Vintage Pre-Amplifier Information

A preamplifier has three basic functions;

Impedance matching.
Source selection with clean adequate amplification to line level.
Volume control.

The term preamp can be applied in many ways and is one of the most widely interpreted terms used when discussing audio gear. A preamp may be built into any number of different components and a preamp is also used in the input stage of every amp.

To add to the confusion preamps often function similarly to DI boxes which stands for direct injection. A DI box is a device that converts signals from unbalanced to balanced can also set the output level and impedance in order to connect microphone preamp inputs to a mixer in a pro audio environment. Many preamps include this functionality as well as features such as tone shaping or gain boost, but such features are not required.

Gain refers to the amount your signal level is being increased. The amount a preamp increases your gain is important because every device that receives its signal has an ideal range of signal level that the manufacturer has engineered their product to expect. This can be nominal most of the time, but can make a big difference when blending Hi-Fi gear and Pro audio equipment for instance.

Preamps are typically active in that they require a power supply in order to boost a signal. There are however passive preamps but without the addition of power the energy of your signal can only be rearranged or dissipated, but never increased.

Tone can be affected by a pre-amp and is modulated in many different ways including EQ controls, warmth controls that affect subtle qualities, or decrease or increase distortion levels. Some users expect lots of tonal and EQ controls while others prefer want absolute transparency/simplicity. It comes down to a matter of taste.

Impedance refers to the efficiency of signal transfer from one piece of gear to another. An ideal impedance relationship involves low output impedance values connecting to gear with high input impedance values. Unmatched impedance can result in a lower signal level that may affect things like tone and clarity.

It is important to note that with vintage gear some components may be affected by age and may need maintenance. This can include fader lubrication, contact cleaning, replacing fuses, and capacitors. These things should not dissuade you from vintage gear as the reward is often well worth the trouble. Always consult your models service manual when considering maintenance. For vintage models these can be obtained from a dealer, or an on-line Hi-Fi resource.