Common amp myths

[Visirale]

I see the usual troll and few new confused people have weighed in...

It was a well-intentioned idea Jimmy but...

...not worth my time.

We are not worthy!!!

We are not worthy!!!

 

[bongomania]

Wow.

Where do I begin.

Naaah...

Back to billable hours. ;-)

I see the usual troll and few new confused people have weighed in...

It was a well-intentioned idea Jimmy but...

...not worth my time.

IOW "I have nothing constructive to say, but I feel an overwhelming urge to say something."

PBG, I expected better from you.

 

[Thangfish]

15" speakers sound slow.

That's my personal favorite!

 

[Psycho Bass Guy]

IOW "I have nothing constructive to say, but I feel an overwhelming urge to say something."

PBG, I expected better from you.

Oh, I have PLENTY constructive to say, all of which I've already said many, many times before. Since it didn't seem to sink in the first few dozen times, why bother with it again?

 

[Bob Lee (QSC)]

Great post, Jimmy! Thanks.

 

[jsingles]

Oh, I have PLENTY constructive to say, all of which I've already said many, many times before. Since it didn't seem to sink in the first few dozen times, why bother with it again?

WOW

 

[Bass Boy]

Oh, I have PLENTY constructive to say, all of which I've already said many, many times before. Since it didn't seem to sink in the first few dozen times, why bother with it again?

They say the thirty-seventh time is a charm!

 

[Bob Lee (QSC)]

This is true, and everybody is misunderstanding his point. He's stating that if 300 watts is enough headroom for what you are doing, adding 700 watts won't change your tone; you're still only using 300.

+1

Enough power is enough power. More than enough is just extra but otherwise gives no benefit unless you actually use it.

 

[Bob Lee (QSC)]

For me at least, the thing that makes it kind of a fuzzy area is that headroom and volume can be more different than you might think. So if 300 watts is not enough power for the general volume level you're going for, maybe 1000 watts is enough to avoid squashed transients and muddy low end

Maybe that's what you meant?

 

[Bob Lee (QSC)]

"That's because they run in class AB, where the amp is not only pushing the speaker foward, but also pulling it back. SS amps, or at least the cheap ones, run in a more efficient class C, D, H, etc. Where the amp really only pushes the speaker out, then the magnet of the speaker pulls it back naturally.

Uh, no.

"tube watts" basically refers to a power amp that is class AB, which 99% of tube power amps are, and 99% of SS [bass] amps are not. Watts are watts, but when you add a speaker in there, "tube watts" are over twice as loud.

Again, … uh, no.

Most SS power amps are class AB. Class C (SS or tubes) is really used only in RF. Class H power amps are almost always class AB as well. Class D power amps are becoming more popular, but they act on the entire signal waveform just like the others.

 

[NKUSigEp]

Underpowering a cab can cause speakers to blow if you send the amp into clipping.

This is the number one myth of all time. It's debunked all the time, yet it's repeated here at least once a day, and many major manufacturers still claim this to be true on their websites. The only thing that blows speakers is forcing them to work harder than they're capable, and that's done by overpowering them. If an underpowered amp goes into clipping and blows a cab built to take more power, it's because the clip momentarily caused the amp to put out way more power than the speaker could take. But if the amp's peak power rating is lower than the cab's RMS power handling, it's highly unlikely. You're much more likely to blow a speaker with an overpowered head because it will still be putting out clean volume while your poor speakers struggle and beg for mercy.

Not entirely wrong...but there are some assumptions to be made. Underpowering a cab won't blow your speakers, but what most people are referring to is when you're using a really low wattage amp to power really high wattage speakers, and trying to compete with other instruments for volume. So you end up having to really crank all the levels on the amp causing it to clip severely and basically end up sending a DC voltage straight to your speakers.

 

[Beefbass]

6-pages deep and it's still going, I must say I am shocked....I figured the bashing would be running wild by this point and this topic would be locked by now

Keep it going

Give it time

 

[Bob Lee (QSC)]

Not entirely wrong...but there are some assumptions to be made. Underpowering a cab won't blow your speakers, but what most people are referring to is when you're using a really low wattage amp to power really high wattage speakers, and trying to compete with other instruments for volume. So you end up having to really crank all the levels on the amp causing it to clip severely and basically end up sending a DC voltage straight to your speakers.

No, clipping is not DC.

 

[JimmyM]

Jimmy-

great thread idea, and few TB-ers could get it going and entice discussion like you can.

HOWEVER, and this is a big however, if this is about debunking then IMO you shouldnt have started out the thread by trying to debunk them yourself. You are an artist, not an engineer. Any actual debunking of common myths MUST avoid the very things that have perpetuated the myths. No offense, but you don't do that.

Now, this could be a terrific thread if you restate the common myths, perhaps even numbering them, and then provide links to the technical explanation/debunking/support of the myth. AND THEN you could encourage commentary by some of the exceptionally helpful and informed TB-ers who can interpret the techie versions into laymans terms.

I think you (we?) should shoot for a
STATED MYTH - TECH LINK - laymans translation and discussion format.


Anyway, good stuff.

Thanks. Point taken, but hey, for 3 am, thats about the best I can do

 

[JimmyM]

Not entirely wrong...but there are some assumptions to be made. Underpowering a cab won't blow your speakers, but what most people are referring to is when you're using a really low wattage amp to power really high wattage speakers, and trying to compete with other instruments for volume. So you end up having to really crank all the levels on the amp causing it to clip severely and basically end up sending a DC voltage straight to your speakers.

If your amp ever puts out DC voltage to the speakers when it clips, something is very wrong. It's not the voltage...if it does blow the speakers, it's because the transients from the clipping momentarily pushed the wattage past the point the speakers can take.

 

[JimmyM]

I see the usual troll and few new confused people have weighed in...

It was a well-intentioned idea Jimmy but...

...not worth my time.

You'll be back...nobody can resist me

 

[NKUSigEp]

No, clipping is not DC.

Not at all in any case whatsoever?

It's been a few terms but from what I learned, clipping is when an AC signal is clipped, in essence cutting a portion of the waveform, correct or not? And if so, clipping COULD potentially result in a DC signal if there is enough clipping present, right?

I've seen some kids...ok, who am I kidding. A while ago I blew a 4x10 using a 15 watt Crate practice amp via the speaker out on the amp and that's what I was told happened.

 

[Rick Auricchio]

Nope, if the waveform has any change at all, it's not DC.

And, in the case of your Crate, you blew the amp, not the speaker, right?

 

[JimmyM]

Not at all in any case whatsoever?

It's been a few terms but from what I learned, clipping is when an AC signal is clipped, in essence cutting a portion of the waveform, correct or not? And if so, clipping COULD potentially result in a DC signal if there is enough clipping present, right?

I've seen some kids...ok, who am I kidding. A while ago I blew a 4x10 using a 15 watt Crate practice amp via the speaker out on the amp and that's what I was told happened.

The DC myth is also a very popular one. But all the qualified techie types on here say it's a myth, including Bob, so I'm satisfied it's a myth.

 

[Bob Lee (QSC)]

As Jimmy said, if an amp puts out DC, there's something wrong with it. Regardless of whether it clips or not. But clipping itself is not DC.