Paul White 深入Focusrite Compouder內部探尋它的工作原理
The Focusrite 白金系列被認為是將Focurite產品平價化的推進到一般工作室使用者的它琚A不過除了簡化的設計之外，他們更是透過不同於以往的研發步驟，使新系列的機器有不同於原來高價版系列的音響特性，所有已推出的白金系列都包含有嶄新的設備來改進聲音的特性，當然，新的Compunder系列也不例外。
The Compounder 是一台雙軌的壓縮限制器，並且整合有擴展以及閘控弁遄A除此之外尚有低頻擴展部分能夠在處理後明確的增強低頻的Punch力道(請參?How Low Can You Go?' 的方塊文章). 這個弁鉏W加了Compounder的份量，我會在稍後的評論中更仔細來談論它。先不管Bass Expander， 對Compounder的基本描述來說，聽起來跟釵h的競爭產品聽起來差不多， 但是他有幾點設計原理倒是值得一提，舉例來說，除開用單一的VCA電壓控制放大器來提供擴展/閘控以及壓縮/限制的增益，設計者選擇在每個部分使用不同形式的增益控制元件，也因而使得使用者在機器上可以有更多對聲音特性的控制能力，一般來說，堆疊式排列的增益控制元件由於現貨供應的VCA都有增加失真以及雜訊的情形，所以會導致表現不佳，當你堆疊愈多，這種情形會愈累積愈嚴重， 不過在Compounder裡面，擴展/閘控以及壓縮/限制部份是利用感光電阻電路，這種電路在開始作用之前是不會助長雜訊的，換句話說，如果你沒有啟動限制或是閘控弁遄A電路基本上表現是被動的、線性的，如同一般電阻一樣，當電路開始工作，它比傳統的VCA放大器具備平坦的響應，所以像閘控在開關時所產生的click雜訊會因此大大降低， 同時，這種電路有200kHz的音頻帶寬，能使聲音的處理過程更加明確以及透明。
FOCUSRITE COMPOUNDER £499
pros
Comprehensive control system, including bass enhancement.
Clean, musical signal path.
Separate expander/gate, compressor and limiter sections.
cons
The inexperienced user could get the unit to distort by setting very fast attack and release times. However, the manual does include typical settings for specific applications, so this shouldn't be a serious problem.
summary
The Compounder is a powerful, flexible and well behaved addition to the Platinum range, and its bass enhancer is a genuinely useful bonus. 
某些已經推出的Focusrite動態處理器使用商業性的VCA増益控制元件，但是想要取得一台處理聲音時不會造成不必要失真的機器是很昂貴的，因此，在妥協使用低成本的商用VCA時， Focusrite也同時使用自己開發的Class A設計的配對電晶體元件， 當奇數的VCA元件產生基數諧波失真時使耳朵產生極微小的不悅時，Class A 設p將會在過度驅動時產生壓倒性的第二諧波，使得耳朵在注意的不適時就會被大量的偶數諧波所壓制，因此，在Compounder的失真圖表上，即使訊號達到20dBu之後，雜訊仍然一無所有，你必須在機器上調到很大的數值之後才可能聽得到失真。
The Compounder
如同其餘的Platinum白金系列一樣使用銀色的電鍍外殼， 1U寬度的Compounder 包含兩個對等的軌道，可以連結起來配對當成立體來控制，也可獨立當成兩台獨立的訊號處理器。背板具有接地補償的非平衡式接頭以及平衡式XLR輸入/輸出接頭，輸出非平衡式端子是-10dBV而 XLR部分則是 +4dBu。 輸入則與輸出具有相同的工作數值，不過-10dBV 與 +4dBu是可以透過背板的按鍵切換， 另一個端子則是side-chain輸入用途，讓其他的外部訊號可以將閘控使用在創意的運用上，如利用編輯好的大鼓或是節拍器來控制刷吉他和弦時的閘控開關..等。
每一軌的控制面板分成兩個部份，擴展/閘控以及壓縮/控制部份，首先讓我們看看擴展這個部分，它有兩個旋鈕讓你控制Threshold以及Release/Hold，但是另外有6個按鍵以及4段式的LED増益抑制米特計，(以下原文介紹一些工作原理，基本上不針對這台機器，所以就偷懶不翻譯..)Threshold sets the level below which gating or expansion will take place, as selected by the Expand button (the circuit operates as a conventional gate when this button is out), and when the Hold button is pressed, the Release/Hold control sets the time the gate stays open after the input (or external Key signal) has fallen below the threshold, after which it closes fairly rapidly. This is the mode used to create the well-known gated reverb sound, though it has other uses! There is no variable attack control, but a button allows the gate to be set to a fast attack for working with percussive sounds, while the next button along allows the gate attenuation to be set to either 15dB or 70dB. The 15dB setting enables the gate to quieten pauses without silencing them altogether, while the 70dB setting effectively mutes all the audio during pauses.
Expand puts the circuit into expander mode rather than gate mode, so that gain reduction is increased progressively as the signal falls further below the threshold. This functions rather like a soft gate and may be more forgiving on things like vocal tracks. Two further buttons select the Key input as the gate triggering source and allow the entire section to be switched in or out. All the main Compounder function buttons have integral red status LEDs that show through the switch cover when the switches are depressed.
The compressor section is pretty comprehensive, and most of the controls will be familiar to anyone who's ever used a compressor before. There are knobs for Threshold, Ratio, Attack, Release and Make-up gain, which is pretty standard, 有兩個多出來的模式旋鈕包含bass enhancement(低頻加強) 以及 分離限制器的Threshold Level。限制器的 threshold 範圍可以在12 以及 26dB之間變化，使你可以做更精細的控制，一組分離的Bypass按鍵可以讓你切換這兩個範圍，同時有一組紅色的限制 LED燈，當訊號到達 threshold點的時候會亮。
As well as the compressor In button, there's a switch to select hard- or soft-knee operation and another to select an auto-release time mode - useful if your programme dynamics keep varying. A five-section LED meter monitors the compressor input up to 20dB, and the Ratio control actually goes up to infinity and beyond so you can get those classic pumping effects where loud sounds are pushed down and quiet sounds are pulled up above them. A further seven-section LED meter shows the compressor gain reduction up to 24dB.
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低頻擴展可以從平坦到肥之間來變化，從50Hz附近開始增強，不過，按下一個叫Huge的鍵則可以將頻率提升到100Hz，所以比較寬廣的低頻頻帶都會被增強， 這些旋鈕提供你足夠的Punch。
在立體操作時，壓縮以及限制部份可以利用兩個[分離的按鍵各自獨立操作，擴展/閘控則沒有Link連結弁遄A而大部分的場合來說冶應該希望如此。
In Use
As the Compounder算是三合一的機器，所以最好是分開來看每個部份的表現如何比較好，首先擴展/閘控部分具備積極的動作，在鼓上面選擇快速的Gate設定工作表現很完美，如同許多閘控機器一樣，設定很快的attack time以及快速的release會使開關出現低頻的失真，但是，一般來說你不會將release time設定得這麼快，在一般設定時，不論使用在哪種聲音上都不會產生click的聲音，但是要認真點說，擴展模式表現會是比較好的，它讓訊號表現很溫和，對於Vocal來說依該是最好用的。外部的key 功能是用來與閘控模式結合，Hold用來製造gated reverb 或是做聲音的碎拍表現。 在舞曲上這是很常使用的技巧，刷Chord的吉他可以使用編輯好的鼓聲來驅動，而產生類似節奏樂器的感覺。
壓縮部份因你使用Hard或是Soft的Knee設定表現有所不同，很明顯的 很明顯的在Red系列之後Focusrite將Soft Knee壓縮的表現給模擬了起來，因此聲音壓過後的表現是平順而透明的，這看來或是在這種場合使用：你必須在許多副作用變得明顯時使用大量的壓縮。
Hard-knee 相對之下則較有個性，並且可以看是要比要有力道的大鼓或是Bass而有不同的選項，大的聲音還是蠻渾圓而具有音樂性，不過比較有Punch並且比Soft-knee更明顯有壓縮的感覺，很有趣的是，限制器看來作用非常迅速，despite the fact that opto circuits are known for being a little on the sluggish side, and checking with the designers confirmed that they have incorporated lots of feedback to sharpen up the response. Normally, the limiter is set just below the clipping threshold of the destination device to catch errant peaks, but this one sounds very '60s if you deliberately drive it into hard limiting. The effect may not be everybody's cup of tea, but it's another creative tool if you want it.
我把低頻加強的功能放到最後，因為這通常是在壓縮器上看不到的功\能，在一般的設定下，你需要不錯的監聽喇叭才能正確聽到這個效果，因為低音的改變通常是在50Hz甚至下，而多數的近場監聽喇叭在這段頻率表現都會失去準頭，這個設定是給舞曲混音給外場具備重低音的喇叭系統時使用， 按下HUGE案件會延伸他作用的頻譜，使一般的喇叭也能聽到效果，, 這通常比只使用EQ要來的好控制並且更清晰，.這部份要加多少妳必須小心的使用，不過謹慎點用，你可以增加混音的暖度並且使整個低音的底部更具重量感，而不會讓整個中頻的變化變模糊。
結論
Compressors are personal things, but Focusrite have tried very hard to make this one suitable for transparent gain control as well as for more obvious 'beefing up'. The signal path is extremely clean and doesn't suffer the high-end blurring of some designs, nor is the compression over-obvious in soft-knee mode. The separate limiter works very well, as does the expander/gate section, though with both the gate and the compressor, when using a fast attack, you have to be careful not to set such a short release time as to cause audible distortion. The auto-compression mode handles inconsistent sources very well, including vocals and bass guitar, while the Bass Enhancer will appeal to anyone wanting to add weight to their sound.
Given the competitive price of the Compounder, there are no real weaknesses and it's certainly versatile. Because all compressors have their own character, there is no obvious equivalent, so if the Compounder fits your budget, make sure you give it a test drive to see what it can do for you. 
