My amp needs to be louder, said the novice

[soundguruman]

And one more thing to consider, while I am at it...

Square wave, distortion sounds much louder to the human ear.

Clean guitar, at 100 watts...
sounds equal to the human ear in loudness
as distorted guitar at 40 watts, or even less...
To the human ear, distortion sounds wayyyyyy louder.

So if you play clean or distortion, there is a huge difference between them in loudness, to the human ear.

[JHow]

50 watts to 100 watts, 3db increase, n'est-ce pas?

dBW (Decibel-Watt)

[soundguruman]

50 watts to 100 watts, 3db increase, n'est-ce pas?

dBW (Decibel-Watt)

See, another good example is:
I can take 50W Marshall, and knock it down to 18 Watts, by changing it to triode operation. (instead of pentode)

But then, at 18 watts, the difference in actual volume loudness, is almost UN-detectable to human ear.
Not many people could even hear the difference in volume.

I can take Marshall 100, and Marshall 50, side by side...
and almost nobody could hear the difference in volume.

The human ear can't hear the change. Until the change is HUGE.

[soundguruman]

So you see,
to make the Same Amp Louder...

The distortion loudness is in the amp.

The acoustic loudness is all in the speaker.

The key is the speaker, not the power of the amp.

[g1]

"If you take a 50 watt amp and double the power to 100 watts, if all else is the same, you will hear only 3 decibels louder output."

That is not correct.
It takes quite a bit more increase in power to double the actual loudness.

Actually it is you who incorrectly read what he said. He said double the power, not double the loudness.

But, if you are using a more efficient speaker, you are on the right track to increase loudness, without increasing power.
(I was the first person in this forum to point out this fact...remember?)

Go ahead and keep patting yourself on the back, "guru of Oz", but Enzo was discussing this in post #2, so how were you the first one to mention it?

And why should we leave speakers out of it? A speaker with 3db greater efficiency will make it the same louder as doubling the power. A speaker with 6db greater efficiency will have the same effect as QUADRUPLING your power.

Except that his explanation is wrong.

No, Enzo's explanation was quite correct to anyone capable of reading and comprehension. Doubling power to a given speaker cab give a 3 db increase in loudness. Doubling loudness is a completely different thing.

[soundguruman]

"If you take a 50 watt amp and double the power to 100 watts, if all else is the same, you will hear only 3 decibels louder output."

Like I said before, that's incorrect.

"you will hear only 3 decibels louder output."

If you hear 3db louder output, you have doubled the loudness of the amplifier. FACT.

BUT double the power does not equal double the loudness. That's a very common misconception. I am not surprised.
It takes several times the power, (not double) to double the loudness. Typically 6 to 10 times the power...to double loudness.

Everything I said, is correct, and you can test it for yourself.

[eschertron]

"If you take a 50 watt amp and double the power to 100 watts, if all else is the same, you will hear only 3 decibels louder output."

Like I said before, that's incorrect.

"you will hear only 3 decibels louder output."

If you hear 3db louder output, you have doubled the loudness of the amplifier. FACT.

BUT double the power does not equal double the loudness. That's a very common misconception. I am not surprised.
It takes several times the power, (not double) to double the loudness. Typically 6 to 10 times the power...to double loudness.

Everything I said, is correct, and you can test it for yourself.

I hope that we are all in agreement on everything except perhaps what the term "loudness" means.

You are correct that a 3dB increase in loudness is an audible increase, but is not perceived as double, even though it is a doubling of the acoustic power. It takes about an entire Bel (that's 10 decibels for those unfamiliar with the metric system ) for the human ear to register a doubling in loudness. SO yes, it takes 10 50W amps to sound twice as loud as a single 50W amp.

I hope the confusion is simply how people are using the term "loudness". I'm not sure that it has an actual mathematical definition.
Are you claiming that, in theory, doubling the power of a device does does not increase the acoustic power output by 3dB (3.01dB actually), or are you saying that in practice there are other factors to consider that prevent the acoustic power from actually reflecting the doubling of the source power? If the latter, I think that most forum members may agree with you that output trannys, speakers, etc. can have an effect on the power transmission. In fact, this and other threads have been discussing those very things.

If you disagree with the theory, however, allow me to submit Sound Power, Intensity and Pressure that gives the power formula. And yes, on every calculator I've used, 10*log10(100W/50W) = 3dB.

[Jazz P Bass]

What are you on about SGM?

(or on?)

+ 3db = 2 x the Power
+ 6db = 2 x the Amplitude
+10db = 2 x Perceived Volume.

[g1]

I think one of the (many) things that the grand guru is confused about is doubling in power versus doubling in loudness (spl). It's a "very common misconception", and easy beginner mistake to make.

If you hear 3db louder output, you have doubled the loudness of the amplifier. FACT.

That is absolutely wrong. If you HEAR 3db louder output, you have increased the loudness a bit. To HEAR double the loudness takes 10db increase, not 3db.

BUT double the power does not equal double the loudness. That's a very common misconception

Well, that's what you just said, you said doubling the power (3db increase) had "doubled the loudness of the amplifier. FACT "

But be absolutely sure NOT to admit you made a mistake, the real SGM would never, ever do that .

To put it in very simple terms: doubling the power into a given speaker will give 3db (slight) increase in spl (loudness).
To double the perceived loudness (spl) takes 10db increase, or TEN TIMES as much power into same given speaker.

[Blick Fang]

Hey Guys

The 3db fun is awesome but.........It's the same cabinet for both amps. I wish I could use Jazz P Bass's advice and test it. But the back is not removable and I would have to unmount a speaker. I suppose I COULD do that but don't really want to.

[eschertron]

Hey Guys

The 3db fun is awesome but.........It's the same cabinet for both amps. I wish I could use Jazz P Bass's advice and test it. But the back is not removable and I would have to unmount a speaker. I suppose I COULD do that but don't really want to.

Yeah, heh heh... we do seem to go off on our tangents, now and again!

As g-one and Tom Phillips have said, a SS amp rated at 150W into 4 Ohms is not 150W into 8 Ohms. So comparing apples to apples, the SS amp - into an 8-Ohm load - is probably rated about 100W, as compared to the Bugera tube amp at 120W. If the loudest clean (clean-ish) signal that you can get out of each amp is comparable in apparent loudness, I'd think that would be about right.

[The Dude]

Typically, about 6-10X increase in power to double the loudness 3 db.

3dB has not, is not, nor will ever be considered "double the loudness". Your argument is based on false information.

[g1]

Yes, sorry about the hijack of your thread.
As Eschertron suggested, set them both up to go as loud as they can cleanly, don't worry about what the knobs say, use your ears. How different is the loudness? Does the SS amp have a built in limiter/compressor?

[The Dude]

The TBX150H owner's manual says "160Wrms/320Wmax" at 4 ohms- "158.7Wrms" at 1%THD. It does not specify any other parameters of the rating or how it was achieved, nor does it specify a rating at 8 ohms. I'd like to see a schematic (couldn't find one) to see what this amp uses for output devices. I'd be willing to bet that these specs are inflated.

As an example: I recently had a customer bring in a bunch of Behringer B212 speakers with blown woofers. The cabinets clearly said on the rear that they were rated at 800W. When I took them apart, it said right on the 12's 250W Peak. It's not just Behringer doing this either. I see it quite often these days.

Sure tube amps are going to be louder for various reasons- EM influence of output transformers, smoother saturation, etc., etc. My point being that SOME of the discrepancy here is also because amps are not spec'd these days like they once were. For instance, if you ever played through some of the older SS amps like maybe the old Acoustics, they were genuinely loud and kept up pretty well with tube amps. They were rated realistically. A 100W SS Acoustic amp built in the '70's is perceptively louder than most current model 100W SS amps.

Manufacturers seem to be getting better at "stretching the truth".

[The Dude]

(2 in a row.....sorry, but another subject)

Another thing lacking from this discussion is that tube amplifiers have output transformers and generally SS amps do not. When transistors clip, the effect is well heard and the waveform more immediately goes to a very unpleasant sounding square wave. Because of this, SS amps generally have more negative feedback to control gain at peak levels. This purposely limits max volume. A square wave fed through a tube output stage and output transformer is rounded off and is more tolerable to the ear. (What happens when you feed a square wave through a transformer?) The effect of this is that much less, if any, negative feedback is necessary for a tube amp. The wave form is still distorted by definition (the output is not exactly equal to the input), but it is much more tolerable and, up to a point, not noticeable at all to the ear. This means that we can go past the same peak power with less audible distortion.