jphalter@ihuxb.UUCP (n) (11/02/83)
Dynamic headroom for amps is the latest in a series of efforts by audio manufacturers to increase wattage ratings above the standard RMS per channel value. In the early 1970's, amplifiers were rated using various rating schemes to the apparent wattage. RMS per channel produced the lowest rating, so only the most reputable audio manufacturers used it. Common tactics were RMS per channel x 2 (since stereo), EIA rating (generally 4 x RMS), IHF, and IHF peak rating (6-8 x RMS). The feds stepped-in around 1975 and created the present standard which allowed only RMS per channel AND required a 3 hour burn-in at 1/3 power before measuring rated RMS power. 1/3 power is quite a drain on many amps and they get very hot in the process. The latest scheme for power ratings is to advertise dynamic headroom. This is equivalent to "peak" ratings in the past. The bottom line is that a 50 watt amp with 6 dB "dynamic headroom" will produce short term audio peaks equivalent to a 200 watt amp with 0dB headroom. However, the 200 watt amp that passes the 3 hour burn-in will generally be a higher quality product.