Editing Instrument amplifier (section)

===Size and power rating===
In the 1960s and 1970s, large, heavy, high-output power amplifiers were preferred for instrument amplifiers, especially for large concerts, because [[public address system]]s were generally only used to amplify the vocals. Moreover, in the 1960s, PA systems typically did not use monitor speaker systems to amplify the music for the onstage musicians. Instead, the musicians were expected to have instrument amplifiers that were powerful enough to provide amplification for the stage and audience.  In late 1960s and early 1970s rock concerts, bands often used large stacks of speaker cabinets powered by heavy tube amplifiers such as the [[Ampeg SVT|Super Valve Technology (SVT)]] amplifier, which was often used with eight 10" speakers.

However, over subsequent decades, PA systems substantially improved, and used different approaches, such as horn-loaded ''bass bins'' (in the 1980s) and subwoofers (1990s and 2000s) to amplify bass frequencies. As well, in the 1980s and 1990s, monitor systems substantially improved, which helped sound engineers provide onstage musicians with a better reproduction of their instruments' sound.  

As a result of improvements to PA and monitor systems, musicians in the 2000s no longer need huge, powerful amplifier systems. A small combo amplifier patched into the PA suffices. In the 2000s, virtually all sound reaching the audience in large venues comes from the [[PA system]]. Onstage instrument amplifiers are more likely to be at a low volume, because high volume levels onstage make it harder for the sound engineer to control the sound mix. 

As a result, in many large venues much of the onstage sound reaching the musicians now comes from [[in-ear monitor]]s, not from the instrument amplifiers. While stacks of huge speaker cabinets and amplifiers are still used in concerts (especially in heavy metal), this is often mainly for aesthetics or to create a more authentic tone. The switch to smaller instrument amplifiers makes it easier for musicians to transport their equipment to performances. As well, it makes concert stage management easier at large clubs and festivals where several bands are performing in sequence, because the bands can be moved on and off the stage more quickly.