ripple voltage is the amount of deviation from flat DC voltage that develops at the capacitor after the diodes. Less would be better, but at the cost of a much larger input capacitor and the consequentially higher charging currents. This voltage not an absolute. What would be considered a wonderfully low amount of ripple in a 400 VDC power supply, say, 2 volts, would be viewed as grossly excessive in a 10 VDC power supply.

Voltage Drop Across Regulator
All voltage regulators have a drop-out voltage which defines the absolute least amount of voltage across the device needed to ensure regulation. Often, the higher the current demands by the load, the greater this drop-out voltage becomes. This is an often overlooked design consideration. Remember that the wall voltage might fall by 20% and bring the raw DC voltage below the drop-out value.

Voltage Drop Across Rectifier
The diodes used to rectify the AC into DC voltage have a voltage across them that subtracts from the total voltage available. With solid state diodes this is seldom a large concern; whereas, with tube diodes it is seldom a small concern.