SOLID STATE LOGICX Logic Alpha Channel

With the introduction of the affordable SSL Alpha series of outboard processors, Solid State Logic can now be part of any studio's gear roster.
Image placeholder title

Solid State Logic — better known as SSL — has long been famous for state-of-the-art automated mixing boards priced far beyond the budget of the average EM reader. But with the introduction of the affordable Alpha series of outboard processors, the SSL brand can now be part of any studio's gear roster.

Image placeholder title

FIG. 1: The XLogic Alpha Channel fits several high-priced-mixing-board features, including a preamp, 3-band EQ, and A/D conversion, into a single-rackspace unit.

The XLogic Alpha Channel is a single-channel mic/line preamp with a number of distinctive features. In addition to a versatile 3-band EQ, the SSL pre offers output limiting, digital I/O, and a variety of insert and stereo-linking options. Although it is designed for use with DAWs, the Alpha Channel is fully compatible with analog recording applications.

Out in Front

The Alpha Channel's single-rackspace front panel is a straightforward affair, with a silver powder-coat metal panel, plain labeling, and color-coded plastic knobs (see Fig. 1). An illuminated plastic power button is located on the faceplate's extreme left. All the buttons are the same translucent, illuminating type, and glow white, green, red, or orange depending on their function.

Next to the power button is a combo XLR/unbalanced ¼-inch input jack. A series of four input buttons allow the selection of high-impedance input (1 kΩ disengaged, 10 kΩ engaged), -20 dB pad, 48V phantom power, and phase reverse. One very thoughtful innovation is a warning light built into the pad button; it flashes red to alert you when the input gain level reaches overload.

Also in the Input section, one red knob controls input gain (from +20 to +75 dB), and another controls SSL's unique Variable Harmonic Drive (VHD) feature, as found on the SSL Duality console. The VHD circuit colors the audio signal, initially by subtly boosting the proportion of second-order (aka even-order) harmonics. As you turn the VHD knob clockwise (you rockers will appreciate that this knob goes to 11), odd-order harmonics are added, contributing an edgier and more easily audible flavor of harmonic distortion.

The Insert section presents three buttons labeled In, Sum, and Post EQ. At first glance, these different insert modes are somewhat esoteric, but their functions are explained adequately in the multilingual manual. As with a mixing board, the Alpha Channel insert loop allows you to send the preamp signal to another audio device — typically a compressor or multi-effects box — and then return it to the preamp circuit for further processing or output to a recording device.

Engaging the In button sends and returns the insert audio signal before the EQ section. Selecting Post EQ places the insert point after the Alpha Channel's EQ module. Pressing the Sum button mixes the send and return signals internally, enabling such advanced uses as parallel compression processing and mixing in a second signal (such as a bass or guitar DI) when connected to the insert return jack.

EQ and I/O

EQ controls take up about half of the Alpha Channel's front panel. A highpass filter section has two buttons offering a -3 dB rolloff at 40 and 80 Hz; they can be simultaneously engaged to achieve a 120 Hz low cut. An EQ in/bypass switch is located in the middle of the panel. The EQ knobs are divided into three panel sections: LF (switchable low shelving, 40 to 600 Hz; bell curve option, 35 to 500 Hz; black knobs), MF (fully parametric midrange, 300 Hz to 5.2 kHz, green knobs), and HF (shelf only, 1.5 to 22 kHz, red knobs). The EQ gain pots offer cut-and-boost ranges of ±15 dB (low bell), ±17 dB (mid parametric), and ±19 dB (high and low shelf), and they're detented at the zero-gain center point.

Image placeholder title

FIG. 2: The Alpha Channel''s rear panel is basic, with analog audio and S/PDIF I/O and links to daisy-chain additional Alpha Channels.

On the faceplate's far right is the output-level adjust knob (±20 dB), a button to engage the Lite Limit output-limiting circuit, an LED indicator for digital input and analog-to-digital converter (ADC) lock, and a ladder-type LED output meter (-36, -24, -12, -6, -3, and 0 dBfs) that indicates gain before the unit's internal ADC. While there is no actual gain-reduction meter for the limiter, the Lite Limit button varies its color from green to orange to red as greater amounts of gain reduction are applied.

The Alpha Channel's rear panel is sparsely appointed (see Fig. 2). In addition to the standard IEC power connector, it has four RCA jacks (two for linking to other Alpha Channel units, and two for coaxial S/PDIF I/O) and three balanced ¼-inch TRS jacks for analog out and insert send and return. The S/PDIF sampling rate is set internally at 24-bit, 44.1 kHz, and can be changed only by the application of an external signal to the S/PDIF input. The Alpha Channel is not able to accept digital audio input, however, and the S/PDIF jack is for external clocking purposes only (from 44.1 to 192 kHz).

Guerrilla Sessions

I put the Alpha Channel through some rigorous real-world testing during a month of sessions at my Guerrilla Recording studio in Oakland, California. Throughout this period I did need the manual to clarify some digital-recording applications and illuminate the various functions of the insert modes. While the manual addressed most of these issues, it could provide more guidance for nonprofessional engineers on suggested setups and digital clocking issues. A tutorial of this type is available on the SSL Web site under Tips and Tricks (, although this feature has been newly launched at press time and is not clearly written.

The preamp's tonality was consistently pleasing and musical, with an exemplary clarity and detail that should please audiophiles and critical engineers alike. Compared with the solid-state preamps I regularly rely on, the Alpha Channel definitely imparts a bit of extra high-end sheen to most sources, but is rarely too bright and never lacking in tone or warmth.

With a Blue Bottle tube mic on a female vocalist, the SSL yielded a beautifully airy timbre. Acoustic guitar and bass were rich in harmonics and woody warmth, with a clear presence that helped these instruments stand out in a mix. A tambourine delivered immediate and realistic transients, with a crystal clarity that never got harsh through a Neumann TLM 103 condenser mic. Handclaps were also granted a rich sparkle on the same mic.

Recording several orchestral instruments on a session for the band P.A.F. gave me a unique opportunity to check out the SSL's performance in comparison to the highly regarded Grace 101 preamp. With a Royer R-122 ribbon mic on oboe, the Alpha Channel was excellent. The ample +75 dB input gain was a big help, with that quiet instrument miked at a distance of about three feet. Without resorting to added equalization, the SSL contributed some nice extra brightness on trumpet and trombone tracks.

However, on violin the Alpha Channel's high-end emphasis was too much, bringing a grating, sandy edge to a solo track recorded using the smooth R-122. Switching over to the Grace 101 preamp yielded a much more pleasing and listenable result. The SSL worked fine on cello with the relatively mellow-sounding Neumann KM 140 condenser mic, and it also performed well on bassoon with the same recording chain.

Classical clarinet sounded too dark with the Royer R-122—Grace 101 combination, whereas the SSL was just right in the high end. In periodic tests the EQ was always musical, and it was easy to hear the results at subtle settings.

Sparkling Performance

The Alpha Channel's Variable Harmonic Drive is an interesting and valuable feature that actually sounds good. I am always wary of enhancement circuits like this, which to my ear can sound grainy or overly colored as soon as the effect becomes audible. Although I tend to be cautious about using any kind of processing while tracking, setting the VHD about halfway gently enhanced most instruments, adding desirable tone and authority without distortion or excess coloration.

I was surprised to find that the VHD circuit had very little impact on a Hammond organ part, and its thickening effect on female vocals was pretty subtle. But it generally improved chordal guitar parts and was most useful on lower-register instruments.

Though not as versatile as the 4-band EQs on most mixing boards, the SSL EQ was transparent, easily audible, and a worthwhile tool all around. At narrow Q settings, filtering was very tight and surgical. On one session, I was able to effectively reduce the high whine of a digital guitar-harmonization pedal using the narrowest bandwidth without adversely affecting the rest of the frequency spectrum.

The Alpha Channel EQ was very transparent and sweet on a high-tech bass rig recorded with an AKG C 414 mic. In this application, the VHD control also worked very well to bring bass transients forward in the mix, adding punch and definition.

The Lite Limit feature is of course very handy for digital recording, as well as for taming the wide dynamic range of percussion, direct bass, and guitar. Under typical tracking conditions, I noticed no distortion or adverse brickwall-limiting effects when engaging this option.

When feeding a line-level input to the Alpha Channel from a CD player (with the input pad engaged), I was also impressed by the SSL limiter's transparency. Moderate limiting was not audible, and it was only when the input level was dangerously hot, with the Lite Limit button glowing a solid, fiery red, that compression artifacts became apparent. Nonetheless, even with the SSL's output meter lit continuously at 0 dBfs, the unit still demonstrated ample headroom.

A few features on the Alpha Channel took some getting used to. Having only a ¼-inch out really took me by surprise. This choice presents no compromise in audio quality, but it felt like SSL was cutting corners by not including an XLR out for convenience in connecting. And the combo input jack, though a nice space-saving feature, is inconvenient when switching between microphone and line-level or guitar DI inputs during a session.

In addition, it's a shame that SSL put a high-resolution A/D converter in the Alpha Channel but didn't make the converter easier to use by implementing a sampling-rate selector switch. Simple studio setups that are limited to a single digital device, such as a basic DAW interface with only one S/PDIF in and out, may find it cumbersome to clock the Alpha Channel externally at sampling rates other than the unit's 44.1 kHz.

Irrefutable Logic

Clearly, the SSL XLogic Alpha Channel is a piece of gear that doesn't pretend to be flat, either in frequency response or sonic personality. With its glossy high-end timbre, powerful EQ, and effective VHD circuit, this preamp offers superior solid-state sound and a number of exciting permutations for spicing up miked or line-level sources.

Despite the Alpha Channel's proven ability to deliver great sounds, I found a few areas in which it could have justified its price tag by delivering greater value and usefulness to the personal-studio owner: The connection options are limited for a professional device in this price range. Also, I was disappointed by the lack of a sampling-rate display or a sampling-rate selector switch, both of which are standard features on many lower-priced units aimed at project studios.

Limitations aside, the Alpha Channel's major attractions — the SSL preamp, onboard EQ, limiting, and VHD processing — work very well. These features place it solidly in the pro channel-strip category.

Myles Boisen is head engineer at Guerrilla Recording in Oakland, California. Find out more


XLogic Alpha Channel

microphone preamp



PROS: Quality mic/line preamp. Effective onboard EQ, insert, and limiting. Harmonic overdrive circuit. Input overload indicator. Phase inverter. Digital audio output.

CONS: Combo input jack requires repatching for mic or line input. No XLR output. No sampling-rate display or selector switch.


Solid State Logic (SSL)