Focusrite Penta Channel
By Barry Rudolph
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Mix Magazine "Compression And Compressors"
The Focusrite Penta, the fifth product in the Platinum range, is a stereo compressor with 16 editable preset settings housed in a two-rackspace chassis. Penta is actually five products in one (hence, its name): a single-channel, Class-A, discrete mic preamp (the same as is used in VoiceMaster and Digidesign's Control|24 console/surface); stereo compressor; tube emulator; stereo width controller; and A/D converter via an optional upgrade.
Preset compressors date back to early audio times, when compressor settings were internally set with few options available to broadcast stations and disc mastering engineers. Penta is ideal for the project/home enthusiasts who would like to use a compressor properly, but are baffled by dynamics controls and operation. Penta's design is purpose-built for two main tasks in a studio: tracking a single mic or instrument to tape, or hard disk and stereo track compression for mixdowns. The unit was conceived only as a stereo compressor, but Focusrite found that they could add the single mic pre and still make its $495 price point.
The discrete preamp circuit is a compound, differential pair made up of a FET/bipolar transistor hybrid. The FET's high-input impedance allows any type of mic or instrument to be connected to the unit. The bipolar output transistor acts as a very low-noise, constant-current, buffer amplifier. The XLR mic and 1/4-inch, hi-Z instrument inputs are on the front panel only. The rear panel line input/output jacks are 1/4-inch TRS not XLRs, but switchable between -10 dB and +4 dB. Focusrite decided to keep Penta's costs down, so I had to quit asking myself those "How come they didn't?" questions that come with my "totally pro" expectations. At $495 MSRP for a decent mic pre and stereo compressor, you gotta tighten the belt somewhere! Having said that, you still get the pro touches like +48 phantom power, phase flip, highpass filter, a hard-wired gold-contact bypass relay, and a mic/line switch that routes the mic preamp output to the left input channel of the stereo compressor. Mic gain and line-level input gain are set by a ganged pot. Mic gain ranges from 0 to 60 dB; line-level gain ranges from -10 dB to +10 dB with a center 0dB position.
The compressor section uses an optical gain-reduction element rather than a VCA chip...a clever design choice because this smoother type of compression tends to be forgiving even when set improperly. There is no way to unlink the left and right compressor channels, so there will never be image shifting if you like to squash hard. The 16 presets, named for their intended use, are said to be optimized for: kick, snare, ambient (a way to pull more out of room mics and reverb returns), loop (good for squashing drum loops), bass guitar, synth bass, percussion, acoustic picked, acoustic strum, electric guitar, piano, keyboards, vocals, crunch (an extreme setting), mix ("pump"...a sort of big mastering squash) and limit (a peak-limiter setting). All of these presets are selected with the left/right reset-selection buttons that are on either side of the row of 16 LED preset indicators. It would have made more sense to place these left/right buttons next to each other for fast, two-finger operation.
Manual adjustment of the compressor's presets is via six controls with center detent positions equal to the values of the currently selected preset. This method is a far better way to tweeze presets than, say, the original HHB FatMan, where you would first have to match the knob setting manually against the values listed in the owner's manual before switching from Preset mode to Manual mode where further adjustments are possible. With the Penta presets, all the knobs are always active for on-the-fly changes. The six controls are called: Compression (it's really a threshold control), Make-Up Gain, Ratio, Attack, Release, and Tube Sound, which ranges between "cool" and "warm." There is both soft knee and hard knee compression styles. Soft knee provides a smoother start of compression, great for any voice or instrument where you want less strict control over dynamics.
Using the Penta is simple, although I do wish there was a mic pre output jack or insert points for using it independently of the compressor...a good after-market mod! The mic pre is clean, quiet and has plenty of gain. It's better than most preamps in small consoles, and I actually preferred it for certain tracking instruments where I wanted a straight-ahead sound sans glorification and coloring.
The Penta is a colorful unit with stereo input and output LED metering trees, gain reduction meter, input and output clip LEDs, and an ADC LED to indicate that the optional A/D converter is happily in sync. (My review unit did not have the A/D option.) Also, the Compressor In/Out, Soft/Hard Knee, Tube Sound and Image Width buttons all light when active. Image width controls the level of the sum (L+R) and difference (R-L+L-R) components of stereo audio. You can go from tiny or nearly mono-sounding output, to huge for greatly amplified difference information and a very wide stereo sound.
I liked the preset compressor, with the caution that all of the presets are predicated on a 0dB nominal input level. Pushing more or less level into the Penta causes more or less compression. I always found myself adjusting both input level (which is not part of the preset) and compression threshold to get it right. So if your level is around the nominal, then operation is simply picking which preset you like. Preset attack and release settings within the various individual instrument presets were all good choices. They all worked fine for their designated tasks or were very close...within a quick manual adjustment. I wish there were a few more track-compression choices, because I didn't care much for the crunch or mix [pump] presets, although they are nice to have for a quick clamp.
Toggling through the presets, you'll hear a relay clicking as the tube-sound circuit switches in and out (depending on the preset). The tube-sound can be added to any preset, and it's remembered if you change presets and come back. The tube-sound circuit has three FET-based blocks, each biased to generate a specific harmonic. The overall circuit generates second, third and fifth harmonic distortion in amounts dependent upon the rotary control's position. At low settings, it's mostly second, and advancing the knob cranks more third and fifth. Second-order harmonic distortion emulates the softness of a tube compressor. Turning the control more toward warm, I got more of a tube-like "blooming" sound, great for rounding out bright harshness.
Penta has an MSRP of $495, and the optional 24-bit/96kHz A/D board is $250. If you are into value-oriented project/home studio gear, then go get Penta!
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