Preamplifiers: The forgotten audio component
This blog has already explained the function of amplifiers and briefly touched on pre-amplifiers, namely as an electrical component that is often integrated inside a loudspeaker. Yet preamplifiers also exist as external devices and were widely used in the early days of hi-fi when they fulfilled a number of practical functions. For instance, they were often used to connect source devices such as record players, tape recorders and radio tuners to an amplifier. With the help of a regulator or other dials, one could select the playback device as well as regulate the highs, mids and bass of the sound.
This was the situation in the 1980s when the control panel of a preamplifier resembled an airplane cockpit. Today, high-end pre-amplifiers only have two dials – one for volume and one for channel selection. The various playback devices are generally connected directly to an A/V receiver or amplifier. Alternately, one can use a control unit, especially in the case of active loudspeakers that do not require amplification.
Preamplifiers as stand-alone devices external to a hi-fi or home cinema systems have become a rarity. Once the first CD players with integrated volume controls came on the market, preamplifiers became somewhat redundant. In general, single source devices became standard (which was the CD player for a long time) and amplifiers were used which included the ability to switch between source devices. Both of these developments precluding any need for a preamplifier.
The basic quality level of preamplifiers of the time was also to blame for their discontinued use. There were exceptions, but by and large, the sound they delivered was often tinny and unbalanced. If they continued to be used, it had more to do with a desire to increase a system’s connection possibilities than any attempt to improve the sound. Since this function has, in the meantime, been totally usurped by A/V receivers and control stations, one barely sees preamplifiers at all these days – except in high-end audio. With high-end systems, a good preamplifier still plays an important role. At least many hi-fi experts seem to think so. Many are of the opinion that the sound quality is improved when a high-quality preamplifier is in operation between the source device and the amplifier.
There is another type of preamplifier that is still used today, especially with record players: the phono amp. All record players with moving magnet and moving coil systems require these special preamplifiers in order to boost the signal so that the actual amplifier is able to process it. Phono amps also equalize the signal.
Yet over the years, many manufacturers have included integrated phono amps in amplifiers or directly into the record players themselves. Amplifiers with integrated phono amps can be recognized by the presence of a phono input. A phono input is really a standard stereo cinch input that is typically labeled “phono.” This means that the signal entering this input will be enhanced. Should the record player have its own integrated phono amp, than the signal that it delivers should not be connected to a phono input on an amplifier. You can tell if your record player has an integrated phono amp by checking the user manual or finding the corresponding product description on the Internet.
As control devices
What many people take to be an amplifier is really nothing of the kind. Control devices may look like standard amplifiers or A/V receivers, yet their job is really to do what preamplifiers did back in the 1980s: They help manage the various source devices without actually amplifying any of the signals they deliver. Happily, this is not necessary today since control devices are typically used together with active loudspeakers; that is, loudspeakers that contain integrated amplification units. Such active loudspeakers often don’t include enough connections on their control panels which is where control devices come in.
Coda: Today’s preamplifiers are integrated into amps and receivers
Even if separate preamplifers aren’t generally used today, they can still be found everywhere under different names, often integrated into amplifiers, A/V receivers or record players. Anywhere a signal is boosted to an even level for an amplifier to process, a pre-amplifier is at work. The other main task of a preamplifier – the management and control of various playback devices is today the domain of control devices that are often connected to active loudspeaker systems.
The only place one is still likely to find an external preamplifier is in the area of very high-end hi-fi. Where perfection is an expectation, value is placed on delivering the highest quality signal to an amplifier for processing. In this case, a correspondingly high-end and expensive preamplifier is employed.
All pictures: Property of Teufel Audio
Title Picture: By Mbartosi (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Picture #1: By Ookami-no-rei (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons