In the case of amplifiers, it is a bit of both as the technology has
been there, so some makers may have been conservative or felt the need
to keep it reasonably useful sounding by limiting their measurement to
20khz. Another reason is that they may not have been able to measure
higher with their test gear and felt that was good enough as did the
rest of the buying public evidently. Really until speakers could
produce higher frequencies, it was (pardon the pun) mute. In the case
of modern loudspeakers, there has been a significant increase in
implementation of the materials and design to allow frequency
extension and that has definately made it more attractive for
amplifier manufacturers to either redesign their amps or simply
remeasure with more accuracy to get the higher numbers. As a case of
how both the technology has progressed and how the ability to quantify
it has diminished, Jacques Mahul of JM Lab has said of the limits of
their new beryllium tweeter that they state its response to be flat
out to 40khz, but that it could be much higher than that. That is as
high as they can measure accurately with their microphones. The output
of amplifiers can be measured on equipment without having to use
microphones, so that is quite different. Speakers have an acoustic
output and that is what has to be measured there as it is their whole
point.
-Bill
www.uptownaudio.com
Roanoke VA
(540) 343-1250

"Chelvam" wrote in message
...
Hi all,

To the best of my knowledge, almost all amplifiers' specification
used to
state the Bandwidth to be on the average 20hz to 20khz. There were
some,
such as Chord and a number of tube/valve amplifier with rated full
power
bandwidth upto 100khz. Lately, i.e after SACD and DVD -A many
amplifer now
state bandwidth up to 100Khz.

My question, did any significant design or circuit changed to meet
the above
20khz in the last 5 years or is it mere renumbering in the specs?

The same happened in the frequency response specs. It used to be 40
or more
to 20KHz. Now all of sudden the speaker manufacturers are promoting
speakers
meeting the new formats reqirements and stating max upto 35khz and
more.
Renumbering or redesign?

Over to you guys...