Its time I learn about Watts
Khean
what it really means when they say an amplifier is X Watts or Y
Watts. And then now I learn that a tiny Acoustic Image is 300 Watts
while my giant Fender Bassman is 40 Watts. Can somebody, please
explain clearly to me, right from the beginning, the ABCs of Watts.
Are there different ways of measuring Watts? Is an Acoustic Image
really more powerful than a Fender Bassman? You mean it's LOUDER, or
what do you mean? So how many Watts do I go for in what situation?
Thanks!
alexdgtr
I'm a self described "mechanically challenged" type individual but
picked up the book "The guitar amp handbook: understanding amplifiers
and getting great sounds" by Dave Hunter. It's roughly $US17 and a
great bang for the buck (it's also quite a nice book w/ glossy colored
pictures). The format follows the KISS rule and there's also some
sections on building your own amplifier which too much for me.
steve
blindly formulated
the following incoherence:
Watts is the measure of the electrical power consumed by the amp, not the
level of sound ouput. There is a relationship between power consumed and
the amount of sound output, but it isnt necessarily 1 to 1. Im convinced my
45W Heritage is much(!) louder than my 50W marshall, for example. I
suspect the number of filters and effects as well as the efficiency of the
circuits and speakers have everything to do with the power/sound
relationship. Also, the human ear has it's own qualities that probably play
into the perception of loudness. It's no simple topic, that's for sure.
steve
--
"The accused will now make a bogus statement."
James Joyce
ott...@hotmail.com
Not simple topic for sure, when you get done with Watts, you'll have
to get into Ohms as well, too confusing for me.
Bg
jim
"steve" <st...@steve.com> wrote in message
news:1Oydnc3MG8i96nDY...@rcn.net...
Hi Steve,
How did that Heritage amp work out? Are you happy with it? I'm thinking of
getting one.
Thanks,
Jim
Joey Goldstein
> For decades I have gone through Life without bothering to lean about
> what it really means when they say an amplifier is X Watts or Y
> Watts. And then now I learn that a tiny Acoustic Image is 300 Watts
> while my giant Fender Bassman is 40 Watts. Can somebody, please
> explain clearly to me, right from the beginning, the ABCs of Watts.
> Are there different ways of measuring Watts? Is an Acoustic Image
> really more powerful than a Fender Bassman?
Yep.
> You mean it's LOUDER,
Yes, and cleaner.
> or
> what do you mean? So how many Watts do I go for in what situation?
> Thanks!
For playing clean jazz I never go below 60 watts, and would rather have
100 watts or more.
40 watts is about the bare minimum and won't do well with a loud drummer
unless your amp is mic'd.
--
Joey Goldstein
http://www.joeygoldstein.com
http://www.soundclick.com/bands/joeygoldstein
joegold AT sympatico DOT ca
Marc Sabatella
> while my giant Fender Bassman is 40 Watts.
Meaning if you leave both turned on in different houses for 1000 hours,
the electric company will charge one house for 300 kilowatt-hours of
power consumption and the other for 40.
> Is an Acoustic Image
> really more powerful than a Fender Bassman? You mean it's LOUDER, or
> what do you mean?
Well, it apparently consumes more electricity, if the numbers you post
are to be believed - I don'[t really know the specs of these amps in
particular. Whether or not all power quoted on the spec sheet
translates directly into volume is another matter. Most likely, the
speaker(s) in the AI might not be actually using all that power - the
amp may be designed to drive *external* speakers with most of that
power. Plus some amount of that power might be dedicated to running
effects, crossover circuitry, or other things not directly related to
volume per se. But sure, all else equal, more power should translate
roughly into more volume, just as more wood on a fire roughly translates
to a brighter/hotter fire.
---------------
Marc Sabatella
ma...@outsideshore.com
Music, art, & educational materials
Featuring "A Jazz Improvisation Primer"
http://www.outsideshore.com/
momalle3
A wat is just a unit of measure--"One watt is one ampere of current
flowing at one volt." Voltage and current and amerage are different
ways of measuring electricity, a watt is a unit of measure at their
interaction.
Wattage is only part of the measure of volume. if all things stay the
same --the cab, the signal going in--it takes ten times the watts to
produce double the volume. Volume levels have more to do with speaker/
cabinet efficiency than they do with wattage--a more efficient speaker
is much louder at the same number of watts. Wattage also indictaes
headroom, or the volume level you can get to before noticing
distortion, The greater the wattage, generally the more clean volume
you have available--but once again, speaker/cabinet efficiency ahs a
lot to do with it.
Amp maker lie about wattage all the time. But in general, the more
watts, the more clean volume, not necessarily the more volume. You'd
need to go to 500 watts to make a 50 watt amp sound twice as loud
steve
formulated
the following incoherence:
> Hi Steve,
> How did that Heritage amp work out? Are you happy with it? I'm thinking
> of
> getting one.
> Thanks,
> Jim
Hi Jim:
I love it. It's remarkably true to the sound of the guitar, and has lots of
punch. Gotta watch that feedback, though, and I dont think it would be good
far anything but jazz.
steve
--
"The accused will now make a bogus statement."
James Joyce
danny...@cox.net
> > And then now I learn that a tiny Acoustic Image is 300 Watts
> > while my giant Fender Bassman is 40 Watts.
>
> Meaning if you leave both turned on in different houses for 1000 hours,
> the electric company will charge one house for 300 kilowatt-hours of
> power consumption and the other for 40.
>
> ---------------
> Marc Sabatella
> m...@outsideshore.com
This is totally incorrect. The AI uses highly-efficient switching
circuitry for both its power supply and power amp stages, so it draws
almost no power unless its being played at very high output levels. A
good rule of thumb is that the hotter an amp runs, the more power it's
wasting. I leave a Clarus 2R on almost all the time and it barely gets
warm. Try sticking your hand into an idling Fender Bassman and see
what happens.
The power rating of an amp is the amount it can deliver to a simulated
speaker load under specified test conditions. The amount that it draws
at full power can be slightly higher, as in the AI, or much higher, as
in almost any tube amp (and many conventional solid-state ones).
Danny W.
richard...@yahoo.com
Amperage is analogous to the amount of water, like in cubic feet.
Voltage is analogous to the water pressure.
So, if you were trying to run a factory with a water wheel for power,
the amount of power you put in would depend on the amount of water and
the amount of water pressure.
The factory is analogous to the amplifier.
How much product the factory actually manufactures is analogous to the
loudness of the amp -- and it surely depends on more than the power
input.
BTW, the equations in basic electrical engineering (RLC circuits) are
the same equations that apply to hydraulic and mechanical systems, so
this analogy holds water.
tomb...@jhu.edu
None of the first ten replies have given you the answer you need.
1) If you're interested in the loudness of an amplification system,
that is measured in decibels, not watts. The loudness is determined in
part by the output power of the amp, but also in large part by the
sensitivity of the speaker. A low-wattage amp with a sensitive speaker
could very well be louder than a higher wattage amp with a less
sensitive speaker.
2) Also, each amplifier will have two wattage measurements. One gives
the max power consumed by the amp. The other gives the max output
power the amp is capable of. The first statistic tells you nothing
about how loud the amp is. The second stat is the relevant one for
estimating loudness.
3) Assume two combo amps, each with the exact same cab and speaker.
Will the 50 watt amp be twice as loud as the 25 watt amp? No. The
relationship between watts and decibels is not direct. Many people
argue that the general rule of thumb is that to double your loudness,
you have to increase your wattage ten-fold. So by that rule a ten watt
amp is about twice as loud as a one watt amp. A hundred watt amp is
about twice as loud as a ten watt amp.
I think there is more to it than that. Distorted tones will sound
louder than clean tones. SPL (sound pressure level) is also a
significant factor.
In short, this topic is far too complex to learn about from a
newsgroup.
tomb...@jhu.edu
> On Mar 6, 7:25 am, "Khean" <tiankh...@gmail.com> wrote:
>
> > For decades I have gone through Life without bothering to lean about
> > what it really means when they say an amplifier is X Watts or Y
> > Watts. And then now I learn that a tiny Acoustic Image is 300 Watts
> > while my giant Fender Bassman is 40 Watts. Can somebody, please
> > explain clearly to me, right from the beginning, the ABCs of Watts.
> > Are there different ways of measuring Watts? Is an Acoustic Image
> > really more powerful than a Fender Bassman? You mean it's LOUDER, or
> > what do you mean? So how many Watts do I go for in what situation?
> > Thanks!
>
> None of the first ten replies have given you the answer you need.
Sorry, didn't mean Mike. He posted while I was writing.
Joey Goldstein
True. But in practice, the RMS rating that most amplifier manufacturers
give their amps is a pretty good guide as to what to expect.
A 22 watts RMS amp won't have much headroom.
An 80 watts RMS amp will much more.
Both amps may seem to be capable of getting almost just as loud as each
other, but the 22 watt amp will be distorting well before the 80 watt amp.
Tim McNamara
ott...@hotmail.com wrote:
> Not simple topic for sure, when you get done with Watts, you'll have
> to get into Ohms as well, too confusing for me.
I have resistance to the whole topic.
steve
blindly formulated
the following incoherence:
> > Not simple topic for sure, when you get done with Watts, you'll have
> > to get into Ohms as well, too confusing for me.
>
> I have resistance to the whole topic.
Shocking!
Max Leggett
>On 6-Mar-2007, smacked up and reeling, Tim McNamara <tim...@bitstream.net>
>blindly formulated
>the following incoherence:
>
>> > Not simple topic for sure, when you get done with Watts, you'll have
>> > to get into Ohms as well, too confusing for me.
>>
>> I have resistance to the whole topic.
>
>Shocking!
When stressed, I always meditate. Ohm ........
-------------------------------------------------------
Is it not strange that sheep's guts should hale
souls out of men's bodies?
Willie 'The Lion' Shakespeare
-------------------------------------------------------
Tim McNamara
"steve" <st...@steve.com> wrote:
> On 6-Mar-2007, smacked up and reeling, Tim McNamara
> <tim...@bitstream.net> blindly formulated the following incoherence:
>
> > > Not simple topic for sure, when you get done with Watts, you'll
> > > have to get into Ohms as well, too confusing for me.
> >
> > I have resistance to the whole topic.
>
> Shocking!
Some people don't pick up on it, though.
gant...@comcast.net
(someone will argue the point, but this has been my experience) sound
louder than a 100 watt solid state amp. This has to do with how tubes
distort. Onset of distortion /w tubes is usually more gradual and
more pleasing to the ear than w/ a solid state amp. Another factor is
speaker efficiency. A high efficiency speaker (the old JBL D/K/E
series, EV SRO's and EVM's) can put out 4 - 6 dB more sound pressure
for a given input than a less efficient speaker. An increase of 6 dB
is, to the human ear, double the loudness. To get a 6 dB increase in
loudness just increasing the power of the amp you'd have to have 10
times as many Watts. You can see that speaker efficiency is an
important part of the equation. Proper impedence matching is also
important. An amp that's rated at 50 Watts into an 4 Ohm load (like a
Fender Bassman head) will put out about 25 Watts into an 8 Ohm load.
Conversely, the same amp will try to put out 100 Watts into a 2 Ohm
load. You may say "Cool, use a lower impedence speaker and double
your power!", but with a tube amp you run the risk of frying your
output transformer (all tube amps have 'em, and they are neither cheap
nor easy to replace) and w/ a solid state amp you can fry your output
transistors.
Another strange phenomenon is that class A tube amps seem louder
(again, in my excperience) than comparable class A/B push-pull tube
amps. Don't ask me why. All I know is that my Bruno Underground 30
sounds WAY louder than you'd ever think a 30 Watt amp could be.
Certainly as loud as a 50 Watt Bassman. Same w/ Vox AC30's and
similar class A designs.
And the reason tube amps are bigger and heavier has to do w/ the
transformers. Bigger power transformers, plus they need an output
transformer. Lots of wire wrapped around iron core = more weight,
bigger box.
Gantt
ott...@hotmail.com
steve wrote:
> On 6-Mar-2007, smacked up and reeling, Tim McNamara <tim...@bitstream.net>
> blindly formulated
> the following incoherence:
>
> > > Not simple topic for sure, when you get done with Watts, you'll have
> > > to get into Ohms as well, too confusing for me.
> >
> > I have resistance to the whole topic.
>
> Shocking!
My-Ohm-y, these are bad :-)
Bg
Norm K
> 3) Assume two combo amps, each with the exact same cab and speaker.
> Will the 50 watt amp be twice as loud as the 25 watt amp? No. The
While we're on the subject, how does a "2 x 25 watt amp" like a Fender
Princeton Chorus, compare to a 50 watt amp? I don't really understand
what "2 x ___" means compared to a conventional amp.
Norm
gant...@comcast.net
Gantt
Joey Goldstein
> Watts are only a part of the riddle. A 50 watt tube amp will always
> (someone will argue the point,
That'll be me.
> but this has been my experience) sound
> louder than a 100 watt solid state amp.
A 50 watt tube amp will already be breaking up at the volume needed to
play block chords with a loud drummer, especially with a dark tone.
A 100 watt solid state amp will be able to cover that.
However, a 50 watt solid state amp will sound worse at the same volume
because it too will be breaking up but with less pleasing overtones.
A 100 watt Poltone Mini Brute can player louder and cleaner than any 50
watt tube amp.
But a 50 watt tube amp driven into distortion can get louder than the PT
period.
This has been my experience.
gant...@comcast.net
head is awesomely clean at any volume I can stand to play thru it.
I've had a couple of Polytone Mini Brutes. No comparison, either in
loudness or tone. In fact, my Underground 30 is louder than any Mini
Brute I've ever had.
Gantt
On Mar 7, 12:01 am, Joey Goldstein <nos...@nowhere.net> wrote:
> A 50 watt tube amp will already be breaking up at the volume needed to
> play block chords with a loud drummer, especially with a dark tone.
> A 100 watt solid state amp will be able to cover that.
> However, a 50 watt solid state amp will sound worse at the same volume
> because it too will be breaking up but with less pleasing overtones.
> A 100 watt Poltone Mini Brute can player louder and cleaner than any 50
> watt tube amp.
> But a 50 watt tube amp driven into distortion can get louder than the PT
> period.
>
> This has been my experience.
> Joey Goldsteinhttp://www.joeygoldstein.comhttp://www.soundclick.com/bands/joeygoldstein
Keith Freeman
> An 80 watts RMS amp will much more.
> Both amps may seem to be capable of getting almost just as loud as
> each other, but the 22 watt amp will be distorting well before the 80
> watt amp.
speaker may actually be louder than an 80 watt amp with an inefficient
speaker system. Amp manufacturers will build that inefficiency in, in order
to achieve good bass response from small speakers.
-Keith
Portable Changes, tips etc. at http://home.wanadoo.nl/keith.freeman/
e-mail only to keith DOT freeman AT orange DOT nl
Khean
> > A 22 watts RMS amp won't have much headroom.
> > An 80 watts RMS amp will much more.
> > Both amps may seem to be capable of getting almost just as loud as
> > each other, but the 22 watt amp will be distorting well before the 80
> > watt amp.
>
> Only all other things remaining equal. A 22 watt amp with an efficient
> speaker may actually be louder than an 80 watt amp with an inefficient
> speaker system. Amp manufacturers will build that inefficiency in, in order
> to achieve good bass response from small speakers.
>
> -Keith
>
> e-mail only to keith DOT freeman AT orange DOT nl
Thank you for the deluge of email on this topic. As the one who posted
this thread, I have really learned a lot about Watts.
khean
Joey Goldstein
the Fuchs. In my experience, running a preamp set to a clean setting
into a 50 watt tube power amp will get the results that I've been
describing, not those that you are describing.
So it may well be that Fuchs 50 watt amps have more headroom than a
typical 50 tube power amp, but it probably has more to do with the way
the power amp is designed than anything else.
Still, *most* 50 watt tube amps break up at volumes where a Ss 100 watt
amp wouldn't, like playing a block chord solo in a band with a loud
drummer. But if you're at that point where the SS amp is breaking up
it's a much uglier sound than the tube amp breaking up.
--
Joey Goldstein
http://www.joeygoldstein.com
E7sus9
wrote:
>
> - Show quoted text -
I don't mean to correct you, but I don't think that's accurate Gantt.
You don't get more power when you reduce the ohmage, you get more
amperage. The wattage stays virtually the same. Wattage can be figured
a couple of ways, current squared times ohmage, current times voltage
is another. The point is that you can't make more power, and so if you
have less resistance (4 ohms instead of 8 ohms) then you simply have
more amperage, not power (watts).
What I find interesting is that many amps are rated differently. By
that I mean one amp states 50 watts at 4 ohms, the next amp says 50
watts at 8 ohms. In theory it shouldn't matter what the ohmage is, but
in practice amps have slightly less than linear power curves. So you
see weird things like 50 watts at 4 ohms and 55 watts at 8 ohms for
the same amp. Some of your more high end amps will spec it this way.
But at the end of the day it still is only a reference to loudness,
not a perfect relationship. I have a Fender Acoustisonic amp that's 30
amps that'll easily be louder than a lot of 50 watt amps I've heard.
But as Gantt said, it's more important to match the output power for a
one to one relationship. So if your amp has an 8 ohm output, you
should try to make sure that you always load it with 8 ohm loads
(that's one 8 ohm load, not three 8 ohm loads). Hook that up to a 2
ohm load and crank up the volume and you might be taking it to the
repair shop pretty soon.
Maybe to much tech stuff there but hope that helps.
Ron
gant...@comcast.net
years ago!
Here's my math - feel free to correct me as needed:
Ohms Law states that I (current in amperes) = V (voltage) / R
(resistance).
Watts are calculated by W = V x I.
So, for an example, a 100 watt amp (like my old Mesa MK II) would
read
about 28.3 volts into an 8 ohm load. Into a 4 ohm load the voltage
wouldn't change much (in practice it does a little, but not enough to
affect the outcome significantly), so more current would flow.
So, if W = V x I or, doing a little algebra on it, V squared divided
by R, then 28.3v squared = about 800 divided
by 8 Ohms = 100 Watts; divided by 4 Ohms = 200 Watts.
I'm pretty sure the math is right...
But since 4 6L6's can't REALLY put out more than 100 Watts safely,
they'd be overloaded trying and the excess current would overheat the
output transformer. In a solid state amp the output transistors would
allow more current to flow
than they're safely designed for and would overheat and ultimately
fail.
Formulae courtesy Wikipedia, since I can barely remember what color
socks I put on this morning!
Gantt
E7sus9
wrote:
> Hey Ron... You made me use brain cells that I thought I'd killed off
> years ago!
>
> Here's my math - feel free to correct me as needed:
>
> Ohms Law states that I (current in amperes) = V (voltage) / R
> (resistance).
>
> So, for an example, a 100 watt amp (like my old Mesa MK II) would read
> about 28.3 volts into an 8 ohm load. Into a 4 ohm load the voltage
> wouldn't change much (in practice it does a little, but not enough to
> affect the outcome significantly), so more current would flow.
>
> by 8 = 100 Watts; divided by 4 = 200 Watts.
>
> Formulae curtesy Wikipedia, since I can barely remember what color
> socks I put on this morning!
>
> they'd be overloaded trying and the excess current would overheat the
> devices (tubes are voltage devices), would allow more current to flow
> than they're safely designed for and would overheat and ultimately
> fail.
>
> > You don't get more power when you reduce the ohmage, you get more
> > amperage. The wattage stays virtually the same. Wattage can be figured
> > a couple of ways, current squared times ohmage, current times voltage
> > is another. The point is that you can't make more power, and so if you
> > have less resistance (4 ohms instead of 8 ohms) then you simply have
> > more amperage, not power (watts).
>
> > What I find interesting is that many amps are rated differently. By
> > that I mean one amp states 50 watts at 4 ohms, the next amp says 50
> > watts at 8 ohms. In theory it shouldn't matter what the ohmage is, but
> > in practice amps have slightly less than linear power curves. So you
> > see weird things like 50 watts at 4 ohms and 55 watts at 8 ohms for
> > the same amp. Some of your more high end amps will spec it this way.
>
> > But at the end of the day it still is only a reference to loudness,
> > not a perfect relationship. I have a Fender Acoustisonic amp that's 30
> > amps that'll easily be louder than a lot of 50 watt amps I've heard.
> > But as Gantt said, it's more important to match the output power for a
> > one to one relationship. So if your amp has an 8 ohm output, you
> > should try to make sure that you always load it with 8 ohm loads
> > (that's one 8 ohm load, not three 8 ohm loads). Hook that up to a 2
> > ohm load and crank up the volume and you might be taking it to the
> > repair shop pretty soon.
>
> > Maybe to much tech stuff there but hope that helps.
>
>
> - Show quoted text -
Okay, now I had to get the pencil and paper out!
Yep, all you stated looks right, but it's still puzzling. In a
transformer, if you double the current you halve the voltage
maintaining the power available to the transformer (for the most
part). I've never measured the voltage directly on a speaker so I
would have expected it to drop fairly significantly with the increased
current flow. This assumes the amp is at full volume, things aren't
clipping, etc. And yes I would expect things to start to fail with the
lowered resistance and now high current.
Did you ever see a power curve for an amp that states its wattage over
a full range? I haven't, just the specs they put out which don't give
the whole picture. That's why I don't like that now they don't spec it
at the standard 8 ohm load, they seem to pick 4 ohms or some other
ohmage that makes it not a one to one comparison. Without seeing a
full power curve or at least a spec at the same ohmage you don't
really know the wattage for comparison reasons.
Your voltage measurements seem to be the key. Do you know the voltage
drop when you go from 8 ohms to 4 ohms? I just don't understand why
not a significant drop in voltage.
I'm used to figuring wattage in the area of big power items like
transformers, UPS's etc. So the wattage from an amp and to a speaker
seems to be defying my rules of thumb!
Interesting conversation though!
Ron
jdah...@uiuc.edu
as applied to AC circuits. The guitar signal falls into the AC circuit
analysis.
This means that things get much stranger with the math! Complex
impedance
(measured in ohms, but uses trigonometric relationships with AC) is
far different
than simple ohms law for DC circuits. Power output is typically
measured with
a 1kHz sine wave as a reference point. Speakers used in guitar amps
have resistance
and inductance. The inductance is much more of a factor than the
series resistance
when calculating these things. Not a treatise here but just to letcha'
know about
the AC side of things versus DC for ohms.
This was mentioned before but again the Power Consumed by an amp in
Watts
is how much energy consumption the amp requires to do what it does.
The power
output of an amp in watts applies to the signal (from the guitar in
this case) being
delivered to and by the speaker.
Ouch, I tried to forget about this stuff when I quit
electronicking....
ref the Acoustic Image Clarus....yeah, this is a good (make that great
thing)..as electric
bills go up the switch mode power supplies used in the Clarus make
things nicer on your
pocket.....it is true, the signal Watts are higher than the watts it
takes to make the amp
run....UNLIKE my Fender super reverb which puts out 40 watts and uses
much, much more
to work....but then I like the tone...a lot!
John
momalle3
wrote:
These are common arguments but a watt is a watt--it's a unit of
measure. It's like saying "stainless steel teaspoons are bigger than
plastic teaspoons." A "watt" is a unit of measure. "Tube watts" and
"SS watts" are the same thing. So why do people think tube amps are
louder? A ton of reasons. First, there's the cab issue--once again,
the speaker has more to do with volume than the amp. To doa real
comparison, you'd have to run a tube head and an SS head into the same
cab. And then people always forget that watts and decibels are not the
same thing--all things being equal, it takes ten times the watts to
produce twice the apparent volume. So it's no surprise that a 100 watt
SS head does not much sound louder than a 25 watt Deluxe. It would
have to be 250 watts to sound twice as loud into the same cab.
Finally, there's perception. People perceive tube amps to be louder, I
think because in distortion, the signal is clipped--the harmonic range
is reduced, the highs and lows are cut off and you get a big wall of
solid midrange. midrange is where human hearing is most sensitive, by
far. We hear it better. It sounds louder, even if a decebel meter
would not show it as louder. As a bass player, I've seen this 1000
times--if you boost the bass you muddy up the mix and dont' sound any
louder, but if you boost the low mids and cut bass and treble viola!
you sound louder and more distinct, even though your volume hasn't
gone up. Bass players, am I right?
So A watt is a watt. It's hugely complicated by the differences in
cabs, by the fact that amp makers lie, and by the way the ear hears.
And then by the fact that people almost can't help thinking that a 100
watt amp is going to be twice as loud as a 50 watt amp, when in fact
it would need to be 500 watts.
Headroom--I have a little 18 watt all tube ampeg jet--that thing does
not want to distort. You have to really crank it to ten and even then
it won't do a heavy overdrive tone. Other amps can't wait to start
clipping. It's not just the tubes--it's the power and output
transformers, the biasing scheme, the preamp gain the kind of
rectifier, etc.
jdah...@uiuc.edu
that means is there are two 25W amps instead of 1 50W amp. The
advantage
being isolation between channels for stereo etc.
This thing with Watts becomes clearly confusing when you consider
todays Boom Boxes. In (I think it was the late 60's or early 70's)
laws were passed to require
fairness in labelling electronic devices. There was a period back then
when consumer stereo stuff was being rated in Watts by different
standards. You could have
two identical systems and one would be rated at maybe 300W and the
other at 50W. By the mid-late 70's the rules were in place and for a
long time you could
look at output Watts of sound systems and accept that you were getting
a reasonable comparison of that. Sometime in the past several years
this has all eroded
again and now you can find Boom Boxes rated at 285W when under the
(fair rating system) that same item would be rated at far less Watts.
So far as I know this
hasn't penetrated into the guitar amp world and hopefully never will.
What?
Keith Freeman
transistor radio (typically a few hundred mW) and connect it up to a 15"
speaker in an open cab. It will be louder than you expect!
-Keith
Portable Changes, tips etc. at http://home.wanadoo.nl/keith.freeman/
gant...@comcast.net
it once when I was re-biasing one of my amps. I don't know if I still
have the sheet of paper that I wrote it down on or not. I'll poke
around my workshop... I seem to recall that there was a bit less
power available in the lower mid and lo freq range. Using 1000 Hz as
a test seems to give the highest rating.
gantt
On Mar 7, 3:19 pm, "E7sus9" <ronsgui...@gmail.com> wrote:
>
> Okay, now I had to get the pencil and paper out!
>
gant...@comcast.net
Tubes have to be reverse biased to keep them from conducting too
much. Transistors have to be forward biased to make them conduct at
all. I've always thought that tubes respond differently because they
WANT to conduct, whereas transistors, left to their own devices
(oops... bad pun!) don't. Also, tube amps have always seemed to me to
have a bit of natural compression (arguably a form of distortion,
albeit one that most of us enjoy), and some of the classic tube amp
circuits (the tweed Bassman, for example - I think it's a cathode
follower drive stage) have circuitry that introduces a bit of
compression. Compression increases the perceived loudness without
actually increasing the electrical or acoustic energy.
The cab issue is a valid one too. I once owned an Acousic 134. 100
solid state watts into 4 crappy 10" speakers. I ended up hating it,
but during the brief time I had it I did an experiment. I plugged it
into our bass player's 4-12 Marshall cabinet. What a difference! A
vast improvement. I run my Fuchs mod Bassman head into a 2-12 cab
that Mojotone built for me. Lock-joint 3/4" pine box w/ 5/8" baffle
held on by four screws with 2 of the old Mesa Black Shadow 12"
Celestions. It's a great sounding cabinet. I'm convinced that the
light-weight baffle w/ only 4 screws is a big part of the sound. It
almost seems to breath. Big, bright and full sounding w/ great
dispersion on stage. My Mesa amps and cabinets (all 3/4" plywood w/
glued and screwed 3/4" baffles) always sounded loud, tight and boxy
(also had the dispersion of a laser beam).
So is a Watt a Watt? Theoretically, yes, but why does a 30 Watt class
A amp sound so damn loud? Maybe because the gentle onset of distortion
w/ a class A circuit lets you use more of the power? I dunno...
Gantt
da...@redstoneaudio.com
>For decades I have gone through Life without bothering to lean about
>what it really means when they say an amplifier is X Watts or Y
>Watts. And then now I learn that a tiny Acoustic Image is 300 Watts
>while my giant Fender Bassman is 40 Watts. Can somebody, please
>explain clearly to me, right from the beginning, the ABCs of Watts.
>Are there different ways of measuring Watts? Is an Acoustic Image
>really more powerful than a Fender Bassman? You mean it's LOUDER, or
>what do you mean? So how many Watts do I go for in what situation?
>Thanks!
Actually, it is pretty easy, but it is not simple.
"Watts" in "power output" of an amp refers to the amount of power an
amplifier will deliver into a specified load (speaker). Your bassman
is specified for 8 ohms (I suppose--I'm not sure), and most solid
state amps today are specified for 4 ohms. A SS amp rated at 400w into
4 ohms will deliver about 250w into 8 ohms. For a GIVEN SPEAKER,
loudness is proportional to the logarithm of power. I.e., double the
power and the loudness is doubled.
Differences in speaker efficiency adds a confusion factor. Open back
cabinet speaker can be designed to be more efficient such that 40
watts in a open back amp can be very loud. A problem is that these
speakers cannot be used in tuned or closed back cabs. Another problem
is that open back cabs are problematical with hollowbody
guitars--resulting in feedback at lower volumes than when using a
properly designed closed back cabinet.
The AI amps are really that powerful. These amps are high tech,
whereas the bassman is 50's technology. There will always be folks who
prefer the "warm" sound of tubes (which in most cases is due to the
preamp tone circuits and has nothing to do with tube vs solid
state--the only significant difference happens when they are driven
near their limits). The AI amps are powerful enough that headroom
should just practically never be an issue!
Everyone should have an AI amp. Half of the problem is solved.
Converting all that enormous power into acoustic power (sound) is the
job of the speaker. Now here I am referring to clean sound, and not
the extra speaker coloration *desired* by some, mostly non-jazz,
players. But for clean sound, there are some modern speakers that do a
nice job of converting that 250 to 400 watts into prodigious acoustic
power--even 8 inch speakers! Consideration has to be given to lower
frequecies having more limitations due to cone travel, etc. but in
general there is no reason to expect to require a larger speaker to
handle more power within this power range for jazz guitar.
There are some very slight efficiency advantages to a larger cone
diameter, all else being equal, but there are other effects that are
more important in the tradeoff of speaker size. For one, a larger
speaker usually requires a bigger enclosure. Otherwise bad things
happen, such as "boomy", "honk" and other terms that refer to humps in
the frequency response resulting from mismatched speaker drivers with
enclosure volume. All speakers are not equal. Some 10" speaker are
very happy in a ported 1 cubic foot enclosure, and others really need
3x that volume to avoid the undesirable humps.
A last point relates to peak power vs RMS power (more or less the same
as average power). Peak power handling of the amp and speaker are
probably more important for the jazz guitarist than RMS power, since
the peak to average ratio of clean music is fairly high. Eg, passage
with 300 w peaks may have only a 75 to 100 watt average. Overdrive
changes thing dramatically, with peak to average approaching one.
dave
da...@redstoneaudio.com
tubes is due to the fact that because of their lower power, it is
necessary to drive them near their limits. Here, their soft
compressive effects are pleasurable to many ears.
I still prefer clean, but there are those who love the sound of tubes
on the verge of overdrive.
dave
Keith Freeman
> power and the loudness is doubled.
jdah...@uiuc.edu
to be a flat area, unaffected
by tone controls etc or crossover points used during the earlier days.
It has stuck with us.
Most techs these days would use a sine wave, a sweep generator, and
for those lucky enough
to have it, TEF (time, energy, frequency) equipment.
jdah...@uiuc.edu
transistors.
While both are biased to the linear portion of their transfer curves
for audio amplifiers,
the curves for tubes follow Childs Law or Square Law Curvature. The
inherent non linearities
tend to emphasize even harmonics (pleasing to the ear!). Signal flow
is accomplished by the
flow of leectrons. The curves for BJT transistor are natural
logarithms. The non linearities tend
to emphasize odd harmonics (less pleasing to the ear). While electrons
flow in transistors, there
is also another flow, hole flow going in the reverse direction. Many
believe this is why transistors
sound "faster".
and the Good News! FETS and MOSFETS are solid state devices that have
tubelike characteristics.
They consume little power relative to tubes and are the backbone of
tone in amps like the Clarus.
The other biggy that saves power from the electric company in amps
like the Clarus is the switch
mode power supply. It takes from the power company just what is needed
instantaneously to provide
the power you NEED from your guitar! (no, I don't work for them)
Walter Woods and others are the
same. I love the sound of all tube amps and have two of them that I
regularly use. However a tube
stage (like an ART tube MP) with a really good tube in it in front of
an amp like a Clarus is a great
way to go, especially for clean.
art...@invalid.co.uk.invalid
"Brian" <b.al...@gmail.com> wrote:
> Dave has hit upon THE key point when it comes to why people feel 'tube
> watts' are louder than 'Transitor watts'. It's all about compression
> and how each device behaves as you approach clipping.
>
> 1) Tubes tend to naturally compress as they approach their maximum
> output. As they compress, the average output power increases (thus the
> 'volume' you hear) while the peak does not. Tradistional RMS power
> measurements don't really apply because what used to be a sine wave,
> isn't any more because it's compressed. You can demonstrate this using
> a decent compressor and a transistor power . Set te compressor to
> limit at a level just below the point where the transitor amp is
> clipping. Now turn your source up. The volume is getting louder, but
> tere's no clipping. Voila! - Clean Headroom.
>
> 2) When tubes clip, they product even harmonics - which in small
> doses, sound sweet. When transistors clip, they produce odd hamronics
> that sound like ass in any amount. So, transistor amps should never be
> run into clipping, where as tube amps do it all the time. That's why
> the Clarus needs 300 watts to sound as loud as the 30 watt Bassman.
>
> End of my sermon. Brian
>
Item 2 needs further elaboration.
Single transistor and valve/tube preamp stages have surprisingly
similar characteristics, both producing a lot of even harmonics
because of their asymmetry. The valve stage has a relatively low
voltage gain and a high input impedance and is easy to bias. The
transistor stage has a lowish input impedance, an excessively high
voltage gain and its bias is much more temperature sensitive.
In practice, the valve stage can be used on its own and the transistor
stage is almost always elaborated to include many transistors with
feedback to define the gain, e.g. an Op Amp.
When the the relatively low gain valve stage is overdriven, it
initially produces a waveform without sharp edges as it first goes
into clipping, adding mostly 2nd and 3rd harmonics. Further
overdriving will sharpen the edges, but this doesn't happen until
quite a few dB above the onset of clipping.
The multi-transistor stage with feedback, on the other hand, follows
the input waveform nearly perfectly until some part of its internal
circuitry is well into clipping, at which point the feedback fails and
the output waveform steps sharply into clipping. The sharp edges on
the waveform represent high harmonics which are clearly audible and
objectionable. The transition from clean to grossly overloaded happens
with a tiny change in input level.
Overloading the power stage of a valve amp is thought by many to give
the best distorted sound, but push - pull output stages, as used in
most valve amps above a few watts, produce predominantly _odd_
harmonics. If they are perfectly balanced, there can be no even
harmonics at all.
Arthur
--
Arthur Quinn
real-email arthur at bellacat dot com
da...@redstoneaudio.com
wrote:
Man, you're on the ball. I said it wrong. Loudness is proportional to
power :-{ The point I was trying to make is that going from 20w to
30w has the same effect, as perceived by the ears, as going from 200w
to 300w.
dave
steve
formulated
the following incoherence:
> Not simple topic for sure, when you get done with Watts, you'll have
> to get into Ohms as well, too confusing for me.
Abbot and Costello had a "What's [Watts] amps?" routine similar to the
"who's on first" thing. Pretty funny.
--
"The accused will now make a bogus statement."
James Joyce
pmfan57
> On 6-Mar-2007, smacked up and reeling, "Khean" <tiankh...@gmail.com>
> blindly formulated
> the following incoherence:
>
> > what it really means when they say an amplifier is X Watts or Y
> > Watts. And then now I learn that a tiny Acoustic Image is 300 Watts
> > while my giant Fender Bassman is 40 Watts. Can somebody, please
> > explain clearly to me, right from the beginning, the ABCs of Watts.
> > Are there different ways of measuring Watts? Is an Acoustic Image
> > really more powerful than a Fender Bassman? You mean it's LOUDER, or
> > what do you mean? So how many Watts do I go for in what situation?
> > Thanks!
>
> level of sound ouput. There is a relationship between power consumed and
> the amount of sound output, but it isnt necessarily 1 to 1. Im convinced my
> 45W Heritage is much(!) louder than my 50W marshall, for example. I
> suspect the number of filters and effects as well as the efficiency of the
> circuits and speakers have everything to do with the power/sound
> relationship. Also, the human ear has it's own qualities that probably play
> into the perception of loudness. It's no simple topic, that's for sure.
>
> steve
> --
> "The accused will now make a bogus statement."
> James Joyce
There's never been anything louder than my old Marshall 50 was. They
had to repaint the walls in the places I played at.