Gainlab Audio GLA-OC1 Governor

This clever dual‑channel, dual‑slope optical compressor is different from the rest...

Budapest‑based Gainlab Audio are no strangers to the pages of SOS, and the company’s last release, the Bishop channel strip, greatly impressed Matt Houghton in our SOS April 2024 issue. That impressive valve‑based, mono mic/line/instrument preamplifier featured a unique Teletronix LA‑2A‑influenced optical compressor that, interestingly, featured a ‘dual‑slope’, and Matt found it to be both intuitive to operate and capable of delivering a great‑sounding performance. He wasn’t the only user or reviewer to come to that conclusion, so it’s perhaps not surprising that Gainlab decided to created a standalone version of the Bishop’s compressor. The result is the Governor, a dual‑channel optical compressor with valve amplification and an enhanced suite of controls, features and facilities.

Grand Tour

Gainlab’s Governor sits in a 2U, 19‑inch rackmount chassis and is capable of stereo or dual‑mono operation. To make that possible, there are two identical control sets, laid out in horizontal strips that are divided, both visually and functionally, into three sections. The leftmost section of each channel begins with two three‑position metal toggle switches, the first of which selects the compression type (Soft, Medium or Hard) and the second its Tube (valve) Boost frequency profile (Full, Off or Air). As with all the Governor’s toggle switches, yellow LEDs light to indicate the active selection. Sitting next to these is a line of three rotary controls. The first two of these set the thresholds for the dual compression slopes, about which more later. These controls are continuously variable and range from High to Low, with lines to aid setting recall but no other values shown. The third rotary control turns an 11‑position output gain switch, which ranges from 0‑22 dB.

Nestling between the four threshold controls is a Link Off switch, its position reflecting the fact that it affects both channels. This toggles the Governor between stereo and dual‑mono modes: when linked, the lower channel is controlled by the upper control set, with the exception of the side‑chain filter frequency and output level selection, which must be set manually.

The centre section’s black background makes the two channels’ trio of horizontal meters easy to see. Within each trio, the upper two meters (GR1 and GR2) each show the amount of gain reduction (0 to 12 dB) being applied by one of the two slopes, whilst the third displays the output level (‑20 to +20 dBu) with a VU‑like ballistic and includes a true peak hold indicator. To the right of the meters is a pair of rotary switches that set each channel’s side‑chain high‑pass filter (off, 40, 70, 180 or 250 Hz) or select an external side‑chain signal, which is connected using the dedicated quarter‑inch jack inputs on the rear.

The metering shows both the output level and the gain reduction being delivered by each slope.

The right‑hand section carries, for each channel, a compressor in/bypass toggle switch and the two six‑position rotary switches that are used to select the attack and release times. The attack times are named rather than numbered, with a programme‑dependent Auto setting followed by Fastest, Faster, Fast, Slow and Slowest, but the timings are given in the manual (6, 8, 10, 15 and 40 ms respectively). There’s no auto setting for the release, and this allows an additional Slower position to be inserted, giving you a choice of 80, 100, 200, 450, 600 and 750 ms. A final control is one that’s always good to see on a front panel these days: the power on/off toggle switch.

Each channel has an electronically balanced input and a transformer‑balanced output, these being presented on XLR connectors on the rear along with the side‑chain input jacks, a ground‑lift switch and a fused and switched IEC mains power inlet that can accept 110 or 230 Volts AC.

There’s a quarter‑inch jack side‑chain input for each channel, and this can be selected using a control on the front.

Internally, the Governor displays a very high quality of design, construction and attention to detail, and the compressor circuitry occupies three PCBs that sit behind the Governor’s front panel. After the toroidal mains transformer in its screening enclosure, the largest components on display are the channels’ twin‑triode ECC88 valve pairs and Gainlab’s proprietary GLA‑AT3 output transformers. The unit’s stated specifications are just as impressive, with a ±0.5dB frequency response of 20Hz‑20kHz, THD at 0.04% (1kHz, 0dBu) and 0.32% (1kHz, +20dBu), maximum input and output levels of +26dBu and +28dBu, respectively, and a signal‑to‑noise ratio of 105dB (+23dBu, <1%THD).

Dual‑slope Compression

Each channel on the Governor delivers gain reduction based on two compression slopes, and the nature of these slopes depends on the compressor type you’ve selected using the toggle switches on the left of the front panel. A ‘compression slope’ defines the amount by which an audio signal will be compressed once it exceeds the threshold level — so you might think of these as slopes as ratio presets. (A ‘compression curve’, on the other hand, is created by the interaction between the threshold setting, the knee, the compression ratio, and the attack and release times.)

It’s a clever system that gives you a similar degree of control to using two compressors arranged in series, but there’s actually only a single gain reduction element (per channel) acting on the signal. In the side‑chain circuitry, Slope 1 precedes Slope 2, which means that Slope 2 acts on the output of Slope 1’s curve, rather than directly on the gain‑reduction stage’s feedback signal. It’s this interaction between the two compression curves that generates the final control signal for the LDR (light‑dependent resistor) gain cell in each channel.

Slope 2 acts after Slope 1 has done its thing, which means the Governor can deliver results similar to using two compressors in series — and on top of that, you can use the two channels in series to give you even more control over a mono signal!

In the Governor’s Soft compression type, the compression curve for Slope 1 has a wider, softer knee and a lower compression ratio than that of Slope 2. While this differential is maintained across the type shift from Soft through Medium to Hard, the actual difference between the two slopes shrinks as their knees narrow and harden, with the rise in compression ratios. Slope 1’s softer knee overall means that gain reduction actually begins, albeit gently, below the threshold, and rises gradually to reach its preset ratio after the threshold has been exceeded. In contrast, Slope 2’s harder knee means that gain reduction begins to occur later, and reaches its preset ratio earlier than in Slope 1.

For example, imagine you start with Slope 1’s threshold set so 6dB is indicated on gain reduction meter one (GR1) and Slope 2’s threshold is set at High, and no gain reduction is displayed on GR2. If you then lower the threshold of Slope 2, so it starts to drop below Slope 1’s threshold, you’ll see the gain reduction level begin to increase in GR2 and decrease in GR1. Carry on lowering Slope 2’s threshold, and eventually GR1 will show no gain reduction at all. What you’ll hear while you’re doing this is that the transients that survived Slope 1 increasingly come under the control of Slope 2’s curve, until it takes over entirely.

I discovered that I could exploit this inter‑threshold interaction by setting Slope 1’s threshold to just above the point that gain reduction starts to appear on GR1, at which point I was able to access Slope 2’s compression on its own. Another bonus was that, in dual‑mono mode, I could chain the Governor’s channels in series to give me not only the option of bringing in a third slope should I want to, but also an additional three lower‑ratio/higher‑ratio combinations, using Slope 1 from the Soft and Medium compression types from the first channel and Slope 2 (Medium and Hard) from the second channel. What all this boils down to is that the interaction between these two compression curves combines with the attack and release options to provide the user with a level of control over the sound and character of compression that I have never before experienced on a hardware device.

There’s significant creative sound‑shaping potential in the Governor’s dual‑slope architecture, but it always remains intuitive and easy to use.

Tube Boost

The Tube Boost circuit uses the output from a dedicated secondary winding on the channel’s output transformer to increase the gain in its valve output stage. As its name implies, the Full option delivers a full‑frequency boost, leading to an increase in valve‑ and transformer‑related harmonic distortion and a subjective sense of enhanced warmth and overall weight. The Air option is essentially the Full Tube Boost again, but this time filtered so that the boost adds saturation more to the high frequencies. To my ears, Air opens up the top end of the compressed audio, creating a sense of added clarity and presence that helps counteract the sense of high‑frequency loss that can often occur during compression.

In Use

There’s significant creative sound‑shaping potential in the Governor’s dual‑slope architecture, then, but it always remains intuitive and easy to use. For me, the simplest way to set up single‑slope compression was to start with the combination of Auto attack and Slow (450ms) release, then set a threshold and move between compressor types and slopes to find the compression curve that got me into my desired ballpark. After selecting a side‑chain filter frequency to finesse the response, as I went along I’d then shape and fine‑tune the transients and sustain by adjusting the threshold, attack, release and output gain controls.

Other than reading Matt’s review of the Bishop, I’d previously never encountered a dual‑slope/twin‑threshold hardware compressor, so it was an interesting learning curve. To my mind, there’s no set way of approaching it, other than using your ears to gain an understanding of how the two slopes interact with different source dynamics. In general, I followed Matt’s lead: set up the compression on Slope 1, and then gradually bring in Slope 2 to taste. Having said that, if it was a source that I was intending to compress hard — as I might, for example, with drum room mics — I’d often open proceedings with Slope 2 and then bring in Slope 1.

As with all optical compressors, the Governor sounds very forgiving, and once I’d got my head around the dual‑slope approach, its intuitive workflow led me to develop great‑sounding results very quickly. It offers a relaxed, yet somehow also gently firm control in both the lower‑ratio compression types, and this impressed me on a variety of sources, including vocals, guitars and basses (both acoustic and electric), acoustic piano, bowed strings and percussion. Although we’re dealing with multi‑millisecond rather than microsecond attack times, which means a Governor wouldn’t be my desert island drum compressor, the Medium slopes were certainly well‑suited to bringing cohesion to a drum kit, and its Hard setting could easily become my go‑to solution for crushing drum room mics and shaping their sustain envelopes for parallel compression effects, especially with some full‑range Tube Boost dialled in to lend the sound some additional weight and warmth.

Alongside their in‑line roles, the two Tube Boost options are very effective and, indeed, can become very addictive, when used as parallel distortion effects. Full mode, coupled with some judicious EQ in the parallel path, delivered great‑sounding results on acoustic instruments and percussion, and was particularly effective on vocals. The Air setting can also be used very successfully on all of these sources, delivering an enhanced clarity and presence that doesn’t require EQ on the source.

As anticipated, the Governor excelled as a bus compressor, a role in which both its gentle action and its ability to add warmth and weight whilst controlling dynamics and bringing a mix (or submix) into focus was seriously impressive. The Air boost turned out to be a bit of a star in this environment, bringing definition to a submix’s high frequencies in a way that often felt more natural than conventional EQ.

For me personally, getting the best out of the Governor is less about thinking in terms of threshold levels, ratios and attack and release time constants, and more about getting my hands on the controls and listening. Its intuitive operation encourages experimentation, and really that’s necessary if your to explore the ways in which the twin slopes and their individual thresholds interact with each other, with the source, and with the side‑chain filtering, the attack and release controls, the three compression types, and the Tube and Air boosts!

Verdict

At this price, there’s plenty of worthy compression competition for the Governor out there, but I’m not aware of any other two‑channel valve optical compressor anywhere near its price point that can match it for its ease of use, its versatile compression capabilities and its superb overall performance. The Governor also has an attractive asking price, given the exemplary sound quality and creative capabilities on offer. Highly recommended.