Exactly three years ago we had the chance to test the Channel One, a channel strip from SPL. As you'd expect, the unit from Sound Performance Lab stood out not only in sound quality but also in construction, usability and price. This manufacturer is known for offering high-quality gear in which every detail is carefully looked after and which usually brings new ways of doing things.
In this regard, its best-known product may be the Transient Designer (a processor that lets you easily change a signal's attack and sustain), but SPL also has products such as the Vitalizer, Cabulator (soon to be reviewed in ISP), Charisma, MTC...
In these three years, SPL has expanded its product catalog considerably. Part of that expansion includes making 500 series chassis and modules. Another important area in which they've made progress is plugins, where they have a select group of processors, some of them digital emulations of their hardware processors.
As the manufacturer explains, they were eager to put all this research into a new product, and the result is the Frontliner: preamp, de-esser, compressor, equalizer, tape saturation and meters. Optional: Lundahl transformers on the input and/or output, and a digital converter.
This channel strip takes over from the Channel One and builds on its strengths to offer an even better unit...
Preamp
The preamp section uses hybrid solid-state/tube technology based on that of the well-known GoldMike MK2.
The first amplification stage is solid-state, followed by a second stage in which the signal is amplified again, this time with a tube. This duality lets you enjoy the characteristics of a 250 V tube circuit with the low noise and dynamic headroom of transistors (discrete; no integrated circuits are used).
The mic and line inputs are on XLR, and for instruments there's a TRS jack on the front.
In keeping with SPL's usual idea of making its gear as versatile as possible, the signal coming from the preamp section is available on an XLR output before it hits the rest of the voice channel's sections, which is useful, for example, for recording an unprocessed version or conveniently creating a send.
Mic input gain is set with a knob that offers a maximum of 55 dB of amplification. If the optional Lundahl transformer is installed, it not only adds that device's characteristic sound but also increases the available input gain by 14 dB.
When in use, the front instrument input overrides the rear line input, so both can be controlled with a single knob, which allows adjustments of +6 dB/+43 dB for the former and -20 dB/+10 dB for the latter.
The preamp section is rounded out by a high-pass filter (at 85 Hz, 6 dB per octave), the phantom power switch (48 V), a polarity inverter and a -20 dB pad.
The preamp sounds very good and certainly delivers a blend of tube warmth with the cleaner sound associated with solid-state preamps. Compared with other preamps in the same price range (and even some more expensive ones), the Frontliner provides a very balanced sound, with character but without excess. In fact, to provide that tube excess, the unit has a Tube +15dB switch, which drives the preamp's tube section more aggressively.
We won't name names but, on several occasions, the Frontliner was chosen over preamps that cost quite a bit more...
Dynamics
Although each section of the Frontliner can be used independently (see details below), the signal's next stop is the de-esser, based on the 1U "SPL De-Esser" processor.
True to the idea (inherited from the Channel One) that the unit should deliver good results quickly, the de-esser has only one control: amount of reduction.
The sibilant frequencies are selected automatically and, instead of compressing, the unit makes a copy of those frequencies and adds them back with inverted phase.
The processor uses a system called "Auto Threshold," which identifies the signal level and applies the desired reduction accordingly, rather than reducing when a certain threshold is exceeded. So all that's left is knowing when reduction is being applied, which is shown by an LED that lights up whenever the de-esser kicks in. The result is certainly very good, and it makes preventive control of the s's easy. As the manufacturer notes, the phase cancellation method allows the de-esser to operate very transparently, even when applying generous amounts of reduction.
Next, the compressor comes into play. One of the things missing from the Channel One's compressor was a bit more control over the parameters (you could only choose threshold and make-up gain). Although the time constants were well chosen and the compressor worked really well on vocals, it was a shame not to be able to adjust it further so it could be used more effectively on other instruments/applications. SPL seems to have been aware of this, and on the Frontliner they've included knobs for attack time (from 0.1 to 1000 milliseconds), release time (from 0.03 to 2 seconds) and compression ratio (from 1:1.2 to 1:infinity). These controls let you fine-tune the compressor down to the millimeter (or rather the millisecond), but the Frontliner also offers another very interesting feature, based on the Kultube, another SPL product: if you engage the Auto switch, the attack and release times are taken from their respective knobs but vary automatically around those values depending on the signal. This offers a very appealing mode of operation, since it lets you set the compressor manually and then the unit itself makes small dynamic adjustments that improve the response. Perhaps the label should read "semi-auto"?
Once the compressor was set, pressing Auto preserved the character achieved most of the time, and even improved it. Especially when we pushed it into somewhat "extreme" compression: pressing Auto kept the effect but removed some of the excesses that didn't sound good. After several days of use, the Frontliner's compressor proved very versatile, not only on vocals but also in other applications, where it stood out, for example, by (literally) crushing a mono drum overhead to get that typical "over-compressed" sound, or by adding roundness and punch to kicks and other percussive elements.
EQ and Saturation
The EQ section has three filters, two of which are semi-parametric:
The first is called LMF (Low/Medium Filter) and allows adjustments of +/- 12 dB, with an independent control for selecting the frequency (between 30 and 700 Hz).
The MHF (Medium/High Filter) is similar, except that the frequency range runs from 680 Hz to 15 kHz. Both use a variable Q system, which narrows the filter's bandwidth the greater the cut or boost.
The third filter, called the "Air Band," has a fixed frequency of 17.5 kHz and allows adjustments of +/- 10 dB.
As a whole, the EQ section is very musical, both the air band and the two semi-parametric bands. It's very easy to find boost points that sound good; even for cleanup tasks (subtractive EQ), where a narrower Q is usually used, the section proved useful.
Perhaps the only drawback is the lack of a semi-parametric high-pass filter. There is a fixed high-pass (the one at the unit's input), but it would be perfect if the cutoff frequency could be adjusted. And, while we're at it, if the two semi-parametric bands were fully parametric. As mentioned, the Q of these filters is very musical, but for some applications a narrower Q wouldn't hurt.
As is common in this type of channel, a button lets you place the EQ section before the compressor.
The last section the signal encounters (even if the EQ is placed before the compressor) is the saturation stage. This stage is independent of the "Tube +15dB" option on the input and, in fact, its purpose is different, since it's designed to emulate tape saturation.
A knob controls the amount of signal (from 0 to 100%) sent to this section, to add the harmonics typically associated with tape running into saturation (usually a denser, more powerful sound). As with every section of the Frontliner, the tape saturation proved very useful and well calibrated, since it allowed everything from subtle doses of saturation to much more obvious effects. It's especially useful on somewhat weak vocals (or other instruments), since it gave them body and brought them forward in the mix.
Meters, buttons and other options
Every section (de-esser, compressor, EQ/saturation) has its own switch to engage or bypass it and easily check the effect it adds.
The metering section offers a VU meter showing the signal at the unit's output. It's calibrated from -20 dB to +5 dB, although a switch lets you change the sensitivity to -10/+15 dB to measure hotter signals.
In addition, the meter can show VU (average) or PPM (peak) levels, and it can also measure the amount of gain reduction applied by the compressor, so you can set the amount of make-up gain accordingly.
Finally, the Output control (-20 dB / 0 dB / +5.5 dB) sets the output level (to other gear or to the optional AD converter), and a MUTE button silences the Frontliner's output while the rest of the controls remain active, which is very useful for calibrating the levels of the different sections without sending sudden level changes to the monitors.
The AD 2376 card is installed at the back of the unit (users can do this themselves) and lets you sample the signal at a bit depth of 24 bits, at rates of up to 96 kHz.
The signal is provided as S/P-DIF (professional), on both an RCA connector and a Toslink (optical) connection. A second RCA connector lets you sync the converter with the DAW you're using so the sample rate is selected automatically (this connector does not accept Word Clock input).
To take advantage of the S/P-DIF's second channel, a TRS connector on the back sends the line signal from another piece of gear to the AD card.
Finally, the Frontliner can also be fitted with transformers on both the input and output (unlike the AD card, the transformers must be installed at the factory; users can't do it themselves).
Analog Plugins
So far, the Frontliner comes across as a very useful voice channel in which every section is functional and musical, on both vocals and other instruments. That in itself is worth highlighting, since not every stage of a voice channel is always so good. However, as we said at the beginning of the article, SPL always likes to go a little further, and the Frontliner was no exception.
A very notable feature of this unit is that each section has its own input and output, so they can be used independently. In other words, you can use the preamp for one signal while applying the de-esser to another, compressing the kick and equalizing the acoustic... A concept the manufacturer wants seen as having Analog Plugins at your disposal.
On the back there are XLR inputs and outputs for each "analog plugin." A set of buttons lets you include them in or remove them from the main channel. These buttons also let you group the different sections together, exclude or include them as a block, etc. The order of the processors can't be changed within the unit (except for EQ pre/post compressor), but if you connect all the inputs and outputs to a patch bay, that wouldn't be a problem. In fact, SPL's idea is for the Frontliner to have all its inputs and outputs connected to a patch bay, so you "have several units in one."
Conclusions
The preamp sounds very good and lets you go from the cleanest sound to nice tube effects. The improvements over the Channel One are significant, both in the sound of the various sections and in terms of the compressor's features.
It's common for channel strips to offer lots of processing options, but it's also common for not all of them to be equally good; usually one of them is weaker. That's not the case with the Frontliner: every section is really good and versatile. The connection possibilities are very extensive and make the whole much greater than the sum of its parts.
Considering this unit's quality, options and price, it's an option well worth considering.
Technical specifications
If you're thinking of getting one, here are some details:
INPUTS and OUTPUTS:
Mic input: XLR
Line input: XLR
Instrument input: TRS
De-esser input: XLR
Compressor input: XLR
EQ/saturation input: XLR
Preamp output: XLR
De-esser output: XLR
Compressor output: XLR
EQ/saturation output: XLR
Main output: XLR
LEVELS:
Maximum output level: 21.5 dBu
Mic input gain: +13 dB / +68 dB
Line input gain: -20 dB / +10 dB
Instrument input gain: +6 dB / +43 dB
FREQUENCY RESPONSE / THD (1 kHz, 0 dBu):
Channel strip: 10 Hz – 50 kHz / 0.03%
Mic preamp: 10 Hz – 50 kHz / 0.03%
Line preamp: 10 Hz – 50 kHz / 0.03%
Instrument preamp: 10 Hz – 50 kHz / 0.03%
De-esser: 10 Hz – 140 kHz / 0.002%
Compressor: 10 Hz – 180 kHz / 0.007%
Equalizer: 10 Hz – 60 kHz / 0.01%
COMPRESSOR:
Attack time: 0.1 to 1000 ms
Release time: 0.03 to 2 s
Ratio: 1:1.2 to 1:infinity
Make-up gain: 0 dB – 20 dB
EQUALIZER:
LMF: Semi-parametric. +/- 12 dB at 30-700 Hz
HMF: Semi-parametric. +/- 12 dB at 680-15 kHz
Air Band: Bell centered at 17.5 kHz. +/- 10 dB
DIMENSIONS: 482 x 88 x 261 mm (2U)
WEIGHT: 5.7 kg
