On Thu, 02 Oct 2003 19:56:27 +0100, Laurence Payne
wrote:


Any really good amplifier will be able to handle full power
more-or-less continuously - certainly for several minutes - without a
problem.

And wouldn't object to being asked to deliver considerably more if
momentarily demanded? You seem to be arguing against transient
headroom :-)

Anyone who knows anything about amps *does* argue against 'transient
headroom', which is just another word for a cheap power supply. Take a
£15,000 Krell amp, for instance. This will deliver close to a kilowatt
into an 8 ohm load forever, with virtually *no* 'transient headroom'.
You think this makes it lacking in 'slam'?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article , Stewart Pinkerton
wrote:
On Thu, 02 Oct 2003 19:56:27 +0100, Laurence Payne
wrote:


Any really good amplifier will be able to handle full power
more-or-less continuously - certainly for several minutes - without a
problem.

And wouldn't object to being asked to deliver considerably more if
momentarily demanded? You seem to be arguing against transient
headroom :-)

Anyone who knows anything about amps *does* argue against 'transient
headroom', which is just another word for a cheap power supply.

In that case, I'm afraid I don't know much about amplifiers. :-)

My own view/experience is that it can be quite useful in the context of
reproducing musical signals to arrange for the amp/PSU to have a short-term
power ability that is well above the sustained power ability. The reasons
for this in my view are;

1) Most music tends to include relatively brief musical transient events
which reach short-term levels well above the mean level.

2) Allowing the rail voltages to fall under sustained demand helps reduce
the power dissipation in the output devices compared with what you get if
you try to maintain the same rail levels as existed for short-term high
power bursts. This keeps the device tempeatures down, etc, which can be
useful.

The main disadvantages are in my view:

1) The sustained mean power levels measured in a review tend to be
under-reading the actual ability (e.g. the 700 I designed only rated at
200Wpcs 'rms' sic both channels sinewave driven, but could actually
deliver around 300Wpc mean per channel for a tenth of a second or so. (This
is not the peak 'instananeous' transient value, which I'd agree is
misleading.) Thus in terms of actual use the 200Wpc perhaps didn't really
indicate how much the amp could provide with music.

2) You have to ensure the amp does not produce distortion or become upset
in some way when the rails fluctuate. This seems sensible, anyway, to me,
as it avoids things like distortion crosstalk between channels.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Stewart Pinkerton
wrote:
On Thu, 02 Oct 2003 19:56:27 +0100, Laurence Payne
wrote:


Any really good amplifier will be able to handle full power
more-or-less continuously - certainly for several minutes - without a
problem.

And wouldn't object to being asked to deliver considerably more if
momentarily demanded? You seem to be arguing against transient
headroom :-)

Anyone who knows anything about amps *does* argue against 'transient
headroom', which is just another word for a cheap power supply.

In that case, I'm afraid I don't know much about amplifiers. :-)

My own view/experience is that it can be quite useful in the context of
reproducing musical signals to arrange for the amp/PSU to have a short-term
power ability that is well above the sustained power ability. The reasons
for this in my view are;

1) Most music tends to include relatively brief musical transient events
which reach short-term levels well above the mean level.

2) Allowing the rail voltages to fall under sustained demand helps reduce
the power dissipation in the output devices compared with what you get if
you try to maintain the same rail levels as existed for short-term high
power bursts. This keeps the device tempeatures down, etc, which can be
useful.

The main disadvantages are in my view:

1) The sustained mean power levels measured in a review tend to be
under-reading the actual ability (e.g. the 700 I designed only rated at
200Wpcs 'rms' sic both channels sinewave driven, but could actually
deliver around 300Wpc mean per channel for a tenth of a second or so. (This
is not the peak 'instananeous' transient value, which I'd agree is
misleading.) Thus in terms of actual use the 200Wpc perhaps didn't really
indicate how much the amp could provide with music.

2) You have to ensure the amp does not produce distortion or become upset
in some way when the rails fluctuate. This seems sensible, anyway, to me,
as it avoids things like distortion crosstalk between channels.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

On Thu, 02 Oct 2003 19:56:27 +0100, Laurence Payne
wrote:


Any really good amplifier will be able to handle full power
more-or-less continuously - certainly for several minutes - without a
problem.

And wouldn't object to being asked to deliver considerably more if
momentarily demanded? You seem to be arguing against transient
headroom :-)

Anyone who knows anything about amps *does* argue against 'transient
headroom', which is just another word for a cheap power supply. Take a
£15,000 Krell amp, for instance. This will deliver close to a kilowatt
into an 8 ohm load forever, with virtually *no* 'transient headroom'.
You think this makes it lacking in 'slam'?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Any really good amplifier will be able to handle full power
more-or-less continuously - certainly for several minutes - without a
problem.

And wouldn't object to being asked to deliver considerably more if
momentarily demanded? You seem to be arguing against transient
headroom :-)

On Thu, 2 Oct 2003 19:16:30 +0100, "Tim S Kemp"
wrote:


"The Old Fogey" wrote in message
. com...
Can anyone define 'Slam' in the context of audio power amps?

The ability to deal with sudden short lived transient sounds - preferably
without affecting the rest of the output of the amp. Normally acheived with
good PSU design and big power reserves and capable of transient output well
beyond the units continuous ratings.


This doesn't feel right. A transient capability well beyond the
continuous rating of an amplifier speaks of poor design and an
inability to handle large signals well. In fact it is one of the
fake-power-ratings refuges of the charlatan - the old instantaneous
peak power syndrome beloved of Sinclair Radionics.

Any really good amplifier will be able to handle full power
more-or-less continuously - certainly for several minutes - without a
problem.

If slam really isn't just another piece of marketing nonsense, then it
must have a reality based in a particular sound produced by an
amplifier - that would make it some sort of specialist device for
music production, not Hi Fi reproduction.

d

_____________________________

http://www.pearce.uk.com

In message , Tim S Kemp
writes

"The Old Fogey" wrote in message
. com...
Can anyone define 'Slam' in the context of audio power amps?

The ability to deal with sudden short lived transient sounds - preferably
without affecting the rest of the output of the amp. Normally acheived with
good PSU design and big power reserves and capable of transient output well
beyond the units continuous ratings.





Apart from the fact that good PSU design means that the amp has no power
reserve! ie, that it has a well regulated PSU, so the long term output
power capability is the same as the short term one.
--
Chris Morriss

In message , Tim S Kemp
writes

"The Old Fogey" wrote in message
. com...
Can anyone define 'Slam' in the context of audio power amps?

The ability to deal with sudden short lived transient sounds - preferably
without affecting the rest of the output of the amp. Normally acheived with
good PSU design and big power reserves and capable of transient output well
beyond the units continuous ratings.





Apart from the fact that good PSU design means that the amp has no power
reserve! ie, that it has a well regulated PSU, so the long term output
power capability is the same as the short term one.
--
Chris Morriss

Some amps do have more SLAM! I can personally vouch for this and demonstrate
it! and it can be measured accurately and scientifically with a db Meter and
a seismograph.

If you take a big Krell or McIntosh and throw it on the ground it will
produce allot of slam, but if you take a wee Cyrus and throw it on the
ground the same way it produces way less slam. this can easily be measured.
On the other hand, if you take a Cyrus and launch it from a trebuchet it can
produce more slam than the krell dropped from head height.

Slam is what happens when two objects collide. It's to do with velocity x
mass / d (density of arrival surface) = s (slam) = energy expelled during
impact

I recommend the trebuchet method for launching if you want to test out your
own equipment. subs are the most fun.

Stew.



"Tim S Kemp" wrote in message
. ..

"The Old Fogey" wrote in message
om...
Can anyone define 'Slam' in the context of audio power amps?

The ability to deal with sudden short lived transient sounds - preferably
without affecting the rest of the output of the amp. Normally acheived
with
good PSU design and big power reserves and capable of transient output
well
beyond the units continuous ratings.

On Thu, 2 Oct 2003 20:02:32 +0100, "Stewart"
wrote:

Some amps do have more SLAM! I can personally vouch for this and demonstrate
it! and it can be measured accurately and scientifically with a db Meter and
a seismograph.

If you take a big Krell or McIntosh and throw it on the ground it will
produce allot of slam, but if you take a wee Cyrus and throw it on the
ground the same way it produces way less slam. this can easily be measured.
On the other hand, if you take a Cyrus and launch it from a trebuchet it can
produce more slam than the krell dropped from head height.

Slam is what happens when two objects collide. It's to do with velocity x
mass / d (density of arrival surface) = s (slam) = energy expelled during
impact

I recommend the trebuchet method for launching if you want to test out your
own equipment. subs are the most fun.

Stew.

I've seen an upright piano thrown by trebuchet, and I can vouch
personally for the truth of your theory!

d

_____________________________

http://www.pearce.uk.com