Clipping the signal would make the waveform look like a square wave, and the fact that it is a waveform defines it as being AC, that is, alternating current.
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Common amp myths
- Thread starter JimmyM
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+1This all very interesting, but you are all avoiding the gorilla in the room--the greatest myth of all:
"If I can just sell my old Watt Wonder amp and Frumpus Short Circuit pedal, I can buy a ThunderAudio Bowel Atomizer head and be G.A.S. FREE FOREVER !"
Bluesy Soul
There exists a perfect amp (or bass for that matter) for me which will end my GAS forever...
I have been trying to come up with something to say that hasn't been said over and over before. Your comment seems to open up a possibility: Prove it with an oscilloscope.
An engineer who really understands tube amps could choose waveforms (hopefully including signals recorded from real basses) which clearly illustrate the purported benefits of tube power amps. Then they could measure the waveforms and publish the data online. This would prove that the effects are real, and tell us what their magnitude is.
I can not resist (oooh - was that a pun...?):
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to quote:
"Clipping is a form of waveform distortion that occurs when an amplifier is overdriven, which happens through attempts to increase the voltage or current beyond its maximum power capability. Driving an underpowered amplifier into clipping is the most common cause of loudspeaker failure."
oh my.
Well, Wiki has been wrong before...
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to quote:
"Clipping is a form of waveform distortion that occurs when an amplifier is overdriven, which happens through attempts to increase the voltage or current beyond its maximum power capability. Driving an underpowered amplifier into clipping is the most common cause of loudspeaker failure."
oh my.
Well, Wiki has been wrong before...
There seems to be a lot of conflicting ideas in regards to underpowering a speaker so I'll remain objective about it till someone can personally demonstrate it to me. I think there's enough debate to where we can't actually classify it as fact or fiction (at least on here just yet). Perhaps submit to the mythbusters? LOL
My favorite myth is that you have to have a lot of watts to get a lot of volume.
My favorite myth is that you have to have a lot of watts to get a lot of volume.
And is wrong again. Who would you believe, engineers here on TB, some of whom make their living dealing in audio, or Wikipedia, a free for all clusterf$*% that anyone can edit at will?
Rephrase it however you want - if you can list ONE single 300 watt SS amp that'll keep up with a healthy SVT, or ONE single 200 watt SS amp that can keep up with a Marshall Major - given the same bass, cab, and acoustics - I'll admit that I was wrong...
A Marshall Major is a very loud amp - so is an SVT - comparitively, most SS amps in the 200-300 watt range are not considered loud by anyone's standards...
- georgestrings
I would say that a more relevant test than using an O-scope would be using an SPL meter to record volumes between amp types with the same ratings - with all other variables being the same... After all, people *usually* listen to what an amp puts out more than they care how it's output shows up on an O-scope... - a "real world" test, if you will...
- georgestrings
most tube amps are push-pull design, and some solid state ones two, and they are also louder. It's all about what class the amp is.
Tube watts is referring to class A or (usually) AB.
Any solid state amp on the market that less than $1,500 is probably not class A or AB.
Most amps use efficient switching designs. These designs are efficient because they operate either at full on or full off, the most efficient settings. They basically send modulated pulses of square waves to the speaker, and because of the speakers inertia, it smooths everything out and you hear a sine wave. because it just sends little pulses, it has less power loss inside the amp, but they also have a lower damping factor (control over the speaker)
http://en.wikipedia.org/wiki/Switching_amplifier
These amps use pulse width modulation
http://en.wikipedia.org/wiki/Pulse-width_modulation
In the class A or AB design that tube amps use, the power amp sends the speaker an (theoretical) exact replica of the input signal, only louder. it has much more control over the speaker.
http://en.wikipedia.org/wiki/Electronic_amplifier#Power_amplifier_classes
That's probably why tube amps are louder. in a class A or AB amp, the amp is putting more into the speaker than switching amps.
Tube watts is referring to class A or (usually) AB.
Any solid state amp on the market that less than $1,500 is probably not class A or AB.
Most amps use efficient switching designs. These designs are efficient because they operate either at full on or full off, the most efficient settings. They basically send modulated pulses of square waves to the speaker, and because of the speakers inertia, it smooths everything out and you hear a sine wave. because it just sends little pulses, it has less power loss inside the amp, but they also have a lower damping factor (control over the speaker)
http://en.wikipedia.org/wiki/Switching_amplifier
These amps use pulse width modulation
http://en.wikipedia.org/wiki/Pulse-width_modulation
In the class A or AB design that tube amps use, the power amp sends the speaker an (theoretical) exact replica of the input signal, only louder. it has much more control over the speaker.
http://en.wikipedia.org/wiki/Electronic_amplifier#Power_amplifier_classes
That's probably why tube amps are louder. in a class A or AB amp, the amp is putting more into the speaker than switching amps.
You snatched the words from my mouth. If we're citing authorities as credible as Wikipedia, I'd better check with my dog, Thud, on this topic as well.
Bluesy Soul
(Thud is a Labrador Retriever and, as a representative of the straight-coat, short-haired breeds, he says he never worries about waveforms or clipping!)
Where you are coming from is using your ears, and trying to tell us that we're wrong. I am sorry, but anytime your ears are involved, that is perception. And yes, you are perceiving the tube amp as being louder. As has been pointed out several times, you perceive tubes as being louder because the distortion isn't awful to your ears, so you can crank and think it is louder, among other factors. If numbers are your thing, let's set up an example.
Two amps, one tube, one ss, both rated at 100 watts, both with .001% THD at 75 watts, .1%THD at 85, and 1%THD at 100.
Even if all those things are equal, you hear "bad" distortion with the SS amp much earlier than with the tube amp.
On top of all that, your "real world" tests are completely unscientific and speculative also. I am going out on a limb, but can you prove to us that the gain structure in both amplifiers was set up exactly the same?
Anyways, to do this scientifically you would use a sine wave from a signal generator, and the gain structure of both amps would be set up identically, and you would use the sine wave at differing levels of output and record the SPL at the speakers. You would then see that both amps would be equal, watt for watt.
Check any electrical engineering book and get back to me on where it states that there is such thing as one type of watt being more powerful than another. It simply is not true.
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
- 12,668
- 2,036
- 67
- Disclosures
- Former Technical Communications Developer, QSC Audio
Uh, no.
The vast majority of SS power amps are class AB.
Tube amps doe not have "more control" over the loudspeaker.
I don't think you actually read those Wikipedia articles that you provided links to.
Some old myths really die hard, huh?
Apparently. He refutes one argument by questioning a form of logic which he in turn uses in his own argument...
You got to it before I could. I'm not sure where the whole "most SS are not AB" is coming from. Until fairly recently, most SS were AB, right?
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
- Jul 3, 2001
- 12,668
- 2,036
- 67
- Disclosures
- Former Technical Communications Developer, QSC Audio
You can always set one amp to be louder than another. Using a sound level meter can verify it, but what would it show?
So, you're saying that setting up an SPL meter, and seeing which one is louder would not be a valid determining method??? That would certainly take the human ear out of the equation... As far as gain structures are concerned - does it really matter, if a bass is plugged directly into an amp, which is then plugged directly into a cab - and both amps are tested in exactly the same method??? I'd say that if both amps have different gain structures within themselves, and that contributes to a volume difference - then the louder amp is still more powerful...
- georgestrings
I guess you don't understand the numerous explanations given. LOUDNESS IS NOT A SCIENTIFIC MEASUREMENT!!
You are perceiving something and stating that to be fact. The reason the 200 SS amp can't keep up is because it reaches a certain level of THD beyond which you get distortion, whereas with the tube amp you can keep on pushing well beyond that point and you perceive it as getting louder, when all you are doing is adding distortion and compression to your signal.
Using the amp's own controls, wouldn't you say that the amp that will create the most volume is most likely more "powerful"??? - atleast as far as any actual usefullness is concerned, that is...
- georgestrings
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