I have been reading around and have noticed that many tube amps have output ratings very low (8W for example). However, from what I have read, they still put out sound that is loud and accurate (if not too loud at full volume). Yet speakers hooked up to a 100W amp is also loud yet it has more than 10times the power rating. How can 8W be as loud as 100W? Is the signal more efficient? Please let me know, as I am always curious and am thinking about building this tube amp as a first DIY amplifier. http://www.s5electronics.com/gpage1.html
Thanks for your time.
-Ed
Thanks for your time.
-Ed
The only way efficiency comes into play is with your speakers efficiency at moving as much air for the same power...
A 94dB efficient speaker would produce x more amount of noise for 10 watts than would a 80dB efficient speaker for 10 watts
or something like that, I have no idea how the mathematics are done...
Other than that, a 50 watt amp is only 1/4 louder than 25watts, No?
Same as a 400watt amp producing 2x of the output power of a 100 watt amp or something like that.
A 94dB efficient speaker would produce x more amount of noise for 10 watts than would a 80dB efficient speaker for 10 watts
or something like that, I have no idea how the mathematics are done...
Other than that, a 50 watt amp is only 1/4 louder than 25watts, No?
Same as a 400watt amp producing 2x of the output power of a 100 watt amp or something like that.
I'll tell you one thing for certian tho
My cheapo Magnavox 10 watt mid-range all-range with whizzers can fill this entire room and corridor with sound without any boxes on a 20w per channel transistor amp while my $150 ones in boxes inside a 3 way give HEAPS of bass that you can hear for a mile, but have NO mid-range to speak of when compared to these beauties
May be a bit confusing but it's all in there somewhere.
My cheapo Magnavox 10 watt mid-range all-range with whizzers can fill this entire room and corridor with sound without any boxes on a 20w per channel transistor amp while my $150 ones in boxes inside a 3 way give HEAPS of bass that you can hear for a mile, but have NO mid-range to speak of when compared to these beauties
May be a bit confusing but it's all in there somewhere.
Hi guys;
>>>...Other than that, a 50 watt amp is only 1/4 louder than 25watts, No? Same as a 400watt amp producing 2x of the output power of a 100 watt amp or something like that...<<<
Double the output power and you get +3dB increase in perceived volume, all else being equal. Quadruple the output power and you get +6dB increase in perceived volume. +10dB is generally regarded as being "twice as loud", perceptually.
Now, as for the original question, it comes down to the use of the term RMS (Root Mean Square, or "average"). Music is produced as transient peaks, so two amps that have identical RMS ratings (their ability to produce output power on average for a long time period) may not sound equally loud if one can produce more PEAK watts. Where this gets dicey is that there's no agreement on just HOW to go about measuring those peak watts. Marketing depts used to play all manner of games with output wattage ratings giving inflated, meaningless, numbers. That's why the FTC stepped in and set standards for measurement (which are now routinely sidestepped by doing things like using 8 ohm static loads, 1kcps sine waves, and only driving one channel - all of which is legit, so long as it's in the fine print).
Perhaps a better way of dealing with the issue of "peak watts" is to measure "peak transient voltage" for a time period determined to represent most musical transients.
One other consideration is the slew rate - a "slow" amp may not be able to produce a rapid transient signal at all to it's full peak. Thus a "faster" amp can tend to sound louder than a "slow" amp. The speed is called "slew rate" and is a measure of rate of change of volts with respect to time - thus if an amp can't "swing" up to the full output voltage in the short time that a transient signal is present, it won't pull the same number of output volts for that transient (it's like it rounds the top off, get it?).
Hope this helps.
All the best,
Morse
>>>...Other than that, a 50 watt amp is only 1/4 louder than 25watts, No? Same as a 400watt amp producing 2x of the output power of a 100 watt amp or something like that...<<<
Double the output power and you get +3dB increase in perceived volume, all else being equal. Quadruple the output power and you get +6dB increase in perceived volume. +10dB is generally regarded as being "twice as loud", perceptually.
Now, as for the original question, it comes down to the use of the term RMS (Root Mean Square, or "average"). Music is produced as transient peaks, so two amps that have identical RMS ratings (their ability to produce output power on average for a long time period) may not sound equally loud if one can produce more PEAK watts. Where this gets dicey is that there's no agreement on just HOW to go about measuring those peak watts. Marketing depts used to play all manner of games with output wattage ratings giving inflated, meaningless, numbers. That's why the FTC stepped in and set standards for measurement (which are now routinely sidestepped by doing things like using 8 ohm static loads, 1kcps sine waves, and only driving one channel - all of which is legit, so long as it's in the fine print).
Perhaps a better way of dealing with the issue of "peak watts" is to measure "peak transient voltage" for a time period determined to represent most musical transients.
One other consideration is the slew rate - a "slow" amp may not be able to produce a rapid transient signal at all to it's full peak. Thus a "faster" amp can tend to sound louder than a "slow" amp. The speed is called "slew rate" and is a measure of rate of change of volts with respect to time - thus if an amp can't "swing" up to the full output voltage in the short time that a transient signal is present, it won't pull the same number of output volts for that transient (it's like it rounds the top off, get it?).
Hope this helps.
All the best,
Morse
Our ears are logarithmic. We can barely hear an increase of 3dB.
3dB = twice the power.
8W to 100W is just over 10dB, just a little louder. 10dB = 10 times the power. The 100W amp is just a little louder.
An 8W amp with 100dB speakers will sound exactly as loud as a 80W amp into 90dB speakers.
3dB = twice the power.
8W to 100W is just over 10dB, just a little louder. 10dB = 10 times the power. The 100W amp is just a little louder.
An 8W amp with 100dB speakers will sound exactly as loud as a 80W amp into 90dB speakers.
Ok... to examples. We have speaker rated 86db/1w/1m. Everytime you double the power applied to the voice coil your speaker will put out 3db more SPL. In order to reach 92db you'll need to apply four times the power - 4w. In order to reach 110db you'll need to apply 256 times the power - 256w.
Imagine a speaker rated 98db/1w/1m - a very efficient speaker. In order to reach 110db you'll only need to apply 16 times the power to the voice coil.
That explains why a low wattage tube amp can easily destroy your ears when used with sufficiently efficient speakers.
Imagine a speaker rated 98db/1w/1m - a very efficient speaker. In order to reach 110db you'll only need to apply 16 times the power to the voice coil.
That explains why a low wattage tube amp can easily destroy your ears when used with sufficiently efficient speakers.
Morse, interesting question
Got an interesting question for you or anyone else for that matter.
"+10dB is generally regarded as being "twice as loud", perceptually."
I certainly agree.
On "millionaire show" I believe the question was asked:
"How much louder is a 30db signal than a 10db signal?"
The choices given were:
A) 3
B) 200
C) 100
D) 1000
What would be your answer?
Got an interesting question for you or anyone else for that matter.
"+10dB is generally regarded as being "twice as loud", perceptually."
I certainly agree.
On "millionaire show" I believe the question was asked:
"How much louder is a 30db signal than a 10db signal?"
The choices given were:
A) 3
B) 200
C) 100
D) 1000
What would be your answer?
My "guess" 10^2 - or 100 times louder. A full scale explanation here: http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l2b.html
Yes...Ed...you mentioned 100Watts? are you rounding that from a tube or tranny amp ?big diff.... The nice rounding-off from tube amp clipping can add more fullness to the sound, although not for Hi Fi users.
So it's a well known fact that many say < a 50Watt tube amp can sound just as loud a 100W tube amp>.
Okay..there's only 3dB power difference for the electronics to fudge up from 50W to 100W.........i.e roughly 14V into 4 ohms v.s 20V into 4 ohms. Looking at a voltmeter or analyser between the two output voltage levels (6dB) doesn't seem much of a change, but it's usually a change in the hardware parts, i.e beeffier PSU and perhaps o/p tranny.
Catch.........3dB differences from LS speaker sensitivities can mean life or deafness for many SE amps. i.e .....it's suicide for many SE amps to liven up low efficency speakers less 87dB or even 90dB 1W/1metre, unless one owns Klipsches.
Don't ignore specs! Do the +/- game; 3dB from amp then add to speaker or vice versa for a relevant power level. So the more speaker (chassis) units there are in a given cabinet the louder and more spacious the sound will be, for a given impedance, amp power & loudness intensity level. That's why I'm an advocate of putting as many speaker units in a cabinet, so long there is still an impedance match with the amp.
In this rough example, comparing two chassis units with same imp;
Profess chassis unit = 99dB and other
Kef B300B = 86dB....(low effic Hi Fi)......an 100W amp would be required for the Kef unit compared to only 25 watts for the same loudness from the first unit with a lower power requiremnt.
<what always happens ??>: the lower sens units risks burn out because someone connects a higher powered amp whereas the higher efficiency unit excels.
Just to recap...
6dB =2xVolts; 10dB=3xVolts; 20dB=10xVolts;30dB=30xVolts:
3dB=2xWatts;10dB=10xWatts, and so on.
rich
So it's a well known fact that many say < a 50Watt tube amp can sound just as loud a 100W tube amp>.
Okay..there's only 3dB power difference for the electronics to fudge up from 50W to 100W.........i.e roughly 14V into 4 ohms v.s 20V into 4 ohms. Looking at a voltmeter or analyser between the two output voltage levels (6dB) doesn't seem much of a change, but it's usually a change in the hardware parts, i.e beeffier PSU and perhaps o/p tranny.
Catch.........3dB differences from LS speaker sensitivities can mean life or deafness for many SE amps. i.e .....it's suicide for many SE amps to liven up low efficency speakers less 87dB or even 90dB 1W/1metre, unless one owns Klipsches.
Don't ignore specs! Do the +/- game; 3dB from amp then add to speaker or vice versa for a relevant power level. So the more speaker (chassis) units there are in a given cabinet the louder and more spacious the sound will be, for a given impedance, amp power & loudness intensity level. That's why I'm an advocate of putting as many speaker units in a cabinet, so long there is still an impedance match with the amp.
In this rough example, comparing two chassis units with same imp;
Profess chassis unit = 99dB and other
Kef B300B = 86dB....(low effic Hi Fi)......an 100W amp would be required for the Kef unit compared to only 25 watts for the same loudness from the first unit with a lower power requiremnt.
<what always happens ??>: the lower sens units risks burn out because someone connects a higher powered amp whereas the higher efficiency unit excels.
Just to recap...
6dB =2xVolts; 10dB=3xVolts; 20dB=10xVolts;30dB=30xVolts:
3dB=2xWatts;10dB=10xWatts, and so on.
rich
Interesting question
I think Morse hit it right in his answer.
The question asked about how much "louder", which is perceived by the listener.
Yes, 20db (30 - 10db = 20db) is 100 times more power, but loudness, which is perceived by the listener, would be about 3-4 times.
Think of turning up the "bass" tone control. It may be 15db, but doesn't sound 80 times "louder".
I think the question is flaky, like mixing two different concepts. Wouldn't the correct question be, for 100 to be the answer,
"how much more power is 30db than 10db?"
The lady got the wrong answer, 3, and 100 was given as the right answer.
Cheers.
I think Morse hit it right in his answer.
The question asked about how much "louder", which is perceived by the listener.
Yes, 20db (30 - 10db = 20db) is 100 times more power, but loudness, which is perceived by the listener, would be about 3-4 times.
Think of turning up the "bass" tone control. It may be 15db, but doesn't sound 80 times "louder".
I think the question is flaky, like mixing two different concepts. Wouldn't the correct question be, for 100 to be the answer,
"how much more power is 30db than 10db?"
The lady got the wrong answer, 3, and 100 was given as the right answer.
Cheers.
Hi Positron;
*LOL*!
It's one of those "define your terms" situations. Is the "signal" given in terms of potential (voltage) or power (watts)? Is the definition of "loudness" PERCEIVED loudness or is it a measure of amplitude of output signal with respect to the reference input signal (i.e. a linear measure of V/V0 or P/P0)?
Let's say it's voltage and perceived loudness. Then a 20dB difference represents doubling the volume. Let's say it's voltage and linear amplitude with respect to the reference voltage. Then 20dB represents 10 times the reference voltage. Let's say it's power and perceived loudness. Then 20dB represents 4 times the apparent loudness. Let's say it's power and a linear measure of power with respect to the reference level - then it's 100 times the reference power level.
Now you know why I never wanted to be on a game show!!
All the best,
Morse
*LOL*!
It's one of those "define your terms" situations. Is the "signal" given in terms of potential (voltage) or power (watts)? Is the definition of "loudness" PERCEIVED loudness or is it a measure of amplitude of output signal with respect to the reference input signal (i.e. a linear measure of V/V0 or P/P0)?
Let's say it's voltage and perceived loudness. Then a 20dB difference represents doubling the volume. Let's say it's voltage and linear amplitude with respect to the reference voltage. Then 20dB represents 10 times the reference voltage. Let's say it's power and perceived loudness. Then 20dB represents 4 times the apparent loudness. Let's say it's power and a linear measure of power with respect to the reference level - then it's 100 times the reference power level.
Now you know why I never wanted to be on a game show!!
All the best,
Morse
hmm i've heard of this before. My guitar teacher just got a 250 watt tube amp for his guitar. (i'm jealous... i got his old solid state 150w) He said that when you buy tube amps, multiply the wattage by three to get the wattage it would sound like with solid state. Obviously a watt is a watt, so thru the same speakers it would be just as loud. but with the same cab on this his was ear peircing loud at half volume(course we had ear plugs) and mine well.. wasnt. even though it was turned up all the way.. i dunno
All I'm going to add to this soon-to-be-long thread is that 1. tube amps distort softly so maximum power is reached more gracefully. (Unless it's a chunky amp with 30-40dB NFB! 
) That means you can run much closer to maximum power output with less average distortion. 2. SS is mainstream, and as such the ratings are embellished, sometimes substantially. PMPO ratings, for example, and silos of pure cow excrement. However, tube amps are typically sold for their mystique, appearance and price tag, with little regard for the power. (Obviously a 300W amp is going to go for a hell of a lot more than a 8W amp, unless it's a WE300B amp. . .so. . .never mind ) 3. A solid state radio may designed so that even with the volume control maxed out, the program material (which due to compression and AVC is going to be a reliable signal strength coming out of the demodulator) will never cause distortion in the output. That is, there purposely isn't enough gain in the system to overdrive the output. Of course, much cheaper radios are just poorly designed throughout and this WILL still happen...
Oh, and 4., all amplifiers tend to have a standard input voltage of say .1, .5, 1 or 2 or 5V of whatever units (RMS, average, peak, peak-to-peak), so between a 5W and a 100W amp, which one will have more gain from input to speaker? So which one will SEEM louder, even though the material may never peak to even 1W?
Tim
) That means you can run much closer to maximum power output with less average distortion. 2. SS is mainstream, and as such the ratings are embellished, sometimes substantially. PMPO ratings, for example, and silos of pure cow excrement. However, tube amps are typically sold for their mystique, appearance and price tag, with little regard for the power. (Obviously a 300W amp is going to go for a hell of a lot more than a 8W amp, unless it's a WE300B amp. . .so. . .never mind ) 3. A solid state radio may designed so that even with the volume control maxed out, the program material (which due to compression and AVC is going to be a reliable signal strength coming out of the demodulator) will never cause distortion in the output. That is, there purposely isn't enough gain in the system to overdrive the output. Of course, much cheaper radios are just poorly designed throughout and this WILL still happen...Oh, and 4., all amplifiers tend to have a standard input voltage of say .1, .5, 1 or 2 or 5V of whatever units (RMS, average, peak, peak-to-peak), so between a 5W and a 100W amp, which one will have more gain from input to speaker? So which one will SEEM louder, even though the material may never peak to even 1W?
Tim
Hi Tim;
All true, and point (4) is one that's well worth bearing in mind for DIY'ers.
Most mainstream hifi kit will be at red faced max power out with the volume control around 12 o'clock - and it's designed to be pretty darn' loud at the 9 o'clock position. In other words, it throws away half the adjustability of the volume control to give a false impression of power at a "low" volume setting ("Hey, if it's this loud 1/4 of the way up, how loud is it all the way up" ANS: You'll never be able to use it past "half way up", so it's a silly question...).
Generally I try to design the gain stages in my DIY hifi's so that with the source I'm using I'll make use of the whole volume control. Suit yourself, but I like having the extra adjustability.
Marketing has fouled up the mainstream hifi pretty thoroughly, by introducing un-necessary features and altering designs in fundamental ways that are intended to stand out better on paper and in a crowded showroom for a 5 minute audition rather than sound better or work better over the long haul - which is one reason I went back to DIY.
Save the money, build your own hifi and enjoy better music reproduction....oh well, preaching to the choir!
All the best,
Morse
All true, and point (4) is one that's well worth bearing in mind for DIY'ers.
Most mainstream hifi kit will be at red faced max power out with the volume control around 12 o'clock - and it's designed to be pretty darn' loud at the 9 o'clock position. In other words, it throws away half the adjustability of the volume control to give a false impression of power at a "low" volume setting ("Hey, if it's this loud 1/4 of the way up, how loud is it all the way up" ANS: You'll never be able to use it past "half way up", so it's a silly question...).
Generally I try to design the gain stages in my DIY hifi's so that with the source I'm using I'll make use of the whole volume control. Suit yourself, but I like having the extra adjustability.
Marketing has fouled up the mainstream hifi pretty thoroughly, by introducing un-necessary features and altering designs in fundamental ways that are intended to stand out better on paper and in a crowded showroom for a 5 minute audition rather than sound better or work better over the long haul - which is one reason I went back to DIY.
Save the money, build your own hifi and enjoy better music reproduction....oh well, preaching to the choir!
All the best,
Morse
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