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Are Class D amps really 5 times less powerful than A/B?
- Thread starter mbell75
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Also, it depends on the specific amplifier. I have a GK 800RB that has no limiter (that I know of) and is designed to overdrive gracefully. It's as loud in practice, maybe even louder, as a Markbass Little Mark (first gen, the traditional ones, all yellow with black text; they weren't sold outside of Italy, AFAIK), which is 150W more powerful. But the Little Mark has a non-defeatable limiter and it is also always clean (well, it's the Markbass sound signature), while the 800RB tends to have some grind to it (which is fantastic, but not always what you want). Of course, they are both Class AB amps, and both well designed.
Also this methodology would probably suffer from the effect of the fletcher munson curve. The perceived tonal balance of a sound changes as the sound increases in volume even though the actual tonal balance remains the same. The typical effect of this being that when we hear two sounds with identical tonal properties we will perceive the one with the higher volume as "better" sounding.
I think it's just because Johnny Rotten has such a soothing voice
It was a little raggedy last Sunday….
Always the wiseguy, he quipped "I'm getting on and I need my electrolytes"; sure enough, he had his Gatorade bottle. The bass player was no Jah Wobble, but he hit his mark.
Not sure if this has already been said but:
1. Class D is NOT digital. However, many Class D amps use a digital Switching POWER SUPPLY. I believe this is the origin of confusion (well, this and because people regurgitate marketing BS as a means to falsely portray a modicum of technical understanding).
If you are completely new to how amplifiers work, think of it this way (this is a gross oversimplification, but basics are needed): a power amp (not inclusive of a pre-amp stage) consists of at least (usually) 2 main parts - a) a gain stage using devices such as tubes or semiconductors that amplify a signal, and b) a power supply that takes the 110 volts from your wall outlet and converts AC/DC, and regulates/adjusts the voltage that feeds the aforementioned gain stage device.
Class D, Class A, Class A/B etc. is a references to the gain stage (the circuit that actually AMPlifies the signal of your instrument). In Class D, just like in Class A, Class A/B etc., the gain stage is analog, not digital.
Two very popular forms of power supplies are: a) Linear Power supplies - they use a (relatively) big transformer mated to a series of capacitors and resistors, and b) Digital switching power supplies that perform voltage adjustment and AC/DC rectification via tiny microprocessors (not big transformers or capacitors, etc.)
Class D Amplifier circuits have the benefit of being small, powerful and very efficient. Digital switching power supplies also have the benefit of being small, lightweight and very efficient. As such, the two are very commonly paired together, thus providing users with a small, lightweight package that provides a lot of power relative to its size.
A designer/manufacturer can ABSOLUTELY pair a digital switching power supply with a heavy Class A amplifier circuit (I have actually built two amps with this configuration). Alternatively, a tiny Class D module can absolutely be paired with a large, relatively heavy linear power supply.
2) A Watt IS a Watt. The perception of more power from Class A/B likely has to do with a) higher distortion levels, and b) the fact that Class D are overwhelmingly mated to Digital Switching Power supplies. Remember, I said Digital Switching power supplies do NOT have the big capacitors? Well, the benefit of large capacitors is that they have the capacity to temporarily store electricity. This means that a linear supply that has a bunch of big capacitors has the ability to deliver very large amounts of current for millisecond long, instant transient spikes. A digital power supply can not do this to the same extent. In practice, it means an amp with a linear supply can provide 100 watts continuous power into an 8 ohm load, but extremely short burst power (dynamic headroom) of over 200 watts. Conversely, that same gain stage paired with a digital supply can provide the same 100 watts continuously into an 8 ohm load, but only 125 watts of transient spike power.
Some marketing materials from some vendors don't help the issue.
Johnny spent hours sitting at a picnic table chatting with everyone who wanted to talk to him and smoking.
Even in my limited understanding, I know that Class A through D are amplifier design topologies, not differentiators between analog and digital circuitry. If so, why didn't we have Class S for solid state amps?
I noticed he lost a bunch of weight recently, fortunately. A couple years ago he looked ready to pop.
Matt, the English Beat sax player, posted an Instagram pic of he and Johnny back stage, and Johnny looked like his face was melting.
I was knocked out by how great Debbie Harry looked after being in a similar situation. Clem was an animal, and Glen Matlock sitting in on bass was a pleasant surprise.
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I have a Fender Rumble 15 which is 15 watts and a Dr. Z Z-Plus (class A) which is also 15 watts. I can plug a 6-string guitar into either one. Rediculous comparison. Now if I were to put the Dr Z. up against my Rumble 100, it's about equal. Hmmmmmm. All the technical mumbo jumbo aside, pretty sure that is what the Boss guy is referring to in the real world.
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No! And thanks you for bringing it to our attention!
Not sure I understand your intent, but thanks for the reminder as to why I rarely visit Talkbass the last several years (after being very active 16/15 years ago).
Not to Johnny it wasn't, I'm sure! After that lawsuit over the Disney show, he has not been happy with any of the others.
It probably depends how you define loudness. Loudness, as in perceived volume and power calculations based on waveform amplitude alone are not the same thing. What matters is the power factor of the output waveform. A 50W tube amp flat out at full saturation will sound louder than a notional 50W (i.e the same peak to peak voltage into the same speaker) of clean class D power because compression, 'sag' and other harmonic distortion artefacts of the 'starved' tube amp change the power factor of the waveform - it becomes 'squared off' top and bottom, which not only increases the power factor (area under the curve) by the addition of harmonics, but also creates faster slew rates which add to the percieved intensity. It is also why compressors are used to add thickness and heft, and why there really is no such thing as a truly transparent compressor - they all change the waveform which must, by necessity, change the tone.
When operating at a given output in the clean 'linear' region, say both delivering 1W into the same cabinet and with plenty of headroom in reserve there should be very little difference provided the power supplies can keep up. Watts are always Watts. The power factor is a measure of how those Watts are distributed and delivered over time. Static analysis of power based on Ohms Law (P=IV) will not provide the answer.
YMMV
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His reply would have made more since if you had read the entire thread, but I don't blame you for skipping over all 5 bajillion pages. He wasn't being rude to you… just poking fun that you basically came in and corrected the OP in the same way that at least 20 other people had done, and yet there was still confusion and debate over the first couple of pages.
Sorry, I don't mean to run you off. It's just that that comment has been made repeatedly over the last 14 pages. I guess I was sarcastically commenting on the tendency for folks to post before they actually read what's going on in the thread.
Again, I hope it doesn't run you off. Stay and become as snarky as the rest of us!
If I have a STV CL plugged into a good cab like a Barefaced Big Twin I can be louder than anyone really needs to be. If I try to use a 300 watt GK MB or Aguilar TH SS head into the same cab, it will not perform well against a pair of 412 half stacks and a heavy drummer.
I think we are all also aware that the breakup of that SVT CL or AD200B is far more pleasant than the breakup of any SS amp. A 300 might reach the same volume as a tube amp but it will sound like butt in the process.
Try with an Ampeg SS amp, not another brand.
Last year I was interested in going all tube with an SVT 2. I made a several shootout against my SVT 7. Could see any reason to go full tube. Way heavier, less power, harder to maintain.... And they sounded the same for the tone I like.
I only play clean.
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