CJH Posted March 9, 2019 Share Posted March 9, 2019 (edited) Hi all. I am trying to understand the behaviour of the Moon 330A amplifier and the first 5 watts of class A amplification before changing to class A/B. I am thinking of a possible purchase but want to understand what this means for me as this is a HUGE investment for me. My speakers have a sensitivity of 84dB spl (2.83V, 1m) and are 8 ohms. From googling it an 8 ohm speaker at 2.83V, 1m specification is the equivalent of 1W at 1 meter. I also see that the resistance varies at different frequencies, but for now I will work on 8 ohms to keep things relatively simple. I know this is quite technical and there are many, many things that need to be taken into consideration, but as a general rule of thumb would my thinking below be reasonable? 5 Watts into an 8 ohm speaker of 84dB spl (2.83V, 1m) will produce a 7dB increase in spl resulting in 91db at 1 meter. With a decrease of 6dB per the doubling of distance we get: 85dB at 5 watts at 2 meters listening distance. 81.5dB at 5 watts at 3 meters listening distance. 79dB at 5 watts at 4 meters listening distance. That means that for a Moon 330A amplifier that runs class A to 5 watts, at a distance of three meters I will be able to get about 81.5dB spl before it switches over to class A/B. Grammar warning below! Forgive me... The other question I have is, if I set the volume of the amplifier such that it outputs 5 watts and do not change it, will the amplifier wattage output change as the dynamic range of the music changes? Would I have to set the volume to be at 5 watts for the loudest part of the music to stay in class A mode? Any guidance and comment on my thinking is valued, as well as comments on anyone who actually owns a Moon 330A amplifier. Thanks. Edited March 15, 2019 by CJH Remove the word "pure" as it is causing off topic debate. Link to comment Share on other sites More sharing options...
georgehifi Posted March 9, 2019 Share Posted March 9, 2019 (edited) It's the upper mids highs you should be looking at for the Class-A below that B is fine if well designed amp, as crossover distortion "is said" to be detectable by the ear in the upper mids/highs. But here's something for you to ponder over, say a violin is being bowed in it's upper frequencies and it's within the 5w of Class-A and sounds sweet as a nut, but then a low organ note comes in, would that violin stay in Class-A sweet as a nut, or is it now Class-B and tearing your ears out off, with the organ and is nothing in Class-A, where does the 5w of Class-A go?? Cheers George Edited March 9, 2019 by georgehifi Link to comment Share on other sites More sharing options...
andyr Posted March 9, 2019 Share Posted March 9, 2019 5 hours ago, georgehifi said: It's the upper mids highs you should be looking at for the Class-A below that B is fine if well designed amp, as crossover distortion "is said" to be detectable by the ear in the upper mids/highs. But here's something for you to ponder over, say a violin is being bowed in it's upper frequencies and it's within the 5w of Class-A and sounds sweet as a nut, but then a low organ note comes in, would that violin stay in Class-A sweet as a nut, or is it now Class-B and tearing your ears out off, with the organ and is nothing in Class-A, where does the 5w of Class-A go?? Cheers George Sorry George - I'm not trying to stalk you (this being the 2nd post of yours I have just responded to) ... but once again, I don't comprehend your post. "Where does the 5w of Class-A go?" AIUI, the amp was outputting <5w when just the violin was playing. So the amp was in "Class A" mode. Once the organ comes in (I presume you mean with bass notes - not treble notes), the amp is outputting >5w. So it is now in "Class B" mode - it's no longer in "Class A" mode. The "5w of Class A" hasn't magically "disappeared" ... it has simply shifted into Class B, due to the suck of power by the organ's bass notes. And if it's a good-sounding Class AB amp (as mine are) ... the violin would certainly not be "tearing your ears off". Andy Link to comment Share on other sites More sharing options...
Gryffles Posted March 9, 2019 Share Posted March 9, 2019 I’m not 100% sure why you’re asking these questions @CJH Is it for technical understanding or something else? I read it that you want to listen in class A.......could be wrong though Link to comment Share on other sites More sharing options...
georgehifi Posted March 9, 2019 Share Posted March 9, 2019 (edited) 12 hours ago, andyr said: I don't comprehend your post Simple There's nothing better sounding in hiend audio than a good recording (eg: RR Scheherazade) of a violin being bow gently in it's upper frequencies using good class-A amp into ESL's or Plasma tweeters. Put in a Class-B amp and it all turns to **** It's a quiz for all with 5w class-A A/B amps, what happens to the sweet class-a sound solo sound of the gently bowed violin because it only used up to 5w all class-a, then an organ comes in playing in underneath "in the same space in time", does the violin remain Class-A sweet or does it go into Class-B edgy sounding, because to organ is now using 50w and sending the amp into class-B Cheers George Edited March 9, 2019 by georgehifi Link to comment Share on other sites More sharing options...
Bronal Posted March 10, 2019 Share Posted March 10, 2019 People seem to be assuming that amps can segment their outputs between Classes A and B. I would have assumed that once an amp reaches its Class A limit, it switches to Class B. I think the OP should be more concerned about dynamic headroom than how much Class A he's got. His amp is rated at 125 Wpc continuous into 8 Ohms and, while that seems a lot, he's likely to need a lot more than that to cope with dynamic peaks with speakers that are only 84 dB sensitive to start off with. Otherwise he may notice harshness that he is blaming on lack of Class A, whereas it's just the amp clipping. 2 Link to comment Share on other sites More sharing options...
andyr Posted March 10, 2019 Share Posted March 10, 2019 (edited) 1 hour ago, Bronal said: People seem to be assuming that amps can segment their outputs between Classes A and B. I would have assumed that once an amp reaches its Class A limit, it switches to Class B. I think the OP should be more concerned about dynamic headroom than how much Class A he's got. His amp is rated at 125 Wpc continuous into 8 Ohms and, while that seems a lot, he's likely to need a lot more than that to cope with dynamic peaks with speakers that are only 84 dB sensitive to start off with. Otherwise he may notice harshness that he is blaming on lack of Class A, whereas it's just the amp clipping. Absolutely! 6 hours ago, georgehifi said: It's a quiz for all with 5w class-A A/B amps, what happens to the sweet class-a sound solo sound of the gently bowed violin because it only used up to 5w all class-a, then an organ comes in playing in underneath "in the same space in time", does the violin remain Class-A sweet or does it go into Class-B edgy sounding, because to organ is now using 50w and sending the amp into class-B Cheers George Of course the violin goes into Class B - as the whole amp is now in Class B (due to the extra power draw of the organ notes). But the violin won't necessarily sound "edgy" when the amp is in Class B. Andy Edited March 10, 2019 by andyr 1 Link to comment Share on other sites More sharing options...
MLXXX Posted March 10, 2019 Share Posted March 10, 2019 (edited) 2 hours ago, Bronal said: People seem to be assuming that amps can segment their outputs between Classes A and B. I would have assumed that once an amp reaches its Class A limit, it switches to Class B. I can't comment specifically on the circuitry for the amp the OP is considering purchasing, but the classic way a solid state Class AB output stage works is to have a resting current high enough for both sides of the complementary pair output stage to remain on as long as the output waveform doesn't exceed a certain amplitude. This is Class A operation. For argument's sake, let's assume as an example that Class A occurs if the instantaneous value of the output waveform stays within the limit of plus or minus 2 volts. If and when the instantaneous amplitude of the output waveform goes beyond that limit, this will involve one side of the output stage ceasing to conduct for the duration of that voltage excursion. (If it did conduct, it would waste power by trying to pull the output waveform in the opposite direction.) For that part of the waveform we have pure Class B operation. To use our example, if the output waveform covers the range from minus 10 volts to plus 10 volts, the parts of the waveform that lie within 2 volts of zero will be handled in Class A mode, but the parts that go beyond that will be handled in Class B mode. So in the situation @georgehifihas raised of a quiet violin sound and a loud low frequency organ sound together, the violin sound may be reproduced entirely in Class A mode over the milliseconds when the low frequency organ tone waveform crosses zero, and may be reproduced entirely in Class B mode over the milliseconds when the low frequency organ tone is at its positive or negative peaks. With good design of a Class AB output stage, the transition from Class A to Class B should be seamless to the human ear. However there is audiophile lore that disagrees. @CJH, I would encourage you to go to a showroom for a demonstration of a Moon 330A and other amps set up for the same output level into the same speakers, to determine whether you can hear any differences, and if so how significant they seem to be. Edited March 10, 2019 by MLXXX 1 Link to comment Share on other sites More sharing options...
Wimbo Posted March 10, 2019 Share Posted March 10, 2019 84 DB sensitive speakers, or should I say inefficient with an amp thats rated at 125 watts continuous into 8 ohms and running 5 watts class A. WTF, you need to get hearing aids mate to hear the class A segment of your amp. That amp is not class A as far as I'm concerned. Its Class A/B and that means nix if it sounds good. 3 Link to comment Share on other sites More sharing options...
CJH Posted March 10, 2019 Author Share Posted March 10, 2019 Thanks all for your feedback. @Gryffles I am trying to understand from a technical standpoint how the switch over from class A to class A/B works, and if in the end I am just going to be landing up with class A/B amplification anyway. In this case I could save quite a lot of cash and just get a straight A/B amp. I have a particular interest in the class A sound as I have never owned class A for many reasons, cost being one of them. I am interested if my ears could really hear the difference. As can be seen from my posting, my speakers sensitivity don't lend themselves well to small wattage amplifiers. The hot Australian climate also tends to not encourage high power class A amplification.... @Bronal Food for thought. I don't have a new amp as yet, but I take your point that 125W for these speakers may be low depending on the volume levels used with 84dB sensitivity. I tend to listen to music quietly as I live in an apartment where any loud music quickly results in a visit from the body corporate. @MLXXX I might just have to take my speakers with me, but I agree that in the end, its the ear and hairs on the back of the neck that must make the decision, not the specifications on a piece of paper Now to find a 330A in Canberra...... 1 Link to comment Share on other sites More sharing options...
CJH Posted March 10, 2019 Author Share Posted March 10, 2019 @Wimbo True, if it sounds good to your ear it does not matter what class the amp is... I take your point that I would have to play at very low volume levels to stay in class A. Maybe a Plinius SA103 would be better suited Now I just need $9000! And air conditioning to keep the listening room cool... In the end my speakers are not suitable for class A amps with those sensitivity levels without some serious cash outlay... One day, maybe! Link to comment Share on other sites More sharing options...
Wimbo Posted March 10, 2019 Share Posted March 10, 2019 50 minutes ago, CJH said: @Wimbo True, if it sounds good to your ear it does not matter what class the amp is... I take your point that I would have to play at very low volume levels to stay in class A. Maybe a Plinius SA103 would be better suited Now I just need $9000! And air conditioning to keep the listening room cool... In the end my speakers are not suitable for class A amps with those sensitivity levels without some serious cash outlay... One day, maybe! What speakers have you got? If you can tell us, I'm sure some people will be able to help you with the right amp. And not necessary for $9k. In response to dynamics. Telarc released a disc back in 83 that had a dynamic peak of 25db. Thats a ratio of 300 to1. So, if your amp was running around 1 watts continuous, that peak would ask for 300 watts. Ouchies. Link to comment Share on other sites More sharing options...
andyr Posted March 10, 2019 Share Posted March 10, 2019 3 hours ago, CJH said: @Wimbo True, if it sounds good to your ear it does not matter what class the amp is... I take your point that I would have to play at very low volume levels to stay in class A. So with your inefficient speakers (which are actually a bit more efficient than mine! ) ... why don't you just give up on this concept of a Class A amp - and use Class AB like most of the rest of us? Or buy some 100dB horns. Andy 1 Link to comment Share on other sites More sharing options...
Mendes Posted March 10, 2019 Share Posted March 10, 2019 9 minutes ago, andyr said: So with your inefficient speakers (which are actually a bit more efficient than mine! ) ... why don't you just give up on this concept of a Class A amp - and use Class AB like most of the rest of us? Or buy some 100dB horns. Andy +1 Synergy is everything.... Link to comment Share on other sites More sharing options...
Bronal Posted March 10, 2019 Share Posted March 10, 2019 4 hours ago, CJH said: @Gryffles I am trying to understand from a technical standpoint how the switch over from class A to class A/B works, and if in the end I am just going to be landing up with class A/B amplification anyway. In this case I could save quite a lot of cash and just get a straight A/B amp. I have a particular interest in the class A sound as I have never owned class A for many reasons, cost being one of them. I am interested if my ears could really hear the difference. As can be seen from my posting, my speakers sensitivity don't lend themselves well to small wattage amplifiers. The hot Australian climate also tends to not encourage high power class A amplification.... I have a Plinius amp that is switchable on the fly between A and A/B. You're welcome to have a listen and see if you can tell the difference. Link to comment Share on other sites More sharing options...
Volunteer sir sanders zingmore Posted March 10, 2019 Volunteer Share Posted March 10, 2019 13 hours ago, Bronal said: His amp is rated at 125 Wpc continuous into 8 Ohms and, while that seems a lot, he's likely to need a lot more than that to cope with dynamic peaks with speakers that are only 84 dB sensitive to start off with. Otherwise he may notice harshness that he is blaming on lack of Class A, whereas it's just the amp clipping. This^ Link to comment Share on other sites More sharing options...
Gryffles Posted March 10, 2019 Share Posted March 10, 2019 5 hours ago, CJH said: am trying to understand from a technical standpoint how the switch over from class A to class A/B works, and if in the end I am just going to be landing up with class A/B amplification anyway. In this case I could save quite a lot of cash and just get a straight A/B amp. I have a particular interest in the class A sound as I have never owned class A for many reasons, cost being one of them. I am interested if my ears could really hear the difference. As can be seen from my posting, my speakers sensitivity don't lend themselves well to small wattage amplifiers. The hot Australian climate also tends to not encourage high power class A amplification.... Understand why you’re interested in class A, I am too. The amps I’ve liked the most have all been class a but not with inefficient speakers such as yours. Go and have a listen to some class a amps and in particular see if you can demo a Sugden A21se with 90dB and upwards speakers. You’ll soon know if it appeals to you Link to comment Share on other sites More sharing options...
Guest scumbag Posted March 10, 2019 Share Posted March 10, 2019 (edited) Hi, Most class ab apps run class a to a given ouput. In most cases it might be milliwatts though. This might help to explain the concept of the transition from class a to class b at least from a pass labs pov, https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.passlabs.com/press/leaving-class&ved=2ahUKEwjdoeiNuvjgAhUJXSsKHRtnBisQFjAAegQIAxAB&usg=AOvVaw1NNOitrkjgFJLNwFx58T0d I had an pl x150.5 that was rated to 10 watts class a and then 150 watts class b. I couldn't tell the difference between the 2 modes of operation but that will vary between amps. It was an amp that sounded great at low volumes but it also has plenty of power when you needed it. You really need to listen to that amp with your speakers to figure out what it sounds like across different volumes. If you are also interested in 2nd hand then keep an eye out for a Pass Labs unit perhaps. My current PL amp runs class a up to 50 watts peak then 110watts rms class b into 8 ohms so it gives me all the headroom i need. Edited March 11, 2019 by scumbag Link to comment Share on other sites More sharing options...
CJH Posted March 11, 2019 Author Share Posted March 11, 2019 (edited) @WimboI recently picked up a pair of B&W PM 1's which have always caught my interest. These speakers seem to cause a LOT of discussion and debate with various audio circles. B&W seem to be polarising in certain circles. I have always wanted to try them out but at the time I just could not make peace with the $4000+ price tag. It will be interesting to see what these speakers can do. From reading they are quite different from the traditional B&W voicing. I have never owned any other B&W speakers before so I couldn't make a comparison. I am particularly taken by the build quality and the shape which is really beautiful. The PM 1's surprised me in that they sound much bigger than they actually are, but from further reading and this forum thread, they need good powerful amplification. These PM 1's are my current project which I have been posting about. As you can see from this posting I was toying with the idea of class A amplification..... I have driven them with a Primare I22 amp which is rated at 80 watts into 8 ohms. From this discussion 80 Watts sounds pretty low power for these speakers. I must say the Primare held its own very well at the volume levels I listen at. This amp is back with the Sonus Faber Chameleon B setup again. My last project was the Sonus Faber Chameleon B's [87 dB 4 ohm] which I finally paired up with a Primare I22 amp with the DAC. This is a great little value setup which I use for easy listening. My source is a Cambridge Audio Azure 752BD which I found to be very versatile. I seem to enjoy the audio section as well which seems to be quite good. I have had this since new and never felt the need to change it. Edited March 11, 2019 by CJH Link to comment Share on other sites More sharing options...
rantan Posted March 11, 2019 Share Posted March 11, 2019 (edited) 1 hour ago, CJH said: @WimboI recently picked up a pair of B&W PM 1's which have always caught my interest. These speakers seem to cause a LOT of discussion and debate with various audio circles. B&W seem to be polarising in certain circles. I have always wanted to try them out but at the time I just could not make peace with the $4000+ price tag. It will be interesting to see what these speakers can do. From reading they are quite different from the traditional B&W voicing. I have never owned any other B&W speakers before so I couldn't make a comparison. I am particularly taken by the build quality and the shape which is really beautiful. The PM 1's surprised me in that they sound much bigger than they actually are, but from further reading and this forum thread, they need good powerful amplification. These PM 1's are my current project which I have been posting about. . FWIW, I have owned and used a pair of PM1 speakers since just after their original release. It was love at first sight ( and sound ) and it remains to this day. I have been using these (mainly ) with my Luxman L 550 A II Class A ,which although only 20 watts P/C is a current meister and I have never had any problem, playing them at any level, on any type of music in my 6X 4.5 metre room. It is just such a great combination and all these years later, I still marvel at the enjoyment I get from them. I know for certain that these speakers are controversial and even polarising and I understand that completely and although I have several other amplfiers and several other pairs of speakers, I still love this combination and wouldn't ever consider selling either. ****Edited to show correct model number of amplifier.*** Dunno what this is worth to you but it is just an owner's long term experience with inefficient speakers and a Class A amplifier. I wish you well with the project. Edited March 11, 2019 by rantan 1 Link to comment Share on other sites More sharing options...
Wimbo Posted March 11, 2019 Share Posted March 11, 2019 (edited) 26 minutes ago, rantan said: FWIW, I have owned and used a pair of PM1 speakers since just after their original release. It was love at first sight ( and sound ) and it remains to this day. I have been using these (mainly ) with my Luxman 505 Class A ,which although only 20 watts P/C is a current meister and I have never had any problem, playing them at any level, on any type of music in my 6X 4.5 metre room. It is just such a great combination and all these years later, I still marvel at the enjoyment I get from them. I know for certain that these speakers are controversial and even polarising and I understand that completely and although I have several other amplfiers and several other pairs of speakers, I still love this combination and wouldn't ever consider selling either. Dunno what this is worth to you but it is just an owner's long term experience with inefficient speakers and a Class A amplifier. I wish you well with the project. Are you saying that its like the Marantz PM5 in Class A which is 20 watts and can be switched to 100 watts class B? Bit lost on that statement bro. It can't be anything like the Levinson ML2's I would expect. Anyway, I used to sell PM1's and they only ever sounded good with a good high current amp IMO. Great sounding speaker in a small room. As good as a pair of 805's IMO. They still don't work a large room IMO Pardon for all the IMO's. Edited March 11, 2019 by Wimbo Link to comment Share on other sites More sharing options...
rantan Posted March 11, 2019 Share Posted March 11, 2019 (edited) 19 minutes ago, Wimbo said: Are you saying that its like the Marantz PM5 in Class A which is 20 watts and can be switched to 100 watts class B? Bit lost on that statement bro. It can't be anything like the Levinson ML2's I would expect. Anyway, I used to sell PM1's and they only ever sounded good with a good high current amp IMO. Great sounding speaker in a small room. As good as a pair of 805's IMO. They still don't work a large room IMO Pardon for all the IMO's. I agree. The Luxman is a high current amplifier and is rated 20 WPC Class A and described thus by the company. I also agree that the PM1 can be as good as the 805 and that they require current, of which the Luxman has in good measure. Obviously I wouldn't use them if my room was twice the size but it is what it is and they work superbly on the Luxman. As you would know, the proof is always in the music Edit: apologies mate. My Luxman is the L550 A II. cheers. Edited March 11, 2019 by rantan Link to comment Share on other sites More sharing options...
CJH Posted March 11, 2019 Author Share Posted March 11, 2019 (edited) 40 minutes ago, rantan said: It was love at first sight ( and sound ) and it remains to this day. I have been using these (mainly ) with my Luxman 505 Class A ,which although only 20 watts P/C is a current meister and I have never had any problem, playing them at any level, on any type of music in my 6X 4.5 metre room. It is just such a great combination and all these years later, I still marvel at the enjoyment I get from them. Interesting. What model are you using? I want to do a little more investigation into it... Your room sounds a little larger than mine.... Edited March 11, 2019 by CJH Link to comment Share on other sites More sharing options...
rantan Posted March 11, 2019 Share Posted March 11, 2019 2 minutes ago, CJH said: Interesting. What model are you using? I want to do a little more investigation into it... My apologies, I posted the wrong model number in my first post. The Luxman amplfier in question is the L 550 A II. Apologies for the confusion. Link to comment Share on other sites More sharing options...
CJH Posted March 13, 2019 Author Share Posted March 13, 2019 On 11/3/2019 at 8:13 AM, scumbag said: Hi, Most class ab apps run class a to a given ouput. In most cases it might be milliwatts though. This might help to explain the concept of the transition from class a to class b at least from a pass labs pov, https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.passlabs.com/press/leaving-class&ved=2ahUKEwjdoeiNuvjgAhUJXSsKHRtnBisQFjAAegQIAxAB&usg=AOvVaw1NNOitrkjgFJLNwFx58T0d I had an pl x150.5 that was rated to 10 watts class a and then 150 watts class b. I couldn't tell the difference between the 2 modes of operation but that will vary between amps. It was an amp that sounded great at low volumes but it also has plenty of power when you needed it. You really need to listen to that amp with your speakers to figure out what it sounds like across different volumes. If you are also interested in 2nd hand then keep an eye out for a Pass Labs unit perhaps. My current PL amp runs class a up to 50 watts peak then 110watts rms class b into 8 ohms so it gives me all the headroom i need. That is a very good document. That provides good information on many of my questions I was pondering on. I have read it and will be reading it again a few times! Thanks. Link to comment Share on other sites More sharing options...
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