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Patrick Turner
 
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Default KISS 102 by Andre Jute



Anonymous wrote:

KISS 102 by Andre Jute
This text is copyright Andre Jute 2004 and may not be reproduced except=

in the thread KISS xxx on rec.audio.tubes
THE VOLTAGES IN THIS AMP WILL KILL YOU. GET EXPERIENCED SUPERVISION IF =

IT IS YOUR FIRST TUBE AMP. /13

This is an article I wrote many years ago to explain how many watts an =

amp really needs, and what those dB numbers mean.

THE MYTH OF THE WATT
Andre Jute

HOW MUCH POWER DOES YOUR AMP REALLY NEED?
We all know that it the simplicity of valve gear that makes them sound =

so good. We also all know that a lot of transistor gear is vastly overpow=
ered for no good purpose. But what is less commonly admitted is that good=
many valve amplifiers are also overpowered.

Another way of putting this is that push-pull pentodes are for most of =

our applications as music lovers quite unnecessary.

The problem is that most people shy away from the complication of calcu=

lating how much power they actually need, and simply accept the always-ge=
nerous recommended power rating given out by loudspeaker manufacturers.=


The perceived complication is mistaken. You can discover how many watts=

your intended amp should put out with your preferred speakers in your ow=
n room with nothing more involved in the line of electronics than a voltm=
eter, which is of course part of any multimeter.

Even if you dont have a multimeter, all the required math is so simple =

and approximate that mental arithmetic will do the job fine. Or the simpl=
est of calculators, which can multipy, divide and find square roots, if y=
ou want to work with those irrelevant decimal fractions. You do not need =
a set of log-tables.

PRINCIPLES

How loud your amp will drive your speakers depends on how much power it=

puts out, the sensitivity of your speakers, how far from your speakers y=
ou listen, and the size, shape and furnishings of the room.

Taking these factors from the back, the room is a given. We will assume=

an average size of room it really doesnt make all that much difference. =
The shape of the room can be finetuned with baffles and the furniture cha=
nged or moved around to alter reflexivity/absorption.

The sensitivity of speakers are normally specified as so many decibels =

(dB) output for each watt input, measured at one meter the at one meter=
is often left out and but is always assumed. One meter is 39 inches. It =
will do no harm to think of it as one yard or three feet.

If you find a specification that reads xdB at one meter for 2.83V tha=

ts just 1W across an 8ohm speaker impedance. Well come to the importance =
of the speaker impedance in a moment.

An 80dB speaker is insensitive, one of 90dB or better is sensitive.

A good rule of thumb is that a symphony orchestra playing full fortissi=

mo in an acoustically sound hall will reach a punter in a good seat (say =
about four to six rows back, directly or nearly directly behind the condu=
ctor) at 90dB. In a theater with drapes on the walls and other soft furni=
shings, the sound pressure will be less. The purpose of high fidelity is =
the nearest approach to the concert hall. We can thus say that a lover of=
orchestral music who wants to reproduce the concert hall experience requ=
ires 90dB acoustic level at his ears, regardless of where he sits. That 9=
0db will then take care of any possible peak in the sound for most of the=
time the acoustic level will be much lower.

The physics of sound are simple and depend on the volume required and t=

he distance from the speaker. It is said that the smallest change in volu=
me that everyone can hear is three decibels some can detect a change of o=
ne decibel. All this is at around 1000 cycles, with hearing acuity and di=
scrimination increasing towards the higher frequencies, but you neednt wo=
rry about that. Working in three decibel steps gives you a small margin o=
f safety.

Every additional three decibels requires double the power. Thus, if a s=

peaker has a sensitivity of 81dB, to hear 90dB at the same one meter from=
the speaker, an additional 9dB must be powered, so the power required is=
1x2x2x2 or 8W.

Every doubling of the distance (over one meter) requires an additional =

6dB or quadruple the power to maintain the same acoustic sound level. So,=
taking our 81dB speaker above, we require 8W to hear 90dB at one meter a=
nd 8x4 or 32W to hear the same 90dB at two meters.

That, in a nutshell, is the argument for sensitive speakers.

It is also only theory. In a normal room reflections reduce the amount =

of power required to give the same sound level at double the distance, an=
d beyond double the distance the sound pressure level does not fall much =
unless the room is abnormally large or very differently furnished from th=
e rooms normal people live in.

As a rule of thumb, you can reduce the requirement of the extreme case =

we have now reached--to drive a truly insensitive speaker at peak orchest=
ral levels at a distance of two meters or 7ft8in--by at least a quarter t=
o allow for reverberative effects. So now we are down to 32-8 =3D 24W.

Next, consider that this pressure level, unless you are into monaural s=

ound, is for two speakers. So each channel of the amp (or monobloc) requi=
res only half: 24/2 =3D 12W.

However, this gives no safety margin for overload (or for rock fanatics=

) so lets double it to 24W or even treble it to 36W.

All of this is still only theory but it does prove that if you choose y=

our speakers stupidly, you will have to build or buy a stupid amp to driv=
e them. On the other hand, if you keep your head, you dont have to go in =
for the masochism of monstrous horns, divorces etc.

MEASURING EXACTLY--THE PLUTOCRAT WAY

A way of measuring precisely how many watts an amp you want to buy or b=

uild should put out is to use whatever amp you have to hand and measure w=
ith a true RMS multimeter how many volts it puts into a speaker when driv=
en so hard that your ears hurt.

This level, say 96dB, if constantly used, will reduce your hearing to f=

requencies below 4000Hz before you are forty. It is negligibly below the =
97dB level of an automatic rivetter at 35ft: would you want that outside =
your window all day? 96dB also represents four times the power required t=
o listen to a realistic reproduction of a full symphony orchestra playing=
at its lusty loudest. With that much to spare, there will always be over=
load provision and your amps, if properly designed, will be able to work =
forever only in the strictly linear part of their curve.

Unfortunately a true RMS meter is an expensive item more likely to be f=

ound in the toolbox of a professional than of most amateurs. (But see the=
Velleman K7105 Handheld Oscilloscope Kit which has an inbuilt RMS meter =
and costs only only $229 from Old Colony it is also a storage oscilloscop=
e complete with software to download waveforms to your computer and manip=
ulate them, it measures frequency, AC peak to peak and DC voltage.)


A MORE PRACTICAL WAY FOR HOBBYISTS

For this exercise you need a voltmeter. Anything that measures whole vo=

lts up to about 50V will do.

A brief diversion on meters, inspired by some comments from Glen Pitt-P=

laddy, to whom I am grateful for this as for much other assistance. To me=
asure what you use at civilized levels, you would use a milli volt meter =
to show that your amps hardly ever put out more than a volt, which comes =
to less than a watt, but here we want to go into deliberate antisocial ov=
erdrive. If you have access to a millivoltmeter with a range of say 20V o=
r 30V, that will give a better result than your standard multimeter becau=
se the standard DMM is optimized for 50 or 60 cycle working and therefore=
does not give a wholly accurate picture at 1000 cycles, never mind 20,00=
0. But dont sweat it this is rough work and almost any meter will do. Bes=
t of all, if you can borrow one, is a wattmeter, also called a power mete=
r, from which you can read the wattage directly without doing any mental =
arithmetic at all.

Attach the leads to speaker outputs of the amp, with the speaker also a=

ttached. WEALTH WARNING: DONT OPERATE VALVE AMPS WITHOUT SPEAKERS OR DUMM=
Y LOADS OF THE SAME IMPEDANCE ATTACHED TO THE OUTPUTS.

Now turn the speakers up as loud as you can bear and note how many volt=

s are being put on the speakers by the amp at the peaks.

Here is all the math you will require. You probably already know that w=

atts out equals voltage squared divided by resistance:

Watts out =3D (V x V)/R

but note that here we are talking about the power on the speaker side o=

f the output transformer (in the case of a valve amp). Textbooks normally=
use this formula for the power before the transformer and ask you to cal=
culate further losses in the transformer. We have made that allowance alr=
eady by measuring beyond the transformer a shortcut. The V is for the mea=
sured volts and is multiplied by itself to save the bother of measuring c=
urrent consumed as well. The R stands for resistance but is here the spea=
ker impedance which is usually 4, 6 (many KEFs), 8 or 16 ohms for modern =
speakers.

You dont need to know the sensitivity of speakers you have in your poss=

ession to run this test.

Lets see how it works in practice. I have bought a pair of QUAD ESL63 b=

ut it will be a while before they reach here. Meanwhile I want to build a=
single-ended tube amp to drive the ESL63, which have a sensitivity of 86=
dB for 2.83V, i.e. for one watt input to the speakers over their 8ohm nom=
inal impedance I should measure sound output of 86dB at one meter. I want=
to know how powerful my amp should be to drive my new speakers.

The speakers I do have here include a single first series QUAD ESL (cor=

rect name, no digits) with a nominal impedance of 16ohms, and a pair of B=
ang Olufsen Beovox S25 with a nominal impedance of 4ohms. The sensitivit=
y of the ESL63 will almost certainly fall between these two, so their pow=
er requirements will define upper and lower limits for the ESL63. The amp=
s in my study, where I am running the test, are QUAD II rated at 15W. I s=
it five feet from my speakers, but for the test moved to two meters that =
gives yet another safety margin.

When the single QUAD ESL was driven to unbearable levels in my room wit=

h me sitting two meters from it, the voltmeter never read more than 10V. =
At this level I could stand it for no more than seconds at a time and fea=
red my classic speaker would break up. Ten volts represents a driving for=
ce of (10V x 10V)/16ohms or 6.25 watts. Even 12V represents only 9.0W. Re=
member, we have here a built-in over-power and sound level factor of four=
times and then a bit. (We shall return to the importance of this apparen=
tly huge discrepancy below.) For a pair of these speakers, each amp, in o=
rder to keep up the same sound pressure level, would have to put out only=
half the power required for a single speaker. That works out to a sensib=
le lower range of 3.25W and an absolute, insane, maximum of 4.5W.

Repeat the experiment with the BO speakers. They require 6V for a sound=

pressure level that has to be shut down after only seconds because we wa=
nt to use our ears for the rest of our lives. Once we saw 8.5V but I stop=
ped that by pulling the plug because it was further from the speakers tha=
n the pre-amp was. 6V across 4ohm impedance represents 9W as above and th=
e outrageous 8.5V works out to 18W. In this case it is per side, because =
we had two speakers running on the test.

At no time did my nominally 15W QUAD II amps sound distressed, nor the =

speakers. With quality gear your ears provide the limit of endurance.

I repeated the test with Quad and Bang Olufsen transistor amps, as wel=

l as with custom KT88 and trannie amps but the results were the same. Tha=
t is what one would expect, because it is the speakers requirement for po=
wer we are measuring nothing to do with the amps. Tests on other odd spea=
kers here revealed how economical of power drivers properly designed for =
PA duty can be but that is another story.

WHY WE NEED AT LEAST FOUR TIMES OVERAGE WITH A COMMON CHEAP DMM

What we just did, measuring with an averaging non-RMS cheap digital mul=

timeter, makes electrical engineers uneasy.

Here is a list, by George R. Gonzalez, of a few things wrong with our c=

heap meter method:

Speakers cant be modeled as X ohm resistors. They vary up to 600 depen=

ding on frequency. Theyre also inductive or capacitive as heck. W equals =
E squared over R just doesnt apply when R is extremely variable and has i=
nductive or capacitive components. 8 ohms for a voice-coil speaker is a b=
allpark figure, usually measured for some midrange frequency. It could go=
up to over 100 ohms at bass resonance point and at over 10kHz.

Voltmeters of under $400 or so measure average AC voltage, not RMS whi=

ch is the basis for power. They read correctly for a sine-wave, but music=
isnt a sine wave.

Non-RMS voltmeters also average the power over a fraction of a second.=

Music has peaks of up to 20 times the average power. So a voltmeter will=
read a long way below the peak voltage.

If you have more people in the room, or a window open, or add a rug, y=

oull need a lot more power.

Music with lots of bass requires much more power than music with more =

normal balance. AHA may sound good at X watts, but hip-hop may need 5X wa=
tts to sound equally loud.

All these little points can add up to a very large error in estimating=

power.

Absolutely. What all this comes down to is that if you dont have specia=

list knowledge and measuring instruments, youd better allow very large ma=
rgins. We have overcome these problems to the maximum extent possible wit=
hout expensive equipment by:

a) measuring with the speakers attached (instead of with a fixed dummy =

load attached to the speaker output terminals, as professionals use), so =
that their impedance variations are taken into account

b) measuring at a minimum of 6db over a symphony orchestra going full f=

ortissimo, which allows a basic minimum of 400 margin (generally much mor=
e) for transients

c) measuring at hurtful volumes with your favourite music rather than w=

ith "neutral" signals, and calculating for antisocial automatic rivetter =
volumes

d) using another method (calculating from the speakers nominal impedanc=

e) as a double check

e) adding an arbitrary 200-300 margin, so that our visible mimimum marg=

in is 9 to 12db over a rather loud 90db (if you commonly play your music =
at 102dB you will soon be deaf!) which is ample headroom

f) arriving at results long hallowed by actual practice (well, actually=

, our results are higher than traditionally accepted tube practice and a =
lot higher than modern single-ended afficionados commonly find satisfacto=
ry)

We dont want to pretend this is precision engineering! But still, tube =

amps and speakers arent rocket science. Near enough--as long as it is nea=
r enough on the high side--is more than good enough.

SPECIFYING AN AMP FOR ABSENT SPEAKERS

So how many watts should my projected amp produce to drive the ESL63 wh=

en they arrive? Well, the Quad literature supplies the interesting inform=
ation that the speakers are not intended to run at more than 10Vrms conti=
nuous, that distortion sets in at 40Vrms, and that the maximum permitted =
peak is 50Vrms. But we know that Quads own tranny amps have output limite=
rs at 20V when they are used with the ESL63!

The literature also claims the ESL63s sensitivity as 86dB for 2.83V but=

reliable friends have measured it in my room as 85dB, so we shall work w=
ith that.

Here we go: 1W gives 85dB at one meter, double to 2W for 88dB, double a=

gain to 4W for 91dB, which is more than enough for the loudest music I pl=
ay. So we have 4W at one meter but I sit 5ft away, say 1.5 meters. Lets c=
all it 2 meters and allow the rest for an additional margin, so 4Wx4 is 1=
6W for two speakers, or 8W per speaker. Allow one quarter reduction for t=
he room effects, so the barest minimum is 6W per side. But lets not be me=
an with our margins. Lets double that, or treble it, as the theory demand=
s. So now we have 12W to 18W, including generous margins. Remember too th=
at this theoretical approach always overestimates the power required.

To show you how approximate this all is and how the small bits of margi=

n multiply up, lets not call my 1.5 meters distance from the speakers 2 m=
eters, lets temporarily call it precisely 1.5 meters. Now the calculation=
above is 4W for 91dB at one meter as before, and then becomes 4W x 2.25 =
or 9W for 1.5 meters, of which half is 4.5W per speaker, and less 25 for =
room effects leaves 3.375W absolute minimum. Double for overload is 6.75W=
and treble 10.125W, down to almost half of what we arrived at by conserv=
atively including a small margin along the way. Okay, lets go back to the=
big round figures, which I remind you were 12W or 18W.

By rearranging the formula we already know, we discover that the voltag=

e created by the power source (the amp) across the impedance of the speak=
ers equals the square root of the product of the power in watts and the s=
peaker impedance in ohms. So we can calculate that across the 8ohm resist=
ance of the ESL63 an amp producing 18W would put 12V on the speakers and =
that an amp producing 12.5W (slightly higher than the twice-minimum power=
calculated above) would put 10V on the speakers. Why do these numbers so=
und so familiar?

Now, single-ended 2A3 are obviously best left to the horn-merchants and=

other masochists. (It is not worth counting the owners of a good pair of=
first series ESL even if, as seems likely from the serial numbers, there=
are probably plenty out there they mostly drive them with QUAD II and ha=
ve no interest in selling their speakers to wannabee 2A3ers.)

But either a single-ended big transmitting valve of the 211/845 class o=

r two 300B in parallel single-ended configuration will give 18W at a walk=
=2E

As a radical alternative, we could possibly (though no one I know does =

actually do it) generate 12.5W from a single 300B by putting 400V on the =
plate with a grid bias of -84V, at which it will draw 80mA plate current,=
and outputting through a transformer with 2500ohm resistance. That is on=
the last line of the Recommended Operating Conditions as specified by We=
stern Electric for the 300B. A 2.5Kohm single ended output transformer is=
catalogued by Sowter in the UK (as the SE7-A) and another by Audio Note =
UK, so were not talking about custom windings. A small part of the 12.5W =
will be lost in the transformer (note that we are now back to approved ac=
ademic electrical engineering practice, taking our power output from the =
valve before the output transformer) and some more oomph will be unrealiz=
ed because no-one in his right mind drives a 300B right up to the 5 total=
harmonic distortion at which WE took their figures, but even incompetent=
ly-built amps along these lines, tied to a!
pair of ESL63, will still have enough welly to damage your ears perma=

nently.

So what can we conclude? Surprise, surprise. You dont need horns to enj=

oy single ended tubes to their fullest, indeed to painful volume levels! =
And, unless you choose your speakers while operating on auto-pilot, or dr=
ive them at psychopathologically anti-social levels, around 8 or 9 watts =
will do all the business you will ever require. Come to think of it, wont=
a pair of parallel single-ended 2A3 produce 7W?

Naw, lets leave sweaty footprints and go for the full megalomaniac 15 W=

atts!



I want to thank:

--Bob Bolton for giving me the rare tube-operated RMS millivoltmeter th=

at I used for doublechecking the end results given as examples in the art=
icle

--Glen Pitt-Pladdy for a most illuminating discussion of the abilities =

and limits of professional meters and the shortcomings of cheap multimete=
rs, particularly with reference to their frequency bandwidth

--Bill and Declan at Real McCoy Audio for interrupting their teabreak t=

o triplecheck my results with modern professional measuring instruments


Copyright 1995, 1997 Andre Jute
Andre Jute was educated at universities in South Africa, Australia and =

the United States in psychology, economics and business management. He ha=
s worked in advertising, management consulting, and as a political and mi=
litary advisor, and is now Chairman of the graphic and industrial design =
house Communication Jute. He is a distinguished novelist and writes a col=
umn on classical music read every week by 9.2m music lovers. Before takin=
g up tube amp design, he designed and built complete automobiles.

NEXT: CALCULATING THE POWER OUR AMP NEEDS

v13


I assume the copyright does not extend to including a copy of your above =
text in a reply
in a public forum in which you have placed the copyrighted text.

I basically agree with all you have said but getting the message out to t=
he nervous nellies who
feel insecure about owning only 20 watts is difficult.
Beacuse it is almost as easy to make a 50 watt amp as it is to make a 20 =
watter, I give them two KT88 in UL or CFB like Quad II and be done with i=
t, or 4 SE output tubes in parallel to make 32 watts instead of 8 watts.

My speakers here are about 90 dB sensitive, my room is about 8M x 7M x 3M=
average ceiling height,
and sloped "cathedral" or at least like a church, or a barn.
Nobody sits closer than 3 meters, which places them nearly central in the=
room
when the speakers are about 1.2M off the walls and away from corners.

Quad II amps are barely adequate, so are Leak 20, at a tweaked max of 15 =
watts/channel, and anything
else with a pair of EL84 in pentode, but my 22 watt SEUL do very well ind=
eed,
as does any PP amp with 40+ watt capacity.

The sound sweetens up and is more accurate with the more powerful tube am=
ps.

I have used SE pentode 6BQ5 in a stereo receiver I have, and the sound is=
ok
for background music, but I'd occasionally want to turn it up, but then f=
ind difficult patches of music
to sound a bit muddy.
Same goes for 6AM5 pentode output stages in an client's amp I tried;
the OPT losses in this AM radio concoction left only 3 watts of audio at =
the terminals.
He has got a pair of Coral full range drivers to be fitted into a large b=
ass box,
and with their better sensitivity, he should find 3 watts to be better.
My kitchen wide AF bw AM radio has one EL34 in triode for 6 watts max, an=
d a 12" 1953 quite sensitive Rola
speaker which would have been one of their best speakers of the day,
which I have augmenetd with a dome tweeter for above 4 kHz.
I only use 1/2 a watt, and sound is terrific, especially on the occasiona=
l world music shows etc on
AM Radio National.


To measure speaker voltages, any rms meter will give some indication of p=
ower levels
but its a fairly inaccurate way to measure the levels using music unless =
its
quite compressed "busy" rock and roll as played from FM radio stations wi=
th only
6 dB dynamic range.

Pink noise is another sound source which isn't bad to measure speakers
in confunction with an SPL meter.
Just crank up the noise until you get a constant 90 dB,
and take a look at the the oscilliscope monitoring the the signal.
If there is no clipping seen on the signal, the amp is handling it.
Then continue to crank the noise and record the SPL.
A volt meter won't leap about with a noise source, and you can

In recent tests here of the SE35 amps I just sold, the new owner visited =
with
an SPL meter, and some rock and roll CDs, and had me crank the amps
until the cones started the "DC woble dance" and we measured peaks of 96 =
dB SPL.
To cause the DC voltages to start leaping around in the amp, there *must*=

have been some considrable clipping of the signal, so perhaps 35 watts wa=
s barely adequate for this owner.
I have visited him at his residence, and he sometimes likes it real loud,=
not all the time,
but when he cranks it, he wants clarity, not mud.
He needs 4 output tubes per channel, not just 1.
Another client with a 50-50 also did the same thing, but can't afford the=
extra for 4 or 6 output tubes per channel.
His 22 yr old son sure likes it louder than us old farts, like I did when=
I was 22,
some 35 years ago, when I worked as a builder on very noisy sites, and ro=
de a motorcycle
and did all the usual noisy things young folks did.
But I always remembered to stuff my ears with cotton wool for the really =
noisy patches of my life,
like shooting nails into concrete, or lengthy spells with a power saw or =
angle grinder, or riding
hundreds of miles to camp by a quiet creek in the countryside to enjoy a =
girl.
I still hear up to 13 kHz, with little ear generated noise which often be=
comes the main worry
for those who have heard too much sound over too long a period.
People don't just go deaf from over doing it, they often get tinnitus so =
bad it drives them nuts.
I don't pretend to be like the Kalihari bushman of 70 who still hears a m=
osquito at 15 feet.
To him the orchestra would be quite deafening.
Frequency range isn't the only thing about hearing which is important and=

what the mind does with what it hears is more important.
I need subtitles for operas sung in English, and most pop stars waste the=
ir breath singing to me,
unless they are Rye Cooder or Taj Mahal, who really *want me* to understa=
nd the lyrics.
I don't know very many people who hear more than 15 kHz, something I chec=
k
when I test the speakers they bring to me for a fix; I test their speaker=
s and their
hearing on the spot with an amp and oscillator.

So these days 20 *good* watts / channel is all I really need with the 90 =
dB/W/M speakers I have,
but as I said, its not hard to use a little more hardware to get 50 watts=
=2E

If one must measure speaker voltages, then I suggest the use of a peak vo=
ltage
meter designed to "detect" the audio voltages and convert them into
slowly decaying DC voltage will give you a better indication of the real
situation at a given set of speakers during listening.

This entails the use of a circuit with a signal diode feeding about a 0.0=
1 uF cap with a 2.2meg
discharge resistor, and the output of the cap taken to a sensitive DC met=
er, with a resistive divider
to to reduce the detected DC by about 0.7, therby converting the detected=
direct voltage into
indicating the maximum RMS voltage meaured, rather than the average RMS v=
oltage
of a dynamicly moving signal voltage.
Drumbeats and transients can thus be measured and captured to allow a met=
er needle to
quickly swing up to near their crests and stay there long enough for us t=
o see them.

The use of a diode circuit connected off the amp output won't spoil the s=
ound significanly
while we measure it since the cap voltage reaches a level which "rides al=
ong"
on the crests of the loudest passages, so the diode only conducts occasio=
nally when the
peak voltage level has sagged a bit to cause the nest transient to push i=
t back up.
The diode has a forward voltage drop of 0.5v approx, so some allowance sh=
ould be made
in the end DC R divider to allow for this.
Its only going to be useful with loud sound.

For more accurate "fast capture and hold" measuring, perhaps a signal vol=
tage detector
using an opamp and diode arrangement in the feedback path will give
excellent measurements at all levels but the novice will be entirely baff=
led
by the principles and the discipline needed to design and construct a pea=
k and hold
meter where one can view a slow moving DC voltage following the tallest
music peaks.
But I recall such a method I have outlined being used by authors in Wirel=
ess World
in some 1970s copies.
Some DVM do have a peak and hold facility, and you enage the peak and hol=
d, and
the readout numbers are those of the loudest signal. You can watch them r=
apidly
ramp up, then play an entire CD, and thus get the highest voltage for tha=
n CD.

If you want to be free of clipping on transients, methinks the measuremen=
t by RMS method
need be used with caution, and there is something to be said for more tha=
n just enough headroom.

I had a party here last year to celebrate my boarder's 40th.
We used all 50 watts per channel, much needed for the Bob Marley, and all=
that *real bass*
and to rev up a house full of people who'd had a few!!!

A client of mine uses over 300 watts to power his sub and LF.
He wants the recording of a the Space Shuttle rocket taking off to sound
like you are not 3 miles away.

But when I want to hear Jaqueline Dupre playing her cello, 12 watts/chann=
el is fine.

Patrick Turner.











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mick
 
Posts: n/a
Default

On Sun, 14 Nov 2004 15:46:15 +1100, Patrick Turner wrote:

Some DVM do have a peak and hold facility, and you enage the peak and
hold, and the readout numbers are those of the loudest signal. You can
watch them rapidly ramp up, then play an entire CD, and thus get the
highest voltage for than CD.


I got such a DMM from Maplin quite a while ago (they still do it - WG022
at about 60UKP I think) but I had forgotten that it had max/min hold on
it! I just tried the above (but only for one track) and got a max reading
of just over 1.9v with the music "fairly loud". That's a smidgen above
0.45W per channel if you believe in 8R speakers. That seems to be about
right to me. I can't run "concert hall" volume with small kids next door.
:-)

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info


  #3   Report Post  
Tim Williams
 
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"Patrick Turner" wrote in message
...
Anonymous wrote:

Pat, Andre. This is for BOTH of you.

-=-=-

You a

[X] Clueless Newbie [ ] Lamer [X] Aol'er
[ ] "Me too"-er [ ] Pervert [ ] Geek
[X] Spammer [X] Nerd [ ] Elvis
[ ] Fed [X] Freak [X] Scientologist
[ ] Scammer [X] Dumbass [ ] Pre-teen
[ ] Obnoxious Advocacy Freak

You Are Being Flamed Because:
[ ] You posted binaries in pieces LESS than 5000 lines
[ ] You posted something asking for warez sites
[XXXXXX] You quoted an ENTIRE post in your reply (and then some, Pat)
[X] You continued a long, stupid thread
[ ] You started/continued an off-topic thread
[ ] You posted a "YOU ALL SUCK" message
[X] You posted a blatently obvious troll
[ ] You said "me too" to something
[X] You suck
[ ] Your sig/alias/server sucks
[ ] You posted a stupid pyramid money making scheme
[ ] I think you might be a fed
[ ] You posted in 3lIt3 CaPiTaLs because you think that makes you cool
[X] You didn't do anything specific, but appear to be so generally
worthless that you are being flamed anyway

To Repent, You Must:
[X] Give up your Internet access
[ ] Hang yourself
[ ] Tell your Mommy you've been a bad boy
[X] Jump into a bathtub while holding your monitor
[X] Actually post something relevant
[X] Install a brain that actually works
[ ] Read the FAQ
[X] Be the guest of honor in alt.flame for a month


In Closing, I'd Like to Say:
[X] Get a life
[X] Never post again
[X] Age 10 more years before you post again
[ ] You couldn't do anything with a brain if you had one
[X] Go to hell
[ ] Yer momma's so fat/stupid/ugly that etc...
[X] Get *ucked, you pathetic loser
[ ] All of the above


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