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IGS Audio Tubecore ME

Stereo Vari-mu Compressor
Published May 2012
By Matt Houghton

IGS Audio Tubecore ME

Well known in their native Poland, IGS Audio are now making their products available in the UK. How do they fare against the competition?

IGS Audio are a Poland-based company who have already developed a decent reputation in that country but, until recently, have been less well known elsewhere. Although their own products haven't appeared in the pages of SOS before now, they are the OEM manufacturer for the Tobias Lindell designed 17x compressor, which I reviewed back in SOS February 2012, the build quality of which seemed to be good.

IGS's range includes several 'homages' to some well known (and currently available) processors, for which their approach seems to be to keep costs down where possible (for example, through the use of dual-layer PCBs where the original designs use point-to-point wiring), without compromising on sound quality. IGS claim that there are benefits to using PCBs, not least that it enables them to be consistent in the quality of production, and to much more closely match channels in a multi-channel device. It's an approach that makes sense to me.

As well as these 'heavily inspired by' designs, though, IGS manufacture some original products. They're still inspired by good classic analogue designs — there's nothing ground-breakingly new or novel — but they are nonetheless original IGS designs. Amongst these are their two 'Tubecore' vari-mu compressors, one of which is called the 'Tracking Edition' and the other, reviewed here, the 'Mastering Edition', or Tubecore ME. The difference between them (apart from the price, with the Tracking Edition coming in slightly cheaper) is largely in the controls: on the ME, one set of controls governs both channels, which should make it easier to use for stereo-bus compression and stereo-mastering duties; whereas the tracking version presents with two separately controllable channels, which makes it rather more appropriate for tracking duties, where you're more likely to want to process two mono sources through it concurrently — or, of course, one mono source through two different stages of compression.

The Nitty Gritty

The Tubecore ME arrived at the SOS offices well packed. In the box, as well as the unit itself, there was a brief-but-useful user manual, and a reassuring three-year warranty certificate. My first impressions were much as I'd expected, given my experience of the 17x: the 2U rack case and front panel were sturdy and firmly screwed together; all the switches and knobs felt pleasingly firm and were generously spaced, making them easy to access and tweak; and the white legends on the front panel were both unfussy and easy to read. In other words, it is a good, no-nonsense user interface, in typical vintage style.

The aforementioned knobs come in two sizes. Three larger ones govern the input gain, the compression threshold and the make-up gain/output level, and the two smaller ones are used to adjust the attack (20-100 ms) and release (0.2-1.2 seconds) times. A handful of silver toggle switches (from left to right, a -6dB pad on the input, a channel-link facility, a compression in/bypass toggle, and a larger on/off switch) complete the front-panel controls, and two backlit VU meters (one per channel) and a power-present LED provide visual feedback.

Before powering up, I had a peep inside the box, a job which required a Torx screwdriver, and everything seemed neatly laid out. In vari-mu designs, the gain-reduction part of the circuit is based on vacuum tubes (valves), and in this case the design is based around low-distortion, long-life, military-grade Russian 6N1P-EW types, which are similar to the widely used ECC88 or 6DJ8, but require a higher heater current. Lundahl LL1540 input transformers are used, and Sowter 9745 types are used to balance the output stage.

On the front panel, you can see how nicely spaced the controls are, and how easy to read the legending is.On the front panel, you can see how nicely spaced the controls are, and how easy to read the legending is.

The manual suggests a number of uses for the Tubecore ME, ranging from the mastering compression implied by the name, through drum-bus compression, to adding analogue character to stereo sources such as drum machines and synths. Curiously, IGS didn't include any mono sources in that list: it would, of course, be possible to press it into service using just one channel at a time, but if that's going to be your main application you'd be better off with the less expensive tracking variant.

On Trial

To test the Tubecore, I set it up as an external plug-in in my DAW, so that I could quickly and easily insert it at different points in a number of projects, and switched it on. The first thing I noticed was that this unit, like most valve devices, takes a while to reach a stable operating temperature where it will give consistently of its best. That's a fact acknowledged in the manual, where it's recommended that you power up around 20 minutes before use, and I'd recommend doing that if you want to get the best performance from the Tubecore, and particularly if you're trying to pick up a mix where you left off.

I started using the Tubecore to gently compress some stereo mixes, the first of which was a reasonably sparse stereo acoustic track comprising only acoustic guitar and vocals. Even before trying to achieve any gain reduction, I could hear a subtle but pleasing analogue character, which I ascribed to a combination of tubes and transformers. I was able to use the input gain control to impart a tiny bit more character, too. There was that oh-so-slight smoothing of the acoustic guitar pick transients that I've come to expect and enjoy from tube gear, and it brought out the breathiness of the vocal part rather nicely, too.

The analogue I/O is presented on balanced XLR connectors, but there's no side-chain input.The analogue I/O is presented on balanced XLR connectors, but there's no side-chain input.

Moving on, I went in search of some gentle gain-reduction, just to even out a few peaks and troughs in the recording: I brought down the threshold and played with the attack and release settings. I used nothing too severe on this sort of material, of course, but the results were rather good. It did its job as a compressor smoothly and pretty transparently, without adding a whole lot more character than it was already imparting — which is just the ticket for material like this.

The next opportunity I had to use the Tubecore in anger (or should that be 'blissful pleasure'?) was on some rock and pop material, where I tried using it in a few different bus-compressor roles. It performed well in each role, but it acquitted itself particularly well on backing vocals, the drum mix and on the stereo mix bus, where the gentle nature of the compression, and the tangible sweetening of the analogue circuitry worked really well. The BVs in question were layered parts that had been spread across the stereo spectrum, via panning and a little delay and reverb. I was able to get a bit more heavy-handed with the gain reduction here than I had on the earlier track, and glue the BVs together while still leaving them smooth and natural-sounding.

Strapping the Tubecore across a rock-track's drum bus brought instant gratification, and I was able to tease rather more character and attitude out of the processor than in other roles. I found that I could balance the release control with a relatively fast attack (not that this processor 'does' fast, in the snappy solid-state sense) to emphasise a bit more bounce in the rhythm. This worked nicely, combining with the overall sonic character of the Tubecore, which I'd place somewhere between that of the Manley and Thermionic Culture units mentioned in the alternatives box, to create a vibey, yet smooth sound.

So, despite the name, this processor is clearly not all about mastering. In fact, the Tubecore is capable of more weapons-grade abuse too: soloing the drum bus so that I could experiment away from the mix, I found that I could actually really mangle the sound if I wanted to, and arrive at a big-beat sort of sound, making the drums really pump and squeeze. This isn't the Tubecore's raison d'être, and there are probably other units I'd pick ahead of it in this role, but it's nice to know it can travel into that territory.

The 'tracking' version of the Tubecore affords the user separate controls over each channel.The 'tracking' version of the Tubecore affords the user separate controls over each channel.

Pole Position?

On the whole, then, I think the Tubecore is a really good, very versatile compressor, and although a high-quality valve processor is never going to be cheap, a combination of keeping the design simple and using PCBs in place of point to point wiring means that the bang-for-buck in relation to similar-sounding processors is actually rather good. What's more, it imparts exactly the sort of sonic character that you'd expect of a high-quality vari-mu compressor. The build quality is good, high-quality components are used throughout, and the stepped controls are great for recall when working across different projects. The three-year warranty helps to bolster the confidence, too.

It's part of my job, of course, to find points of criticism, but the only 'cons' I can think of — and I did try — are the omission of features that I personally like to see on compressors, and which appear on some better known units. An external side-chain input would be nice, as would a side-chain high-pass filter and a wet/dry facility for quick and easy parallel compression. But such things would add to the complexity and the cost and are entirely unnecessary for some people. All in all, then, the Tubecore ME gets a big thumbs-up from me!  


There are lots of valve compressors available, new and second-hand, but the two current products that the Tubecore puts me most in mind of are those from Manley and Thermionic Culture. Both company's products are rather pricier than the Tubecore, but to some extent this reflects the fact that they offer functionality that the Tubecore lacks. For example, both the Manley Vari-mu and the Thermionic Culture Phoenix MC Master offers those side-chain high-pass filters I commented on in the review, and Manley offer mods to allow the Vari-mu to be switched between L/R and M/S modes.

Published May 2012

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