SPL Channel One Mk3

With a Transient Designer, a de‑esser and an unusually versatile input section, there’s more to SPL’s recording channel than most.

Sound Performance Lab (SPL) have been making high‑quality audio gear since 1983. They first made a name for themselves with their Vitalizer, but it’s probably their next innovation, the Transient Designer — the first dynamics processor that didn’t rely for detection on the input signal crossing a level threshold — for which they’re now best known. Now, SPL’s pro audio range includes everything from preamps, channel strips, audio interfaces and mixing desks to mastering gear, monitor controllers and high‑quality headphone amps, and with the last of those they also cater for the hi‑fi market.

For review here is the third iteration of their Channel One. Like its predecessors, this analogue recording channel comes in a vented 2U 19‑inch rackmount chassis, but while it borrows plenty from the Mk2 version, this is a significant redesign that goes much deeper than the darker and, to my eye anyway, more impressive and easier to read front panel. The most notable changes to the feature set include a revamped preamp section, and this is now joined by a dedicated valve‑based saturation processor. The MkII’s headphone monitoring facilities have been dropped too and although this was a high‑quality feature, it’s one that I suspect many users will have found superfluous. More than compensating for that is the inclusion of a Transient Designer, which should increase this device’s appeal and versatility significantly. The de‑esser, EQ and compressor sections seem largely unchanged, but the metering has been rethought: the previous version had LED meters for gain reduction and output level, whereas we now have a large moving‑coil meter that can be switched to show gain reduction, input level or output level. A switch sets this meter’s 0VU position to correspond to output levels of +6, +12 or +18 dBu (that’s the only means of user calibration). What’s less obvious from the pictures is that SPL have opted for beefier power rails (±18V), and that the build quality on the inside is impeccable, with traditional through‑hole components used throughout.

Ins, Outs & Amplification

At the start of every channel strip comes the preamp, and this one is more versatile than most. There are actually two versions of this device: the regular one is electronically balanced, while the presence of Lundahl input and output transformers differentiate the Channel One Mk3 Premium. The mic amp is a discrete solid‑date design, but it’s joined by a separate valve saturation processor. So, between the main gain control knob (9‑68 dB for the mic inputs, and continuously variable) and the Saturation knob (turning this first switches in this circuit, then over 30 detented positions take you up to 100%), you can already access a range of sonic characters.

There’s particularly generous flexibility when it comes to the inputs. On the back are two separate mic inputs (unusual for a mono device), and a dedicated line input, all on XLRs, while on the front there’s a high‑impedance TS instrument input, which takes precedence over the line input when a jack is inserted. A toggle switch selects the source (Mic A, Mic B, Line/Inst), while separate switches for each mic input engage +48V phantom power. Three more switches operate a 20dB pad, a polarity inverter and a fixed 80Hz 6dB/oct high‑pass filter. Though not indicated (that would have made the panel crowded) the gain range for line signals is ‑20 to +16 dB, and for instruments ‑6 to +30 dB. And if you have the input transformer option that adds a chunky 14dB to the values on the scale.

Unusually, the Channel One Mk3 has two separate mic inputs for the same preamp, as well as a preamp direct out and two paralleled main outputs.

With the dual mic inputs and the saturation effect now being independent of the preamp gain, it’s easy to compare the sound of two different mics (even if you must set the gain for each when you switch). I imagine the input setup could also appeal to the songwriter who regularly records two or three sources one at a time: you could have your go‑to vocal and acoustic guitar mics plugged into the mic inputs, an amp modeller plugged into the line input, and patch a bass in the front whenever required: flip a switch, set the gain and you’re ready to roll. No repatching required!

On the back, a preamp direct output is joined by two main outputs — the latter are identical, running in parallel — and all are XLRs. So you could, for instance, capture a clean signal from the Channel One when recording, and then return a line‑level signal to the unit for mixdown processing. Or, since the preamp output is active at all times, you could record a clean signal as a backup and have the confidence to try more assertive processing. Or perhaps you want to capture a clean signal but use a processed one for a live‑streamed broadcast. Or maybe you’d like both a clean and processed version for parallel processing... there’s lots of potential. Also on the back, are a ground‑lift button, a power switch, a voltage selector and an IEC power inlet. (Sadly there’s no global power on/off on the front; it’s now rare that I want everything in my rack on at once.)

The valve circuit features automatic level compensation, and this proved so useful.

One For All

The valve saturation stage, based around a 12AX7 valve, is separate from the preamp and gives you plenty of control over the amount of distortion.As I said above, the Channel One Mk3 has plenty of processing options and each section on the strip, other than the preamp, has its own engage/bypass button. The valve saturation circuit is based around a Sovtek 12AX7LPS valve with a 250V anode supply and this is, by default, the next stage after the preamp, hence its position on the front panel. But a button (blue when engaged) beneath the VU meter can move it post‑EQ (and pre the output stage). The valve circuit features automatic level compensation, and this proved so useful — the levels only start to creep up at extreme drive settings, and only by 6dB. The saturation sound can be beautiful, as you’d expect with a real valve, with subtle thickening distortion at the lower end of its range, and a pleasing ‘flair’ and ‘crunch’ when driven hard.

Next comes the de‑esser. This has low (centre frequency 6.4kHz, bandwidth 4.4kHz) and high (11.2kHz and a bandwidth of 5.5kHz) buttons that illuminate yellow when engaged, and both can be active simultaneously. An S‑Reduction knob sets the amount of de‑essing from ‑0.5 to ‑12 dB, and ess detection (rather than the de‑essing activity itself) is indicated by a single LED in the metering section.

SPL’s famous Transient Designer section follows this on the faceplate and in the default signal path, and the controls comprise just an on/off button and two pots, each with centre detents for the neutral position. Attack can boost/cut transients by ±15dB, while the Sustain range is ±24dB. As with all SPL Transient Designers I’ve used over the years, this works very well, and I’ve loved having this sort of control on an all‑purpose recording channel: it allows you to manipulate the character of anything with a percussive element (be it a drum, or the plucking or hammering of a string) in a way threshold‑based processors cannot.

More than most channel strips: as well as the preamp, compressor and EQ, the Channel One Mk3 features a de‑esser and a Transient Designer.

From here the signal enters the compressor, a low‑noise and low‑distortion dual‑VCA circuit based around THAT 2181B ICs. This has only two control knobs. One, labelled Compression, is a threshold control that can be set from 0 to ‑20 dB, while Make‑Up Gain can be set from 0‑20 dB. You can’t chance the time constants, so it wouldn’t be my first choice for drums and percussion and I wouldn’t recommend going overboard with this while tracking, but used sensibly on vocals and dialogue it sounded as smooth and unobtrusive as you might hope for in a recording channel.

The three‑band EQ is the last processor in the default chain and on the panel, but it can be switched to come before the Transient Designer. The broad LMF bell band can be set anywhere from 30 to 700 Hz, while the MHF band, another bell, spans 680Hz to 15kHz. Both offer ±12dB of gain through centre‑detented pots, while the frequency selectors are detented throughout to aid recall. The Air band is described as a coil‑capacitor bell. This has a fixed centre frequency (19kHz) and offers ±10dB of gain, and as with all so‑called Air bands, the extremes of this EQ curve reach well down into more easily audible parts of the spectrum. It enables you to subtly lift (or reduce) the sense of air or breathiness without things becoming too harsh (depending on the source, of course!). I found that it can be helpful in taming the brightness of some cheaper capacitor mics too.

After the EQ there’s an output level control, a pot and that runs from +6 to ‑20 dB, and a mute button, which does what you’d expect but also deactivates the meter. Finally, there’s a single overload LED in the centre section — this lights up when an overload is detected at any point in the signal chain, not just the preamp or the output, which is a nice, thoughtful touch.

Every processing section can be switched in/out, and the EQ and valve stages can be moved to different positions in the signal path.

One Love?

A lot of brands now jostle for attention in the channel strip market. Curiously, I don’t see so many opinions online about SPL as I do of many competitors — and really we should, because everything of theirs I’ve used has been good, classy‑sounding gear, and the Channel One Mk3 not only continues that tradition but I’d say it’s an improvement on what’s gone before. Not only does it sound great to my ears, but there are real innovations here that give it capability not found (at least to my knowledge) in any other single device else. The ability to compare mics so easily makes it an outstanding candidate for anyone wanting a single, do‑it‑all channel strip, while having the preamp direct output available at the same time as two processed ones, and the ability to switch any stage in/out of the signal path and move some around, makes it yet more versatile.

So I’d use the Channel One Mk3 as a main vocal strip without hesitation. The clarity of the preamp and the controllable saturation really lend themselves to that, and the de‑esser is a real plus — not many channel strips have this, and particularly when boosting higher frequencies with EQ, as is fashionable, they can be really helpful. The only real ‘weakness’ (if, indeed, it can be called that) is the compressor, as there will be some who crave more control. But it sounds good, plenty of people will enjoy the speed and simplicity of this ‘two‑knob’ approach, and because it comes at the end of the chain, you could easily use a standalone one (or plug‑ins).

This is by no means just a vocal channel, though, and not least because of that Transient Designer, which is a great bonus. Yes, there are plenty of transient shaping plug‑ins now, including SPL’s own, but while some offer more control I’ve yet to hear one that sounds as ‘forgiving’ as the analogue hardware versions, especially when a significant transient boost is called for. Combining the Transient Designer, tube saturation and compression can do wonderfully explosive things to drum sounds, whether kit pieces or, say, a room mic, although you do need to remember that this is a mono device and there isn’t a way to stereo‑link two units. What’s more, you can control the result of such carnage using the EQ section and, to an extent, the de‑esser too. Alternatively, you can deploy the Transient Designer much more conservatively. For example, I had great success using it to balance the pick and sustain on a fingerpicked acoustic guitar, before compression.

In short, there’s not much here to dislike, and plenty to like. The preamp sounds clean and detailed, and it offers plenty of gain. There’s real valve ‘colour’ on tap, and there are more processing and output options than on pretty much any channel strip of comparable quality or price. So if you’re looking for a single ‘do it all’ channel strip, this one deserves serious consideration.

Information

Channel One Mk3 £2199. Channel One Mk3 Premium £2499. Prices include VAT.

SCV Distribution +44 (0)330 122 2500.

sales@scvdistribution.co.uk

www.scvdistribution.co.uk

spl.audio

Channel One Mk3 $2199. Channel One Mk3 Premium $2487.

spl.audio