从前我们总是想当然的认为，USB声卡不靠谱，还是选购火线声卡比较保险。是的，曾经有一段时间我也这么认为。但是RME刚上市的Fireface UC让我对USB声卡有了新的认识，我想同样也会让大家对USB声卡的看法产生极大的改变。如果USB声卡拥有1394火线声卡同样的速度、同样的稳定、同样的音质（当然还有同样的价格），我想大家一定会更愿意选择USB声卡，因为几乎任何一台电脑或者笔记本都具备至少一个USB接口，但配备1394火线接口的几率却低了太多太多（尤其在苹果自家都不一定配备火线接口的今天）。
RME Fireface UC不论从外观还是配置都和Fireface 400火线声卡几乎完全相同：模拟线路8进6出；一个立体声耳机输出；一对ADAT光纤输入输出（可切换为SPDIF）；一对SPDIF同轴输入输出；两对MIDI输入输出以及一对时钟BNC输入输出接口。
声卡为1U机架高度，1/2机架宽度。前面由左至右分别是：1、2话筒\线路输入通道为两个Neutrik TRS/XLR Combo接口（XLR插入时为话筒输入状态，TRS输入时为线路输入状态）；3、4线路\乐器输入通道为两个TRS\TS兼容接口。前四路输入通道旁都有CLIP（失真）、SIG（信号）指示LED，前两路有48V幻象电源指示。接下来是一个编码器旋钮，短按旋钮切换通道/电平模式，长按切换单通道/Link双声道控制模式，旋转切换通道和调整电平。上面的LED显示窗可显示当前通道或电平增益值。右侧是两排指示LED灯，左侧一排是各种数字信号的状态指示，右侧是MIDI信号的状态指示。最后是立体声TRS耳机输出接口。
声卡后面板由左至右分别是：12V电源输入、电源开关、高速USB2.0接口以及剩余的音频接口。它们包括6路TRS平衡线路输出；4路TRS平衡线路输入；两进两出的通过伪miniDIN-9b<=>4XMIDI的转换线传输的MIDI接口；BNC时钟输入输出接口（可打开75欧内部终结器以适配50欧时钟线缆及连接器）；ADAT光纤输入输出以及SPDIF同轴输入输出，ADAT在44.1/48K状态支持到8路信号进出；88.2/96K支持到4路；176.4/192支持到2路进出。
声卡内部电路板使用RME Fireface 400的电路板，布线相当合理。话放部分使用PGA2500，TI/BB出品的数控话筒放大器芯片，而且被广泛应用，Prism Sound Orpheus和Apogee Duet都有使用这枚芯片。运放放大器使用NJM4580，数模模数转换部分使用AK4620—地球上最好的Codec之一，普遍用于中高档音频接口中。主信号处理由一枚Xilinx XC3S700A FPGA完成，这枚FPGA具有很高的性能，拥有20个18x18乘法器，做个简单混响都没问题，Fireface UC强大的软件控制能力主要来自于这枚芯片。时钟部分使用Xilinx的DCM作为主时钟合成器，利用了Xilinx DLL锁相环技术，并参考一枚50M音频合成晶振来控制时钟。USB控制器使用SMSC USB3250通用高速USB2.0芯片，并参考一枚20M时钟恢复晶振。 大部分电容都使用NCC的KY系列优质电容；电源部分采用开关电源方案，核心器件来自安森美半导体[ONS]和国家半导体[NS]，并使用了二级线形稳压。
官方性能参数：
Analog
AD, Line In 5-8, rear
• Resolution AD: 24 bit
• Signal to Noise ratio (SNR): 110 dB RMS unweighted, 113 dBA
• Frequency response @ 44.1 kHz, -0.1 dB: 5 Hz – 20.6 kHz
• Frequency response @ 96 kHz, -0.5 dB: 5 Hz – 45.3 kHz
• Frequency response @ 192 kHz, -1 dB: 5 Hz - 90 kHz
• THD: < -100 dB, < 0.001 %
• THD+N: < -98 dB, < 0.0012 %
• Channel separation: > 110 dB
• Maximum input level: +19 dBu
• Input: 6.3 mm TRS jack, electronically balanced
• Input impedance: 10 kOhm
• Input sensitivity switchable to Lo Gain, +4 dBu, -10 dBV
• Input level for 0 dBFS @ Lo Gain: +19 dBu
• Input level for 0 dBFS @ +4 dBu: +13 dBu
• Input level for 0 dBFS @ -10 dBV: +2 dBV
• Resolution AD: 24 bit
• Signal to Noise ratio (SNR): 110 dB RMS unweighted, 113 dBA
• Frequency response @ 44.1 kHz, -0.1 dB: 5 Hz – 20.6 kHz
• Frequency response @ 96 kHz, -0.5 dB: 5 Hz – 45.3 kHz
• Frequency response @ 192 kHz, -1 dB: 5 Hz - 90 kHz
• THD: < -100 dB, < 0.001 %
• THD+N: < -98 dB, < 0.0012 %
• Channel separation: > 110 dB
• Maximum input level: +19 dBu
• Input: 6.3 mm TRS jack, electronically balanced
• Input impedance: 10 kOhm
• Input sensitivity switchable to Lo Gain, +4 dBu, -10 dBV
• Input level for 0 dBFS @ Lo Gain: +19 dBu
• Input level for 0 dBFS @ +4 dBu: +13 dBu
• Input level for 0 dBFS @ -10 dBV: +2 dBV
Line In 3-4, front
• as AD, but:
• Signal to Noise ratio (SNR): 105 dB RMS unweighted, 109 dBA
• Gain range via rotary encoder: 0 up to +18 dB
• Maximum input level, Gain 0 dB: +19 dBu
• Maximum input level, Gain 18 dB, Inst: -16 dBu
• CLIP LED: -2 dBFS
• SIG LED: -65 dBFS
• as AD, but:
• Signal to Noise ratio (SNR): 105 dB RMS unweighted, 109 dBA
• Gain range via rotary encoder: 0 up to +18 dB
• Maximum input level, Gain 0 dB: +19 dBu
• Maximum input level, Gain 18 dB, Inst: -16 dBu
• CLIP LED: -2 dBFS
• SIG LED: -65 dBFS
Microphone 1-2, front
• as AD Line In 5-8, but:
• Input: Neutrik XLR/TRS Combo jack, electronically balanced
• Input impedance: XLR 2 kOhm, TRS 8 kOhm balanced
• Low Roll Off –0.5 dB: 18 Hz, -1 dB: 12 Hz
• Gain range: 0 dB, +10 up to +65 dB
• Maximum input level XLR, Gain 0 dB: +10 dBu
• Maximum input level XLR, Gain 65 dB: -55 dBu
• Maximum input level TRS, Gain +0 dB: +21 dBu
• Maximum input level TRS, Gain +65 dB: -44 dBu
• CLIP LED: -2 dBFS
• SIG LED: -65 dBFS
• as AD Line In 5-8, but:
• Input: Neutrik XLR/TRS Combo jack, electronically balanced
• Input impedance: XLR 2 kOhm, TRS 8 kOhm balanced
• Low Roll Off –0.5 dB: 18 Hz, -1 dB: 12 Hz
• Gain range: 0 dB, +10 up to +65 dB
• Maximum input level XLR, Gain 0 dB: +10 dBu
• Maximum input level XLR, Gain 65 dB: -55 dBu
• Maximum input level TRS, Gain +0 dB: +21 dBu
• Maximum input level TRS, Gain +65 dB: -44 dBu
• CLIP LED: -2 dBFS
• SIG LED: -65 dBFS
DA, Line Out 1-6, rear
• Resolution: 24 bit
• Dynamic range (DR): 110 dB, 113 dBA @ 44.1 kHz (unmuted)
• Frequency response @ 44.1 kHz, -0.1 dB: 1 Hz – 20.4 kHz
• Frequency response @ 96 kHz, -0.5 dB: 1 Hz – 44.8 kHz
• Frequency response @ 192 kHz, -1 dB: 1 Hz - 80 kHz
• THD: -100 dB, < 0.001 %
• THD+N: -96 dB, < 0.0015 %
• Channel separation: > 110 dB
• Maximum output level: +19 dBu
• Output: 6.3 mm TRS jack, servo-balanced
• Output impedance: 75 Ohm
• Output level switchable Hi Gain, +4 dBu, -10 dBV
• Output level at 0 dBFS @ Hi Gain: +19 dBu
• Output level at 0 dBFS @ +4 dBu: +13 dBu
• Output level at 0 dBFS @ -10 dBV: +2 dBV
DA – Phones, 7/8, front
• as DA, but:
• Output: 6.3 mm TRS jack, unbalanced
• Output impedance: 30 Ohm
• as DA, but:
• Output: 6.3 mm TRS jack, unbalanced
• Output impedance: 30 Ohm
Digital
• Clocks: Internal, ADAT In, SPDIF In, word clock in. Optional LTC/Video in
• Low Jitter Design: < 1 ns in PLL mode, all inputs
• Internal clock: 800 ps Jitter, Random Spread Spectrum
• Jitter suppression of external clocks: > 30 dB (2.4 kHz)
• Effective clock jitter influence on AD and DA conversion: near zero
• PLL ensures zero dropout, even at more than 100 ns jitter
• Digital Bitclock PLL for trouble-free varispeed ADAT operation
• Supported sample rates: 28 kHz up to 200 kHz
• Low Jitter Design: < 1 ns in PLL mode, all inputs
• Internal clock: 800 ps Jitter, Random Spread Spectrum
• Jitter suppression of external clocks: > 30 dB (2.4 kHz)
• Effective clock jitter influence on AD and DA conversion: near zero
• PLL ensures zero dropout, even at more than 100 ns jitter
• Digital Bitclock PLL for trouble-free varispeed ADAT operation
• Supported sample rates: 28 kHz up to 200 kHz
Digital Inputs
Word Clock
• BNC, not terminated (10 kOhm)
• Switch for internal termination 75 Ohm
• Automatic Double/Quad Speed detection and internal conversion to Single Speed
• SteadyClock guarantees super low jitter synchronization even in varispeed operation
• Not affected by DC-offsets within the network
• Signal Adaptation Circuit: signal refresh through auto-center and hysteresis
• Overvoltage protection
• Level range: 1.0 Vpp – 5.6 Vpp
• Lock Range: 27 kHz – 200 kHz
• Jitter when synced to input signal: < 1 ns
• Jitter suppression: > 30 dB (2.4 kHz)
• BNC, not terminated (10 kOhm)
• Switch for internal termination 75 Ohm
• Automatic Double/Quad Speed detection and internal conversion to Single Speed
• SteadyClock guarantees super low jitter synchronization even in varispeed operation
• Not affected by DC-offsets within the network
• Signal Adaptation Circuit: signal refresh through auto-center and hysteresis
• Overvoltage protection
• Level range: 1.0 Vpp – 5.6 Vpp
• Lock Range: 27 kHz – 200 kHz
• Jitter when synced to input signal: < 1 ns
• Jitter suppression: > 30 dB (2.4 kHz)
ADAT Optical
• 1 x TOSLINK
• Standard: 8 channels 24 bit, up to 48 kHz
• Double Speed (S/MUX): 4 channels 24 bit 96 kHz
• Quad Speed (S/MUX4) : 2 channels 24 bit 192 kHz
• Bitclock PLL ensures perfect synchronisation even in varispeed operation
• Lock Range: 31.5 kHz – 50 kHz
• Jitter when synced to input signal: < 1 ns
• Jitter suppression: > 30 dB (2.4 kHz)
• 1 x TOSLINK
• Standard: 8 channels 24 bit, up to 48 kHz
• Double Speed (S/MUX): 4 channels 24 bit 96 kHz
• Quad Speed (S/MUX4) : 2 channels 24 bit 192 kHz
• Bitclock PLL ensures perfect synchronisation even in varispeed operation
• Lock Range: 31.5 kHz – 50 kHz
• Jitter when synced to input signal: < 1 ns
• Jitter suppression: > 30 dB (2.4 kHz)
AES/EBU - SPDIF
• 1 x RCA and 1 x optical, according to IEC 60958
• High-sensitivity input stage (< 0.3 Vpp)
• Accepts Consumer and Professional format, copy protection will be ignored
• Lock Range: 27 kHz – 200 kHz
• Jitter when synced to input signal: < 1 ns
• Jitter suppression: > 30 dB (2.4 kHz)
• 1 x RCA and 1 x optical, according to IEC 60958
• High-sensitivity input stage (< 0.3 Vpp)
• Accepts Consumer and Professional format, copy protection will be ignored
• Lock Range: 27 kHz – 200 kHz
• Jitter when synced to input signal: < 1 ns
• Jitter suppression: > 30 dB (2.4 kHz)
Digital Outputs
Word Clock
• BNC
• Max. output voltage: 5 Vpp
• Output voltage @ 75 Ohm termination: 4.0 Vpp
• Output impedance: 10 Ohm
• Frequency range: 27 kHz – 200 kHz
• BNC
• Max. output voltage: 5 Vpp
• Output voltage @ 75 Ohm termination: 4.0 Vpp
• Output impedance: 10 Ohm
• Frequency range: 27 kHz – 200 kHz
ADAT
• 1 x TOSLINK
• Standard: 8 channels 24 bit, up to 48 kHz
• Double Speed (S/MUX): 4 channels 24 bit 96 kHz
• Quad Speed (S/MUX4) : 2 channels 24 bit 192 kHz
• 1 x TOSLINK
• Standard: 8 channels 24 bit, up to 48 kHz
• Double Speed (S/MUX): 4 channels 24 bit 96 kHz
• Quad Speed (S/MUX4) : 2 channels 24 bit 192 kHz
AES/EBU - SPDIF
• 1 x RCA and 1 x optical, according to IEC 60958
• Output level Professional 2.0 Vpp, Consumer 0.8 Vpp
• Format Professional according to AES3-1992 Amendment 4
• Format Consumer (SPDIF) according to IEC 60958
• Single Wire mode, sample rate 28 kHz up to 200 kHz
• 1 x RCA and 1 x optical, according to IEC 60958
• Output level Professional 2.0 Vpp, Consumer 0.8 Vpp
• Format Professional according to AES3-1992 Amendment 4
• Format Consumer (SPDIF) according to IEC 60958
• Single Wire mode, sample rate 28 kHz up to 200 kHz
独家测试：
软件部分，可以说与RME其他声卡完全相同，但是也不妨我们在这里简单介绍。
设置窗口第一页，首先可以设置Sample buffers的大小，最低48，最高2048samples。接下来是输出格式设置，若选择Single Speed会让时钟输出频率32K到48K之间（即使目前频率在192，输出时钟依旧停留在48K）。在Optical后面的下拉菜单中可选择光纤输出格式（ADAT或SPDIF）。SPDIF后可选择消费标准或专业标准，专业标准为平衡格式，省去屏蔽，可接驳AESEBU平衡数字线缆。Clock Mode设置中可对采样频率、时钟源以及Pitch进行设置调整，这里不再赘述。
增益的设置：线路输入，Lo Gain状态0dBFS输出+19dBu；+4dBu状态0dBFS为+13dBu；-10dBV状态0dBFS为+2dBV。线路输出，Hi Gain状态0dBFS输出+19dBu；+4dBu状态0dBFS为+13dBu；-10dBV状态0dBFS为+2dBV。耳机输出设置亦然。话筒输入设置包括了1、2路输入增益控制和48V幻象供电开关，3、4路 乐器/线路 输入设置包括输入增益控制以及 线路/乐器 切换和Pad（衰减12dB）。
Mixer分为三个部分：Input Mixer、Playback Mixer，以及输出端选择。每个输出端都有各自的Input/Playback Mixer设置，只要你打开右上角的Submix，然后选择一路输出，就可以调节由Input端口或Playback端输出到该硬件输出端口的混音了。Alt+鼠标右键拖拽可立体声Link调节推子，Shift微调，Ctrl参数归零。右侧Monitor Main可选择主监听的输出通道;Monitor Phones可选择乐手监听的硬件输出通道，点亮其中一个小喇叭可从主监听听到这路乐手监听的输出信号；Talkback开关可进入对讲状态。顶部Option菜单中MS Processing功能可将当前选择之立体声通道MS编码输出。Preferences设置中：Talkback下可选择控制室对讲麦克输入以及进入对讲状态时对乐手监听内容的衰减量；Listenback下可选择录音室乐手对讲麦克通道以及进入对讲状态时主监听内容衰减量。
Matrix矩阵设置中，纵向是硬件输入端口及软件回放端口，横向是硬件输出端口，用户可以任意的链接它们。Ctrl+鼠标左 在方格中上下拖拽可改变增益衰减量。
当然大家最关心的还是实际使用起来Fireface UC到底如何。首先UC的接口较为齐全，一般工作完全能够胜任。兼容性以及稳定性极佳，目前在我努力的玩弄下UC还没出现过休克情况。录音及回放质量相当优异，话放质量在该价位声卡中很难有对手；回放音质秉承了RME一贯的风格，和Fireface400几乎没差别，中性精准的声音（对不起，这里我没有太多文明用语的华丽词汇）。耳机输出质量不错，600欧耳机音量打到一半声音就让人揉胸胸了。ASIO驱动很和Xie，我设置到最低48samples，录个立体声没任何问题，而且RME自家业在不同平台测试了ASIO性能，有兴趣的请看这里：http://www.rme-audio.de/en_products_fireface_uc_systems.php?page=content/products/en_uc_general。RME的软件部分不用多说，矩阵用起来是相当灵活强大，可以满足你的任何口味的需求。我相信那些曾经说USB声卡不如火线声卡的朋友从此就要收回他的看法了，因为这完全只是声卡设计的问题，和USB以及1394火线没丝毫关系，而且USB兼容性远优于火线传输。
如果您准备购买USB声卡，RME Fireface UC是我目前唯一的推荐。因为不论从音质、性能、稳定性以及兼容性上，Fireface UC超出其他对手太多。
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先感谢祖国，再感谢VR同学的参数测试。
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附测试大图:
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