Class D versus Class AB? The sound quality difference at this stage with higher grade Class D amplifiers is a myth or a result of placebo effect. There is good and bad grades of everything.
Here is a little education.
Class B is deeply flawed because the independent positive and negative transistors do not transition without serious distortion. They are not as linear or as responsive when going from zero potential to a certain voltage. But they do perform uniformly from a running voltage to any change in voltage. Sooo, Class AB places a bandaid on the problem by applying a bias voltage so that both positive and negative transistors are 'ON' to a degree all the time, even without a signal. The two opposing voltages cancel one another. But in the process create great waste and lots of heat is generated. Now they have been at Class AB since I was riding shotgun for Wells Fargo stagecoach lines (not actually)....so it is well refined. But bottom line is Class AB is a bandaid for Class B warts. It's like the pot calling the kettle black.
There is nothing digital about a Class D amplifier. It was just the next alpha designation available. It is a pure analog switching amplifier. The better ones switch and correct at a frequency ten times the sampling rate of CDs and 30 times higher than we will hear. The filtering is so high that it is completely detached from the audible bandwidth and leaves zero switching artifacts. But in the process generates one/fourth the heat for the identical current draw. And you're listening to an MP3 format through junk D to A conversion? In an environment with 50 db of ambient noise if you are at rest and the only one in the cove? How does that Class AB sound when it's choked for voltage because it's pulling 60 percent more current to make the same power?
Triple Darrington AB is well documented to have stabilty issues with highly capacitance loads. So they add a coil to the final stage of the outputs, just before the speakers, to provide a little inductance so there is no risk of oscillation into tweaky loads. Same darn filtering device used in a Class D amplifier.
Now esoteric home HiFi companies have like Krell and Mark Levinson have adopted fullrange Class D amplifiers. Think those cork sniffers are hyper particular?
Prosound is heavy Class D on self-powered fullrange HLCD line arrays.
The Absolute Sound did a feature edition on Class D amplification with prominent home amplifier engineers including Class A, Class AB and tube advocates. With that type of attention in that type of publication, you just cannot cling to antiquated technology from a previous century.
The best ME engineers from yesteryear that once produced AB for Precision Power, Xtant, Rockford Fosgate, Phoenix Gold and Zapco, to name a few, have all adopted fullrange Class D. The companies with domestic engineering have adopted fullrange Class D. Some of the importers have not.
Let's see....Alpine, JL Audio, Hertz/Audison, Rockford Fosgate, Kicker, Wetsounds and just about any company of consequence is focused on Class D for now and the future.
Awesome post David. Thanks for that one.
David just make me sit I aww sometimes idk good info man
Good education Dave, im no amp expert ill admit that. I might have been a little off in what i said compared to what im thinking but i was more refering to Digital Amps vs Analog amps.
I prefer the sound of an Analog amp to a Digital amp. I think it has a warmer richer sound then digital and i perfer to use them even though a Digital amp uses less power, has a smaller foot print and uses less power.
I am not familiar with any mobile audio 'digital' audio amplifiers so I'm not sure what you are referring to.
As for the "warmer richer sound", are we repeating a hand-me-down phrase out of a home esoteric Class A amplifier brochure, or phrasing from a digital to analog convertor brochure, are we using a direct to disc analog LP with an analog moving coil cartridge on an analog turntable with an analog tube phono section in our boat with Focal Utopia speakers? Are we one of the few with golden ears superior to all the best engineers? Or, are we just using digital sources, like CDs and and MP3s, originally recorded on a digital MAC laptop, on bright horn speakers with metal transducers?
Hey man, if we want to describe the sound in such subjective terms to counter objective references then I could say 8-tracks sound "warmer and richer" to me because they sound dull and inarticulate. If you want warmer and richer then turn down the treble and turn up the bass tone controls just a tad. Or buy an inherently warmer speaker or stuff some open cell foam down the throat of those horns.
Amplifiers are supposed to be neutral and invisible with no bias. The good ones accomplish this. Amplifiers are not suppose to mask the deficiencies in other elements of the signal path. If the amplifier measures ruler flat over the entire audio bandwidth and it measures low ultra distortion and it has fast slew rate and it is far more precise than the human auditory system then that amplifier sounds exactly like it measures.
Everything else is placebo effect, owners goggles or mental mast......never mind.
I just couldn't help but laugh i shoulda tried that with my pro 60's
Originally Posted by EarmarkMarine
Holy tech speak. It never seems to fail that when someone talks about their audio project that somehow people get blasted off into science conversations. Why is that??? It seems like the thread is pushed that way. Why not just start a new thread and talk about this stuff? It's fun reading, but when I'm done, I often think...how did this relate to the Op's question.
On the amp tech stuff, my take is a little different... Class AB amplifiers definitely sound different. Heck, class AB versus class AB amplifiers sound different. There is no such thing in the real world as a completely neutral sounding amplifier. Not at the level we are talking about here in mobile marine world. Some companies spend quite a bit more to use bipolar output sections, versus jelly bean mosfets. And some use more expensive mosfets. And some bring into the mix Triple darlington supplies. Others use hard regulation and soft regulation and they ALL of this affects performance, all have tonal differences. To put all Class AB amps in the same bucket is really omitting a lot to the audience.
Class D amplifiers in 2013 within the confines of whats in the market are based on one of 3 chip sets. Several of the brands mentioned all share them. I'd prefer to keep this general and not a brand war. There's no doubt that class d brings more efficient use of power. In my opinion, its at all gold standard sound quality wise in the mobile environment and wont be for many years to come. Possibly in the future... but not even close right now in comparison to higher end A/AB designs. I'd also agree that this technology is expensive at the mfg level and does offer huge power gains over clas a,b,ab designs. I dont agree with the comparison on what is happening on wakeboard boats versus pro audio companies are doing is the same. Thats just a huge stretch... my gosh the cost basis are gigantic. focusing on just the industry at hand (marine), though many Class D platforms share chipsets, there are big time differences between a 199 class D amp and 1000 from brand xyz. There is so much more to this than efficiency within the class d montra. My issue isnt with Class D at all. It's with making broad sweeping statements that Class AB is antiquated and D is not. I think the statement that needs to be made here is that Class D is definitely here to stay and that companies everywhere are working hard to improve the sound quality at a price that wont break the bank. There is still work to be done in that department.
Along those lines, people also need to understand that there are some real genuine concerns with this design platform. The Radiated EMF knocks out radio which is a big problem for cars... If speaker impedance dips to low, these designs become very unstable very fast (more so than higher end AB designs). Failure can be catastrophic (and in fairness any amplifier by any design class can have catastrophic failure). Are these reasons to stay away from Dclass that are on the market? Heck no... but they are big time on the radar of companies bringing these products into the market.
It should also be noted, that a lot of the amazing efficiency we'd like to get excited and advertise about goes right out the window under low impedance loads. These amps are super eff at their highest impedance rating. And that is excellent!!! In the boat world, we often times see companies producing speakers with nominal impedances that when parrelled, bring the nominal load under 2ohms with dips even lower which create havoc with an amplifier. How an amplifier fails to operate and under what conditions is very important. There is no doubt that Class D brings some great things to the table. I totally agree. But to categorically place all class AB amplifiers as junk in comparison is absurd. It's like comparing NASCAR to F1 Euro. Lots of technology in both races but completely different. Sometimes the best solution is marrying the two technologies together... we see multi channel AB amplifiers with D class mono amplifiers. Why do companies do this? Cost vrs performance. It really depends on what people want to pay for.. cha ching.
Full disclosure:, I write this to bring perspective. Not to take a Brand position. Most of you know I work for a mobile audio company. And those that attended the CES show in Jan, probably know that the company I work for will offer both platforms in 2013. Even as thats the case, all class D designs give us are more tools in the tool belt audio configuration wise. So please lets not make this a he says this because of that conversation. There truly are some fantastic class A/AB amps on the market, home and car and marine. In fact, I think my favorite all time amp is a Audison Thesis. At 13K a piece, I'll take zero...but oh man is it amazing. All of this is relative folks....
The thread got derailed specifically in post #17. Prior to that, opinions flowed freely without reprisal. Mike Mandley specifically called out the posts of two other members, MLA and myself. But when opinions differed from one brand's agenda, he felt threatened and compelled to address that. He could have given his own opinion without referencing or contradicting the posts of others. That is precisely what triggers these exchanges. The other action that typically triggers these exchanges, certainly in my case, is when one manufacturer comments on another manufacturers products or targets the lead dog to build his own brand awareness. The veiled digs can be so obvious and transparent. Just look at post #27 that is loaded with digs to alternate products and technologies.
Now you come on here and do exactly the same. You criticize the technical nature and content of other posts then go on your own technical rant....that by the way has no substance....just random bits of info.
I stated from the beginning that there are different levels of quality within all topologies. It is in print beforehand. Also, don't dispute things without offering a specific fact. I have supporting facts if you want to question something specific beyond a general criticism. Like for instance, Prosound. My coworker, Odin, has done live acoustic engineering for years in the evenings and weekends. He also plays in a successful band. My son has a degree in acoustic enginnering, has his own studio and works in the live sound equipment industry. I'm exposed to a lot.
Now what is particularly misleading is that Class D amplifiers lose efficiency at lower impedances. Is that true? Asolutely! As an example, they can drop from 84 percent efficiency at 4-ohms to 71 perecent efficiency at 2-ohms. However, what wasn't mentioned is that Class AB drops from an inherently low efficiency in the same way as the impedance drops. In fact, since the bias applied to Class AB amplifiers is constant, they can dip down to 20 percent efficiency at very low output power levels. So please share the entire story rather than placing a self-serving spin on it.
We have the luxury of electronics switchers. I would like a few local Dallas members to do a blindfold test between a good Class AB and a good Class D amplifier to see if they can detect which is which. If the novice cannot hear a difference on far superior speakers than you will ever find in a boat, then we should be able to put this to rest. So step up and accept that challenge please. You hand pick the blindfolded guys and I'll videotape the results. I'm excited!
Which Class D amplifiers knock out reception in cars? I know of some Class AB and H amplifiers that do knock out reception. Class D and Class AB often share the same type pulse width power supplies. Old school Class D amplifiers from a decade ago? Sure. Today with any of the brands that I am familiar with? Absolutely not. Man, that's just plain deceptive.
Class D stabilty issues at low imedances? Yeah, the Infinity amplifiers from a decade ago liked one narrow impedance range. The Exile Class D monoblocks are rated to 1-ohm. Again, those kind of statements are just plain deceptive to the core. Just designed to cast doubt.
Now let's start a new thread about authentic power specs. Who provides them and who does not.
Dave i didnt call out anyone in that post. I said you both Know a Lot about the AMPs and you push the D class amps a lot.
Originally Posted by EarmarkMarine
This is true.
I wasnt trying to start anything negative by that post.
I was simply stating my opinion on what i think i like better as an amp.
Im sorry everytime i post something in Audio you think im trying to attack you.
Frankly i dont say anything intentionaly argumentive, or bad about you MLA or anyone on this forum.
Those people who dont have the big dollar system i treat exactly like those who do.
I think you just think im always trying to attack you because i feel like everytime i post in Audio you DO ATTACK me.
Me and you have gone round and round, and i have told you and MLA in PMs my intent is not to battle you guys. I purposly dont promote, or demote any brands on this site.
I think you take comments to personally. I don't think anyone is attacking you, just trying to make sure accurate info is in the threads.
You consistently post inaccurate or biased information.