When interconnecting various electronic devices commonly encountered in audio systems, the issues of impedance and impedance matching between components usually arises. Specifically, impedance matching seems to be a common concern among audiophiles. Although one should not simply dismiss the matter, more often than not the concern expressed is far greater than the occurrence of any real problem encountered.

A common "rule of thumb" for matching the output impedance of a line-level device such as a preamp output to the input impedance of an amplifier is 1:10. This means that if the output impedance of the preamp is rated as being 1K-Ohm, then the amplifier being connected should exhibit no less that a 10K-Ohm input impedance. While this can be used as a good guideline, it is by no means a "rule."

In all actuality, one will not experience much in the way of any negative effects if the "rule" is reduced to 1:4. In this case, a reduction of signal being fed into the amplifier will only be about -2.5dB. Although this is an extreme example, in most cases simply increasing the volume control of the preamp a little can easily accommodate for such a modest loss.

Only in those cases where an impedance miss-match results in either a significant change in the frequency response or an increase in distortion arising within the preamp, should there really be any concern. In those cases, unless an individual has detailed information regarding the preamp, there really is no way to know beforehand short of personal experimentation. If the user experiences audible distortion or a reduction of bass and/or high frequency response, then they will ultimately be forced to select either a different amplifier or preamp to eliminate the condition. One alternative to this would also be to insert a "line-driver" type device. This component typically does not provide any voltage gain, but it will often exhibit a much lower output impedance, which should remedy the issue. Nevertheless, most modern equipment is relatively immune to these effects, so the likelihood of encountering such problems is very slim and should not be a primary concern when selecting audio components.