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SSL Alpha Channel

Channel Strip
Published March 2007
By Paul White

SSL Alpha Channel

In the last few years, Solid State Logic have been concentrating a lot of effort on the project studio market, and the new Alpha Channel makes their high-end console technology available in an affordable rackmounting channel strip.

Once associated only with stratospherically-priced professional mixing consoles, Solid State Logic are perhaps one of the most successful recent examples of an audio company reinventing itself. The big consoles are still there, of course, but the company now have a strong presence in the project-studio market, with products such as the Duende and numerous rackmount spin-offs from their analogue consoles.

Design & Construction

The new Alpha Channel is a fairly traditionally set-out channel strip, comprising a mic/line/instrument front end with a three-band console-style equaliser, all packed in a stylish 1U rack case. The EQ is, in essence, a mono version of the three-band EQ used in the stereo channels on the G-series console, while the preamp is a slightly modified version of the VHD mic pre from the E-series Signature Channel.

At the end of the signal chain is what SSL refer to as a Lite Limiter, adjusted by means of a single control. A single Neutrik Combi connector handles the input options (unbalanced jack with 1MΩ impedance, or balanced XLR) while the analogue output is on a balanced jack rather than the more usual XLR, which makes it simpler to connect to a patchbay or typical audio interface. An analogue insert point is also furnished on a pair of quarter-inch jacks, and a couple of RCA phono sockets allow two units to be linked for precise stereo tracking. Both the send and main outputs have a low (40Ω) impedance, ensuring that the unit will be comfortable with any load and also capable of driving long cable lengths where necessary.

Two further RCA phono connectors handle S/PDIF in and out, so this unit can be used to feed a relatively inexpensive soundcard (provided, of course, that it has an S/PDIF input) and the recorded result won't be compromised by budget converters. By default, the Alpha Channel's internal clock runs at 44.1kHz, with a 24-bit converter resolution. Any clocking has to be done via the digital input, as there is no separate word clock input, and some users may question this design feature. However, if sync'ed to an external digital source, the unit will operate at sample rates in excess of 96kHz (32Khz to 108kHz).

SSL Alpha ChannelAll 13 front-panel buttons are illuminated and are clearly labelled, although under normal studio lighting, the button lights are rather bright and may actually prevent you seeing the legending properly. The power button glows dimly if the unit is in standby mode and more brightly when it is powered up and running. In keeping with convention, the input socket is on the left of the panel and is accompanied by switches for Hi-Z (1kΩ or 10kΩ to match different mic types), a 20dB pad, 48V phantom power and phase. Next to the single gain control is a second knob to set the amount of harmonic distortion added to the signal. Initially this adds mainly second harmonics but, as the setting is increased, these are joined by third harmonics in much the same way as you'd expect from a tube circuit. The gain doesn't change as you adjust the harmonic control, so it is easy to judge its effect, which is reassuringly subtle and similar in character to tube mic warmth.

The insert point can be bypassed from the front panel and is also switchable pre- or post-equaliser. A third button, Sum, mixes the send with the return, so you could patch in an effects unit here and add the effect to the direct dry sound, controlling the effect level on the external unit. In addition to the EQ, there's a low-cut (high-pass) filter operated by two buttons, their various combinations offering bypass, 40Hz, 80Hz, or — when both are pressed — 120Hz roll-off frequencies. To the immediate right is the EQ bypass button, followed by the EQ controls, which are set out very much in the style of an SSL console strip. At the low end, the filter may be switched from Bell (band-pass) to the more conventional high-pass. Here, the frequency range is variable from 40Hz to 600Hz, with a gain range that appears to be ±15dB, though this detail is omitted from the technical specifications. For the mid range, which is fully parametric, there are the usual three controls to set frequency, bandwidth and gain, and the frequency range is 300Hz to 5kHz. There is only a single mid-frequency band, and I'd really prefer its range to extend down another octave, as there are often boxy artifacts in the 150 to 250 Hz range. There's no shortage of range on the shelving high control, though, as the frequency range is from 1.5kHz to 22kHz, again with plenty of gain range available. Checking the sound with the EQ set flat and in circuit and then comparing it with bypass revealed no audible difference, which is always a good sign.

The rear panel of the Alpha Channel includes sockets for inserts and balanced analogue out, as well as S/PDIF digital in and out.The rear panel of the Alpha Channel includes sockets for inserts and balanced analogue out, as well as S/PDIF digital in and out.

That leaves the Lite Limiter, so called because it provides subtle limiting prior to the ADC. It is worth noting that, when the insert point is switched in, the pre-insert send level is reduced by 12dB to maintain adequate headroom if the insert point is active, which is useful in the event of the external device adding significant gain. Normally, the limiter button lights up green, but it changes to orange and then to red when the limiter is applying gain reduction. Again, there's no real description of exactly how this limiter works, but it appears to be progressive, with a soft-clip-type character that responds in a manner not unlike tape saturation. It is, subjectively, relatively benign, as long as it is used only as a safety net to catch unexpected peaks.

To the right of the limiter is a simple six-LED level meter and a status lock to confirm that the ADC is locked when a digital source is being used as clock master.


There are dozens of worthy channel strips; comparing the Alpha Channel to other solid-state designs, it's less costly than a Neve 1084 and closer to a Rupert Neve Designs Portico 5032 and Chandler TG Channel in price, but is a little different in concept from either. The Trident S40 also includes a classic preamp with console-style EQ, and may be a suitable alternative.

Studio Test

Tested with a large-diaphragm vocal mic, the audio path was clean and solid-sounding with the harmonic control adding just a hint of lower-mid warmth and thickness without sounding overdone. How the EQ section performs is, of course, very important in a product of this type, and this was smooth, musical and hard to abuse. When I dialled in more high end, I got breath and sizzle without harshness, while bringing up the low end added weight without making the whole thing sound flabby. The mid control was also very gentle and musical, to the extent that I found myself wishing it was a bit more assertive in cut mode. In boost mode it sounded more musical than most parametric EQs I've tried, even at the higher Q (narrower bandwidth) settings. The lack of any frequency calibrations, other than at the extreme of the controls, was a bit irritating, as was the omission of the cut/boost range, and I would have liked that mid range to go down to 150Hz or so. But I can't argue with the sound: this is an EQ that will allow you to polish your sound rather than simply chisel lumps out of it! I particularly liked the option of switching the low band to shelving or bell mode, as bell mode is often more appropriate for tweaking bass instruments and kick drums.

Having an on-board limiter standing guard before the converter input felt reassuring, and the designers have managed to give this a soft characteristic, so it deals with most peaks in a smooth and largely invisible way — and although it made its presence known if I hit it hard and often, that's not what a safety limiter is for. I found no solid technical details relating to the type of converters used but, again, the quality seems good, with no obvious difference between the sound after digitisation and the original analogue version. The only possible issue is the fixed 44.1kHz internal clock that I mentioned earlier.


What it all boils down to is that, if you tend to record most of your tracks one at a time, the Alpha Channel provides you with the sound and the core facilities of an SSL console without you having to buy the whole thing. I really liked the gentle EQ and the clean audio path and, given what's on offer, the price is pretty attractive too. 

Published March 2007