Are Class D amps really 5 times less powerful than A/B?

[groovepump]

You need the RMS power rating of an amplifier to compare apples to apples. Manufacturers like Quilter and (I assume) MESA will give this as their rated power cuz they're legit and value their reputations. So when Quilter says their BB800 is 800W, they mean it. RMS. And if your speaker can't handle that, you will cook it. But other manufacturers sell a 2000W class-D amp for $300 and it weighs 1 LB and is the size of a pack of cigarettes, well they use marketing lies to make it look like you're really getting something of a deal. And it's THESE guys who create the idea that the tube amps are "louder". The tube amp watt rating is the real rating. Plate current x plate voltage. A class-D amp with comparable RMS rating (real watts) will also create similar sound level. The speakers don't have any idea where their drive is coming from and they have no personal bias.

 

[BassFalcon]

@mbell75 Your understanding of the word "digital" as it relates to amps is incomplete and incorrect. Please head the advice of those correcting you. They are correct, and unfortunately, you are not correct in this matter. There is no such thing as a "digital" amp. Class D does not stand for "digital". There is nothing related to digits at all. The switch mode power supply many class D amps use could be confused as being digital as @abarson and others have mentioned above, but that still doesn't make it digital. We promise.
Also, a watt is watt. It doesn't care how it came in to being, it is a unit of energy. To accurately compare watts to watts between amps you need to know Total Harmonic Distortion, or THD, and also what type of watts are you talking, RMS, Peak, "music power". Etc.

 

[Passinwind]

Ok. Again, every class D combo bass amp Im aware of has a digital power section. Give me some examples of class D combo bass amps with analog power sections. Thanks

Every single one I'm aware of. Digital audio = assigning stepped bit values to the waveform and then converting those bit values back to analog. Class D = pulse width modulation and then associated demodulation, both analog processes.

Ok, I have asked 3 people and none have replied, maybe you can help. Name me at least one Class D combo bass amp that has an analog power section rather than digital.

Fender Rumble 100.

 

[dalahorse]

I know class D amps are generally more efficient than class A and A/B. So I suspect their overall power consumption is probably 1/5 that of class A and maybe A/B. But, when it comes down to it, watts are watts at the output stage (assuming they are measured the same way). Differences in voicing, gain, EQ, bandpass, and compression will impact apparent loudness between various amplifiers.

 

[marchone]

Three pages in. So that was clear as mud.

 

[SirMjac28]

The real question is does aged horse ever get tired of being summoned to these threads to sort us all out?

All I know is I plug my bass in and heavy metal comes out on my Mb200 and my 700rbii

Good enough for me

Calling @agedhorse

 

[SirMjac28]

 

[Wasnex]

You need the RMS power rating of an amplifier to compare apples to apples.

That's still only part of the puzzle. Different amps with the same power rating can have different burst power ratings. So one amp might start to clip right at the RMS rating and another amp may be able to produce clean transients that are significantly higher than the RMS rating. Since music is dynamic, higher burst power often relates to higher SPL.

As far as how an amp transitions into saturation, that is more dependent on designer intent than amplifier topology. My Hiwatt DR103 seems designed to produce max clean power. It's noticeably louder than my other 100W tube amps, but I would not say the output section clips in a particularly pleasing manner. For pushed bass tones I would choose either my Matamp GT120, Matchless Thunderchief, or possibly my Mesa D180.

Some solid-state amps are designed to produce pleasing distortion. My GK RB series amps get compressed and makes a nice grind when pushed hard.

In my experience, many tube amps don't even make their clean power rating. From the bench tests I have come across, Orange AD200Bs do not make 200W clean, SVTs generally do not make 300W clean, and Mesa 400s and 400+s don't even make 300W clean.


Also as tube amps approach their clean power rating they tend to get compressed before the break over into OD. Some people perceive a compressed signal as louder, but I seem to key more off of the ability to produce clean transients when I am playing bass.

So even though I love my tube amps, if I were forced to choose only one amp, it would probably be a hybrid with a big solid-state output section.

 

[Jim C]

If the focus of this thread is power ratings and output volume, and we assume the same speaker cabinet and output source being equal, I think the equation comes down how are you measuring output power and at what level of distortion.

Wasnex's explanation from the advertisement (assuming it is accurately stated) of peak power certainly makes sense. Output power is being rated differently.
Tube amps of equal rated watts can actually be louder when they are allowed to run at a higher level of distortion.
Some SS amps will do this too.

Fender Rumble 100.

And possibly the best selling combo amp of all time. Nice example!

 

[agedhorse]

Ok, that might be true but can you name any Class D bass amps with analog power sections? I can't think of a single one. Most every Class D is digital.

No, this is not true.

Virtually EVERY class D amp is analog, non-linear (using PWM as a modulation mechanism). I have designed many bass amps (way more than 3) and they are all analog, non-linear power sections. I have also designed many bass amps (way more than 3) that use all analog, linear power sections. I have also designed bass amps using both SMPS and non-linear line frequency analog power supplies.

Is this a question of semantics?

Everything You Need to Know About Class D Amplifiers - Blog - REL.

Are Class AB amps better than Class D? If we're talking about wide bandwidth for music through your loudspeakers, the answer is likely to be simply and definitively "Yes." But when it comes to powering subwoofers, the answer is less clear cut.

How Do Class D Amps Work?
Class D amps, also known as "digital" amplifiers, work by shifting the sample frequency at which they operate up to extremely high frequencies. In doing so, they use MUCH smaller power transformers which takes up far less interior space—something that is always at a premium in subwoofers. In some cases, it saves almost 10% of interior volume, space that can go back into producing deeper bass and higher output

This is completely wrong on so many levels. Their description of "class D" actually has nothing to do with class D but is describing SMPS which is entirely different.

No, it's not clear cut at all. Class AB is not necessarily better for wide bandwidth audio (ie. full range), there are class D amps today that are far better than class AB, though if you go back 20+ years that may not be as true).

Ok. Again, every class D combo bass amp Im aware of has a digital power section. Give me some examples of class D combo bass amps with analog power sections. Thanks

Name one.

Combo amps w/ analog power sections... Shuttle's, ShuttleMax's and Countour 500, but there's also the Shen "LT" series that were used for uprights and other acoustic applications.

Gosh, those digital class D amps again.....

I switched to class D amps a several years ago (Ampeg SVT 7 Pro). I don't see any single reason why I would go back to anything else. Same power, tone for a portion of the weight.
About the power: A 500W class D amps is the same as a 500W class A/B amp. Period

When done well, few if any can tell the difference in double-blind testing. IF they know what they are playing then obviously their eyes will tell the difference (marketing).

Some people can't hear a difference between analog and digital, you are clearly one of those people. Im sure you prefer streaming music to vinyl too

IMO, this is an insulting statement.

Then why does every Class D combo bass amp have a digital power section?

Because they DON'T!!!

What sucks about that, is that Class D amps don't start to open up til you're over halfway on the master. They're weak and frail sounding til then. So, there's that sweet spot on Class D amps, just like everything else, where you get the best product the amp can give you. Little more, bad. Little less, frail.

I disagree with this, I have't seen it to be true on any class of amp.

A lot of the rating of these amplifiers is all marketing crap. I see it when the amplifier's rated at, maybe 200 watts, but when you look at the AC input rating, the input current multiplied by the voltage is nowhere near the output rating. A 200W class-D amp may have an input rating at 40W. The damned thing can't produce more power than it gets from the wall. Class D amps are maybe 90-95% efficient (my guess) which means they will produce less "power" than they consume. Sometimes the mfr gives output wattage rating as the maximum current the amp can deliver under a short circuit (maybe for a millisecond or whatever) and mutipliplies that by the voltage rail of the amp (maybe it's 100VDC, or whatever). So you get a ficticious "power " rating of the amp that is impossible to pass on as usable output watts. It's marketing crap.

Except that you don't understand how the AC input power ratings are derived and why it's done this way, that's why you are confused and accusatory. Actually, your description of audio ratings are also incorrect. When you post stuff like this, I encourage you to do some (real) research and learn about it before posting.

I have discussed this before but it seems that it needs to be "refreshed"...

The AC input power is required by safety agency standards, and it's required to be the greater of the power consumption at 1/8-rated audio power into the lowest or most demanding load, or if intended for crest factor, than that higher number MAY be used. This is entirely independent of the amplifier class.

Why is it done this way? Because 1/8-rated audio power represents the average internal thermal loads that the amplifier will see under long term (ie. continuous) use when presented with an average full range signal driven to the point of clipping. There are a whole series of thermal tests that are performed on the amp during certification to insure that no component exceeds its safe working temperature (as defined in the standards). There are also additional thermal tests that are done at a series of higher power levels (called abnormal operating conditions) as well as a third series of thermal tests conducted under fault conditions.

For some companies in the pro audio world (and I do this to some extent as well), they will specify AC power consumption at 1/8-rated power (mandatory) as well as 1/4, 1/3, 1/2 and maximum rated power, this data is used for other reasons mostly related to branch circuit calculations and feeder or generator dynamic capacity in fixed and large portable installations.

 

[5StringBlues]

Up next, what works best? Regular clothespins, or the springy kind?

 

[Killing Floor]

Speaking of people having no clear understanding of a Watt…

How come a lemon gets soft and juicy as it ages and a lime gets hard and dry and physically smaller as it ages? Shouldn't they age the same since they are both sour citrus tree fruits? Asking for a friend.

 

[marchone]

Up next, what works best? Regular clothespins, or the springy kind?

They're both technically "springy". Coil vs torsion bar.

 

[Grinderman]

If we're talking about wide bandwidth for music through your loudspeakers...

say what?

 

[marchone]

say what?

Not my question there.

 

[groovaholic]

Speaking of people having no clear understanding of a Watt…

How come a lemon gets soft and juicy as it ages and a lime gets hard and dry and physically smaller as it ages? Shouldn't they age the same since they are both sour citrus tree fruits? Asking for a friend.

Duuude...that's a mighty personal question.
I won't ask whether you identify more with the lemon or the lime...

 

[4stringsjack]

Some days I wish there was a dislike button.

Thanks @agedhorse and @Passinwind for bringing the goods.

 

[Grinderman]

This thread... oy.

 

[4stringsjack]

What's the best class D amp for recording metal in a non-digital format?

 

[HolmeBass]

Ok. Again, every class D combo bass amp Im aware of has a digital power section. Give me some examples of class D combo bass amps with analog power sections. Thanks

I think you are mistaken.

PCM or PWM do not require digitization of the signal; there are no D/A or A/D converters in most class D bass amps.

Maybe you're thinking of modeling amps?