混世魔头
原帖由 @532 于 2017-9-25 09:22 发表 跟你讲 太阳能的除非你直接接电瓶 不然逆变器出来的我怀疑都变成高阶三角函数了
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原帖由 jun4rui 于 2017-9-30 09:05 发表 posted by wap, platform: iPad 看了下铁三角的唱机也就2K不到，反正是玩玩，到时候买一台就好了，唱片收藏一点就好了
天外飞仙
原帖由 amiliy88 于 2017-9-30 07:42 发表 posted by wap, platform: Android 我是光伏供应商，来
原帖由 mogle 于 2017-9-30 07:32 发表 自己虽然没有 但公司有 ap555这东西现在只要做音频相关的 那家公司不买一个
魔神至尊
原帖由 lkskk 于 2017-9-29 14:20 发表 本来不想在TG讨论玄学问题，一张口就水电火电满地球跑。黑胶作为模拟音源可能比开盘弱一点，但是起码简单的多，片源也好找的多。比起一般的数字音源，黑胶的密度和信息量是有优势的。而且由于模拟音源的天然优势，在 ...
http://www.npr.org/2012/02/10/146697658/why-vinyl-sounds-better-than-cd-or-not Why Vinyl Sounds Better Than CD, Or Not February 10, 20121:00 PM ET Heard on Talk of the Nation According to Rolling Stone magazine, sales of vinyl albums continue to grow, setting a new record in 2010. Does vinyl reproduce sound better, or is it just a trend? Two audio experts join guest host John Dankosky to talk about the science of audio, and how perceptions can shape the sound experience. JOHN DANKOSKY, HOST: Up next: how to tell your CD from your MP3, from your AAC. But first, let's start with the LP. When I was a kid, music took up a lot of room - not in your hard drive, but in your life. Being an audiophile meant devoting shelves and shelves and shelves and shelves to your album collection. And when you moved out of your parents' house, out of your first apartment, you hauled milk crates filled with your music collection onto your next life. And these days, most of us probably get our music in the form of downloads - no heavy boxes, but no fancy cover art, either. Lots of audiophiles say that when it comes to sound quality, nothing beats vinyl. These purists wonder if digital files can really give you that analog sound of our youth. For the rest of this hour, we'll be talking about the science of audio, what all those bit rates and sample frequency terms mean, and we'll find out how your perceptions could affect what you hear. First, though, here's Laura from Main St. Jukebox in Stroudsburg, Pennsylvania. LAURA: I prefer vinyl. It's - listening to music is an experience, and a full experience includes putting on the record, moving over the needle and sitting back and rocking out. DANKOSKY: OK. We know what she thinks. She works at a record store. Let's find out from our guests. Sean Olive is director of acoustic research at Harman International. He joins us from the studios of NPR West in Culver City, California. Welcome to SCIENCE FRIDAY, Dr. Olive. SEAN OLIVE: Welcome, John. Thank you for inviting me. DANKOSKY: And Scott Metcalfe is director of recording arts and sciences at the Peabody Institute of Johns Hopkins University. He joins us from WTMD at Towson State. Thank you so much for joining us, Scott. SCOTT METCALFE: Thank you, John. DANKOSKY: So, first of all, I'll ask you, Scott: vinyl or CD? (SOUNDBITE OF LAUGHTER) METCALFE: I enjoy both formats, but my preference is definitely CD. DANKOSKY: Now, why CD? METCALFE: Well, I think it has a lot to do with the fact that I'm primarily a recording engineer, as far as working with music. And it's - the closer thing to what I'm sending into the recorder is very much what I'm getting back out. With analog formats, although the sound can be very pleasing in certain styles, it's definitely imparting its own sound on it. And I think, to an extent, it's that sound that some people are really drawn to. But it's nice as an engineer to have the confidence of knowing that what I'm putting into - in most cases these days, the computer - is pretty close to what I'm going to get out. DANKOSKY: Sean Olive, I have to ask you. I think I know your answer, but vinyl or CD? OLIVE: Definitely CD. DANKOSKY: Yeah? So tell me why. OLIVE: Well, I mean, I grew up listening to records up until about '85, when the CD was already out. And I was involved in testing loudspeakers up at the National Research Council in Canada. And we were testing cartridges at that time, and it was quite apparent that the amount of distortion coming out of these devices was very high compared to CD. So what we found was that vinyl was a limiting factor in our ability to do accurate and reliable listening tests on loudspeakers, and we had to find a more reliable and more accurate medium. DANKOSKY: I just wanted to say quickly, I'm John Dankosky, and this is SCIENCE FRIDAY, from NPR. So when we're talking about all of this digital technology, there's a lot of terminology that I don't think everyone completely understands. Maybe I'll ask you, Scott Metcalfe, first. What is dynamic range? METCALFE: Dynamic range we can think of initially as a musical term, meaning the range from the loudest notes being played to the softest notes being played. And when we talk about dynamic range in a recording medium, we're talking about the range between the noise floor - sort the bottom point where the noise becomes a distraction - to the top point, where it starts to introduce harmonic distortion, where the, technically, the waves that are being captured start to change in their form, and they're no longer precisely what we're feeding into it. DANKOSKY: How about dynamic compression? METCALFE: Well, dynamic compression is a tool that we may apply to reduce the overall dynamic range. That can be done in a creative sense, where we can apply, say, dynamic compression to a vocal track that needs to sit over a jazz trio, for example. So if the singer gets too loud, it doesn't jump out of the track, and if gets too quiet, it doesn't get buried behind the other instruments. The term can sometimes be applied to vinyl in that the physical limitations of what the medium is able to store and reproduce is such that it can be advantageous, particularly in the lower frequencies, to reduce the dynamic range - meaning the low notes that are being captured - to reduce the dynamic range to do a couple of things. One, it's going to prevent the needle from jumping right out of the groove if it gets too extreme. The other is that if we reduce the overall dynamic range going to the disc itself, we can actually fit more material, more length, onto each side of the disc. With CDs, there isn't that trade-off. We have a, you know, easily, 80, 90 dB or more of dynamic range to work from, and we don't have to worry about any - although, unfortunately, it's very popular to put dynamic compression on a lot of modern music, but it's not a - it's not necessary. Technically, it's more an aesthetic choice or trying to be louder than the other band on the street. DANKOSKY: We'll be talking a bit about some of these new, modern ways of compressing music. If you want to join us: 1-800-989-8255, or 1-800-989-TALK. Vinyl or CD or MP3? Can you tell the difference? Jerry's in Missouri. Hi, Jerry. Go ahead. JERRY: I'm one of those old-school audiophiles that used to have the Discwasher and the expensive turntables and $300 cartridges. And when CDs first came about in the mid-'80s, some of the early digital recordings, even the digital recordings that were reproduced on LP - Pablo and Fantasy both did that with jazz groups - sounded kind of trebly. And I guess it's the aural equivalent of looking at the dots or pixels of a not very fine photograph. I still have friends that swear by vinyl records. My daughter is really into vinyl records. But to me, I have the recordings of the same - exact same things. And, of course, anything, I think, done in the last decade or more has a fuller sound. And, of course, you don't have that problem of when you have a quiet passage in something, you're hearing the mechanical sound of that needle going across the vinyl and/or - even as careful as you've been with your records - sort of pops and clicks. DANKOSKY: Yeah. Sean, what do you say to him? OLIVE: Yeah. Well, first of all, when CD first came out, a lot of the CDs that were released were actually recordings made for vinyl. And those master tapes, rather than remastering, they just made them into CDs. So a lot of the, you know, objectionable sounds of CD was actually because the record companies didn't bother to remaster these old recordings. And this is something that I learned from Phil Ramone, who admitted this that, you know, there was a reason why these bad CDs first sounded bad, but it had nothing to do with the medium. And it was the actual recordings. DANKOSKY: Well, we're going to talk more. We're going to give a little listening session right after this short break. (SOUNDBITE OF MUSIC) DANKOSKY: This is SCIENCE FRIDAY, and I'm John Dankosky. We're talking this hour about the science of audio. My guests are Sean Olive, director of acoustic research at Harman International, and Scott Metcalfe, the director of recording arts and sciences at The Peabody Institute of Johns Hopkins University. OK. We're going to do a little listening test, here, guys. We have an LP and a CD of the same song. We're going to play each of them and see if you can hear the difference. (SOUNDBITE OF SONG, "FOOL IN THE RAIN" ROBERT PLANT: (Singing) Oh, baby. Well, there's a light in your eye that keeps shining. Like a star that can't wait for a night. I hate to think I've been blinded, baby. Why I can't I see you tonight? DANKOSKY: So we're listening to, of course, some Led Zeppelin on the background. I'm sure that our guests down the line can hear pretty clearly which one is the vinyl and which one is the CD, huh? METCALFE: Sure. Yeah. DANKOSKY: Yeah. And the big thing is all this surface noise that's on the front, but is that the big difference between these two recordings? If you were somehow able to take out all the scratches, the remnants of all these years of listening to Led Zeppelin, would you be able to really tell that much of a difference? METCALFE: I think so. In fact, Sean kind of alluded to this a little bit earlier in talking about Phil Ramone. But one of the issues, too, when people say, well, I have this on CD and I have it on vinyl, and the vinyl just sounds so much better, it may not be an apples-to-apples comparison, because the flip was also true where - particularly stuff that's been re-released, remastered onto CD, it's gone through an entirely different mastering process and, I'm sorry to say, in some cases, without the original staff involved, you know, the original engineering staff or production staff. If it was really just a business decision, let's get this off master and get it out there. DANKOSKY: Well, and we wanted to ask you about that quickly, because we see these things. They come out after, you know, almost every 10 years, there's a remastered version of the same record. What exactly is happening with this remastered? METCALFE: Well, it's - in some ways, it's up to the mastering engineer what's happening there. With - I would say, at best, an old recording, you know, any kind of noises or artifacts or anomalies from either the recording process or just from the ageing of the material, if that can be cleaned up, I think that makes a lot of sense. Modern recordings, though, are comparatively louder. That's kind of a subjective term. But if you were to play a CD, let's say, from 20 years ago and compare that to a CD that just came out recently, I don't think many of the listeners would be, you know, they will have experienced this, that you have to turn a new CD down a lot. There's a lot of dynamic compression that we talked about before being used on modern CDs. And in some cases, the depth of field, the depth of sound that people talk about, enjoying about vinyl that they say is missing from the CD may, in fact, be a result of the compression to make that old recording more competitive for the modern market. I - in preparing for today, I though, jeez, this would be a great thing to do over at school, is do a recording and put it onto vinyl without any additional processing, put it onto CD without any additional processing, and that's really gonna be the apples-to-apples comparison of those two. It's two hard now to take something off the shelf and assume that they're gonna be the same thing. DANKOSKY: I think our caller Bill, though, from Indiana maybe gets it, one of the points here between vinyl and CD. Bill, go ahead. BILL: Yes. I wanted to agree with the - at least I believe the point that the first lady was talking about, that although the sound of CDs and MP3s and that sort of thing is certainly better, there's a whole ritualistic quality of taking a vinyl record out and placing it on the turntable, using a little device to clean the dust off of it, setting the needle on, watching a little stroboscope to make sure it's turning at exactly 33-and-a-third revolutions a minute that I miss with the new technology that you can just pop in or turn on a button or whatever, and all of a sudden you're listening to it. And I just - the incorporation of your other senses and everything is just something that I really miss with the new technology. DANKOSKY: Yeah, that smell of taking the record out of a jacket the very first time. I know what you're talking about, Bill. BILL: Oh, absolutely. (SOUNDBITE OF LAUGHTER) METCALFE: John, you know, there's a couple of things that come to mind with that. One is that I completely agree, and I'm not preaching that one format is really better than the other, because I would never tell an artist, no, you shouldn't paint on canvas because I think paper looks better. So there's that extent. There's also - we have lost the ritual, and we've lost the experience of sitting down and focusing on just a recording. What we've gained, in a way - and I'm not saying one's necessarily that much better than the other - is most people walk around with a huge collection of music on their belt or in their jacket pocket. And I think we probably consume more music now than we ever did. So there's a little bit of a tradeoff there. We can still make room for the experience if that's our interest. DANKOSKY: Sean Olive, how about this perception that may change the way we feel about how one piece of music sounds over another? OLIVE: Right. Well, there's a number of factors involved in our perception of sound quality, and a lot of them have nothing to do with the sound itself. So in the research that we do, we've looked at the - and we call these things nuisance variables or biases. So one of the ones that we deal with is psychological nuisance variables, which have to do with your knowledge or expectation of what you're hearing. Thomas Edison knew this a hundred years ago. He said people will hear what you tell them to hear. So if you're aware of - that you're listening to a violin, you've been told it sounds great, if it costs more money, all of those factors play into your perception of how it sounds. DANKOSKY: And I can only imagine that in your line of work, sometimes people will spend a whole lot of money on a set of speakers, and they'll think those speakers have to sound much better because they just cost me a lot of money. OLIVE: Right. And often it's a case where the price has very little to do with the sound quality. DANKOSKY: Is that really true that you can't really buy your speakers on a price point? OLIVE: No. I mean, we have many examples where we do double blind tests, and some of the competitors are very expensive, but they don't sound very good because I think it's a matter of, you know, the more expensive the speaker is the fewer you sell. So your R and D budget is much smaller, and you just don't have the money to spend on good measurements, for example. DANKOSKY: Let's go to Brian in Ann Arbor, Michigan. Hi, Brian. BRIAN: Hi there. I appreciate the discussion on the CD versus LP, but wanted to add into the mix CD versus MP3 and AAC, et cetera, because we're losing a lot of information when we go to that next level. And it's kind of sad that that's the way we consume music now. DANKOSKY: And that's exactly what we want to get to. So, Scott Metcalfe, what happens here? We're talking MP3s and different types of MP3s. Maybe you can explain the differences between these various formats. METCALFE: Sure. Well, the - I was referring to before with the portability of music now. That's the upshot of MP3s and AACs. And even in my work, when I'm working with an artist who's not nearby, it's very convenient to put a demonstration of a mix or an edit, into a compressed format like that that I can put on to an FTP server, and they can download and audition. But there is definitely a quality difference. Just today, I put an actual CD in the FedEx to a client that I'm working with so he can hear exactly what it sounds like, not like what, you know, what we are working with online. There is loss - there's a loss of depth of field in a smaller format. Just to say, though, MP3 and AAC excludes a lot of details. You can have very low-resolution MP3s that offer you really small file sizes but a pretty big hit in sound quality. And you can get bigger MP3s or what we would call the kind of the next generation of MP3, which is the AAC, which most people know as the format of iTunes. The equivalent AAC to MP3, to my ears, does sound better. And when I get into the higher ranges like 190, 320 kilobits per second, those are pretty respectable sounding. And I'll use those, you know, as audition levels. The types of things I hear in the MP3s that I don't hear in the original, excuse me, in particular things like drums. A snare drum tends to sound more like noise to me. The rattle of the snares loses its definition. The stereophony of the sound gets a little bit collapsed. You know, if I'm listening in the car and there's a lot of noise there, I'm not terribly concerned about it. I go into my home to listen. I listen in the recording studio, and it's blatantly obvious to me. Or occasionally, I'll hear somebody playing, you know, through a PA system at a party or, you know, a reception or something from an MP3, and it's almost painful for me to listen to. And I think if we did a quick comparison there, people would know what I'm listening to. DANKOSKY: Well, we have some comparisons that you sent along to us, and we want to listen to those now. We have an original recording of a rock band that you made. And maybe you can just tell us about - when you say an original, how is this made? What are we listening to, this first track? METCALFE: Yeah. This is a band called Bronze Radio Return from Hartford, Connecticut, and we - Chris Henderson, who's the lead singer of the group and songwriter, was a student of mine back at The Harrt School in Connecticut. And I had brought him down to - into a class that I was teaching down at Yale in the sound design, Yale School of Drama sound design department. And we brought the band and we recorded the class project. And so that's the material I decided to use. And I tested this on my own just to see what we would get. And immediately, I picked up on the cymbals and the snare drum having kind of this distortion noise quality to them that... DANKOSKY: Yeah. METCALFE: ...I didn't pick up in the original. DANKOSKY: Well, let's listen to a little bit of this original recording first here. (SOUNDBITE OF SONG, "OVER YOUR HEAD" CHRIS HENDERSON: (Singing) ...this place because the water is over your head. It's over your head. DANKOSKY: Now, we're going to play a little bit of an 8-bit recording, and this is what you would consider to be almost like an old-style MP3. And we - I think most people should be able to hear this even on their car stereos, the difference here. (SOUNDBITE OF SONG, "OVER YOUR HEAD" HENDERSON: (Singing) ...this place because the water is over your head. DANKOSKY: So what are we losing in there, Scott Metcalfe? METCALFE: Sure. Well, first of all, that wasn't really a format that people downloaded. The reason I put that in there is that it illustrates what the difference is or what is being lost with bit rate and sample rate. Sample rate - the higher the sample rate, the higher audio bandwidth you're able to capture. And most people would say that, on average, human beings hear up to about 20,000 cycles, wave cycles per second. So a CD is going to capture sound - not capture sound, but reproduce sound of 44,100 samples per second. And we have a little formula that says if you divide that in half, whatever our sample rate is, we divide that in half, and that's what we're going to be able to capture. So the recording you just played was a 12 kilohertz sample rate. So therefore, we are only hearing up to six kilohertz. So we are missing a lot of overtones, a lot of content in there. And the 8-bit just means there's - essentially, there's quite a bit more noise. There is a lot of information that was lost there. DANKOSKY: We're going to hear this original recording that you made. Once again, this higher fidelity recording. Let's listen for a moment here. (SOUNDBITE OF SONG, "OVER YOUR HEAD" HENDERSON: (Singing) ...this place because the water is over your head. DANKOSKY: And now, we're going to go to an MP3, a more traditional MP3 recording. The type that you might download now. (SOUNDBITE OF SONG, "OVER YOUR HEAD" HENDERSON: (Singing) ....this place because the water is over your head. DANKOSKY: Now, I say Scott, I can't hear really any different through my headphones and probably, at home you can't hear any difference. But you sent us an interesting comparison here, and the next thing that we're going to hear is what's missing. What's essentially missing between the original and the MP3. Let's listen to this. (SOUNDBITE OF SONG, "OVER YOUR HEAD" HENDERSON: (Singing) ...this place because the water is over your head. DANKOSKY: So explain this, Scott. The data we're hearing there is what? It's just stuff that's out of the original recording to make this MP3, to compress it if you will? METCALFE: Yeah. This is a fun little trick that we do when we want to really hear the difference between two pieces of audio depending on what kind of process we're applying to it. And what I did was took the excerpt, the original excerpt, and I inverted the polarity, which is a technical term for anything that was the positive side of the waveform is now on the bottom, is negative and vice versa. So when you sum them together, if they're the same exact thing, you hear absolutely nothing. If you hear anything at all then you're hearing what's different between those two recordings. So this is just a cheap and simple way of hearing what was lost. And, you know, of course, my job requires me to listen really critically, but - and I wasn't sure how much I was going to get over the headphones here over the ISDN line. But I could clearly hear a lack of low frequency in the MP3 and just the real thinness to the rest of the texture. I'm not sure how much is that lost over the FM broadcast. DANKOSKY: Well, I think an awful lot is lost. I'll just say quickly that I'm John Dankosky, and this is SCIENCE FRIDAY from NPR. Now, Sean Olive, younger people listen mostly to MP3s. Do you think that this affects their preference in audio speakers? Do they have an appreciation for higher fidelity sound anymore? OLIVE: Well, that's an interesting question because in the last couple of years there's been a lot of press saying that kid, you know, we're approaching the death of fidelity because of the younger generations have been raised on MP3 in low-quality earbuds. And that they now, you know, may prefer that over high-quality sound. So about a year ago, we did a small study where we brought in high school students and more recently college students and we asked them to listen to MP3 at a low bit rate, 128 kilobits per second, versus CD. And, of course, it was a blind test, so they weren't aware of which was which. And what we found out was that in most cases, they prefer the CD over the MP3. And then we random through some speaker tests, where they heard four different loudspeakers that varied from one that was very accurate and neutral to one that was quite the opposite, and quite surprisingly they prefer the most accurate neutral loudspeaker. DANKOSKY: Now, has your industry had to change it all with the idea though that because the music industry is making MP3s as the commodity, do you have to do different things in order to make a lower resolution piece of music sound good through a set of speakers? OLIVE: No. We basically designed our speakers so that they will sound good if you play good sound and music through them. We don't try to compensate for - in the loudspeaker system for deficiencies in the MP3 or vinyl. We are working out some algorithms that will try to improve low-quality MP3 so it sounds closer CD quality. DANKOSKY: I want to get to Zack(ph) in San Francisco. Hey, Zack. ZACK: Hi. You're actually speaking to my question right now. As you're talking about formats on how to use the CDs and MP3, it seems to me that a lot of the newer music coming out is more manipulated and actually made to be heard on earbuds or actually on cell phones. It's more distorted or twangier(ph) or treblier(ph) , if you will. DANKOSKY: Scott, what do you say? Is that true, Scott Metcalfe? METCALFE: I'm not sure how much how that happens, but it is another place where, you know, years ago the litmus test was always, let's go play this in the car and see what is sounds like. If it sounds good there, it's going to sound good everywhere. I do know a lot of people - and I've done this myself - who will listen on earbuds since that's going to be the most common way that the music is going to be listened to. You know, it brings up an interesting point though is that as people gets faster connections at home and storage on phones and computers, it becomes comparatively much less expensive. More record labels - right now, it's kind of the boutique labels, but we're seeing more record labels offering very high resolution downloads for purchase. And, you know, iTunes has gone up to give the option of downloading. I think it's iTunes Plus, where you get a much higher quality file than you did. So it'll be kind of interesting to see what - if the market sort of stirs us. The market stirred us towards the portability of music. It'll be interesting to see if the demand starts to come back. DANKOSKY: If we can hit, we can start to head the other direction. Well, Scott Metcalfe, director of recording arts and sciences at The Peabody Institute of Johns Hopkins. Thank you so much for joining us. METCALFE: Thank you. DANKOSKY: And thanks also to Sean Olive, director of acoustic research at Harman International. Thank you. OLIVE: Thank you. DANKOSKY: Thanks to Scott for the clips we played. We heard "Over Your Head" by Chris Henderson of the Hartford band, Bronze Radio Return, in New York. I'm John Dankosky, in for Ira Flatow with SCIENCE FRIDAY. I guess we're going to leave a little bit of Pink Floyd. Copyright © 2012 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information. NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
今年6月，广东记者采访率广交从欧洲归来的著名指挥家余隆，问他在家里听音乐是喜欢听唱片，还是数字音乐。余隆不假思索地回答：“当然是数字音乐。”同样的问题在不同场合也问了谭盾，谭盾也是一样的回答。这些时代音乐的弄潮儿，他们虽然年纪也不小了，但”先进性“的代表能力丝毫不弱。
原帖由 jjx01 于 2017-9-30 09:17 发表 955493 动态能保证到70db
原帖由 @nai 于 2017-9-29 13:07 发表 是这个意思。还有更便宜的，可以玩玩试试
原帖由 jun4rui 于 2017-9-30 09:48 发表 posted by wap, platform: iPad 年纪大了，现在觉得一个方面走到很高其实也没啥意思，不如把面放广泛一点，保持一定素质，少数方向走高端就够了
原帖由 nai 于 2017-9-30 09:30 发表 黑胶唱机的指标肯定是全面低于现代数字音源 但黑胶和数字音源的主要差别，黑胶理论上是没有丢失信息量（模拟录音前提） 数字音源是采样获得，不论采样率多高，信息量肯定是丢失了一部分 数字录音的黑胶，情况就 ...
原帖由 reg-neo 于 2017-9-30 09:49 发表 posted by wap, platform: iPhone 信噪比那么低的玩意，信息量丰富？
