Review: SSL XLogic Alpha Channel & XLogic Alpha VHD
Installing an SSL once involved stopping traffic, cranes, high stress and all hands on deck! Oh, how times have changed.
26 August 2007
Review: Robin Gist
The great thing about having been around for a while as a top-end audio manufacturer is that you accumulate lots of intellectual property in the form of proprietary circuits and industrial designs. And as any good businessperson will tell you, you need to capitalise on your ‘IP’ in as many different ways as possible. To this end we’ve seen companies like Neve, API, Chandler/EMI – and in this case, SSL – release ‘real’ and ‘virtual’ recreations of old devices in recent years, as well as new products that use the prestige and heritage of the company name to get a leg up in the very competitive pro audio market.
The XLogic Alpha Channel and XLogic Alpha VHD Pre from the Solid State Logic camp are two such products that borrow circuit elements from both the ‘G’ and the newest ‘Duality’ series large format consoles that aim to give ‘prosumers’ a touch of that SSL sheen!
Both these single unit rack-mountable devices are built in Old Blighty utilising a single printed circuit board approach with sealed power supplies. The Alpha Channel is intended as an all-in-one digital audio workstation front-end solution, incorporating a mic preamp with variable harmonic drive (VHD), a low-frequency roll-off section, a cut down G-series EQ section, a limiter, an analogue-to-digital converter and some flexible routing options via a switchable insert/sum point, but more on this later.
ALL FOUR SSL
The VHD Pre consists of four separate mic preamps each with input and output gain controls, rear-mounted XLR connectors, a VHD control, a 48V phantom power switch, a pad switch that doubles as an input level indicator using the ‘traffic light’ metering scheme, a Hi-Z switch and a front panel instrument input. Strangely, there are no phase inversion switches, which is a real oversight in my opinion. The Alpha Channel, which has an identical mic pre section, except for the combo instrument/XLR input connector, has a phase inversion switch! So why not the four-channel preamp? When I enquired as to why this was the case, the response was that users could easily flip the phase using their DAW software later, and that there wasn’t enough real estate on the front panel to accommodate these switches!
This forces you, when using the VHD Pre in a multi-mic tracking situation, to monitor through your software and possibly put up with latency and all its attendant problems. For the few extra dollars it would have cost to include phase inversion switching, SSL has really missed the boat on this because we all know the importance of relative phase in a multi mic setup – right?
SSL-AC
One further gripe is the power supply connector on the VHD Pre. The Alpha Channel uses a standard IEC power lead but in the case of the VHD Pre, the supply is external to the unit and is connected via a plastic thinly-covered five-pin DIN plug. I’m told we will see a lot more of this style of connector in the future, but I think it’s a case of power connector devolution. DIN plugs make very poor power connectors and are currently used as MIDI connectors – could not some newbie try and power their VHD Pre with SySex data?! Probably not – but they are certainly not professional power connectors!
SSSOUND
So what do the preamps sound like? Well, the preamps themselves have plenty of headroom, providing a clean and open sound (with the VHD control set to zero) providing up to 76dB of mic and 82dB of instrument gain. As I mentioned before, these units have their roots in other SSL products and in the case of the mic pres, the VHD circuit can be found on the current Duality series console (which has replaced the ‘K’ series as SSL’s new flagship large format console). It is this feature that can give your sound some subtle SSL character.
The ‘Variable Harmonic Distortion’ control works by increasing second and third order harmonic distortion with increasing input level – the harder you drive the preamp and the more you increase the VHD control the more harmonic distortion you get. Using the VHD control will also increase gain up to an extra 6dB depending on how much of it you use. I liked the sound of the VHD as it added fullness and warmth to lower frequencies and impact and a distinctive edge to percussive sounds. The VHD control is nevertheless something that should be used judiciously (or perhaps even applied later to source material – or a whole mix – as an alternative to dialling it in during the tracking stage). After all, the distortion artefacts the VHD circuit adds to a recording cannot be undone later.
SSL-EEK Q
The ‘cut down G-series EQ’ in the Alpha Channel (as it’s described in SSL literature) is a three-band ‘semi-parametric’ design offering up to 19dB of boost or cut. With a low frequency section ranging from 30–300Hz in shelf mode, changing to 35–500Hz in switchable bell mode, a variable-Q mid section from 300Hz to 5.2kHz and a shelving high frequency section from 1.5kHz to 22kHz. This EQ is very versatile and useful. However, one problem I do have with the EQ, is that apart from the extremities of the controls, there are no frequency markings, which I really dislike and think could be addressed. I particularly liked the sound of the LF section, using it with great effect to beef up an electric bass guitar recording. The whole EQ section can be globally switched in and out of the circuit, and there are also two LF roll-off switches prior to the EQ section at 40 and 80Hz. When both are on, you get a combined roll off at – you guessed it – 120Hz.
NEED TO KNOW
ALPHA SPECS
For those of you who like your specifications in detail, there are equivalent input noise (EIN) figures, electrical and mechanical specifications and other useful bits of information on the Alpha Channel at: www.solid-state-logic.com/music/xlogic_achannel_specs.html
I could not find the same specific electrical information for the VHD Mic Pre (to compare the mic pres in the two units) but I hope I’m safe in assuming the preamp specs would the identical. In the ‘unusual specifications’ department – and one for all you high-flying sound engineers out there – both units are operational to an altitude of 3000m above sea level and non-operationally to an altitude of 12,000m – I’m sure it’s useful to know what heights your non-working gear can reach! But what about the depths?
SSL-OUT
The output section of the Alpha Channel consists of a ±20dB output level control, a ‘Lite’ (with a light!) Limit switch and an LED output meter. The limiter works at a threshold of 6dB below the 0dB clipping point on the output meter. Like the pad switch, the Lite Limit switch also works as a meter in ‘traffic light’ mode, showing when and how the limiter is working, and by cranking up the output you can make the limiter work even harder for that specially limited sound. But when used in a more conventional manner the limiter functions well, stopping sudden peaks that could cause clipping, and is sonically quite transparent. A control to vary the threshold of the limiter would have been nice but I guess you can’t have it all. The output feeds both the balanced TRS analogue output and the left hand side of the RCA S/PDIF connector, which defaults to a clock rate of 44.1k. The right hand side of the S/PDIF output is pre the insert, the EQ and the Lite limiter. It is also 12dB down compared to the signal on the left, to prevent the A/D converter clipping, but also allowing for the recording of two separate, digitally fed mono tracks into a DAW with one being an un-EQ’d, unlimited ‘safety version’ of the other, which is a great idea. The SSL-designed converter will accept external clocking via the S/PDIF input connector at a range of rates from 32 to 108k. I don’t know why the designers didn’t increase their target market with a 192k clocking option but, again, its absence is probably another one of those pesky fiscally-based corporate decisions.
SUMMED UP
Although physically placed immediately after the mic pre section of the Alpha Channel, I wanted to cover the insert and sum section last as it offers some interesting routing options for DAW users. The insert send can be used to feed a channel on a desk (and, subsequently, headphones) for zero-latency monitoring, while the analogue output simultaneously feeds the input to the DAW for recording with or without EQ or Lite limiting. The digital output can be used also in a dual-mono track mode for recording processed and unprocessed audio as described above. Additionally, using the send and return on the insert allows you to include your favourite compressor or processor into the chain – nice. The manual also usefully advises using the insert return to combine the output of a DI and a miked signal to get a blended sound of an amplified instrument, e.g. a bass or electric guitar. The DI signal can be left un-EQ’d by the Alpha Channel if the insert ‘post-EQ’ switch is on while the miked signal retains the Alpha Channel EQ and/or the limiting if so desired. Two Alpha Channels can be linked using the ‘link’ RCA connectors on the rear of the unit. When these connections are made, the Lite limiters are side-chained and, according to the manual, the units will then retain a stable stereo image (unfortunately I couldn’t test this assertion since I only had one unit).
AM I SSSOLD?
The Alpha Channel is very flexible in its I/O, processing and routing options, giving users multiple tracking choices either through analogue and/or digital connectivity. The Alpha Channel sounds very good and the EQ certainly has that SSL quality to it. The unit meets the ‘all-in-one DAW front-end solution’ criterion and would ably suit anyone looking to add some SSL gloss to their recordings. The tonal character of the VHD in the VHD Pre is subtler than that of the EQ in the Alpha Channel and as such, will make you feel less like you’ve bought a slice of that SSL signature sound. But if you’re looking for four channels of clean-sounding preamplification with plenty of gain and headroom, and the added ability to wind in some harmonic distortion, then the VHD Pre could be just what you’ve been looking for.
RESPONSES