geezin' Posted March 5, 2022 Share Posted March 5, 2022 My Fisher receiver recently went south and being the impatient sort I ordered a PA3s class d amp to tide me over 'til I can get around to fixing it. Damn. I am hearing things in music I've been listening to for decades never heard before. My speakers are entry level Klipsch but have stepped up to play very well with the Topping. I'm sitting here listening to Carlos Santana's soaring guitar and percussion with a depth and clarity I thought I'd never be able to afford. Complex music is accessible to my aged and abused ears. I am more than impressed. Honestly the speakers have impressed me as well. I have always enjoyed them but this is a whole new level. Now to get those Heresys... 1 Quote Link to comment Share on other sites More sharing options...
CWelsh Posted March 5, 2022 Share Posted March 5, 2022 Until recently, I've thought of Class D as being cheap, crap amps. Just shows how wrong assumptions can be. These things are unbelievably detailed. 1 Quote Link to comment Share on other sites More sharing options...
captainbeefheart Posted March 5, 2022 Share Posted March 5, 2022 47 minutes ago, CWelsh said: Until recently, I've thought of Class D as being cheap, crap amps. Just shows how wrong assumptions can be. These things are unbelievably detailed. There are good and bad versions for all amplifier topologies. All Class D means is the output transistors are not being used as linear devices but rather as switches turning on and off around 100,000 times per second between rail voltage. Some don't even have filters at the output to filter out the switching frequency and they rely upon the natural low pass filter hooked up to the inductance of the voice coil. Although the basic function between different models of Class D amps is the same some just do it much better than others and they just keep on making improvements. Zetex came out with a chipset that is supposed to be amazing and the next big step on improving Class D amps. I forget which amp company (NAD?) uses these chips in their Class D amps but they confusingly call the amp Class Z as a marketing tool because they were one of the first companies contracted to use the new chips from Zetex. Get it, Class Z, and the name of the company Zetex, pretty clever marketing boys 2 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted March 5, 2022 Share Posted March 5, 2022 First time for me to hear that output devices are used as switches and not linear devices. I have read articles on the principles of class D but have never heard it broke down in layman terms like Captain just did. I understand how class D works a little bit more now. I first read about class D decades ago with speculation back then of them taking over the audio amplification world. Never materialized until now and I can see and understand how it will eventually be the amplification for the masses. Class A will still be sought by discrimination audiophiles but expect other classes will fade out of favor. I have not keep up with what is new in the class D world and am not familiar with Zetex. I look forward to hearing more. Quote Link to comment Share on other sites More sharing options...
geezin' Posted March 5, 2022 Author Share Posted March 5, 2022 As a rank amateur to electronics I am baffled by the subject but interested. I've found that low cost doesn't necessarily mean low performance. That's true in my field as well however you must choose carefully. So is a class D inherently inferior to class A? Or does it carry a stigma from past attempts being less than? I am surprised...no stunned at the amount of detail I was missing w/the old Fisher. it's so much easier to discern the various instruments and separate them in my head to listen. I had read that these inexpensive Chinese amps were surprisingly good deals for the money. Do the class A amps (Schiit Aegis?) actually sound that much better? if not what's the advantage of the other types of amps? 1 Quote Link to comment Share on other sites More sharing options...
Edgar Posted March 5, 2022 Share Posted March 5, 2022 1 minute ago, geezin' said: So is a class D inherently inferior to class A? That is an ill-posed question. Is a Jeep inherently inferior to a Ferrari? If you're going to the racetrack, then yes. But if you're navigating the Rubicon Trail, then the answer changes. Each topology has its advantages and disadvantages. If one topology was the clear winner in all categories, then the others would have disappeared by now. 2 Quote Link to comment Share on other sites More sharing options...
geezin' Posted March 5, 2022 Author Share Posted March 5, 2022 17 minutes ago, Edgar said: That is an ill-posed question. Is a Jeep inherently inferior to a Ferrari? If you're going to the racetrack, then yes. But if you're navigating the Rubicon Trail, then the answer changes. Each topology has its advantages and disadvantages. If one topology was the clear winner in all categories, then the others would have disappeared by now. Would you care to elaborate on those differences for me? That was my intent for the "ill posed" query. I do understand the "horses for courses" philosophy. Quote Link to comment Share on other sites More sharing options...
CWelsh Posted March 5, 2022 Share Posted March 5, 2022 1 hour ago, geezin' said: Would you care to elaborate on those differences for me? That was my intent for the "ill posed" query. I do understand the "horses for courses" philosophy. I'm in the same boat. I need to find an Electronics for Dummies book to gain understanding of even the basics. I read the Captain's explanation and understand that linear and switching amps work differently to amplify a signal, but that is about as much as I comprehend. This is why I love reading what all these smart people say in the various forum threads because I am learning...maybe not much and not fast, but I understand more than I did six months ago. Quote Link to comment Share on other sites More sharing options...
henry4841 Posted March 5, 2022 Share Posted March 5, 2022 Class A is where the transistors are run as high as safely possible. In other words hot. The only drawback I can quickly remember of class A is the heat factor and expense of a costly chassis with big heat sinks to dissipate the heat. That being the case a class A amplifier is the most linear of all the classes. In other words the best sound theoretically. Human factors weigh in though meaning not all class A amplifiers are built or designed where they sound superior. In other words a cheap class A amplifier may not sound as good as a good class A/B or D. Hope this make sense. Just for reference Nelson Pass of Passlabs and Firstwatt is considered one of if not the best amplifier designer in our generation. Quality is built in as well but everyone that I have heard, many, sound different from each other. 2 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted March 5, 2022 Share Posted March 5, 2022 - Quote Link to comment Share on other sites More sharing options...
CWelsh Posted March 5, 2022 Share Posted March 5, 2022 3 hours ago, henry4841 said: Class A is where the transistors are run as high as safely possible. In other words hot. Is this also true of Class A tube amps? Quote Link to comment Share on other sites More sharing options...
Edgar Posted March 5, 2022 Share Posted March 5, 2022 4 minutes ago, CWelsh said: Is this also true of Class A tube amps? Yes. 1 Quote Link to comment Share on other sites More sharing options...
Edgar Posted March 5, 2022 Share Posted March 5, 2022 5 hours ago, geezin' said: Would you care to elaborate on those differences for me? That was my intent for the "ill posed" query. I do understand the "horses for courses" philosophy. You can find generalizations about all of the classes just by searching. Like anything else, the magic is as much in the execution as in the design. One advantage of Class A is that the amplifying device(s) never turn off, so there is no anomaly associated with switching on and off. One disadvantage is that Class A dissipates a tremendous amount of energy as heat. Don't even bother with Class B. It is intentionally nonlinear, and is seldom if ever used for high fidelity audio. One advantage of Class AB is that it is far more efficient than Class A. One disadvantage is that it can suffer from crossover distortion when the device(s) switch on and off. One advantage of Class D is extreme efficiency. One disadvantage is that an inherently nonlinear process is linearized (approximately) by passive filters. Those filters interact with the loudspeaker impedance in ways that are not always agreeable. Which one sounds best? It all depends upon the design, the implementation, and the application. All of the advantages listed above can be ruined with a bad design. All of the disadvantages can be minimized with a good design. 4 Quote Link to comment Share on other sites More sharing options...
CWelsh Posted March 5, 2022 Share Posted March 5, 2022 I want to see if I'm starting to actually absorb some of this stuff so please bear with me... If I understand correctly, a class A/B amp will operate in class A up to a certain point then switch to class B which will push the tube or transistors at less than the maximum level which will reduce the heat and (may) reduce the quality of the output signal somewhat. Also, if I'm correctly understanding something the Captain said in the Cheap Forum Amp thread, there is some distortion introduced at the point the amp transitions from class A to B. However, from what I'm understanding from the Amplifier Power Requirement thread, our highly efficient Klipsch speakers require so little power, most A/B amps will be operating in class A for most listening needs. Please correct any misunderstandings. Quote Link to comment Share on other sites More sharing options...
CWelsh Posted March 5, 2022 Share Posted March 5, 2022 @Edgar LOL...you typed faster than I did. Thank you for the further explanations. This is very helpful! Quote Link to comment Share on other sites More sharing options...
Edgar Posted March 5, 2022 Share Posted March 5, 2022 Just now, CWelsh said: If I understand correctly, a class A/B amp will operate in class A up to a certain point then switch to class B which will push the tube or transistors at less than the maximum level which will reduce the heat and (may) reduce the quality of the output signal somewhat. Well, that's a bit of an oversimplification. Ideally, one device will amplify the positive half of the waveform, and nothing but the positive half. Another will amplify the negative half and nothing but the negative half. It is probably obvious that this would require one device to turn off instantly and the other to turn on instantly, which is basically impossible in the real world. So in Class AB there is a small region of overlap where both devices are amplifying; one is in the process of turning off while the other is in the process of turning on. This region where both are operating is often referred to as "operating in Class A", but as I said, that's an oversimplification. Quote Also, if I'm correctly understanding something the Captain said in the Cheap Forum Amp thread, there is some distortion introduced at the point the amp transitions from class A to B. Yes. Again, in this region one is turning on and the other is turning off, so some distortion can result. Quote our highly efficient Klipsch speakers require so little power, most A/B amps will be operating in class A for most listening needs. Sort of, see above. If you have efficient speakers and you want to operate in Class A, then use a low-power Class A amplifier, IMHO. 1 Quote Link to comment Share on other sites More sharing options...
CWelsh Posted March 5, 2022 Share Posted March 5, 2022 7 minutes ago, Edgar said: Well, that's a bit of an oversimplification. Ideally, one device will amplify the positive half of the waveform, and nothing but the positive half. Another will amplify the negative half and nothing but the negative half. It is probably obvious that this would require one device to turn off instantly and the other to turn on instantly, which is basically impossible in the real world. So in Class AB there is a small region of overlap where both devices are amplifying; one is in the process of turning off while the other is in the process of turning on. This region where both are operating is often referred to as "operating in Class A", but as I said, that's an oversimplification. Ah...I was thinking that describes a "push-pull" amp. Quote Link to comment Share on other sites More sharing options...
Edgar Posted March 5, 2022 Share Posted March 5, 2022 2 minutes ago, CWelsh said: Ah...I was thinking that describes a "push-pull" amp. There can be Class AB push-pull amps, and there can also be Class A push-pull amps. 1 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted March 6, 2022 Share Posted March 6, 2022 3 hours ago, CWelsh said: Is this also true of Class A tube amps? Edgar beat me to the draw. I agree with all the post Edgar has made, well described. I think Nelson Pass said it this way. The different classes are like relay runners. Class A runners take the baton and run all out without ever swapping the baton. The first A/B runner takes the baton and runs all out till he swaps the baton and then slows down when it is passed. The second runner then runs all out until he swaps the baton. In class B the first runner stops then passes the baton to the second runner who go's all out until the baton is swapped again. Deep down in me I still lean towards Class A knowing the signal stays pretty pure in the amplifier. As pure as the present designers can build them. I also like Class A designs with just the minimal amount of parts like Nelson Pass builds amplifiers. I still have one powerful A/B amplifier that sounds fantastic along with some Class D that sound really good as well. Much as what Edgar said. 1 Quote Link to comment Share on other sites More sharing options...
Edgar Posted March 6, 2022 Share Posted March 6, 2022 9 minutes ago, henry4841 said: Class A runners take the baton and run all out without ever swapping the baton. I guess in Class A push-pull two runners hold the same baton for the entire race. 1 1 Quote Link to comment Share on other sites More sharing options...
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