转贴一个非常牛的国内高手制作的DAC--8分时并联HiFi音频DAC
创梦的东东！感觉在国内也算顶尖技术了，比国内某些一天到晚吹嘘的产品技术含量高太多！
声明：非广告！介绍给大家看看，国内也是有牛人的。
所谓分时间并联就是几个DAC并联的时候，DAC输出的模拟信号不是同时出现在后级的LPF(或者IV)电路上，8个DAC输出的模拟信号是分8个不同的时间，顺序叠加上去的.简单的讲，如果直接并联，从一个电压到下一个电压，并联得到的是一下子变大8倍的一个模拟量，分时并联是则是分八个阶梯累加上去的（当然中间过程时间非常短)；这样做的好处可以使得模拟输出的曲线变得更光滑，听觉上密度感会更强.
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8分时并联是在看了金嗓子DP800 机器，有感而作，从设计到调整，历时大概2年，中间修改了几次板子
第一版设计参见： http://bbs.hifidiy.net/viewthread.php?tid=165031&highlight=%2Bcdream
第二版参见： http://bbs.hifidiy.net/viewthread.php?tid=327623 第一版设计完成在2008年9月，想来到现在已经两年多了，光阴如箭啊；这里是第二版的改良版，架构基于第二版基础上.8分时并联的优点是各个DAC能互相插补误差，输出平滑模拟曲线，听感细腻，顺滑.
参数规格：
数字接收：WM8805 低抖动(50ps)
DAC：WM8740 x8
数据处理：XC95288XL
数据处理方式：I2S数据信号8分时输出给DAC(wm8740)，DAC输出通过叠加运算(电压)输出模拟量，此模拟量通过低通最终输出
数字输入采样率：44.1KHz,48KHz,96KHz
输入信号支持：Coaxial， BNC， Optical(光纤), AES(平衡),I2S
模拟输出：XLR(平衡),RCA(单端)
输出电平：
单端：3.2V
平衡：+/- 3.2V
输入电压：AC220V
RMAA 测试报告:
测试用的声卡是EMU 1212
这是单独测试:
http://www.cdream5.com/htm/te/DAC8_44_1 24bit.htm
这是对比测试，含EMU1212 自身环路测试(外部环路),DAC8 测试报告,参考的厂机 THETA DSPro PrimeII:
http://www.cdream5.com/htm/te/C2.htm
DAC部分:
左右声道独立板子，一个DAC含两个声道的信号，经过数字处理后，让它都只输出一个声道的数据，然后将两个输出信号并联，即一个DAC芯片就是一个2并联，4个，就是8并联，时序也是8分时架构，1DAC输出后，1号DAC工作，接着3号DAC工作，最后4号DAC，完成8分时序
效果图：
局部:
资
RMAA 测试报告:
测试用的声卡是EMU 1212
这是单独测试:
http://www.cdream5.com/htm/te/DAC8_44_1 24bit.htm
RightMark Audio Analyzer test report
| Testing device | DAC8_44.1 24bit |
| Sampling mode | 24-bit, 44 kHz |
| Interface | |
| Testing chain | External loopback (line-out - line-in) |
| RMAA Version | 6.2.3 |
| | |
| | |
| 20 Hz - 20 kHz filter | ON |
| Normalize amplitude | ON |
| Level change | 0.2 dB / 0.2 dB |
| Mono mode | OFF |
| Calibration singal, Hz | 1000 |
| Polarity | inverted/inverted |
Summary
| Frequency response (from 40 Hz to 15 kHz), dB | +0.06, -0.49 | Good |
| Noise level, dB (A) | -102.5 | Excellent |
| Dynamic range, dB (A) | 104.9 | Excellent |
| THD, % | 0.0005 | Excellent |
| THD + Noise, dB (A) | -93.0 | Very good |
| IMD + Noise, % | 0.0024 | Excellent |
| Stereo crosstalk, dB | -100.2 | Excellent |
| IMD at 10 kHz, % | 0.0041 | Excellent |
| General performance |
| Very good |
Frequency response
| From 20 Hz to 20 kHz, dB | -0.86, +0.06 |
| From 40 Hz to 15 kHz, dB | -0.49, +0.06 |
Noise level
| | Left | Right |
| RMS power, dB | -100.8 | -102.9 |
| RMS power (A-weighted), dB | -101.2 | -103.8 |
| Peak level, dB FS | -83.3 | -83.4 |
| DC offset, % | +0.0 | +0.0 |
Dynamic range
| | Left | Right |
| Dynamic range, dB | +104.2 | +104.4 |
| Dynamic range (A-weighted), dB | +104.8 | +105.1 |
| DC offset, % | -0.00 | -0.00 |
THD + Noise (at -3 dB FS)
| | Left | Right |
| THD, % | +0.0005 | +0.0005 |
| THD + Noise, % | +0.0022 | +0.0022 |
| THD + Noise (A-weighted), % | +0.0022 | +0.0022 |
Intermodulation distortion
| | Left | Right |
| IMD + Noise, % | +0.0024 | +0.0025 |
| IMD + Noise (A-weighted), % | +0.0024 | +0.0024 |
Stereo crosstalk
| | Left | Right |
| Crosstalk at 100 Hz, dB | -94 | -106 |
| Crosstalk at 1000 Hz, dB | -92 | -106 |
| Crosstalk at 10000 Hz, dB | -93 | -102 |
IMD (swept tones)
| | Left | Right |
| IMD + Noise at 5000 Hz, | 0.0027 | 0.0028 |
| IMD + Noise at 10000 Hz, | 0.0039 | 0.0039 |
| IMD + Noise at 15000 Hz, | 0.0055 | 0.0056 |
这是对比测试，含EMU1212 自身环路测试(外部环路),DAC8 测试报告,参考的厂机 THETA DSPro PrimeII:
http://www.cdream5.com/htm/te/C2.htm
EMU1212_EX LOOP
DAC8_44.1 24bit
THETA DSPro PrimeII
RightMark Audio Analyzer test
Testing chain: External loopback (line-out - line-in)
Sampling mode: 24-bit, 44 kHz
Summary
| Test | EMU1212_EX LOOP | DAC8_44.1 24bit | THETA DSPro PrimeII |
| Frequency response (from 40 Hz to 15 kHz), dB: | +0.03, -0.22 | +0.06, -0.49 | +0.02, -0.14 |
| Noise level, dB (A): | -110.4 | -102.5 | -93.7 |
| Dynamic range, dB (A): | 110.9 | 104.9 | 95.0 |
| THD, %: | 0.0006 | 0.0005 | 0.0033 |
| IMD + Noise, %: | 0.0012 | 0.0024 | 0.0064 |
| Stereo crosstalk, dB: | -108.8 | -100.2 | -87.4 |
Frequency response
Noise level
Dynamic range
THD + Noise (at -3 dB FS)
Intermodulation distortion
Stereo crosstalk
This report was generated by RightMark Audio Analyzer 6.0 
