标签: audio

在硬件设计时，经常会涉及音频的Audio Jack部分，Audio Jack的原理图库也是多种多样，经常让人困惑不解。最近看到知名连接器厂家CUI DEVICES的一篇文章 Understanding Audio Jack Switches and Schematics，觉得写得不错，尤其是图解很是简单明了，简单翻译记录下，也可以去翻看原文： https://www.cuidevices.com/blog/understanding-audio-jack-switches-and-schematics Audio Jack原理图 Audio Plug也就是音频插头可以由2-6或者更多导体构成，每段导体有不同的名字，通常为Sleeve、Tip、Ring等。下面以3段式的立体声连接器为例，下面是基本的原理图，不包括开关： 在理解Plug和Jack的连接关系时，可以想象下，将Plug从左到右插入Jack，如下图所示： 上图解释了Jack原理图库中信号线的含义。 Audio Jack开关 Audio Jack除了信号中，还通常带有开关。下面在端子2（tip）增加一个开关10。这个开关如下面的左图所示， 在未插入状态时通常为闭合状态。端子10和端子2直接连接，因为这个开关位于tip位置，所以通常被称为tip switch。 现在我们再次想象plug从左到右插入，当tip和端子2接触时，将端子10推开，两者断开连接。 与之类似，多个开关可以存在于不同触点上，下面是个4插头的例子， 有3个开关位于tip，ring1和ring2位置上。 这个看起来很复杂，但原理和单个开关相同，只是多个两个类似的开关。 到目前为止，我们看到的开关都是通常闭合的，也有一些是通常断开的、SPDT、DPDT。这些开关中许多是和音频信号隔离，用于其他控制电路。 Audio Jack开关应用 应用场合决定了选用那种Audio Jack以及是否带开关。如果只是需要简单的插入耳机并听音乐，并不需要audio jack带有开关。如果需要在speaker和headphones之间切换，检测plug是否插入，使用插入的plug控制电路的其他部分，或者使用音频混音板，那就需要开关功能。 在speaker和headphones之间切换音频 下图中的第一个，plug没有插入，端子10和11两个开关闭合，音频信号直接传送到speaker上，在第二个图中，plug插入后，端子10和11被打开，音频进入headphones. 检测Plug插入 相似的方式，当plug断开端子10时，可以检测plug插入。 控制电路中独立于音频的其他位置 下图中的4-6独立于音频信号1-3，这里利用了SPDT开关，在未插入时，4和5连接在一起，在插入后，5和6连接在一起。这就利用插头在功能A和B之间切换。

Type-C Audio的崛起 智能型手机集合了上网、通讯、观影、听音乐等办公娱乐功能于一身的携带型产品，每支手机上标配一个3.5mm耳机孔似乎是一件理所当然的事情，但近几年，每家手机厂商却都陆续取消了3.5mm耳机孔，这是为什么呢？ OPPO是第一只取消3.5mm耳机孔的手机，于2014年推出的R5，采用USB Micro B转3.5mm Dongle的方式来取代3.5mm耳机孔，主要是为了设计出更薄的手机，这台手机厚度仅4.85mm，成为时下最薄的智能型手机。而Vivo也随后推出机身厚度4.75mm的X5 Max ，同时也保留3.5mm耳机孔。 在讨论该不该取消3.5mm耳机孔时，2016年由Apple发表的iPhone 7宣布取消3.5mm耳机孔，为整个手机市场做了结论取消了3.5mm耳机孔后，除了可以将手机做得更轻薄外，剩余的空间可塞入更大容量的电池，延长手机的待机时间等。而USB Type-C的出现，达到了一个连接孔可拥有多种用途，不但可减少Host端的连接孔数量，还可将高解析的音频DAC芯片外置成为一个独立的选购商品，降低手机成本。于是其他厂商也陆续跟进，开始着手取消智能型手机产品上的3.5mm耳机孔。 关于USB DAC与市场趋势 您了解DAC芯片是什么吗？为什么3.5mm耳机孔与DAC有关系呢？ DAC(Digital-to-analog converter) ，是将数字信号转换成人类能够聆听的模拟信号的设备。对于精度的需求，高阶与低阶的DAC可以有数倍的成本差异。 具备3.5mm耳机孔的手机，皆需要DAC来将数字音乐转换成模拟音频才能透过耳机聆听，而手机内建的DAC芯片通常不会放太高的成本，有些甚至直接与手机CPU整合在一起，所以对耳机有特别爱好的人都很清楚，使用高阶耳机连接手机的3.5mm是绝对无法达到该耳机的细腻音质。 因手机厂商逐渐取消3.5mm并统一改为USB Type-C单一接口，造就Type-C Audio的市场崛起，DAC透过UDA规范设计成一个独立的USB Type-C产品，并依照用户的需求，规划出各种高低等级的DAC产品如下： DAC类： 消费者可以依照自己手边耳机的等级，选择相对应、适合的DAC产品，即可在手机上享受细腻的音质。 耳机内建DAC类： 由于大多数爱好者的手上仍拥有许多3.5mm的高阶耳机，因此现阶段Type-C转3.5mm的产品是主流，而内建DAC的Type-C耳机目前在售价与表现上不成正比，因为只兼容Type-C、无法向下兼容，难被市场接受，厂商也多半往无线耳机的方向发展，因此这类产品呈现越来越少的趋势。 自从手机上的连接口逐渐由USB micro B转换成Type-C后，Type-C的高带宽与扩充性，一孔多用的功能逐渐成为手机生产厂商的目标，保留耳机3.5mm输出孔的手机比例逐年降低。由下表可看出每年以5%左右的比例逐渐减少，由此预测，到2025年时，保留3.5mm的手机将会低于市占的50%。 （保留3.5mm手机占比） 对手机厂商来说 ：移除5mm可以缩小手机体积、塞入更大电池、更可以逐步将DAC成本cost down。 对音乐供货商来说 ：由于Type-C DAC产品可提供高于44kHz/16bit以上音质输出，音乐供货商开始在无损市场上崭露头角，如：Apple Music, Tidal, Spotify, Qobuz, Tencent Music, NetEase, YouTube Music, Amazon Music, Deezer, Yandex等。 对消费者来说 ：可依需求选择高音质Type-C DAC产品，不再需要使用手机仅44kHz/16bit的5mm输出。 实际案例不良分析： SUT侦测不到Type-C 耳机 SUT连接Type-C 转3.5mm DAC后，电量迅速减少 SUT 连接EC270 Dongle(Type-C公转3.5mm +Type-C母)并连接充电器后，SUT充电电流仅0.35A SUT 连接Type-C 耳机后透过Skype通话没有声音(播放音乐正常） SUT 连接连接Type-C 转3.5mm DAC后无法切换至最高支持格式2ch 24bits 192kHz(仅2ch 16bits 44.1kHz） SUT 连接Type-C 耳机后无法使用耳机上的控制按键切换上下曲 测试规划与方向建议 由于Type-C DAC产品越来越多，因此与手机或其他Host的兼容性是必须经过测试兼容性验证才能让消费者有信心购买、使用，百佳泰基于长期累积的测试经验提出厂商可就以下的测试方向对产品质量测试进行规划。 ☑ Compatibility Test Device detection Plug and Play Test Dongle Test (C to 3.5mm) Dongle Test (C to Multi Devices) ☑ Function Test Microphone Function Test Control button Test Voice Assistants Test Streaming Service Test Hi-Res Audio Format Test Sim card Phone Call Test Calling by LINE, Wechat, Skype, etc.… Test ☑ Power Management Test Charging/Discharging Power consumption

XQ6657Z35-EVM评估板 是基于 TI 双 核 DSP TMS320C6657 和Xilinx Zynq SoC处理器XC7Z035设计的 多核异构平台 ，由核心板与底板 架构 组成。 SOM-XQ6657Z35核心板框图 TMS320C6657 Audio设计 评估板 XQ6657Z35-EVM ， 音频输入输出设计， 其引脚定义如下图： （ TLV320AIC3206IRSBR音频接口芯片） 音频接口截图 XQ6657Z35-EVM音频电路参考 XQ6657Z35-EVM侧视图

1. 我的工作   做了很多年的IC销售，不禁熟视无睹起来。订货、进货、库存、销售、回款；pull in, pull out，订单取消、客户拖款、坏账 …… ，林林总总，不一而足。   不过，有些工作值得重新再来。不需订货、没有库存，当然也没有pull in 、pull out，许多问题也就迎刃而解。   电视机、移动音响等产品风起云涌，时尚的潮流是：轻、薄、小。随之而来的问题就是音响效果普遍较差，声音干涩单薄、声场狭窄、人声含糊，最糟糕的是低音几乎没有。简单的道理是同等档次的喇叭越大、腔体越大，音质越好；反之就越差。   这个矛盾怎样解决？   从事音频电声行业的朋友一定脱口而出，用音效！哈哈，好回答！不过什么是音效呢？我向我服务的美国公司请教Sound Effect是什么？他认认真真地举例子告诉我：比如：电影中那乒乒乓乓的*声、轰隆隆的雷声，这制造的效果就是Sound Effect。   美国人说：我们提供的是Audio Enhancement，是帮助提高声音质量的玩意。这样，我看这个技术应该称为：音质提升。和Sound Effect有些南辕北辙了。不过，在和我客户的接触交流中，大家还是习惯用“音效”，我能明白他们的意思，也就入乡随俗了，呵呵。   说起翻译上的差异，不是身临其境，无法想象！我的老师从来没有教过我Restroom是什么？我望文生义是休息室，机场、商场等公共场所随处可见。而我们熟悉的WC、Toilet却遍寻不到。我问美国朋友WC在哪里？他们云里雾里！他们会用Man’s room或者Lady’s room，也可以猜出Washing room或者Toilet但是 WC，除非跑过江湖的美国人，他们确实不知道，真的不知道！     

I never met Richard Feynman but I am glad to say that I played a small role in preserving what he had to say, especially stories about events in his past. I first encountered Feynman’s physics books when I was in college in the late ‘60s. A picture in the forward of the book showed Feynman playing bongo drums. What kind of a physicist could this be, I wondered to myself. As decades passed, I encountered people who had taken a course from Feynman, usually at CalTech, including physics professor Julian Noble. Walter Thorson, a theoretical chemist who went through school the CalTech-MIT route and taught for many years at the U. of Alberta in Edmonton, is another. In one of our roving discussions, I recall Walter telling me about Feynman’s teaching style and his ability to do contour integrals in the most non-obvious ways. It was hard for Feynman, as brilliant as he was, to teach minds of ordinary brilliance. The former Feynman student who stands out to me the most was a friend of mine and fellow homesteader in the jungle here in Belize who, sadly, died of cancer a few years ago at the age of 51. Mark Ludwig had a doctorate in particle physics. For his PhD thesis, he had worked out by a different means one of the classic math derivations of modern physics. I marveled that it had not been worked out as he did it long before, but it was not a simple feat. Mark went to MIT, and according to his PhD chemist father, was there less than two years. He had gone through all the undergraduate math and physics and was wondering what to do next. A friend of his was going to Cal Tech, but it was long past the deadline for submission of admission applications as a student. On the letters of recommendation of his physics teachers at MIT he got into graduate school at Cal Tech without having obtained a degree from MIT. The only university degree he ever had was a PhD. Later, he dropped out of the hallowed halls of science at CalTech, in part because of what he observed as the dilution of the pursuit of scientific truth by a pursuit of money by his professors. Then there was a bizarre incident that shattered his hard-headed scientific-materialist outlook. In the Pasadena newspaper, an occult group ran an advertisement guaranteeing a “psychic experience” or your money back. Mark rose to such challenges and, determined to get to the bottom of the ruse, responded to the ad - but he did not ask for his money back. I asked him what happened. He responded: “They told me things that only I knew that they could not possibly have known and in enough detail to convince me that there is more going on in the universe than can be explained on the basis of physics alone.” He subsequently returned home and spent time studying the wider picture of reality, continuing it after returning to a physics school that was not as demanding as CalTech or MIT so that he could do both physics and continue “studies of everything” at the same time.   While at CalTech, Mark was one of only two students who dared to take for credit among a class full of auditors Feynman’s course in advanced mathematical methods for physics. The other was Stephen Wolfram who is known for his contributions to symbolic computing of mathematics. Like Thorson, Mark was also not entirely impressed with Feynman’s teaching style, though he was interacting with someone of similar ability. One of Feynman’s colleagues at Cal Tech was the father of Ralph Leighton. Ralph was a school teacher and young friend of Feynman. Both of them had an interest in drumming, and they had drumming sessions together and even built drums. At these sessions, the raconteur (story-teller) Feynman would tell of events from his past. The younger Ralph began to realize that these stories were extraordinary - a goldmine of tales! He brought his tape recorder - an ordinary machine and not of studio quality - to tape them. He then transcribed them into what became the longest top-selling book on the New York Times best-seller list at that time, titled Surely You’re Joking, Mr. Feynman: Adventures of a Curious Character. I later wrote to Ralph that the subtitle was ambiguous in that it could be taken two different ways. He and Feynman had already thought about it and knew of three different meanings. Later in life, while the Soviet Union still existed, Feynman had an interest - kind of a fetish curiosity - about Tannu Tuva, an obscure part of the Soviet Union in Central Asia. The capital city was Kyzyl, and lacking any vowels, Feynman thought that it just had to be an interesting place, a country with a capital having a name with no vowels. (Russian head of state, Vlad Putin, recently disappeared for a week to Tuva on vacation, and did some fishing.) Ralph was Feynman’s co-laborer in the effort to go there. Feynman got a California license plate that said “TOUVA” on it and was trying to devise means of going to the place that was off-limits by the Soviets. He offered to give physics lectures in Moscow, to which the Soviets agreed, and then he could visit Tuva. No, Feynman objected; Tuva first, then the lectures. It was declined. Leighton wrote a book on the project, Richard Feynman’s Last Journey: Tuva or Bust! (W.W. Norton, 1991). Before I tapped into Leighton’s Friends of Tuva website, I had gone to an IEEE conference in Miami, Florida on signal processing and had run across Alan Oppenheim who taught DSP at MIT. At Tektronix, I took his videotape course and was impressed by his mastery of the subject and his ability to deliver highly-refined lectures. I met and talked with him at the conference. (Small world: his sister and my brother Kenneth were working together in heart surgery in Portland, Oregon over that summer while Ken was in medical school.) Oppenheim had developed an extension of linear filtering he called homomorphic filtering. In one of his videotape lectures he explained it and then played an aria of Enrico Caruso from an old 78 rpm vinyl record that had been filtered. It was memorable; Caruso’s tenor voice was filtered out from the background orchestra and it was as though he were singing a capela, with no hint of an orchestra behind him or of scratches on the record. Years later, Ralph began to offer through his Friends of Tuva website audiotape copies of his better recordings. I bought a copy of each of them and was keen to get others of lesser quality. I wrote to Ralph, with homomorphic filtering impressed on my memory, and suggested that he talk with Oppenheim about the tapes. In February 1995 he wrote back on a postcard: “Al Oppenheim has sent me some sound-reduced tapes that are promising. He’s definitely the guy with the know-how. Thanks for the lead!” Some complications arose for Ralph’s purposes and he later wrote a note saying: “MIT’s solution (algorithm) was not well suited for the job, but “Sonic Solution’s No-Noise” did the trick. Thanks for the impetus to get it done!” Oppenheim had referred him to a sound lab in Utah that accomplished the task. The “tapes” are available in digital format and can be downloaded for a very modest price (some free) from Welcome to Feynman Online! Feynman’s safecracker story - one of his best, about how he picked the lock on a safe that contained all of the detailed secrets of the atomic bomb - has also been put in cartoon form as a “Two-Fisted Science” booklet from Gemstone Publishing, P.O. Box 469, West Plains, MO 65775; tel.: 417-256-2224; Two-Fisted_Science@umich.edu I end with a final story about Feynman from another of his students. An acquaintance of mine, Don Page, a physicist at the U. of Alberta at the time of telling of this story, was reminded that during his physics PhD candidacy exam, after failing to give a good explanation of quantum emission from black holes shortly after Stephen Hawking’s prediction of it (when he had been working on the problem himself before Hawking and so in principle, he wrote, could have made the prediction himself “if only I had been much more competent”) was humiliated by being told by Feynman: “Quantum mechanics was invented in 1926. Now it is 1972. You should learn quantum mechanics.” But, he wrote, my embarrassment was mollified somewhat when other members of the committee said, “Dick, Dick, it’s 1973.” Dennis Feucht has his own laboratory, Innovatia, on a jungle hilltop in Belize, where he performs electronics research, technical writing, and helps others with product development. He wrote a four-volume book-set on analog circuit design, has completed a book on transistor amplifier design and is working on a book on power electronics.