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Slew Rates and Mic Pre performance

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Anonymous
August 29, 2005 11:40:07 AM

Archived from groups: rec.audio.pro (More info?)

Trying to get a handle on this Slew Rate spec you often see published
for higher-end mic pre's.

Please correct me if I'm wrong, but from what I've read, it seems that
a preamp with higher slew rate is more likely to capture transients
better and hopefully render a more detailed soundstage. Is this true?

Thanks for helping out.

Harry
Anonymous
August 29, 2005 11:40:08 AM

Archived from groups: rec.audio.pro (More info?)

Harry Houdini wrote:

> a preamp with higher slew rate is more likely to capture transients
> better and hopefully render a more detailed soundstage. Is this true?

No guarantees, but yes, the potential is there, at least as far as
better transient response. Whether that automatically equates to a
"more detailed soundstage" (whatever that means) is not assured.

On the other hand, a preamp with a low slew rate might, by some, be
characterized as "warm."

Slew rate is a parameter that's more important to the designer than it
is to the end user.
Anonymous
August 29, 2005 11:40:08 AM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers (that's me!) wrote:

> Slew rate is a parameter that's more important to the designer than it
> is to the end user.

In support of my esteemed colleague Mr. Allision, I'll add that slew
rate is also important to the marketing department who makes up the
spec sheets. To those who don't know what it means, for numbers that
appear to be large, bigger is better. (and for numberes that appear to
be small, smaller is better)
Related resources
Anonymous
August 29, 2005 12:19:48 PM

Archived from groups: rec.audio.pro (More info?)

"Harry Houdini" <harry@home.com> wrote in message
news:qas5h1dvke7cbsnu97hpa25of0llpvrcis@4ax.com

> Trying to get a handle on this Slew Rate spec you often
> see published for higher-end mic pre's.

For the most part you can ignore them.

> Please correct me if I'm wrong, but from what I've read,
> it seems that a preamp with higher slew rate is more
> likely to capture transients better and hopefully render
> a more detailed soundstage. Is this true?

The study of the properties of the human ear tell a
completely different story. The ear has far from unlimited
bandwidth. Careful experiments comparing music that is
band-limited at high and low frequencies shows that
band-limiting is not audibly signficant, if audio below 16
Khz or higher is free from appreciable losses.

Transients need to be quantified in terms of their size. It
takes 10 times as much slew rate to handle a transient that
is 10 times as large. So, specifications of slew rate are
meaningless unless qualified by the size of the signal being
processed.

A very, very large +22 dBu signal at 22 KHz has a slew rate
of less than 1.3 volts per microsecond. Divide that by
about 10 if you try to keep things under +4.

If you've been reading slew rate specs, you know that 1.3
volts per microsecond is a number that seems ludicrously
low.

Slew rate can be important if wide-band signals that are not
strictly audio signals are involved. However, most good
audio production gear includes features that limits its
response to non-audible signals.
Anonymous
August 29, 2005 5:26:55 PM

Archived from groups: rec.audio.pro (More info?)

"Harry Houdini" <harry@home.com> wrote in message
news:qas5h1dvke7cbsnu97hpa25of0llpvrcis@4ax.com...
> Trying to get a handle on this Slew Rate spec you often see published
> for higher-end mic pre's.
>
> Please correct me if I'm wrong, but from what I've read, it seems that
> a preamp with higher slew rate is more likely to capture transients
> better and hopefully render a more detailed soundstage. Is this true?


yes. It is the amp's capability to reproduce 'transients' or the transition
between two voltages.
Anonymous
August 29, 2005 5:26:56 PM

Archived from groups: rec.audio.pro (More info?)

"Harry Houdini" <harry@home.com> wrote in message
> Trying to get a handle on this Slew Rate spec you often see published
> for higher-end mic pre's.
>
> Please correct me if I'm wrong, but from what I've read, it seems that
> a preamp with higher slew rate is more likely to capture transients
> better and hopefully render a more detailed soundstage. Is this true?

Analog Devices sells a really nice op-amp guide which explains most of
these specifications.

Basically, slew rate is a measure of how fast the output can move from
one level to another. As long as the slew rate is high enough for the
amplifier bandwidth and output level, it's fine.

If the slew rate is not high enough, then the small signal bandwidth
will be different than the bandwidth for large signals. Transients will
not be reproduced properly. Things will sound "smeary." This is called
"slew limiting."

For the most part, slew rate isn't a very useful measure any more, except
to reassure you that it's not too low. It's become like THD, which is
a useful measure to compare similar amplifiers with high distortion levels,
but which is no longer useful to compare modern amplifiers with low levels
of distortion.

But back in the seventies, when a _lot_ of equipment had severe slew rate
limitations, it was a big deal.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 29, 2005 5:29:59 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:TqOdnVCP47HNYI_eRVn-oA@comcast.com...
> "Harry Houdini" <harry@home.com> wrote in message
> news:qas5h1dvke7cbsnu97hpa25of0llpvrcis@4ax.com
>
>> Trying to get a handle on this Slew Rate spec you often
>> see published for higher-end mic pre's.
>
> For the most part you can ignore them.
>

Mainly becuse most electronics nowdays provides more than adequate slew
rates for audio.



> Transients need to be quantified in terms of their size. It takes 10 times
> as much slew rate to handle a transient that is 10 times as large. So,
> specifications of slew rate are meaningless unless qualified by the size
> of the signal being processed.

IT usually specifies the supply rails.


>
> A very, very large +22 dBu signal at 22 KHz has a slew rate of less than
> 1.3 volts per microsecond. Divide that by about 10 if you try to keep
> things under +4.
>
> If you've been reading slew rate specs, you know that 1.3 volts per
> microsecond is a number that seems ludicrously low.
>
> Slew rate can be important if wide-band signals that are not strictly
> audio signals are involved. However, most good audio production gear
> includes features that limits its response to non-audible signals.
>
>
Anonymous
August 29, 2005 5:30:00 PM

Archived from groups: rec.audio.pro (More info?)

"nap" <gospam@yourself.com> wrote in message
news:r5EQe.585$v83.283@newssvr33.news.prodigy.com
> "Arny Krueger" <arnyk@hotpop.com> wrote in message
> news:TqOdnVCP47HNYI_eRVn-oA@comcast.com...
>> "Harry Houdini" <harry@home.com> wrote in message
>> news:qas5h1dvke7cbsnu97hpa25of0llpvrcis@4ax.com
>>
>>> Trying to get a handle on this Slew Rate spec you often
>>> see published for higher-end mic pre's.
>>
>> For the most part you can ignore them.
>>
>
> Mainly becuse most electronics nowdays provides more than
> adequate slew rates for audio.

Always did, but with some notable exceptions at one time.

>> Transients need to be quantified in terms of their size.
>> It takes 10 times as much slew rate to handle a
>> transient that is 10 times as large. So, specifications
>> of slew rate are meaningless unless qualified by the
>> size of the signal being processed.

> IT usually specifies the supply rails.

I'm quite unsure about that.

>> A very, very large +22 dBu signal at 22 KHz has a slew
>> rate of less than 1.3 volts per microsecond. Divide that
>> by about 10 if
>> you try to keep things under +4.

>> If you've been reading slew rate specs, you know that
>> 1.3 volts per microsecond is a number that seems
>> ludicrously low.

Note that +22 is about 13.8 volts peak, but audio gear that
goes to +22 generally has VCC in the 18 volt and up range.

>> Slew rate can be important if wide-band signals that are
>> not strictly audio signals are involved. However, most
>> good audio production gear includes features that limits
>> its response to non-audible signals.

IOW EMI can trigger slew rate limiting.
Anonymous
August 29, 2005 5:58:49 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D ev46r$lng$1@panix2.panix.com...
> "Harry Houdini" <harry@home.com> wrote in message
>> Trying to get a handle on this Slew Rate spec you often see published
>> for higher-end mic pre's.
>>
>> Please correct me if I'm wrong, but from what I've read, it seems that
>> a preamp with higher slew rate is more likely to capture transients
>> better and hopefully render a more detailed soundstage. Is this true?
>
> Analog Devices sells a really nice op-amp guide which explains most of
> these specifications.
>
> Basically, slew rate is a measure of how fast the output can move from
> one level to another. As long as the slew rate is high enough for the
> amplifier bandwidth and output level, it's fine.
>
> If the slew rate is not high enough, then the small signal bandwidth
> will be different than the bandwidth for large signals. Transients will
> not be reproduced properly. Things will sound "smeary." This is called
> "slew limiting."
>
> For the most part, slew rate isn't a very useful measure any more, except
> to reassure you that it's not too low. It's become like THD, which is
> a useful measure to compare similar amplifiers with high distortion
> levels,
> but which is no longer useful to compare modern amplifiers with low levels
> of distortion.
>
> But back in the seventies, when a _lot_ of equipment had severe slew rate
> limitations, it was a big deal.
> --scott




excisely!
Anonymous
August 29, 2005 6:12:47 PM

Archived from groups: rec.audio.pro (More info?)

Up to a point, yes.

After which it's really just marketing hype.

Acoustic soundwaves don't have infinitely fast transients, so as long as
you're system can track accurately while providing the desired gain (in the
case of a mic pre) you're good.

JP

"Harry Houdini" <harry@home.com> a écrit dans le message de
news:qas5h1dvke7cbsnu97hpa25of0llpvrcis@4ax.com...
> Trying to get a handle on this Slew Rate spec you often see published
> for higher-end mic pre's.
>
> Please correct me if I'm wrong, but from what I've read, it seems that
> a preamp with higher slew rate is more likely to capture transients
> better and hopefully render a more detailed soundstage. Is this true?
>
> Thanks for helping out.
>
> Harry
Anonymous
August 29, 2005 7:06:39 PM

Archived from groups: rec.audio.pro (More info?)

Harry Houdini wrote:

> Trying to get a handle on this Slew Rate spec you often see published
> for higher-end mic pre's.
>
> Please correct me if I'm wrong, but from what I've read, it seems that
> a preamp with higher slew rate is more likely to capture transients
> better and hopefully render a more detailed soundstage. Is this true?

Slew rate is the maximum rate that an op-amp ( or any type of amplifier )
can follow rapidly changing signals.

Since transients fall into the rapidly changing category, poor slew rate
might conceivably cause some trouble recreating them accurately.

In actual fact though, it's easy to do some calculations that'll show what
slew rate is needed to cover the audio band.

If you care to do the calculus it's possible to demonstrate that the
fastest change in signal for a sinewave is at the zero-crossing point and
equates to 2 x pi x freq x V pk. Since Fourier analysys shows that signals
can be represented by their sinewave compenents, let's do this for a large
magnitude high frequency signal. ( actually Fourier says this can be done
for *repetitive* signals but the method still holds true in a bandwidth
limited system ).

So a 10V pk ( 20V pk-pk ) signal at 20kHz results in a mximum rate of
change of voltage of ..

2 x pi x 20,000 x 10 = 1,256,637 Volts /sec or 1.25 Volts / usec.

This is higher than a '741 style' op-amp can manage with it's 0.5 V/usec
capability for example.

Most modern op-amps used for pro-audio have slew rates in the region of
10V/usec so can be seen to be free of any such limitation. It's a fairly
severe test doing this for say a 10V swing too.

OTOH - the op-amps behaviour at its slew rate limit is seriously 'pushing
it'.

I'm certainly happy with 10V/usec op-amps in the overall scheme of things.

Graham
Anonymous
August 29, 2005 7:27:52 PM

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

> "Scott Dorsey"
> >
> > Basically, slew rate is a measure of how fast the output can move from
> > one level to another.
>
> ** WRONG - that parameter is "rise time".

It *absolutely* isn't !

When slew limiting the amplifiers output will be a *triangle wave*. Go and see
for yourself.


Graham
Anonymous
August 29, 2005 8:11:33 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:CbydnRPaxewPhY7eRVn-3w@comcast.com...
> "nap" <gospam@yourself.com> wrote in message
> news:r5EQe.585$v83.283@newssvr33.news.prodigy.com
> > "Arny Krueger" <arnyk@hotpop.com> wrote in message
> > news:TqOdnVCP47HNYI_eRVn-oA@comcast.com...
> >> "Harry Houdini" <harry@home.com> wrote in message
> >> news:qas5h1dvke7cbsnu97hpa25of0llpvrcis@4ax.com
> >>
> >>> Trying to get a handle on this Slew Rate spec you often
> >>> see published for higher-end mic pre's.
> >>
> >> For the most part you can ignore them.
> >>
> >
> > Mainly becuse most electronics nowdays provides more than
> > adequate slew rates for audio.
>
> Always did, but with some notable exceptions at one time.
>
> >> Transients need to be quantified in terms of their size.
> >> It takes 10 times as much slew rate to handle a
> >> transient that is 10 times as large. So, specifications
> >> of slew rate are meaningless unless qualified by the
> >> size of the signal being processed.
>
> > IT usually specifies the supply rails.
>
> I'm quite unsure about that.


yes.. you're correct.. since most amps don't go rail to rail that would not
be an accurate statement..

I

nap




>
> >> A very, very large +22 dBu signal at 22 KHz has a slew
> >> rate of less than 1.3 volts per microsecond. Divide that
> >> by about 10 if
> >> you try to keep things under +4.
>
> >> If you've been reading slew rate specs, you know that
> >> 1.3 volts per microsecond is a number that seems
> >> ludicrously low.
>
> Note that +22 is about 13.8 volts peak, but audio gear that
> goes to +22 generally has VCC in the 18 volt and up range.
>
> >> Slew rate can be important if wide-band signals that are
> >> not strictly audio signals are involved. However, most
> >> good audio production gear includes features that limits
> >> its response to non-audible signals.
>
> IOW EMI can trigger slew rate limiting.
>
>
Anonymous
August 29, 2005 9:08:09 PM

Archived from groups: rec.audio.pro (More info?)

Arnie,

Would you care to go into a little more detail on how EMI triggers
slew rate limiting. Very interesting.

>IOW EMI can trigger slew rate limiting.
>
Anonymous
August 29, 2005 9:17:41 PM

Archived from groups: rec.audio.pro (More info?)

Cheers! - everyone - for taking the time to shed some light on the
subject of slew rates. I have a *much* better understanding of what's
going on.

As usual, RAP is a great place to be...



On Mon, 29 Aug 2005 07:40:07 -0400, Harry Houdini <harry@home.com>
wrote:

>Trying to get a handle on this Slew Rate spec you often see published
>for higher-end mic pre's.
>
>Please correct me if I'm wrong, but from what I've read, it seems that
>a preamp with higher slew rate is more likely to capture transients
>better and hopefully render a more detailed soundstage. Is this true?
>
>Thanks for helping out.
>
>Harry
Anonymous
August 29, 2005 9:45:02 PM

Archived from groups: rec.audio.pro (More info?)

"Harry Houdini" <harry@home.com> wrote in message
news:s7u6h19oroqpv05ebfk9mgssd8n5vm6thv@4ax.com
> Arnie,
>
> Would you care to go into a little more detail on how EMI
> triggers slew rate limiting. Very interesting.
>
>> IOW EMI can trigger slew rate limiting.

The maximum slew rate of a signal is 2*pi*signal
frequency*signal amplitude.

EMI can easily be be at a far higher frequency than normal
audio. Therefore it can have a higher maximum slewing rate.
Anonymous
August 29, 2005 10:10:53 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:TqOdnVCP47HNYI_eRVn-oA@comcast.com...

> A very, very large +22 dBu signal at 22 KHz has a slew rate
> of less than 1.3 volts per microsecond. Divide that by
> about 10 if you try to keep things under +4.
>
> If you've been reading slew rate specs, you know that 1.3
> volts per microsecond is a number that seems ludicrously
> low.
>
> Slew rate can be important if wide-band signals that are not
> strictly audio signals are involved. However, most good
> audio production gear includes features that limits its
> response to non-audible signals.

Part of the problem is that the term "slew rate" has a very specific meaning
in the world of electronics. It means the maximum rate of change of an
electronic circuit while the circuit is engaged in *slewing*. Slewing, in
turn, is a situation specific to feedback amplifiers where a stage is
putting out its maximum current charging a capacitor (usually, but not
always, a bandwidth-limiting capacitor designed to allow the amplifier to be
stable). When an amplifier is slewing, it's producing extremely high levels
of distortion for the duration of the slew. You can make an amplifier slew,
usually, by putting a wideband square wave into it and removing any
bandlimiting caps from the feedback network.

Unfortunately, the audio community has broadened the definition of "slew
rate" to also mean "rate of change in non-slewing situations". Hence you see
descriptions of transformers with high or low slew rates, and even
*speakers* with slew rates, which is, you'll excuse me, nonsense.

Now looking at real-world stuff. Arny's example is a +22dBu signal at 22kHz;
this has an actual rate of change of ~1.3V/usec. You don't want it to have a
*slew rate* of 1.3V/usec, because then it's slewing, and sounds horrible. So
you use a safety factor, typically about 8:1, and install a circuit with a
slew rate of 10.4V/usec. That's a wide enough margin that the amplifier
won't see a fast enough rise time to drive it into slewing, assuming
the -3dB bandwidth of the circuit (or something preceding it) is really
22kHz.

Note that, in Arny's example, +22dBu ~= 10Vrms, or about 13.8V peak
(assuming a sine wave). Matching this with an amplifier with a 10V/usec slew
rate is halfway between Walt Jung's liberal rule of thumb (min. slew rate in
V/usec = 0.5 x peak output in V) and his conservative rule of thumb (min.
slew rate in V/usec = peak output in V). Most of the circuits used for mic
preamps (integrated, discrete transistor, or tube) meet at least his liberal
criteria -- the lowest slew rate found in a chip used in pro gear is about
6V/usec (the 5532). With attention to bandlimiting in the feedback network
(see below) and careful design, that ought to be okay for any audio signal
you'll throw at it.

The ideal, of course, is an amplifier that cannot possibly slew, no matter
what signal you give it. That happens when the small-signal bandwidth is
less, by a safety margin, than the large-signal slew-limited bandwidth. You
get that by putting a cap in parallel with the feedback resistor of the
circuit, or by bandlimiting the signal ahead of the active circuitry, with
(say) a transformer. That not only prevents slewing from audio signals, but
also prevents slewing from other stuff, like RFI.

Peace,
Paul
Anonymous
August 30, 2005 1:05:07 AM

Archived from groups: rec.audio.pro (More info?)

Harry Houdini <harry@home.com> wrote:
>
>Would you care to go into a little more detail on how EMI triggers
>slew rate limiting. Very interesting.
>
>>IOW EMI can trigger slew rate limiting.

Whenever I play that recording of Carmen on EMI, the thing starts
mistracking like mad as soon as Rise Stevens starts singing about her
friend Lillas Pastia. Clearly a case of mechanical slew limiting.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 30, 2005 1:56:54 AM

Archived from groups: rec.audio.pro (More info?)

"Harry Houdini"
>
> Please correct me if I'm wrong, but from what I've read, it seems that
> a preamp with higher slew rate is more likely to capture transients
> better and hopefully render a more detailed soundstage. Is this true?


** No - it is basically massive fallacy.

Consumer fraud at its very worst.




........... Phil
Anonymous
August 30, 2005 3:23:45 AM

Archived from groups: rec.audio.pro (More info?)

On Mon, 29 Aug 2005 15:27:52 +0100, in rec.audio.pro Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>
>
>Phil Allison wrote:
>
>> "Scott Dorsey"
>> >
>> > Basically, slew rate is a measure of how fast the output can move from
>> > one level to another.
>>
>> ** WRONG - that parameter is "rise time".
>
>It *absolutely* isn't !
>
>When slew limiting the amplifiers output will be a *triangle wave*. Go and see
>for yourself.
>
>
>Graham
Risetime=digital
slew rate= audio



martin
Anonymous
August 30, 2005 3:23:46 AM

Archived from groups: rec.audio.pro (More info?)

On Mon, 29 Aug 2005 23:23:45 +0200, martin griffith
<martingriffith@XXyahoo.co.uk> wrote:

>Risetime=digital
>slew rate= audio

Another way to say it is that risetime is small-signal
and linear and slew rate is overload, beyond-large-signal,
and non-linear.

Chris Hornbeck
"What I love about Jean-Luc Godard is that he is honest, smart,
and has no humility." -butterfinger, reviewing _Pierrot le fou_, 1965
Anonymous
August 30, 2005 3:32:58 AM

Archived from groups: rec.audio.pro (More info?)

"nap"
> "Harry Houdini"
>>
>> Trying to get a handle on this Slew Rate spec you often see published
>> for higher-end mic pre's.
>>
>> Please correct me if I'm wrong, but from what I've read, it seems that
>> a preamp with higher slew rate is more likely to capture transients
>> better and hopefully render a more detailed soundstage. Is this true?
>
>
> yes. It is the amp's capability to reproduce 'transients' or the
> transition between two voltages.


** Absolutely FALSE !!!

That ability is fully quantified by the parameter " rise time " - a
direct function of bandwidth & HF roll off slope.





............ Phil
Anonymous
August 30, 2005 3:32:59 AM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:3ngh47F1dsfcU1@individual.net...
>
> "nap"
>> "Harry Houdini"
>>>
>>> Trying to get a handle on this Slew Rate spec you often see published
>>> for higher-end mic pre's.
>>>
>>> Please correct me if I'm wrong, but from what I've read, it seems that
>>> a preamp with higher slew rate is more likely to capture transients
>>> better and hopefully render a more detailed soundstage. Is this true?
>>
>>
>> yes. It is the amp's capability to reproduce 'transients' or the
>> transition between two voltages.
>
>
> ** Absolutely FALSE !!!
>
> That ability is fully quantified by the parameter " rise time " - a
> direct function of bandwidth & HF roll off slope.
>
>


from National:

"The slew rate limit is the maximum rate of change of the amplifier's
output voltage "

Slew rate is = dV/dT. Most definately affects the 'rise time '
specification.


So it is certainly not absolutely false as the slew rate affects the
transient response (rise time)


relax..











>
>
>
> ........... Phil
>
>
>
>
Anonymous
August 30, 2005 3:32:59 AM

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

> "nap"
> > "Harry Houdini"
> >>
> >> Trying to get a handle on this Slew Rate spec you often see published
> >> for higher-end mic pre's.
> >>
> >> Please correct me if I'm wrong, but from what I've read, it seems that
> >> a preamp with higher slew rate is more likely to capture transients
> >> better and hopefully render a more detailed soundstage. Is this true?
> >
> >
> > yes. It is the amp's capability to reproduce 'transients' or the
> > transition between two voltages.
>
> ** Absolutely FALSE !!!
>
> That ability is fully quantified by the parameter " rise time " - a
> direct function of bandwidth & HF roll off slope.

Rise time in a properly compensated amplifier will be the same regardless of
signal amplitude.

Slew rate is something else.

It's the *maximum rate* at which the output can swing regardless of other
conditions.

It's typically determined by the internal capacitance at a sensitive node
internal to the amplifier ( often the compensation cap ) and the maximum
current available to charge it negative or positive.

Indeed, positive and negative slew rates may be different.

Graham
Anonymous
August 30, 2005 3:33:00 AM

Archived from groups: rec.audio.pro (More info?)

nap wrote:

> "Phil Allison" <philallison@tpg.com.au> wrote in message
> news:3ngh47F1dsfcU1@individual.net...
> >
> > "nap"
> >> "Harry Houdini"
> >>>
> >>> Trying to get a handle on this Slew Rate spec you often see published
> >>> for higher-end mic pre's.
> >>>
> >>> Please correct me if I'm wrong, but from what I've read, it seems that
> >>> a preamp with higher slew rate is more likely to capture transients
> >>> better and hopefully render a more detailed soundstage. Is this true?
> >>
> >>
> >> yes. It is the amp's capability to reproduce 'transients' or the
> >> transition between two voltages.
> >
> >
> > ** Absolutely FALSE !!!
> >
> > That ability is fully quantified by the parameter " rise time " - a
> > direct function of bandwidth & HF roll off slope.
> >
> >
>
> from National:
>
> "The slew rate limit is the maximum rate of change of the amplifier's
> output voltage "
>
> Slew rate is = dV/dT. Most definately affects the 'rise time '
> specification.
>
> So it is certainly not absolutely false as the slew rate affects the
> transient response (rise time)
>
> relax..

Phil's wrong again.

He really ought to pay more attention.


Graham
Anonymous
August 30, 2005 4:29:27 AM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger wrote:
> "Harry Houdini" <harry@home.com> wrote in message
> news:s7u6h19oroqpv05ebfk9mgssd8n5vm6thv@4ax.com
>
>>Arnie,
>>
>>Would you care to go into a little more detail on how EMI
>>triggers slew rate limiting. Very interesting.
>>
>>
>>>IOW EMI can trigger slew rate limiting.
>
>
> The maximum slew rate of a signal is 2*pi*signal
> frequency*signal amplitude.

What is the steepest slope of the response of a baseband
limited transfer function to a step function input? Can't
remember for sure.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Anonymous
August 30, 2005 4:37:18 AM

Archived from groups: rec.audio.pro (More info?)

Graham Stevenon


** You are pure evil.

Go get bowel cancer.





............ Phil
Anonymous
August 30, 2005 4:37:19 AM

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

> Graham Stevenon
>
> ** You are pure evil.
>
> Go get bowel cancer.

*translation*

I ought to think before posting nonsense.

I'll go put my head in a vat of dingo's kidneys.


Phil the tech boy
Anonymous
August 30, 2005 4:37:20 AM

Archived from groups: rec.audio.pro (More info?)

On 8/29/05 11:12 AM, in article 431325C3.DF57D581@hotmail.com, "Pooh Bear"
<rabbitsfriendsandrelations@hotmail.com> wrote:

>
>
> Phil Allison wrote:
>
>> Graham Stevenon
>>
>> ** You are pure evil.
>>
>> Go get bowel cancer.
>
> *translation*
>
> I ought to think before posting nonsense.
>
> I'll go put my head in a vat of dingo's kidneys.


"...Vat Of Dingo Kidneys"...???????!!??

I haven;t seen this many inventive out-there curses since reading the
Captain Haddock collection.
Anonymous
August 30, 2005 4:37:21 AM

Archived from groups: rec.audio.pro (More info?)

On Mon, 29 Aug 2005 23:09:38 GMT, SSJVCmag <ten@nozirev.gamnocssj.com>
wrote:

>I haven;t seen this many inventive out-there curses since reading the
>Captain Haddock collection.

**He told me to go to Hell and to stay there. I'm
profoundly grateful. But not yet dead.

Very funny stuff overall. There'll probably be a
fan website someday.

Chris Hornbeck
Anonymous
August 30, 2005 4:38:47 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear wrote:

> If you care to do the calculus it's possible to demonstrate that the
> fastest change in signal for a sinewave is at the zero-crossing point and
> equates to 2 x pi x freq x V pk.

Yes, but what is it for a signal that is a band limited step
function instead of a sinusoid?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Anonymous
August 30, 2005 4:43:24 AM

Archived from groups: rec.audio.pro (More info?)

SSJVCmag wrote:

> On 8/29/05 11:12 AM, in article 431325C3.DF57D581@hotmail.com, "Pooh Bear"
> <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>
> > Phil Allison wrote:
> >
> >> Graham Stevenon
> >>
> >> ** You are pure evil.
> >>
> >> Go get bowel cancer.
> >
> > *translation*
> >
> > I ought to think before posting nonsense.
> >
> > I'll go put my head in a vat of dingo's kidneys.
>
> "...Vat Of Dingo Kidneys"...???????!!??
>
> I haven;t seen this many inventive out-there curses since reading the
> Captain Haddock collection.

I can't claim to be entirely original. The "dingo's kidney's" means 'nonsense'
and originated in the Hitch Hiker's Guide to the Galaxy.

http://www.globusz.com/ebooks/Hitchhikers/00000017.htm

See the discussion about the proof or otherwise for the existance of God about
1/2 way through.

Dingos are also an Australian wild dog - which makes this a suitable term for
use in P.A.'s case.

I made up the bit about the vat.


Graham
Anonymous
August 30, 2005 4:49:04 AM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck wrote:

> On Mon, 29 Aug 2005 23:23:45 +0200, martin griffith
> <martingriffith@XXyahoo.co.uk> wrote:
>
> >Risetime=digital
> >slew rate= audio
>
> Another way to say it is that risetime is small-signal
> and linear and slew rate is overload, beyond-large-signal,
> and non-linear.

Very true. I'm not sure I made it clear enough that slewing only occurs in
an 'overload' situation.

That 'overload' could be provoked by applying a step impulse to a gain
stage too. In such a case the amplifier output will slew towards the
required voltage before settling.

This illustrates nicely that square wave testing of audio equipment is not
entirely sensible. Any test signal should not exceed the bandwidth of the
device under test.


Graham
Anonymous
August 30, 2005 4:49:05 AM

Archived from groups: rec.audio.pro (More info?)

On Tue, 30 Aug 2005 00:49:04 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

> I'm not sure I made it clear enough that slewing only occurs in
>an 'overload' situation.
>
>That 'overload' could be provoked by applying a step impulse to a gain
>stage too. In such a case the amplifier output will slew towards the
>required voltage before settling.
>
>This illustrates nicely that square wave testing of audio equipment is not
>entirely sensible. Any test signal should not exceed the bandwidth of the
>device under test.

After this summer's Kevin Phenomenon very little remains
left to be said on the mic preamp topic...

Ha! Had you going there for a second didn't I?

Seriously, your test signal suggestion makes very
good sense to me. Maybe a useful number would be
the bandwidth *itself* of a theoretical input bandwidth
limiting below which the tested device would be some
defined (maybe the usual factor of 8 or 10) amount
below slewing.

Thanks, as always, for your thoughts,

Chris Hornbeck
Anonymous
August 30, 2005 5:34:36 AM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck wrote:

> On Mon, 29 Aug 2005 23:09:38 GMT, SSJVCmag <ten@nozirev.gamnocssj.com>
> wrote:
>
> >I haven;t seen this many inventive out-there curses since reading the
> >Captain Haddock collection.
>
> **He told me to go to Hell and to stay there. I'm
> profoundly grateful. But not yet dead.
>
> Very funny stuff overall. There'll probably be a
> fan website someday.

Don't give me ideas ! ;-)

Graham
Anonymous
August 30, 2005 7:54:14 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Harry Houdini wrote:

> >Would you care to go into a little more detail on how EMI triggers
> >slew rate limiting. Very interesting.

> >>IOW EMI can trigger slew rate limiting.

> Whenever I play that recording of Carmen on EMI, the thing starts
> mistracking like mad as soon as Rise Stevens starts singing about her
> friend Lillas Pastia. Clearly a case of mechanical slew limiting.

Clearly, you've been taking way too much EMI. Back off a little...

--
ha
Anonymous
August 30, 2005 8:09:07 AM

Archived from groups: rec.audio.pro (More info?)

On Tue, 30 Aug 2005 03:54:14 GMT, walkinay@thegrid.net (hank alrich)
wrote:

>Scott Dorsey wrote:
>> Whenever I play that recording of Carmen on EMI, the thing starts
>> mistracking like mad as soon as Rise Stevens starts singing about her
>> friend Lillas Pastia. Clearly a case of mechanical slew limiting.
>
>Clearly, you've been taking way too much EMI. Back off a little...

Or maybe that's just Scott's EMI quantum level comment on the music
warping the local field, or something.

Besides, there's no keeping that boy away from his EMI. We all
tried. He's just incorrectible.

Sad really,

Chris Hornbeck
Anonymous
August 30, 2005 10:32:56 AM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in message news:43139EF0.DCD92BBF@hotmail.com

> This illustrates nicely that square wave testing of audio
> equipment is not entirely sensible.

I agree with that, but on different grounds.

>Any test signal
> should not exceed the bandwidth of the device under test.

Huh?

If a signal exists in the typical use then it is fair game
to use it or something like it for testing.

Good equipment typically has bandwidth limiting in or around
the input stage to make it difficult or impossible to
overload.
Anonymous
August 30, 2005 10:51:25 AM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:43139EF0.DCD92BBF@hotmail.com...

> That 'overload' could be provoked by applying a step impulse to a gain
> stage too. In such a case the amplifier output will slew towards the
> required voltage before settling.
>
> This illustrates nicely that square wave testing of audio equipment is not
> entirely sensible. Any test signal should not exceed the bandwidth of the
> device under test.

Why not? If the device stands a chance of being exposed to wideband signals,
a square wave is a great way to find out whether it will react sensibly
(bandwidth-limited at all levels) or badly (slew-limited at high levels).

Peace,
Paul
Anonymous
August 30, 2005 12:49:09 PM

Archived from groups: rec.audio.pro (More info?)

On Tue, 30 Aug 2005 00:29:27 -0700, Bob Cain wrote:

> Arny Krueger wrote:
>> "Harry Houdini" <harry@home.com> wrote in message
>> news:s7u6h19oroqpv05ebfk9mgssd8n5vm6thv@4ax.com
>>
>>>Arnie,
>>>
>>>Would you care to go into a little more detail on how EMI
>>>triggers slew rate limiting. Very interesting.
>>>
>>>
>>>>IOW EMI can trigger slew rate limiting.
>>
>>
>> The maximum slew rate of a signal is 2*pi*signal
>> frequency*signal amplitude.
>
> What is the steepest slope of the response of a baseband
> limited transfer function to a step function input? Can't
> remember for sure.
>
>
> Bob

It doesn't have one. A band limited circuit has a step response slope that
is proportional to amplitude - hence it is theoretically unlimited. A slew
rate limited circuit, on the other hand, is limited.

d
Anonymous
August 30, 2005 3:56:45 PM

Archived from groups: rec.audio.pro (More info?)

Graham Stevenson


** YOU are a mental retard and an autistic moron.

YOU are a monstrous liar and raving lunatic.

YOU are a notorious usenet stalker and harasser.






.......... Phil
Anonymous
August 30, 2005 3:56:46 PM

Archived from groups: rec.audio.pro (More info?)

On 8/29/05 9:56 PM, in article 3nhsmqF1ka9gU1@individual.net, "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>
>
> Graham Stevenson
>
>
> ** YOU are a mental retard and an autistic moron.
>
> YOU are a monstrous liar and raving lunatic.
>
> YOU are a notorious usenet stalker and harasser.

Ladies and Gentlemen.
Please don;t tap on the glass as we move past the Mysterious Phil Exhibit.
For a long time now, nobody has been able to discern where the voices that
Mr Allison's answering are coming from. Some say he has vision and hearing
beyond the limits of the rest of us and is tormented by what we might only
imagine as 'spirits'. Others say he lives in several dimensions at once and
is aware of us AND those in the Other Plane and carries on several
conversation simultaneously. Whatever the explanation, the unpredictability
and seeming lack of discernment between both Planes makes for some pretty
fascinating watching wouldn;t you say!

Let's move on now to the Hall Of Living Arms.
This was original shown (and believed to be a cinematic trick) in the
original French version of BEAUTY AND THE BEAST. However we were able to
purchase it at auction f.r a v.ry r..s.nable c.st... Pl.as. Don.t .tand t..
Cl.se.a.s.........
Anonymous
August 30, 2005 3:56:46 PM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:3nhsmqF1ka9gU1@individual.net
> Graham Stevenson
>
>
> ** YOU are a mental retard and an autistic moron.
>
> YOU are a monstrous liar and raving lunatic.
>
> YOU are a notorious usenet stalker and harasser.

He's a heck of a nice guy compared to Phildo. ;-)
Anonymous
August 30, 2005 3:56:47 PM

Archived from groups: rec.audio.pro (More info?)

On Tue, 30 Aug 2005 03:10:01 GMT, SSJVCmag <ten@nozirev.gamnocssj.com>
wrote:

>Let's move on now to the Hall Of Living Arms.
>This was original shown (and believed to be a cinematic trick) in the
>original French version of BEAUTY AND THE BEAST.

Too, too great (sorry; don't know how to say it in French).
The 1946 Cocteau original sets a standard for both beauty
and technical trickery still seldom approached.

This summer's _War of the Worlds_ was, comparatively,
pathetic.

An accessible and too-too-fun approach is to study the
finale "ascension" of the beauty-beast pair. Run it in
reverse to understand the dynamics. Beautiful, beautiful
work.

And, no computers needed apply.

Chris Hornbeck
Anonymous
August 30, 2005 4:00:20 PM

Archived from groups: rec.audio.pro (More info?)

"Harry Houdini"
> Cheers! - everyone - for taking the time to shed some light on the
> subject of slew rates. I have a *much* better understanding of what's
> going on.


** No you do not - you PITA troll.




............ Phil
Anonymous
August 30, 2005 4:07:41 PM

Archived from groups: rec.audio.pro (More info?)

Graham Stevenson

> Don't give me ideas !


** YOU never had a single idea in you life you did not steal from someone.

YOU are a fake, a liar and a damn charlatan.

YOU are a piece of sub human garbage.







............ Phil
Anonymous
August 30, 2005 4:19:12 PM

Archived from groups: rec.audio.pro (More info?)

Don Pearce wrote:
> On Tue, 30 Aug 2005 00:29:27 -0700, Bob Cain wrote:
>
>>Arny Krueger wrote:
>>
>>>The maximum slew rate of a signal is 2*pi*signal
>>>frequency*signal amplitude.
>>
>>What is the steepest slope of the response of a baseband
>>limited transfer function to a step function input? Can't
>>remember for sure.
>>
> It doesn't have one. A band limited circuit has a step response slope that
> is proportional to amplitude - hence it is theoretically unlimited. A slew
> rate limited circuit, on the other hand, is limited.

Right, so the slew rate requirement for transient inputs
can't be estimated by the max slope of steady state, HF
sinusoids. Isn't it is higher than the latter would indicate?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Anonymous
August 30, 2005 5:27:32 PM

Archived from groups: rec.audio.pro (More info?)

On 8/29/05 11:40 PM, in article 84k7h1113j2td7kvp8g6m9rqh8c2inuuf0@4ax.com,
"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote:

> On Tue, 30 Aug 2005 03:10:01 GMT, SSJVCmag <ten@nozirev.gamnocssj.com>
> wrote:
>
>> Let's move on now to the Hall Of Living Arms.
>> This was original shown (and believed to be a cinematic trick) in the
>> original French version of BEAUTY AND THE BEAST.
>
> Too, too great (sorry; don't know how to say it in French).

"manifique!" will do merci.
Though I must toss major stylistic-emulation kudos to Harlan Ellison on
that.

> The 1946 Cocteau original sets a standard for both beauty
> and technical trickery still seldom approached.
>
> This summer's _War of the Worlds_ was, comparatively,
> pathetic.

Gilliam is the only director that even TRIES for this level of
art-in-production. He's clumsy by comparison but STILL achieves truly
wonderous things more often than not. MUNCHAUSEN is still a wonder and a
treat. Did you see WHAT DREAMS MAY COME in a THEATER? Jaw dropping stuff in
there.. Like 2001, it doesn;t/can;t work on video.


>
> An accessible and too-too-fun approach is to study the
> finale "ascension" of the beauty-beast pair. Run it in
> reverse to understand the dynamics. Beautiful, beautiful
> work.
>
> And, no computers needed apply.

And again, there's David Lynch...
Anonymous
August 30, 2005 6:14:17 PM

Archived from groups: rec.audio.pro (More info?)

Paul Stamler wrote:

> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:43139EF0.DCD92BBF@hotmail.com...
>
> > That 'overload' could be provoked by applying a step impulse to a gain
> > stage too. In such a case the amplifier output will slew towards the
> > required voltage before settling.
> >
> > This illustrates nicely that square wave testing of audio equipment is not
> > entirely sensible. Any test signal should not exceed the bandwidth of the
> > device under test.
>
> Why not? If the device stands a chance of being exposed to wideband signals,
> a square wave is a great way to find out whether it will react sensibly
> (bandwidth-limited at all levels) or badly (slew-limited at high levels).

Actually, you ask the relevant question I had just been musing over. Namely what
actual inputs might a gain stage see ( 'worst' case ) ?

I doubt that any moving coil mic would present a challenge but I'd be interested
to know what kind of impulse response a condensor mic might provide when say
miking a snare drum.

Any ideas anyone ? Of course once the signal's been through the record -
reproduce train it'll be limited to the system bandwidth anyway but I'd be
curious to know about how it starts off.

Anyone have the kit to digitize such a signal and perform a Fourier analysis ?

Graham
Anonymous
August 30, 2005 6:14:18 PM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote
in message news:43145BA9.CB8A84B7@hotmail.com

> Anyone have the kit to digitize such a signal and perform
> a Fourier analysis ?

Having digitized a lot of stuff with a high-bandwidth system
(well high bandwidth compared to regular studio gear), the
bandwidth champs aren't snare drums, but stuff like
keychains, triangles, tambourines, etc.

Here's some pretty pictures:

http://www.pcabx.com/technical/sample_rates/index.htm

Here's somebody else's pretty pictures:

http://www.cco.caltech.edu/~boyk/spectra/spectra.htm
!