TPA6120耳放电路

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学着自己做耳机放大器

简单的耳机放大器，你也可以做得到
第一个简单耳机放大器：LM386耳放——便宜、好用、低音强劲
用两个LM386搭成一个便携耳放。

LM386音质一般，但对电源要求低，一个9伏的电池即可推得服服帖帖。

如果布局合理的话，成品比半个香烟盒都要小，非常适合随身携带。

电路图参考下面，经个人焊接测试，电路图完美出生，只是当音量调到最大的时候可以听到些许低噪，这个是不足的地方。

而LM386有低音加强的效果，低音控可以考虑尝试一下。

第二个电路耳放：参考拜亚动力E1的高档耳机放大器，效果不用说，一顶一！
这个电路仅献给DIY高手，因为单靠万用板是不可能完成的，想要完美出声，必须得要用双层板制作，且要有合理的布局。

带DAC的TPA6120耳放DIY全过程，兼套件焊接装配教程，标题

带DAC的TPA6120耳放DIY全过程，兼套件焊接装配教
程，标题
======DAC版此处开始参考DAC小板的装配======
PCM2706 DAC小板照图施工，跳线跳JP2和JP3，不然手机可能会提示设备耗电过大
小板和排针，排针装MICRO USB口旁两个、C2旁一个、和输出座即可
配合后面板确定高度，确认插座入槽、按键无卡顿即可
======DAC部分装配完成======
电源开关塞入后面板，焊上线
线接回主板两个点
然后就可以装壳了，先把前面板装好，然后电位器那一侧先进入，调整好位置，调整好LED突起的长度
再装配后面板，因为LED有点亮，再加上机械公差，面板上已贴好海绵胶，遮光的同时塞满空间，最后压上旋钮即可
到此完成装配，恭喜！
这一版螺丝和旋钮改进！旋钮只有一个黑色的了
此耳放因为供电电压较高，正常使用外壳会微温，夏天比较明显，属正常现象
如有任何异常，5A一次性保险会挂掉，完全切断电池，确保安全
鉴于不是所有人都能焊接QFN，电源管理和电源变换部分也不好调试
提供的套件会焊好所有贴片元件并调试好电源管理和电源变换部分
这一次搞了30个外壳，没办法，10个20个外壳实在没有人做，都是50个起，不然就漫天要价
这一批除了两台DAC成品外，还备了9套的元件，其中6套是DAC版本的
需要的朋友，可以点我头像看我随后发布的交易贴，也可以从我以前的交易贴中找到我旺旺详询
外壳工厂正在加工中，仍然采用沙蓝色氧化，不过外壳估计还得等个把星期这样子
技术贴尽量不提到淘宝链接什么的，但是大家都想知道价格
详细的情况请关注交易贴
谢谢捧场！。

AB类耳机放大器的设计与制作

AB类耳机放大器的设计与制作-—---Class AB Amplifier [收藏]
上传者：dolphin 浏览次数:49
Class－AB 耳机放大器的设计与制作
本文所介绍的低失真耳机放大器是常用op＋扩流的改进型.
信号经R1，2/C1低通滤波后送入运放，右声道输出由IC 和晶体管Q1,2,3，4组成。

该放大器的静态电流由Q1,4/R9,10决定，输出级是静态8ma的互补推挽放大器，通过R3，4、R5,6取得负反馈。

正弦波不失真输出测试如下：
纯阻负载输出电压输出功率RMS 32ou5.5v 950mw
150ou8.8v520mw
330ou9。

8v 300mw
680ou 10v150mw
电源采用正负双电源供电，线路见图：
简单的三端稳压并联输出,并用LM431来抬高原7815的固定电压。

由于采用OCL结构的放大,为保护耳机的安全，设计了开机延时并有零点电压偏移的保护线路，如图：
用场效应管的高导通电压特性，就很容易设计RC延时线路，实际制作延时时间为1S. 实际测试也很满意：。

【图】耳机放大器保护电路原理图保护电路电路图维库电子市场网

【图】耳机放大器保护电路原理图保护电路电路图维库电子市
场网
原理图：
耳机放大器保护电路原理图
基本功能：
1.开机延时接通耳机，按照我做的板子，在开机后大约延时3-5秒接通耳机，保护耳机不受开机电流冲击。

2.关机断电，由于电源部分的滤波电容选的比较小，关机后，几乎是同时断开耳机与放大器的连接，保护耳机不受关机的电流冲击。

3.输出直流电压异常保护，经过简单实验，当放大器输出端出现+1.5V的输出电压的时候，可以在1秒内断开连接，而放大器出现负电压输出的时候，则保护动作电压比较高。

工作原理：
原理比较简单，不再叙述了，从线路上分析，DW可以用电阻代替，这里用稳压管的作用就是可以使用比较小的延时电容而获得比较长的延时接通时间，而且在放大电路出现直流输出的时候切断动作也更加干脆，实验的结果确实也是如此。

三端稳压器的输入电容，是根据负载而定的，如果采用的是直流电阻很小的大功率继电器，因该用470UF以上的电容，由于本继电器的电阻比较大，实测为：1K左右，就是说本电路的消耗电流应该在20MA以下，实验中采用47UF的电容可以正常工作，电路中用100UF的电容是可行的，如果此电容过大，会使关机时不能即使切断负载与放大器的连接，对耳机造成冲击。

由于本电路的工作电流很小要是把三端稳压电路换成78M15或者78L15都是可以的。

整整3个小时的时间，终于把耳放的保护电路焊好了，由于元件不凑手，参数与上面的原理图有出入，可喜的是焊接成功，注意输入输出接线端子之间的小黑色长方体就是那个小日本的微型继电器，用来保护耳机是最合适的了，当然，你也可以采用大型的继电器，把她用做喇叭保护，PCB板子上已经按照双继电器的安装形式制作。

SURROUND 算法

-Headset configuration device -FM support -Pop Noise Reduction -Increased Crosstalk performance
馬達產品的新應用 New Feature of Motor
1. Haptics 2. SIM card ejects 3. Camera angle adjustment
先讓我們做個總結
Feature
SmartAMP
HIFI audio HP driver
Hero Parts
TAS2552 TAS2553
PCM5x42 TPA6120 TPA6166
Description
Opulam algorithm + TAS2552/3 is better performance and suit pricing solution for current SP/Tablet audio amplifier.
TPA6166 - Audio Headset Switching and Detection Turnkey Solutions
The American/Apple and China/Nokia headsets have different band configuration GND and Microphone bands are switched in place
HiFi audio is our best solution for end customers. TPA6166 is Class-G Headphone AMP with integrated Headset detection and Passive multi-button support , very great solution. Headset Detection and auto Switching Real world feedback for SP/tablet. Camera control support. SIM card eject Independent 1.5A LED Driver for color compensation architectures Optical Image Stabilization Standalone Switch-Mode Battery Charger with Power-Path Management and OTG The 5Gbps speed of USB3.0 is driving the need for redrivers to open up eye mask and pass compliance for >1M cables 1:2 MHL/USB switch supporting 1080p/60fps 1:3 MHL/USB switch supporting 1080p/60fps Inter Chip-USB Voltage Level Translator

一款分立元件经典传统线路耳放的制作电路）

一款分立元件经典传统线路耳放的制作电路【图文】[日期：2012-03-05] 来源：土炮网作者：佚名[字体：大中小]全分离甲类耳放应该说是耳放DIY的最高境界，分立元件不同于集成电路，需要前期精密的设计和元件配对，后期复杂的调试，不少朋友对于这种放大器都有点头疼。

其实电路设计本身并不难，难的是如何把电路做成一台高品质的耳机放大器。

国内的电子书籍讲理论是头头是道，实践绝对是垃圾到家，这里推荐大家看一下科学出版社出版的《晶体管电路设计》非常实用。

辽宁大学耳机爱好者联盟在一年之前推出了一款便携式耳放作为试水之作，反响还不错，运放搭配合适很容易出好声。

今年在多方帮助下我们设计并制作了我们辽宁大学耳机爱好者联盟第一款全分立元件甲类耳机放大器，和大家交流一下，希望通过本文能激发大家DIY此类耳放的兴趣，同时能更好的识别市面常见耳放的线路，对症下药的进行磨改。

目前市面上使用分立元件的耳放其实不少，但多数都不是全分立元件的，这倒不是成本的原因，采用运放输入，能有效简化线路，利于批量化生产。

全分立元件的优势和缺陷同样明显，和使用运放输入的相比，不容易出好声，不过如果调教得宜那么效果也不是使用运放比得了的。

运放的优势是晶体管配对性非常好，体积小，测试数值较高，不过由于在一个小硅片上做出全部电路，因此存在耐压低，元器件数值有限制，电路不能随意调节等问题。

耳机放大器可以简单地分解成输入级电压放大级和输出级三部分。

输入级是整机的咽喉，对于整机性能有重要影响，不少耳放都采用运放担任输入放大以简化线路。

分立元件耳放一般是采用差分输入其中包括单差分和全对称双差分两种，具体根据使用元件不同又可以分为BJT和F ET两种。

欧洲机器使用单差分比较多，日本机器则喜欢全对称双差分。

这两种线路本身没有高低之分，使用得当都能做出高品质机器。

从DIY的角度讲，我更倾向单差分，因为双差分线路需要异极性配对，成本高一些。

为了提高整机性能，一般输入级都使用了恒流源和共基共射（沃尔曼）线路，一个比较典型的线路如下高文线路这里借用别人一张图，对图片原作者表示感谢。

[电子电路]6P9P制作的耳放电路

6P9P制作的耳放电路感谢到访我的主页：/hechaoscut(文档西游)本文档格式为WORD,若不是word文档,则说明不是原文档。

若图片过大，下载后拉小即可。

在音响家族的系统终端，是电能—声能的转换，音箱和耳机都起到这样的作用。

与音箱相比，耳机有很多局限，比如低音虽然丰厚，但只在耳膜边鼓噪，没有音箱带来的切身震撼感。

此外还有声场，似乎老在前额和脑颅内转，久听容易疲劳。

但耳机也有其先天的优势，耳机基本都是一片轻巧的震膜涵盖全频，没有大部分音箱由多单元组成所带来的分频问题。

频响曲线比较平直，而且有着极佳的瞬态，能轻而易举地捕捉到音乐中的细节。

还有相对低廉的价格，音箱要做到等同的音色和瞬态，价格不知道要上翻多少倍。

此外，虽然只能单人独享，但却可以在大音量下听音乐而不影响他人。

所以买不起天价的音箱，又对音质苛求的，或者家居环境局限没有良好听音环境，耳机发烧实在是一个捷径。

此外，要锻炼自己对声音的鉴别能力，形成自己的听音标准，拥有一套高质量的耳机无疑很有帮助。

一．初识森海塞尔笔者喜欢聆听耳机，特别是高质量的监听耳机。

而在众多品牌当中，对森海塞尔的监听耳机特别情有独钟。

早在1945年森海塞尔(sennheiser)这个德国的公司就成功设计出性能极佳的话筒和耳机，并深受业界好评。

无论从音质、质量、舒适度以及工艺等方面，森海塞尔都有独到之处，其生产的奥费斯(OrpheHS)耳机系统几乎就是世界最佳耳机的参考标准。

笔者是在20世纪90年代初通过音响类的报刊杂志认识这个品牌，了解了当时动圈耳机的“盟主”HD580，在一本地发烧友的家中实听过HD580之后，深深震撼于那细小的方寸之后的庞大场面。

那丝般细滑的高音，空灵飘渺犹如仙境飘来；低频的霸气让人无法想象这阵阵的“气浪”是如何从这小小的耳机里涌出的。

而最让人难以忘怀的是那声音的真实，仿佛在零距离聆听歌者的演唱、乐者的弹奏。

对于当时没有真正接触过什么高档器材、在家里以一堆土炮自乐的笔者来说，这等声音就如同仙乐，简直不是来自人间。

47耳放制作HIFI耳机放大器-PCB-电路图-及全套设计资料(吐血推荐)

对于47耳放的完美改进制作高保真耳机放大器之前一直折腾功放听桌面音箱，半年前忽然打算用用耳机了，于是入了森海的HD595。

虽然50欧的阻抗不算高，但是要发挥出设备的实力耳放还是少不了的。

所以，决定自己动手做一个耳放。

这期间参考了大量关于耳放的资料，最终决定以47耳放电路为基础并加以改进制作一个比较完美的耳机放大器。

便动手做了起来。

一、放大部分47耳放是一位外国人设计的电路，电路如图。

因为电路中有较多以47为参数的元件所以称作47耳放。

传说中的47耳放结构其实是很简单的，第一级运放进行负反馈控制放大倍数进行比例放大，第二个运放进行电压跟随，降低放大器内阻，增加了输出电流，并做声音修饰。

两个运放输出经过两个47欧匀流电阻输出致耳机。

因为反馈取样点在47电阻之后，所以不用考虑电阻带来的损耗。

曾经在网上看过很多47耳放的PCB设计，虽然47耳放的电路十分简单，但是很多PCB却存在着或多或少的布线问题，有些抗干扰能力不是很强，甚至在淘宝上看到很多看似很漂亮的板子却有很大的交流声。

所以自己决定做一个比较完美的47耳放以便把这个电路的能力发挥出来。

于是，开工了。

首先线路图电路没有添加音量电位器，只做了放大部分。

这样一来功能比较独立，方便以后的各种组合。

47原设计使用的运放是OPA2132，这个运放是FET输入型的，所以内阻极高。

而且在低电压下可以正常工作，失调电压与失调电流极小，算是比较高档的运放了。

当然OPA2132的价格也是很高档的。

我作为0收入人士必然不能把这种高档传承下去，于是我选用了这年头满大街都是的NE5532。

NE5532虽然指标相对于OPA2132较差，但是工作于+-15V时音色总体来说还是比较讨人喜欢的。

单片5532耗电相对较大，两片并联就更不用说了，双15V下耗电可想而知。

这就意味着这款耳放将要脱离便携式耳放的范畴转型向台式耳放了。

由于5532失调电压较高而且又是NPN管输入的，如果使用原设计必然会引来较大的输出中点漂移，经过测试最大有30多MV。

高性能耳机放大器 tpa6120a2

FEATURES DESCRIPTIONAPPLICATIONSFilter and I/V Gain StageStereo Hi−FiTPA6120A2SLOS431–MARCH2004HIGH FIDELITY HEADPHONE AMPLIFIER•80mW into600ΩFrom a±12-V Supply at The TPA6120A2is a high fidelity audio amplifier built0.00014%THD+N on a current-feedback architecture.This highbandwidth,extremely low noise device is ideal for •Current-Feedback Architecturehigh performance equipment.The better than120dB •Greater than120dB of Dynamic Rangeof dynamic range exceeds the capabilities of the •SNR of120dB human ear,ensuring that nothing audible is lost dueto the amplifier.The solid design and performance of •Output Voltage Noise of5µVrms atthe TPA6120A2ensures that music,not the amplifier, Gain=2V/Vis heard.•Power Supply Range:±5V to±15VThree key features make current-feedback amplifiers •1300V/µs Slew Rateoutstanding for audio.The first feature is the high •Differential Inputs slew rate that prevents odd order distortion•Independent Power Supplies for Low anomalies.The second feature is current-on-demand Crosstalk at the output that enables the amplifier to respondquickly and linearly when necessary without risk of •Short Circuit and Thermal Protectionoutput distortion.When large amounts of outputpower are suddenly needed,the amplifier can re-spond extremely quickly without raising the noise •Professional Audio Equipment floor of the system and degrading the signal-to-noise •Mixing Boards ratio.The third feature is the gain-independent fre-quency response that allows the full bandwidth of the •Headphone Distribution Amplifiersamplifier to be used over a wide range of gain •Headphone Driverssettings.The excess loop gain does not deteriorate at •Microphone Preamplifiers a rate of20dB/decade.Please be aware that an important notice concerning availability,standard warranty,and use in critical applications of TexasInstruments semiconductor products and disclaimers thereto appears at the end of this data sheet.PowerPAD is a trademark of Texas Instruments. ABSOLUTE MAXIMUM RATINGSDISSIPATION RATING TABLEAVAILABLE OPTIONSRECOMMENDED OPERATING CONDITIONSTPA6120A2SLOS431–MARCH2004These devices have limited built-in ESD protection.The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage.over operating free-air temperature range(unless otherwise noted)(1)(1)Stresses beyond those listed under“absolute maximum ratings”may cause permanent damageto the device.These are stress ratings only,and functional operation of the device at these or any other conditions beyond those indicated under“recommended operating conditions”is not implied.Exposure to absolute–maximum–rated conditions for extended periods may affect device reliability.(2)When the TPA6120A2is powered down,the input source voltage must be kept below600-mV peak.(3)The TPA6120A2incorporates an exposed PowerPAD on the underside of the chip.This acts as a heatsink and must be connected to athermally dissipating plane for proper powerdissipation.Failure to do so may result in exceeding the maximum junction temperature that could permanently damage the device.See TI Technical Brief SLMA002for more information about utilizing the PowerPAD thermally enhanced package.(1)The PowerPAD must be soldered to a thermal land on the printed-circuit board.See the PowerPADThermally Enhanced Package application note(SLMA002)(1)The DWP package is available taped and reeled.To order a taped and reeled part,add the suffix Rto the part number(e.g.,TPA6120A2DWPR).ELECTRICAL CHARACTERISTICSTPA6120A2 SLOS431–MARCH2004over operating free-air temperature range(unless otherwise noted)OPERATING CHARACTERISTICS (1)TPA6120A2SLOS431–MARCH 2004T A =25°C,R L =25Ω,Gain =2V/V (unless otherwise noted)(1)For IMD,THD+N,k SVR ,and crosstalk,the bandwidth of the measurement instruments was set to 80kHz.DEVICE INFORMATIONLOUT LVCC+ LIN+NCNCNCNCNC RVCC−ROUT RVCC+ RIN+ RIN−NCNCNCNCNCNC − No internal connectionTPA6120A2 SLOS431–MARCH2004Thermally Enhansed SOIC(DWP) PowerPAD™PackageTop View TERMINAL FUNCTIONSTYPICAL CHARACTERISTICSTable of Graphs101001 k10 k50 kT H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %f − Frequency − Hz101001 k10 k50 kT H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %f − Frequency − HzTPA6120A2SLOS431–MARCH 2004TOTAL HARMONIC DISTORTION +NOISETOTAL HARMONIC DISTORTION +NOISEvsvsFREQUENCYFREQUENCYFigure 1.Figure 2.0.00010.010.1T H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %f − Frequency − Hz0.001T H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %f − Frequency − Hz101001 k10 k 50 kT H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %V O − Output Voltage − V PPT H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %P O − Output Power − W0.000010.011100.00010.0010.1TPA6120A2SLOS431–MARCH 2004TYPICAL CHARACTERISTICS (continued)TOTAL HARMONIC DISTORTION +NOISETOTAL HARMONIC DISTORTION +NOISEvsvsFREQUENCYFREQUENCYFigure 3.Figure 4.TOTAL HARMONIC DISTORTION +NOISETOTAL HARMONIC DISTORTION +NOISEvsvsOUTPUT VOLTAGEOUTPUT POWERFigure 5.Figure 6.T H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %0.011100.00010.0010.1P O − Output Power − WT H D +N −T o t a l H a r m o n i c D i s t o r t i o n + N o i s e − %0.011100.00010.0010.1P O − Output Power − W−90−80−70−60−50−40−30−200101001 k10 k 50 kk S V R − S u p p l y V ol t a g e R e j e c t i o n R a t i o − d Bf − Frequency − Hz−10− P o w e r D i s s i p a t i o n − WP D P O − Output Power − WTPA6120A2SLOS431–MARCH 2004TYPICAL CHARACTERISTICS (continued)TOTAL HARMONIC DISTORTION +NOISETOTAL HARMONIC DISTORTION +NOISEvsvsOUTPUT POWEROUTPUT POWERFigure 7.Figure 8.POWER DISSIPATIONSUPPLY VOLTAGE REJECTION RATIOvsvsOUTPUT POWERFREQUENCYFigure 9.Figure 10.0.0010.12 k10 k50 kI n t e r m o d u l a t i o n D i s t o r t i o n − %f − High Frequency − Hz−90−80−70−60−50−40−30−20−0101001 k10 k50 kk S V R − S u p p l y V o l t a g e R e j e c t i o n R a t i o − d Bf − Frequency − Hz−10−1C r o s s t a l k − d Bf − Frequency − HzIM Amplitude (At Input) − V PP0.000010.011100.00010.0010.1I n t e r m o d u l a t i o n D i s t o r t i o n − %TPA6120A2SLOS431–MARCH 2004TYPICAL CHARACTERISTICS (continued)SUPPLY VOLTAGE REJECTION RATIOINTERMODULATION DISTORTIONvsvsFREQUENCYHIGH FREQUENCYFigure 11.Figure 12.INTERMODULATION DISTORTIONCROSSTALKvsvsIM AMPLITUDE (AT INPUT)FREQUENCYFigure 13.Figure 14.S i g n a l −T o −N o i s e R a t i o − d BGain − V/V S i g n a l −T o −N o i s e R a t i o − dBGain − V/VOutput Step (Peak−To−Peak) − V1500100209005110070010130050030015S l e w R a t e − V /sµOutput Step (Peak−To−Peak) − V10001005700180060023900S l e w R a t e − V /sµ5003004400200TPA6120A2SLOS431–MARCH 2004TYPICAL CHARACTERISTICS (continued)SIGNAL-TO-NOISE RATIOSIGNAL-TO-NOISE RATIOvs vs GAINGAINFigure 15.Figure 16.SLEW RATESLEW RATEvsvsOUTPUT STEPOUTPUT STEPFigure 17.Figure 18.10M 100k500M1M100M 10k1k10010f − Frequency − Hz−18−15O u t p u t L e v e l − d B V−12−3−9−6−24−2110M 100k500M1M100M 10k1k10010f − Frequency − Hz−12−9O u t p u t L e v e l − d B V−63−30−18−15t − Time − ns100−1000−200V O − O u t p u t V o l t a g e − m V300200400−300−400t − Time − nsV O − O u t p u t V o l t a g e − V15010050200250350300400450500SMALL AND LARGE SIGNAL SMALL AND LARGE SIGNAL FREQUENCY RESPONSEFREQUENCY RESPONSEFigure 19.Figure 20.400-mV STEP RESPONSE10-V STEP RESPONSEFigure 21.Figure 22.t − Time − ns4−40−8V O − O u t p u t V o l t a g e − V12816−12−1620-V STEP RESPONSEFigure 23.APPLICATION INFORMATIONCurrent-Feedback AmplifiersIndependent Power SuppliesPower Supply DecouplingResistor ValuesR LV IThe TPA6120A2is a current-feedback amplifier with differential inputs and single-ended outputs.Current-feedback results in low voltage noise,high open-loop gain throughout a large frequency range,and low distortion.It can be used in a similar fashion as voltage-feedback amplifiers.The low distortion of the TPA6120A2results in a signal-to-noise ratio of 120dB as well as a dynamic range of 120dB.The TPA6120A2consists of two independent high-fidelity amplifiers.Each amplifier has its own voltage supply.This allows the user to leave one of the amplifiers off,saving power,and reducing the heat generated.It also reduces crosstalk.Although the power supplies are independent,there are some limitations.When both amplifiers are used,the same voltage must be applied to each amplifier.For example,if the left channel amplifier is connected to a ±12-V supply,the right channel amplifier must also be connected to a ±12-V supply.If it is connected to a different supply voltage,the device may not operate properly and consistently.When the use of only one amplifier is preferred,it must be the left amplifier.The voltage supply to the left amplifier is also responsible for internal start-up and bias circuitry of the device.Regardless of whether one or both amplifiers are used,the V CC-pins of both amplifiers must always be at the same potential.To power down the right channel amplifier,disconnect the V CC+pin from the power source.The two independent power supplies can be tied together on the board to receive their power from the same source.As with any design,proper power supply decoupling is essential.It prevents noise from entering the device via the power traces and provides the extra power the device can sometimes require in a rapid fashion.This prevents the device from being momentarily current starved.Both of these functions serve to reduce distortion,leaving a clean,uninterrupted signal at the output.Bulk decoupling capacitors should be used where the main power is brought to the board.Smaller capacitors should be placed as close as possible to the actual power pins of the device.Because the TPA6120A2has four power pins,use four surface mount capacitors.Both types of capacitors should be low ESR.Figure 24.Single-Ended Input With a Noninverting Gain of 2V/VIn the most basic configuration (see Figure 24),four resistors must be considered,not including the load impedance.The feedback and input resistors,R F and R I ,respectively,determine the closed-loop gain of the amplifier.R O is a series output resistor designed to protect the amplifier from any capacitance on the output path,including board and load capacitance.R S is a series input resistor.Because the TPA6120A2is a current-feedback amplifier,take care when choosing the feedback resistor.R LV IR LV V I+The value of the feedback resistor should be chosen by using Figure 27through Figure 32as guidelines.The gain can then be set by adjusting the input resistor.The smaller the feedback resistor,the less noise is introduced into the system.However,smaller values move the dominant pole to higher and higher frequencies,making the device more susceptible to oscillations.Higher feedback resistor values add more noise to the system,but pull the dominant pole down to lower frequencies,making the device more stable.Higher impedance loads tend to make the device more unstable.One way to combat this problem is to increase the value of the feedback resistor.It is not recommended that the feedback resistor exceed a value of 10k Ω.The typical value for the feedback resistor for the TPA6120A2is 1k Ω.In some cases,where a high-impedance load is used along with a relatively large gain and a capacitive load,it may be necessary to increase the value of the feedback resistor from 1k Ωto 2k Ω,thus adding more stability to the system.Another method to deal with oscillations is to increase the size of R O .CAUTION:Do not place a capacitor in the feedback path.Doing so can cause oscillations.Capacitance at the outputs can cause oscillations.Capacitance from some sources,such as layout,can be minimized.Other sources,such as those from the load (e.g.,the inherent capacitance in a pair of headphones),cannot be easily minimized.In this case,adjustments to R O and/or R F may be necessary.The series output resistor should be kept at a minimum of 10Ω.It is small enough so that the effect on the load is minimal,but large enough to provide the protection necessary such that the output of the amplifier sees little capacitance.The value can be increased to provide further isolation,up to 100Ω.The series resistor,R S ,should be used for two reasons:1.It prevents the positive input pin from being exposed to capacitance from the line and source.2.It prevents the source from seeing the input capacitance of the TPA6120A2.The 50-Ωresistor was chosen because it provides ample protection without interfering in any noticeable way with the signal.Not shown is another 50-Ωresistor that can be placed on the source side of R S to ground.In that capacity,it serves as an impedance match to any 50-Ωsource.Figure 25.Single-Ended Input With a Noninverting Gain of -1V/VFigure 26.Differential Input With a Noninverting Gain of 2V/VFigure 26shows the TPA6120A2connected with differential inputs.Differential inputs are useful because they take the greatest advantage of the device's high CMRR.The two feedback resistor values must be kept the same,as do the input resistor values.Checking for Oscillations and Instabilityf − Frequency − Hzf − Frequency − HzSpecial note regarding mono operation:•If both amplifiers are powered on,but only one channel is to be used,the unused amplifier MUST have afeedback resistor from the output to the negative input.Additionally,the positive input should be grounded as close to the pin as possible.Terminate the output as close to the output pin as possible with a 25-Ωload to ground.•These measures should be followed to prevent the unused amplifier from oscillating.If it oscillates,and thepower pins of both amplifiers are tied together,the performance of the amplifier could be seriously degraded.Checking the stability of the amplifier setup is recommended.High frequency oscillations in the megahertz region can cause undesirable effects in the audio band.Sometimes,the oscillations can be quite clear.An unexpectedly large draw from the power supply may be an indication of oscillations.These oscillations can be seen with an oscilloscope.However,if the oscillations are not obvious,or there is a chance that the system is stable but close to the edge,placing a scope probe with 10pF of capacitance can make the oscillations worse,or actually cause them to start.A network analyzer can be used to determine the inherent stability of a system.An output vs frequency curve generated by a network analyzer can be a good indicator of stability.At high frequencies,the curve shows whether a system is oscillating,close to oscillation,or stable.Looking at Figure 27through Figure 32,several different phenomena occur.In one scenario,the system is stable because the high frequency rolloff is smooth and has no peaking.Increasing R F decreases the frequency at which this rolloff occurs (see the Resistor Values section).Another scenario shows some peaking at high frequency.If the peaking is 2dB,the amplifier is stable as there is still 45degrees of phase margin.As the peaking increases,the phase margin shrinks,the amplifier and the system,move closer to instability.The same system that has a 2-dB peak has an increased peak when a capacitor is added to the output.This indicates the system is either on the verge of oscillation or is oscillating,and corrective action is required.Figure 27.Normalized Output Response vs Frequency Figure 28.Normalized Output Response vs Frequencyf − Frequency − Hz N o r m a l i z e d O u t p u t R e s p o n s e − d B110M 100k500M1M 100M 10k1k10010f − Frequency − HzN o r m a l i z e d O u t p u t R e s p o n s e − d B110M 100k 500M 1M 100M 10k 1k10010f − Frequency − HzO u t p u t A m p l i t u d e − d B031210M 100k 500M 1M 100M 10k 1k10010f − Frequency − HzO u t p u t A m p l i t u d e − d BPCB LayoutFigure 29.Normalized Output Response vs FrequencyFigure 30.Normalized Output Response vs FrequencyFigure 31.Output Amplitude vs Frequency Figure 32.Output Amplitude vs FrequencyProper board layout is crucial to getting the maximum performance out of the TPA6120A2.A ground plane should be used on the board to provide a low inductive ground connection.Having a ground plane underneath traces adds capacitance,so care must be taken when laying out the ground plane on the underside of the board (assuming a 2-layer board).The ground plane is necessary on the bottom for thermal reasons.However,certain areas of the ground plane should be left unfilled.The area underneath the device where the PowerPAD is soldered down should remain,but there should be no ground plane underneath any of the input and output pins.This places capacitance directly on those pins and leads to oscillation problems.The underside ground plane should remain unfilled until it crosses the device side of the input resistors and the output series resistor.Thermal reliefs should be avoided if possible because of the inductance they introduce.R OR LVR L Thermal ConsiderationsEfficiency of an amplifier+P LP SUP(1)P L+V LRMS2R L,and V LRMS+V P2Ǹ,therefore,P L+V P22R Lper channel(2)P SUP+V CC I CC avg)V CC I CC(q)(3)I CC avg+1pŕp 20V PR Lsin(t)dt+*V Pp RL[cos(t)]p2+V Pp RL(4)Despite the removal of the ground plane in critical areas,stray capacitance can still make its way onto the sensitive outputs and inputs.Place components as close as possible to the pins and reduce trace lengths.See Figure33and Figure34.It is important for the feedback resistor to be extremely close to the pins,as well as the series output resistor.The input resistor should also be placed close to the pin.If the amplifier is to be driven in a noninverting configuration,ground the input close to the device so the current has a short,straight path to the PowerPAD(gnd).yout That Can Cause Oscillationyout Designed To Reduce Capacitance On Critical NodesAmplifiers can generate quite a bit of heat.Linear amplifiers,as opposed to Class-D amplifiers,are extremely inefficient,and heat dissipation can be a problem.There is no one to one relationship between output power and heat dissipation,so the following equations must be used:WhereWhereV P +2P L R LǸ(5)P SUP +V CC VP p R L)V CC I CC(q)(6)P DISS +(1*h )P SUP(7)T A Max +T J Max *ΘJA P Diss(8)− P o w e r D i s s i p a t i o n − WP DP O − Output Power − WTherefore,P L =Power delivered to load (per channel)P SUP =Power drawn from power supply V LRMS =RMS voltage on the load R L =Load resistanceV P =Peak voltage on the loadI CC avg =Average current drawn from the power supply I CC (q)=Quiescent current (per channel)V CC =Power supply voltage (total supply voltage =30V if running on a ±15-V power supply η=Efficiency of a SE amplifierFor stereo operation,the efficiency does not change because both P L and P SUP are doubled.This effects the amount of power dissipated by the package in the form of heat.A simple formula for calculating the power dissipated,P DISS ,is shown in Equation 7:In stereo operation,P SUP is twice the quantity that is present in mono operation.The maximum ambient temperature,T A ,depends on the heat-sinking ability of the system.θJA for a 20-pin DWP,whose thermal pad is properly soldered down,is shown in the dissipation rating table.Figure 35.Power Dissipation vs Output PowerApplication Circuit10 µF5 V µF−5 V OPA413412 V µFTPA6120A2Figure 36.Typical Application CircuitIn many applications,the audio source is digital.It must go through a digital-to-analog converter (DAC)so that traditional analog amplifiers can drive the speakers or headphones.Figure 36shows a complete circuit schematic for such a system.The digital audio is fed into a high performance DAC.The PCM1792,a Burr-Brown product from TI,is a 24-bit,stereo DAC.The output of the PCM1792is current,not voltage,so the OPA4134is used to convert the current input to a voltage output.The OPA4134,a Burr-Brown product from TI,is a low-noise,high-speed,high-performance operational amplifier.C F and R F are used to set the cutoff frequency of the filter.The RC combination in Figure 36has a cutoff frequency of 59kHz.All four amplifiers of the OPA4134are used so the TPA6120A2can be driven differentially.The output of the OPA4134goes into the TPA6120A2.The TPA6120A2is configured for use with differential inputs,stereo use,and a gain of2V/V.Note that the0.1-uF capacitors are placed at every supply pin of the TPA6120A2,as well as the10-Ωseries output resistor.Each output goes to one channel of a pair of stereo headphones,where the listener enjoys crisp,clean,virtually noise free music with a dynamic range greater than the human ear is capable of detecting.PACKAGING INFORMATION Orderable DeviceStatus (1)Package Type Package Drawing Pins Package Qty Eco Plan (2)Lead/Ball Finish MSL Peak Temp (3)TPA6120A2DWP ACTIVE SOPowerPADDWP 2025Green (RoHS &no Sb/Br)CU NIPDAU Level-2-260C-1YEAR TPA6120A2DWPG4ACTIVE SOPowerPADDWP 2025Green (RoHS &no Sb/Br)CU NIPDAU Level-2-260C-1YEAR TPA6120A2DWPR ACTIVE SOPowerPADDWP 202000Green (RoHS &no Sb/Br)CU NIPDAU Level-2-260C-1YEAR TPA6120A2DWPRG4ACTIVE SOPowerPAD DWP 202000Green (RoHS &no Sb/Br)CU NIPDAU Level-2-260C-1YEAR(1)The marketing status values are defined as follows:ACTIVE:Product device recommended for new designs.LIFEBUY:TI has announced that the device will be discontinued,and a lifetime-buy period is in effect.NRND:Not recommended for new designs.Device is in production to support existing customers,but TI does not recommend using this part in a new design.PREVIEW:Device has been announced but is not in production.Samples may or may not be available.OBSOLETE:TI has discontinued the production of the device.(2)Eco Plan -The planned eco-friendly classification:Pb-Free (RoHS),Pb-Free (RoHS Exempt),or Green (RoHS &no Sb/Br)-please check /productcontent for the latest availability information and additional product content details.TBD:The Pb-Free/Green conversion plan has not been defined.Pb-Free (RoHS):TI's terms "Lead-Free"or "Pb-Free"mean semiconductor products that are compatible with the current RoHS requirements for all 6substances,including the requirement that lead not exceed 0.1%by weight in homogeneous materials.Where designed to be soldered at high temperatures,TI Pb-Free products are suitable for use in specified lead-free processes.Pb-Free (RoHS Exempt):This component has a RoHS exemption for either 1)lead-based flip-chip solder bumps used between the die and package,or 2)lead-based die adhesive used between the die and leadframe.The component is otherwise considered Pb-Free (RoHS compatible)as defined above.Green (RoHS &no Sb/Br):TI defines "Green"to mean Pb-Free (RoHS compatible),and free of Bromine (Br)and Antimony (Sb)based flame retardants (Br or Sb do not exceed 0.1%by weight in homogeneous material)(3)MSL,Peak Temp.--The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications,and 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耳机放大器及电路原理2

■任保华图１１ＯＴＬ阴极输出胆耳放图１２ＯＴＬ电子管耳放电路图耳机放大器及其电路(下)图１１是笔者制作的分体ＯＴＬ阴极输出胆耳放的实物图，图１２是它的电路图。

这台耳放的输入级采用了两只并联的孪生三极管，我们不妨称它为双管并联ＳＲＰＰ输入级。

ＳＲＰＰ电路的特点是频响宽、声音华丽，采用双管并联后降低了输出阻抗，提高了灵敏度，不要小看这个改动，它会给你带来比常规单管ＳＲＰＰ输入级更加优良的性能呢！Ｃ２、Ｃ３是旁路电容。

旁路电容使交流信号电流不流经Ｖ１的阴极电阻Ｒ１，于是没有交流信号电流的负反馈，这使输入级瞬态得到提升、频率响应更加平坦。

耳放的功率输出级是典型的阴极跟随器（ｃａｔｈｏｄｅ图１４变压器输出胆耳放图１３变压器输出胆耳放电路图专题ｆｏｌｌｏｗｅｒ），或称阴极输出器。

阴极输出器过去曾经有过一段为声频爱好者狂热追求的历史，在那个时期各种杂志一片赞赏美誉之辞，声称如果把这种电路应用于声频放大器输出级，那么放大器就不会有非线性失真，频率特性会变得异常平坦，扬声器的阻尼问题也可得到很好的解决等等。

一时间阴极输出器似乎成了高保真设备的规范模式了。

日月荏苒，白驹过隙，随着时光的流逝这种电路却不知不觉地被人们淡忘了，在主流的胆机功放中已经很难找到它的身影。

那么阴极输出功率放大器是不是已经失去了昔日的风采了呢？当然不是。

我们知道，阴极输出器的基本特征是：１）高的动态输入阻抗；２）低的输出阻抗；３）通带电压放大系数小于１。

阴极输出器具有这些性能是因为它是一个电压负反馈放大器，所有电压负反馈放大器的优点，如噪声的抑低、频率响应性能的改善，非线性失真的抑低等等，它都具备。

阴极输出功率放大器的致命弱点是它的功率灵敏度太低，要求的输入电压幅度太大，对于前级来说，向后级供给很大的输入电压就可引起很大的非线性失真。

从总体上来讲会得不偿失，另一方面它的输出功率太小，效率很低；高阻抗的优质扬声器的匮乏也是影响阴极输出功率放大器发展的瓶颈。

别致、时尚的山灵迷你音响听山灵PCD300ACD机及PH300耳放前级

别致、时尚的山灵迷你音响听山灵PCD300ACD机及PH300耳放前级◎发烧在线别致时尚的山灵迷你立El响听山灵PCD300ACD机及PH300耳放前级可以听到琴手的运弓手法,可以听到演唱者咬字吐词时口形的变化,我听到的是充满临场感和活生感的声音.尽管音乐规模宏大,动态强劲,但声音不会咄咄逼人,反而因为有着十分恰当的平衡感,速度感和层次感而显得悦耳动听.文/吴志华曾经听过山灵合并式晶体管放大器的旗~.SHANLINGA500,它是面对有着良好经济和居住条件的发烧友而开发的,其雄峻壮美的气势和灵致准确的音色,给我留下了深刻的印象.但对于条件有限的广大音乐爱好者,山灵并没有忘记他们,特别为他们精心打造了造型别致,B,1-~俊逸,优美动听,性价比高的CD播放机PCD300A~n耳机兼前级放大器PH300别致可爱山灵CD播放机PCD300A~n耳机兼前级放大器PH300浑身散发着时尚俊逸的风格.它fl’]~J[J210mm的宽度,70mm的高度,335mm的深度,与一般的器材相比,它们给人以截然不同的清新感觉,其小巧玲珑的身材特别惹人喜爱,也易于在空间相对狭小的卧室中摆放.当然,这种造型的器材摆放在客厅作为主器材,也会给人别76J视析前鹾具一格的美.CD播放机PCD300A前面板左侧的电源指示灯和电源开关,与右侧的五向操作摇杆和耳机输出插座呈对称排布,时尚精致的风格之中又带着古典稳重的元素.对于玩惯MP3和手机五向操作摇杆的朋友,操作PCD300A简直就是一件得心应手,毫不困难的事情.耳机兼前级放大器PH300面板左侧的电源开关和右侧的信号选择开关,以及面板中间偏左的两个专业级的NEUTRIK耳机输出插座,尤其是面板中间偏右的铝质精致音量控制旋钮,更是使人感到从中流淌出来缕缕的古典情怀.通电之后指示灯和显示屏发出蓝幽幽的光,则宣示着一种淡淡的雅致格调.精心打造如果因为小巧的体积而小看这两个小精灵,那就错了.CD播放机PCD300A采用了PHlLIPS的转盘和CD71l伺服系统,具有信号读取准确,可靠耐用的特点:解码芯片是TIBurr—BrownPCM1738,具有24bit的精度和192kHz的取样频率,可以达到117dB的信噪比和00004%的超低失真率:采用了audiograde的电容和四片音频专用的高速单运放OPA604AP.耳机兼前级放大器PH300使用了带屏蔽罩的大型变压器,从一开始就狠下重本;耳机放大核心部分采用了两片最新的CFBTPA612O运耳机放大的核心部分使用了两片TPA6120 运放使用了ALPS电位器作为音量控制PcD300A和PH300使用了许多发烧级的元器件前级放大的核心部分,使用了两支可靠耐用的军用级电子管6N16B.放,组成了双单声道耳机放大电路,结构犹如时下许多高素质放大器般讲究:前级放大电路的核心更是使用了两支可靠耐用的军用级电子管6N16B,组成了着名的,为许多经典名机所使用的分流调节SRPP前级放大电路,具有失真低,动态大,倍率高,线性好的优良特性:而对音质起关键作用的音量调节电位器,则使用了精度达0.5dB的ALPS电位器:PCD300A和PH300的所有输出输入端子,都是大型镀金铜制的发烧制品.尽管使用优质元器件不是器材具有优美动听声音的最终决定条件,但已可以看出山灵打造这WWW.avfline.cornI77两个小精灵时的认真态度.细节毕现,悦耳动听既然CD播放机PCD300A~n耳机兼前级放大器PH300是一套用以推动耳机的小巧组合,那就得先听听它们推动耳机时的表现.将森海赛尔HD600耳机插入到PH300的耳机输出插座时,我听到的是充满生气和活力的声音,令人精神为之一振并兴奋不已.播放NAXOS出品的《SCHUBERT:PianoQuintet”Trout”, AdagioandRondoConcertante》(舒泊特的”鳟鱼”五重奏等,编号:8550658)时,小提琴的声音细致而富于歌唱性,弓弦相擦时,可以感觉到琴弦在琴弓马尾毛上无数毛细纤维相激而振动,不仅带出了娇艳的琴弦感和散发着松香味的琴弓感,而且也带出了温润的琴腔感.大提琴饱满深沉,带着丝丝忧郁不安的情感,预示着SCHUBERT一《》l琏黧镑§《l≤《《《》《{秘鳟鱼的不幸命运,而中提琴则很好地完成与小提琴和大提琴之间的衔接.雄厚而不乏弹性的钢琴声主体,与被适度修饰的声音线条边角一道,共同形成了声音纹理.作为耳机放大器,PH300充分详尽地展示出这个录音丰富逼真的声音细节.由FIM出品的《SuperSound!llI》(编号:FIMXR24073),则能全面地考验器材的表现,对CD播放机PCD300A~u耳机兼前级放大器PH300也毫不例外.播放《SingJoy》时,乐队每一件乐器和合唱队每一位演唱者,都有着清晰准确的定位,因而构成了宽阔而深远的声场.我可以听到琴手的运弓手法,可以听到演唱者咬字吐词时口形的变化,我听到的是充满临场感和活生感的声音.尽管音乐规模宏大,动态强劲,但声音不会咄咄逼人, 反而因为有着十分恰当的平衡感,速度感和层次感而显得悦耳动听. 素质不俗我再将PH300的前级输出接到马兰士PM8001的后级输入上,让马兰士PM8001充当后级放大器的角度,推动三角SOLIS260书架箱.事实证明,作为前级放大器,PH300~{PM8001控制得不错,从而使S0LlS260有着令人满意的表现.CD播放机PCD300A和耳机兼前级放大器PH300,是一对有着不俗素质的小精灵.囹深圳山灵数码科技发展有限公司:0755—26887637鸣谢山灵音响华南营销公司提供器材:020—83880821参考价格:PCD3OOA1800元PH3001800元PCD3OOA的技术规格失真率:<O.002%信噪比:115dB动态范围:11OdB频率响应:20Hz一20kHz耳机输出最大电压:1OOmV/600Q线路输出最大电压:2.OV体积(WHD):210×335×70iraPH300的技术规格信噪比:>90dB频率响应:20Hz一20kHz线路输入灵敏度:350mV/47kQ线路输出额定功率:900mV/47kD 耳机输出额定功率:2400mW/16Q,1200mW/32Q,640mW/64Q,130mW/300Q体积(WHD):210×335×70mm78l晰葡睦。

自己动手,4合一耳放实战DIY

一、耳放的作用。

耳放，是耳机放大器的简称，网上也俗称是耳机的二房。

目前很多高档耳机，都配有耳放，有些人也为中低档耳机、耳塞添加了耳放。

那么，耳放到底有什么作用，加不加耳放，能有多大区别呢？1，耳放作用之一，放大信号。

目前的很多音源，特别是以电池为电源的，为了降低成本、增加播放时间，输出功率都比较小，比如一般CD为10mW左右，有的CD，MD，MP3只有3-5mW，这与50-1000mW额定功率的耳机、耳塞不相适应。

虽然正常听音乐时，输出到耳机的功率只要几mW就足够了，低灵敏度的大耳机需要10mW以上，但这里的功率，是平均功率，对于大动态的音乐，峰值功率可能是平均功率的10-30倍，某些交响乐的峰值功率，可达平均功率的50倍以上，因此，1mW的平均输出功率，有时也需要30-50mW的最大输出能力，否则会出现波形削顶失真。

这个输出能力，对于很多小功率音源，甚至半数以上声卡，都是达不到的。

因此，如果耳机灵敏度不是很高，音源输出功率不是很大，加耳放，对于音质是会有明显提升的。

2，耳放作用之二，匹配阻抗。

如今的绝大部分声卡，都没有了耳机输出插孔，只有LINE OUT插孔。

但大部分人，仍直接将耳机插入LINE OUT插孔听音乐，其实这是不妥的。

LINE OUT输出阻抗很高，一般在数百至几千欧，接入功放或者耳放，阻抗可以完全匹配，接入几十欧的耳机，影响音质在所难免，而且，很多声卡输出电容只有100uF左右，甚至47uF，接入低阻耳机，会对低音信号造成严重衰减。

例如：47uF输出电容的声卡，接32欧耳机，低频截止频率在110Hz，也就是说，110Hz以下的低音，将被严重衰减，此时加耳放，对于音质的提升效果将会很明显。

3，耳放作用之三，调音作用。

很多人说，耳放就是为了保真，调音就是音染，与HIFI的目标背道而驰，调音没有必要。

我认为，适当的调音是允许的，甚至是有必要的，有以下几点原因：a，调音为了更加保真保真，是整个听音系统的事，除了耳放，还包括录音、音乐制作、音源器材、耳机（或音箱）、人耳，还有相关线材，而不仅仅是耳放1个环节的事，如果其他环节有了不可避免的失真，是有可能通过耳放调音来补偿的，虽然耳放不保真了，但整个听音系统会更加保真。

47耳放制作HIFI耳机放大器-PCB-电路图-及全套设计资料(吐血推荐)

对于47耳放的完美改进制作高保真耳机放大器之前一直折腾功放听桌面音箱，半年前忽然打算用用耳机了，于是入了森海的HD595。

虽然50欧的阻抗不算高，但是要发挥出设备的实力耳放还是少不了的。

所以，决定自己动手做一个耳放。

这期间参考了大量关于耳放的资料，最终决定以47耳放电路为基础并加以改进制作一个比较完美的耳机放大器。

便动手做了起来。

一、放大部分47耳放是一位外国人设计的电路，电路如图。

因为电路中有较多以47为参数的元件所以称作47耳放。

两个运放输出经过两个47欧匀流电阻输出致耳机。

因为反馈取样点在47电阻之后，所以不用考虑电阻带来的损耗。

所以自己决定做一个比较完美的47耳放以便把这个电路的能力发挥出来。

于是，开工了。

首先线路图电路没有添加音量电位器，只做了放大部分。

这样一来功能比较独立，方便以后的各种组合。

47原设计使用的运放是OPA2132，这个运放是FET输入型的，所以内阻极高。

而且在低电压下可以正常工作，失调电压与失调电流极小，算是比较高档的运放了。

当然OPA2132的价格也是很高档的。

我作为0收入人士必然不能把这种高档传承下去，于是我选用了这年头满大街都是的NE5532。

NE5532虽然指标相对于OPA2132较差，但是工作于+-15V时音色总体来说还是比较讨人喜欢的。

单片5532耗电相对较大，两片并联就更不用说了，双15V下耗电可想而知。

这就意味着这款耳放将要脱离便携式耳放的范畴转型向台式耳放了。

由于5532失调电压较高而且又是NPN管输入的，如果使用原设计必然会引来较大的输出中点漂移，经过测试最大有30多MV。

HA1.1版_经典音频功率放大器制作40例_[共3页]

· 259 ·第七章集成电路耳机放大器单片TPA6120直接做驱动，音源信号通过电位器直接进入TPA6120。

经过数天的试验，发现这个试验对于DAC 这种低输出阻抗的音源很适合，简单的电路就可以得到很好音质表现。

通过细致地阅读相关资料与多次的验证，发现电位器在不同的位置，对声音和噪声都有明显的影响。

音量的变化，使TPA6120输出的直流电压差异很大。

TPA6120最佳的工作状态是低阻驱动，保持输入端阻抗的不变。

图31.1所示的是TPA6120简单电路的简化原理图。

RP 是音量电位器，它的上、下臂变化会使TPA6120输入端的偏置电阻发生变化，从而让输出端的直流偏移也随之大范围波动，整体的性能受局限，不能很好发挥。

31.1 HA1.1版第二个验证版电路如图31.2所示，即在TPA6120前增加了由两个JRC5534单运放组成的阻抗变换电路，起高入低出的连接效果，并隔离了电位器直接对TPA6120的影响。

同时，改变R3、R4、R5和R6可以调整整个电路的总增益，而TPA6120固定为2倍增益。

C3、C4是带宽限制作用，避免过高的频率进入TPA6120。

这样就使TPA6120工作在一个相对稳定的工作状态，并由前一级来控制增益与音量，适配多种不同的音源，在架构上真正地走向实用化。

为了适应不同耳机的灵敏度，设置了用JRC5534的反馈电阻改变整个电路的增益。

TPA6120是一个电流反馈型（CFB ）放大器，反馈电阻有一定的要求，不能有太大的变化。

所以在这里只是起到一个增益固定为2倍（2X ）的“缓冲”输出级作用。

很多DIY 作品或厂机产品都是这种运放+BUFEER 的电路形式，图31.1第一个验证版的框图图31.2 第二个验证版电路。