PC Speaker Amplifier

333.

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简介:PC扬声器放大器

这是使用LM386和TIP41 / 42的小功率(小于10WATT)晶体管放大器。

虽然输出功率并不令人印象深刻,但它仍然可以作为PC扬声器和MP3播放器的放大器。

当一起生活在一个拥挤的公寓,一半output power from this amplifier easily produce complains by my family.

Anyway, it can drive 8ohm and 4ohm speaker with maximum 12V power supply.

I got the original schematics from the website (http://www.bristolwatch.com/radio/lm386_power_amp.htm, Lm386 Audio Amplifier Adding Push-Pull Output Stage).

As the circuit not using dual polarity (+/-) power supply, overall circuit complexity is not much high and compact size (15cm(W) x 10cm(D) x 5cm(H)) of chassis can be used as shown in the picture above.

I had made several amplifiers with original schematics and the one of them shown in the picture above is the final version which applied slight modifications from the original.

Step 1: Previous Amplifier Version

This is old version of amplifier made according to the original schematics.

It use TIP31/32 transistors as push-pull output stage..

我正在使用公共LM7812电压调节器电路和220V(IN)/ 15V(OUT)壁适配器作为电源,因为放大器电路在正常操作期间需要小于1A电流。

它非常令人满意,因为输出水平足以驱动我拥有的任何8个欧姆或4个扬声器。

与之前使用的商业音频放大器相比,音质也是合理的。

But it seems a high pitch noise is coming out when hearing closely to a speaker.

也许LM386放大器IC似乎产生了高频的嘶嘶声,以及正常放大的音频信号。

因此,该放大器并不经常用作听到几小时通常会让我感到不舒服,因为从扬声器出来的高音高声音。

And sometime RF (radio frequency) burst pickup happen when motorcycle is passing by near my apartment with big noise.

***

我已经搜索了互联网以减少高音嘶嘶声和偶尔的RF皮卡。

下面的原理图是在多个网页中推荐的一些修改应用的结果。

Step 2: Circuit Schematics

由于我不擅长模拟电子产品,因此在上述原理图中的修改不可能进行科学的解释。

但是当我在聆听MP3播放和听到视频的音频输出时,结果非常令人满意,通过修改的放大器电路,可以使用视频的视频音频输出。

由于音频质量是非常主观的,根据个人观点,上面的补救动作不会适合某人。

但是,无论如何没有更多的RF拾音器,并且终于消失了很高的麻烦噪音。

The reasoning of the addition and removing of electronic components are as follows.

***

- Applying low (100uF) and high (0.1uf) frequency bypassing capacitors are recommended to the power supply line of LM386 to remove noise inlet to the amplifier IC

- Reducing gain of LM386 (make open pin 1 and 8 to fix gain as default 20(26dB)) help to remove high frequency noise is also recommended in other web-pages.

- And finally add one more ceramic capacitor (0.1uF capacitor which is numbered as 3 in the schematic above) to LM386 output is claimed for removing any high pitch noise altogether as the ceramic capacitor is acting as low pass filter

***

所有上面的我在网页中发现的所有建议都会被应用和测试一个接一个地测试以产生上面图中所示的最终示意图。

Firstly, I don’t think the one more add-on of ceramic capacitor (number 3 portion in the schematics) to LM386 output as good idea.

因为可能的电容器可以从扬声器输出中移除一些有用的高频音频信号,这对于任何人来说都是非常合理的怀疑。

But the capacitor addition becomes quite effective solution to remove RF pickup and high pitched hissing sound from audio output in the end.

第3步:布线绘图

As stereo output is required, two amplifier circuits are positioned and wired on universal PCB board.

将示意图和接线图进行比较时,可以看到示意图中描绘的每个接线与上面的图中的接线图案匹配。

Similar size of each electronic component is depicted, located and wired together with other components in the wiring drawing.

为了减少整体布线长度,不使用椭圆形和倾斜的布线图案。

橙色的线条有线和连接在PCB的顶端。

同时,其他红色/绿色线条有线连接并连接在PCB的后(焊接)侧。

第4步:零件

在上面的图片中,我不能描绘并解释每个组件。

但是,最重要的节目有价值的组件在图片中描述。

The detail BOM (Bill of Materials) is described in the list below. (Cost of only important component is written. But the cost information is provided just as indicative)

***

- LM386放大器IC X 2(约1 $)

- Tip41(NPN晶体管)X 2,Tip42(PNP晶体管)x 2(每个约1.2 $)

- 1N4148二极管X 4,用于偏置晶体管作为AB类

- LM7812电压调节器(放大器电源)

- 阿尔卑斯山蓝色天鹅绒20K电位器(音量控制,双重20k VR,10 $)

- 1000uF electrolytic capacitor x 2 for filtering DC from audio output

- 100uF electrolytic capacitor x 2 for bypassing low frequency noise from power line

- 10uF electrolytic capacitor x 2 for bypassing power with LM386 IC

- 2.2uF electrolytic capacitor x 2 for coupling audio input to amplifier circuit

- 0.1UF陶瓷电容器X 6用于电力滤波和高频噪声抑制

- 0.33UF薄膜电容器x 1用于LM7812稳压器噪声滤波

- 0.047UF薄膜电容器X 2,用于输出稳定(ZOBEL网络)

- 2.2ohm 1/2W resistor x 4 for transistor loading

- 1K 1/4W resistor x 2 for transistor biasing

- 10OHM X 2,用于用Zobel网络稳定输出

- Speaker cable wiring terminal block (4 Pins, 3$)

- 3.5mm立体声音频输入插座

- 用于15V壁挂电源适配器的圆形电源入口插座

- 通用PCB板约15cm(w)x 10cm(d)

- Acrylic board x 4 (15cm (W) x 10cm (D) x 5mm/3mm (H))

- Metal supporter M3 size (bolt/nut) 3.5cm x 4

- 2个线缆(等级5V且超过2A)

***

Transistor matching is recommended in the web-page where the original schematic is posted.

For better audio quality, usually transistor matching is required for supporting identical physical characteristics of NPN/PNP transistors.

But as matching process is a little bit tricky, I will not mention details in this story.

第5步:布线和焊接

Tin wires (AWG 24 size) are used for making wiring patterns as depicted in the schematics and wiring drawing.

由于在焊接期间出现错误,使用了几个跳线电缆。

作为焊接方法在其他指导中解释(//www.sledutah.com/circuits/raspberry-pi/projects/recent/),我不会在这个故事中描述细节。

但是基本上是根据布线图中所示的细节进行的布线和焊接。

As seen in the picture above, various cables are connected to the amplifier including such as stereo audio cable, 2 wire speaker cables and 15V power supply cable.

第6步:玩进一步发展

As amplifier making is finished, let start to listening some music with it.

The speaker shown in the picture above is Scandyna MicroPod SE which was bought about 10 years ago.

现在,音频电缆连接模型被改变为蓝牙,仍然具有相同的模型形状似乎可供购买。

Personally I’m supposing the speaker’s technical specification and performance is more important than amplifier for audio quality.

扬声器的技术规范如下。

***

- Applications Hi-Fi stereo, AV-Home Theatre systems

- Amplifier requirement 10 - 100 watt

- 标称阻抗4Ω

- Frequency Response 65-20.000 Hz (± 3dB)

***

我描述了PC扬声器的该放大器的用途。

But it can be interfaced with diverse audio sources for playback music or video.

您可以查看以下链接中操作的放大器的视频。

*** <视频链接>

https://drive.google.com/file/d/131MuCqJzu-P7cf5pM...

***

由于智能手机执行录制,音频质量并不多识别。

无论如何,我正在使用这个放大器作为基本设备,用于播放带有PC,覆盆子PI服务器,智能手机等的任何多媒体内容。

As an extension of this project, some add-on functional will be integrated to this amplifier.

Thanks for reading.

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