Amplifier power
 

In article
,
wrote:

Jim Lesurf wrote:

It would depend on various factors: What kind of music you like. How
large your listening room is. What speakers you will be using. etc.


Classical music - not excessively loudly but of course orchestral
climaxes can be loud. Digital sources - not vinyl. Room 11' x 13' x 8'
high (rather small probably for the speakers Focal JMLab Chorus 714V
Power handling 130W max (90W nom) Sensitivity 91dB)

... or just to start an argument. :-)

I've been thinking I'd like to "upgrade" my 20yr old Audiolab 8000A
(50W) in the near future. I was thinking of spending up to £1000 but if
I don't need to spend that much I won't.

I have the feeling that there is no specific *audible* reasons for your
feeling that you should "upgrade". If this is so, my reaction is to
continue to use what you have and spend the money on something else. e.g.
loads more CDs, or LPs, or whatever music you favour. Enjoy the music, not
the equipment-ownership. :-)

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

Amplifier power
 

In article
,
wrote:
On Oct 13, 9:10 am, Jim Lesurf wrote:

And even if they do, the trouble with listening in shops is that the
listening room is very different from where I will be using the
amplifier.

Indeed. However that is a vastly harder problem when choosing speakers
than amplifiers. And you seem to have chosen your speakers, so this
can't be impossibly difficult. :-)

Well, the room in which I compared the speakers was quite a bit bigger
than my actual listening room (11'x13'x8') so I'm not sure really
whether I chose the best of the three I compared. They are probably too
big for my room but then I don't need to have them very loud to "fill"
it.

This is the difficulty with comparing in shops.

Yes. And it tends to matter far less when choosing an amplifier than
speakers. If in doubt, make sure they have a larger room than yours, and
try to get them to play the amp with speakers that have a lower efficiency
and lower impedance. This will make it likely the amp has enough power for
you if OK in the shop.

However if your audiolab seems to you not to clip or overheat I doubt you
will have a problem with most other = 50Wpc amps in terms of power unless
your speakers drop to low impedance. The 8000 series tends to have pokey
small heatsinks[1], but can IIRC deliver reasonably high peak currents.

Above said, I haven't yet seen you say anything that makes me feel you
would benefit from a new amp. Except perhaps in the way of feeling pleased
to own and use a newer and - allegedly - 'better' one.

Slainte,

Jim

[1] The 8000A I have in bits has heatsinks smaller than my old Armstrong
626s. Both designs have tiny heatsinks by 'super fi' standards. (Although
the 8000 disguises this by hiding them inside the box.) Yet generally they
work fine for classical or other acoustic and uncompressed music without
overheating.

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Amplifier power
 

In article , Eeyore
wrote:


wrote:

Jim Lesurf wrote:

It would depend on various factors: What kind of music you like. How
large your listening room is. What speakers you will be using. etc.

Classical music - not excessively loudly but of course orchestral
climaxes can be loud. Digital sources - not vinyl. Room 11' x 13' x 8'
high (rather small probably for the speakers Focal JMLab Chorus 714V
Power handling 130W max (90W nom) Sensitivity 91dB)

An orchestra even in the auditorium can peak at over 120dB.

To recreate that with 90 odd dB sensitivity speakers requires a 1kW / ch
amp.

Probably true if you listen outdoors. :-)

That's why decent studios have such things. Probably about 6 of
them for 5.1 sound.

Do studios routinely use speakers with a 90dB sensitivity? Afraid I don't
know much about that area, but assumed they used speakers of types that
would be less sensitive. Also that their room acoustics and normal levels
different to most domestic replay.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Amplifier power
 

In article , Eeyore rabbitsfriendsandrela
scribeth thus


tony sayer wrote:

I reckon you'd be well pushed to improve of the Audiolab excellent
amplifier even at 20 years old:))..

You must be living in a very weird world then. Its design is utterly
'agricultural' by today's standards. It's barely any better than a decent
semiconductor manufacturer's application note of that era. Frankly it's a joke.
Plus any one you can find will need total re-capping of the electrolytics.

Graham (pro-audio designer with 37 yrs experience)


Bet you'd be hard pressed to tell one apart in a listening test!..

No perhaps not.. their prolly too neutral for your linking;!...
--
Tony Sayer

Amplifier power
 

Jim Lesurf wrote:

wrote:
On 14 Oct, 00:40, Eeyore wrote:
John Phillips wrote:
Eeyore wrote:
wrote:

An orchestra even in the auditorium can peak at over 120dB.

Do you have a reference for this? I have been looking for credible
sources for peak orchestral SPLs in the auditorium for a long while.

It's a 'well known fact' amongst audio professionals. Google it.

For some reason I have come to be wary of claims thrown around on the basis
of being a "well known fact".

It was actually intentionally slightly tongue in cheek, but remeber I am
referring to PEAK levels not average levels which dB meters read.


That sometimes seems to mean, "Loads of
people have been saying it to one another on the basis that someone else
told them. They've been doing this for so long that no-one can recall who
made it up in the first place." :-)

See above.


In other words completely useless because they haven't the tiniest
clue what they're measuring. Thankfully or even orchestras would have
to be banned from playing for HSE reasons.

However I have only semi-credible figures for places in the
auditorium and they only go up to 109 dB SPL.

IIRC I read an old article by John Crabbe a while ago that reported
measurements. I can't recall details, but if I do I'll report them.

Clearly then, you'll know that having two speakers increases the nominal
sensitivity by 3dB for a central sound, and having them in an average
living room gives you another 3dB or so of reverberant sound, so you can
hit a 120dB peak from 91 db/watt speakers with about 23dB of amp power,
which is 200 watts. Not trivial, but readily obtainable from many modern
amps.

FWIW The effect of room reverb in UK domestic rooms might be somewhat
higher than a 3dB gain. I did some analysis of this a while ago (see Hi Fi
News August 2008). Hard to give a figure as it will probably vary from room
to room, but 3dB may be on the low side as an estimate of what is typical.
IIRC some texts also give details that indicate well above 3dB for this.

3dB relative to WHAT ? Are you familiar with nearfield and farfield
measurements ?


That said (again as discussed in the HFN article) there is a distinction
between the actual instantaneous peak measured power, and the peak level
perceived, due to the way human hearing tends to 'integrate' the effect of
short term delayed reflections into one percieved peak.

Quite. It's not simple.

Graham

Amplifier power
 

tony sayer wrote:

Eeyore scribeth thus
tony sayer wrote:

I reckon you'd be well pushed to improve of the Audiolab excellent
amplifier even at 20 years old:))..

You must be living in a very weird world then. Its design is utterly
'agricultural' by today's standards. It's barely any better than a decent
semiconductor manufacturer's application note of that era. Frankly it's a joke.
Plus any one you can find will need total re-capping of the electrolytics.

Graham (pro-audio designer with 37 yrs experience)

Bet you'd be hard pressed to tell one apart in a listening test!..

No perhaps not.. their prolly too neutral for your linking;!...

If you want neutral you need one of my ultra-performance mosfet designs. The actual
'amp block' has a THD+N of 0.0008% @ 1 kHz (SINAD -103dB) measured on an AP with a
residual THD+N of 0.0007% ! The 'back calculates' to a true THD of 0.0004% (SINAD
-108dB). The response is VERY flat too. About -0.2dB @ 10 Hz and 20kHz IIRC.

Oh and I designed it about 19 years ago.

Sadly, the figure is degraded by the op-amp front end (5532s) ! But I could replace
these with LME49720s instead.

Graham

Amplifier power
 

Jim Lesurf wrote:

wrote:
On 14 Oct, 00:40, Eeyore wrote:
John Phillips wrote:
Eeyore wrote:
wrote:

An orchestra even in the auditorium can peak at over 120dB.

Do you have a reference for this? I have been looking for credible
sources for peak orchestral SPLs in the auditorium for a long while.

It's a 'well known fact' amongst audio professionals. Google it.

For some reason I have come to be wary of claims thrown around on the basis
of being a "well known fact".

http://www.musicalfidelity.com/produ..._response.html

" We know for a fact that concert hall peak sound pressure level (SPL) for a
medium sized symphony orchestra is 109-110dB. For a big symphony orchestra or
rock concert the levels are much higher."

And the nearer you sit !

Graham

Amplifier power
 

Jim Lesurf wrote:

Eeyore wrote:
wrote:
Jim Lesurf wrote:

It would depend on various factors: What kind of music you like. How
large your listening room is. What speakers you will be using. etc.

Classical music - not excessively loudly but of course orchestral
climaxes can be loud. Digital sources - not vinyl. Room 11' x 13' x 8'
high (rather small probably for the speakers Focal JMLab Chorus 714V
Power handling 130W max (90W nom) Sensitivity 91dB)

An orchestra even in the auditorium can peak at over 120dB.

To recreate that with 90 odd dB sensitivity speakers requires a 1kW / ch
amp.

Probably true if you listen outdoors. :-)

That's why decent studios have such things. Probably about 6 of
them for 5.1 sound.

Do studios routinely use speakers with a 90dB sensitivity? Afraid I don't
know much about that area, but assumed they used speakers of types that
would be less sensitive. Also that their room acoustics and normal levels
different to most domestic replay.

Check out the big ATCs. Virtually THE standard.
http://www.atc.gb.net/downloads/PRO_P18-19.pdf

It's active but see the amp specs and the max SPL of 121dB. I know studios with
6 of these in a control room.

Graham

Amplifier power
 

In article , Eeyore
wrote:


Jim Lesurf wrote:

wrote:
On 14 Oct, 00:40, Eeyore
wrote:

It's a 'well known fact' amongst audio professionals. Google it.

For some reason I have come to be wary of claims thrown around on the
basis of being a "well known fact".

It was actually intentionally slightly tongue in cheek, but remeber I am
referring to PEAK levels not average levels which dB meters read.

I was aware of that. For all I know, the claim is quite accurate. But the
problem is the one I described.


That sometimes seems to mean, "Loads of people have been saying it to
one another on the basis that someone else told them. They've been
doing this for so long that no-one can recall who made it up in the
first place." :-)

See above.

See above. :-)



Clearly then, you'll know that having two speakers increases the
nominal sensitivity by 3dB for a central sound, and having them in
an average living room gives you another 3dB or so of reverberant
sound, so you can hit a 120dB peak from 91 db/watt speakers with
about 23dB of amp power, which is 200 watts. Not trivial, but
readily obtainable from many modern amps.

FWIW The effect of room reverb in UK domestic rooms might be somewhat
higher than a 3dB gain. I did some analysis of this a while ago (see
Hi Fi News August 2008). Hard to give a figure as it will probably
vary from room to room, but 3dB may be on the low side as an estimate
of what is typical. IIRC some texts also give details that indicate
well above 3dB for this.

3dB relative to WHAT ?

If you look at what Stewart wrote (Hi, Stewart! :-) ) that seems to be
comparing the effect of the room reverb with a situation where such reverb
would be absent. At least that is my understanding of his saying,
"...having them in an average living room gives you another 3dB or so of
reverberant sound..." If that is wrong, I'm sure he will correct me, but
that was what I then was referring to. Sorry if you didn't follow what I
wrote.


Are you familiar with nearfield and farfield measurements ?

Yes - although you haven't said which particular mechanisms you have in
mind for the factor(s) which affect how they differ, so I don't know which
one(s) you have in mind. Have you read the article I referred to?


That said (again as discussed in the HFN article) there is a
distinction between the actual instantaneous peak measured power, and
the peak level perceived, due to the way human hearing tends to
'integrate' the effect of short term delayed reflections into one
percieved peak.

Quite. It's not simple.

That was indeed, part of my point. :-)

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Amplifier power
 

In article , Eeyore
wrote:


Jim Lesurf wrote:

For some reason I have come to be wary of claims thrown around on the
basis of being a "well known fact".

http://www.musicalfidelity.com/produ..._response.html

" We know for a fact that concert hall peak sound pressure level (SPL)
for a medium sized symphony orchestra is 109-110dB. For a big symphony
orchestra or rock concert the levels are much higher."

Interesting that he seems able to narrow down all orchestras to a 1dB range
like that. Reminiscent of the way undergrads sometimes write down a lab
experiment result to as many significant figures as their hand calculator
displays - regardless of having input figures only roughly accurate. :-)

I also still have my natty copy of the 'sliderule' he had sent out with one
issue of HFN. This seems to imply I should change to a more powerful amp. I
confess seeing this was one of the things that prompted my curiosity and
lead to the HFN article I mentioned. Like yourself, I suspect, I've spent
far more hours than any sane person should watching a scope display, etc,
of power amp output whilst playing music to see what demands the music
waveforms place on the amp and speakers.

My personal conclusion was that his sliderule rather over-egged how much
amplifier power I'd need for my domestic use. However my listening room is
somewhat smaller than the Royal Festival Hall... ;-

As I wrote, it seems common for people to make assertions on the basis of
"we know that", or "everyone knows that". But alas making such a claim does
not automatically make an assertion true. Of course, that doesn't make it
false, either.

And the nearer you sit !

....although of course since you mentioned nearfield versus farfield in
another posting you will doubtless be aware that this does not always
follow the 1/r^2 law you might expect from school physics books. :-)

Like John Phillips I've seen assertions about this on many occasions.
However also like him, I can't recall seeing reliable peak measurement
values. Although I do recall reading recently the old article by JC I can't
currently remember which back-issue this was, or what values her got.

The peaks may well reach 120dB [1], that seems quite possible to me. But
plausible assumptions or assertions aren't actually measured results. As I
explained, I've seen all kinds of claims made by people on the "everyone
knows" basis, and have become wary of simply believing everything I'm told.
Up to you what you believe, but I'd prefer evidence when possible.

Slainte,

Jim


[1] You might apply your own "reference what?" question here, BTW. :-)

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html