Amplifier power
 

In article , Eeyore rabbitsfriendsandrel
scribeth thus


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


Humm...

I Wonder how may pro recording bits of gear are around with 5532's;)..


--
Tony Sayer

Amplifier power
 

In article , Eeyore
wrote:


Jim Lesurf wrote:

Eeyore wrote:


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.

For the above to answer the actual question I asked, you would have to be
saying that the above comprises a "90 odd dB" sensitivity speaker with a
1 kW amp. Is that what you were saying? From the specs, I suspect not.

The ATC seems to have four amps, each connected to an individual drive
unit. The amp powers do total a nominal 850W, but this arrangement doesn't
seem to be what you were referring to above. The way you used "90 odd dB
sensitivity", etc, seem to presume a speaker driven by a single amp and
with an nominal '1W 8 Ohms' as the sensitivity ref. Or did you mean
something other than the common way of quoting sensitivities used for
passive domestic speakers? You seem to be mixing apples with oranges
here.

Also, the above seems to be 121dB SPL. I thought at an earlier point
we discussing peaks - i.e. not time-averaged levels. Were you saying that
orchestras deliver 'peaks' with a short-term level of 120dB, or that
the instantaneous peak is 120dB? The MF document you quoted was claiming
levels of 109-110dB SPL and I assumed that was time-averaged from the use
of 'SPL'.

So there does seem to be some ambiguity in the figures being claimed
or asserted.

I appreciate, though, that the ATC should be able to wake you up if
placed just 1m from your ear. Would make an impressive bedside
alarm radio. :-)


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
 

Jim Lesurf wrote:

Eeyore wrote:
Jim Lesurf wrote:

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.

It's certainly true that a domestic room will have a far or ambient field that
is greater than an anechoic chanber. Ever been in one btw ? They're really odd.

But then again does one listen to one's speakers at 1 metre distance usually ?
so the SPL will have dropped off by X dB anyway by the time it reaches the
sofa.


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?

Don't need to. In the near field, SPL will drop off at a rate of 6dB per
doubling of distance (inverse square law). In the far field it's anyone's guess
due to all the factors previously mentioned. Where the far field begins depends
the size of your room and those other factors.


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. :-)

Ok.

Graham

Amplifier power
 

Jim Lesurf wrote:

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. :-)

Seems to be tricky to find anything actually.

This mic has a max input SPL of 134dB which receives the comment "Hi-SPL
handling is perfect for suspension over choirs and orchestras"

http://www.dv247.com/invt/11582/

Graham

Amplifier power
 

tony sayer wrote:

Eeyore scribeth thus
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% ! That '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.

Humm...

I Wonder how may pro recording bits of gear are around with 5532's;)..

Just about most of it in current use.

Did you check the spec of the LME49720 ?
http://www.national.com/pf/LM/LME49720.html

They had to devise a special method to measure the THD without the noise dominating.
They're not even that shockingly expensive.

Graham

Amplifier power
 

Eeyore writes:

Rob wrote:

I have a 20 year old (at least) NAD 3020 - works perfectly but sounds
distinctly soft/mellow compared to a newish SS amp, and indeed an even
older Pioneer receiver. Is this a symptom of old caps, and/or poor design?

I know the 3020 moderately well. It was very well regarded (and designed - I fact I
met the designer) and should still sound at least decent today. At that age,
recapping the electrolytic caps specifically is likely to be a good move.
Especially if you're competent with a soldering iron yourself or have a friend who
is. The parts won't cost much.

So true.

Some ten years ago I did this to a ten plus but not quite twenty years
old amp (not NAD) and the improvement was a jaw dropper.

--
Martin Schöön "Problems worthy of attack
show their worth by hitting back."
Piet Hein

Amplifier power
 

Jim Lesurf wrote:
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.

Well the phono sockets needed replacing 18 months ago - I'd like an
amp with sockets which don't self destruct.

Phileas

Amplifier power
 

On 2008-10-13, Eeyore wrote:


John Phillips 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.

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.

I have indeed Googled it rather extensively. What I mostly see is
unsupported assertion that seems to have been copied without question
from unsupported sources. I have seen no good, well-documented evidence.
This is why I am interested in asking.

I have quite a few health & safety measurements of very good credibility
inside the orchestra and a few at the conductor's rostrum.

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.

You have it quite wrong. The H&S reports (typically for North American
orchestras) are not always perfect but they usually are good enough
at specifying the instrument and what it was set to measure. On the
credibility scale they rate generally well. I am happy to accept peak
levels inside the orchestra well on the eye-watering side of 130 dB SPL.

However while these are good enough measurements for checking musicians'
exposure to sound, they don't give the positional data for source and
measurement to allow projection to levels in the auditorium.

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

A or C weighted on fast or slow response ? The average dB meter is about as useful
as a wet blanket when measuring either impulses or frankly most music. There is no
correlation between industrial hearing damage levels as measured by a typical dB
meter and music because the waveforms and wavefronts are WILDLY different.

Good questions - these are exactly why I am not happy with the
"semi-credible" source in question. BTW this particular source was the
one Musical Fidelity used in the advertising that's been brought up later
in this thread. And used by HFN in its fairly recent "how much power do
you need" articles.

So, at the risk of giving offence I am afraid I am still not prepared to
assign any credibility to unsupported assertions of "well known fact".
For exactly the reasons you state. That's why I am still interested in
seeking credible, well supported data.

--
John Phillips

Amplifier power
 

On 2008-10-14, Jim Lesurf wrote:
In article , Eeyore
wrote:


Jim Lesurf wrote:

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.

Some time ago John Crabbe reported published work in which listeners'
perception of the same absolute loudness was rather different when they
were listening in a large concert hall compared to a domestic listening
room. This would suggest you do indeed need less in SPL terms at home
than you get in the auditorium.

--
John Phillips

Amplifier power
 

Martin Schöön wrote:
Eeyore writes:

Rob wrote:
I have a 20 year old (at least) NAD 3020 - works perfectly but sounds
distinctly soft/mellow compared to a newish SS amp, and indeed an even
older Pioneer receiver. Is this a symptom of old caps, and/or poor design?
I know the 3020 moderately well. It was very well regarded (and designed - I fact I
met the designer) and should still sound at least decent today. At that age,
recapping the electrolytic caps specifically is likely to be a good move.
Especially if you're competent with a soldering iron yourself or have a friend who
is. The parts won't cost much.

So true.

Some ten years ago I did this to a ten plus but not quite twenty years
old amp (not NAD) and the improvement was a jaw dropper.


Mmm, might have a look into that then, thanks. It's more a nostalgia
thing - some desperate attempt to relive my youth :-)

Rob