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TL Audio Fat Track

Valve Preamp & Mixer By Mike Senior
Published June 2008

Part preamp, part summing mixer, all tube: can the Fat Track provide all the 'analogue warmth' your studio needs?

TL Audio Fat TrackDespite the promise of 'all in the box' recording offered by computer-based studios, many computer musicians still find a hardware mixer useful, providing input conditioning, monitoring facilities, and that elusive and intangible 'analogue warmth'. However, owners of small-scale studios who build up productions one track at a time will find many of the facilities on a traditional mixer a bit redundant, so a number of manufacturers now provide equipment to service these needs more efficiently — recording channels, monitor controllers and summing mixers, for example.

TL Audio's take on this concept is the Fat Track, which provides a comprehensive set of such tools for the computer user, combining them with the hybrid valve/solid-state circuitry for which the company have built an excellent reputation. In the chunky desktop box you get two full-featured recording channels, four stereo returns for source selection or summing purposes, headphone and loudspeaker monitor control, and optional ADAT connectivity for multi-channel digital interfacing.

Dual Recording Channels

The contrast between the pleasingly retro glow of the dual VU meters and the piercing hi-tech blue of the power LED will inevitably first draw the eye of the casual observer. Those with more than a passing interest, however, will soon find themselves peering closely at the left-hand side of the control panel, where the unit's input conditioning controls reside. Each of the two channels has the same facilities, comprising a mic/line/instrument preamp, three-band semi-parametric EQ, and a single aux send.

All the Fat Track's analogue I/O (almost all of it balanced) is arrayed in two rows of top-panel jack sockets, and although you might prefer your studio cable salad less proudly on display, this at least makes the socketry easily accessible. The only XLRs present are for the unit's main outputs and mic inputs. The latter have switchable phantom power and can boost mic signals by up to 60dB, although a 30dB pad switch means that you can easily accommodate super-hot sources too. Separate sockets for line and high-impedance instrument inputs can be selected as the channel input via another switch, and both can access up to +/-20dB gain.

Your choice of input signal is fed, with switchable polarity inversion, to the first of the two 12AX7A (ECC83) dual-triode valve stages, which you'll see blushing coyly through front-panel ventilation slots. Two LEDs (Drive and Peak) provide an indication of how hard you're pushing the tube, and if you fancy thrashing it by cranking the Gain knob, you can safely rein in the level before recording with the Fader control that directly precedes the channel's Direct Out.

A 90Hz 12dB/octave high-pass filter follows the valve in the signal path, so that you can get rid of any low-frequency rumble (if not its valve-distortion harmonics) at source, and the audio heads from there to the same euphonic EQ circuit design used in the company's M1 Tubetracker. The fixed-frequency high and low shelves provide +/-15dB gain at 12kHz and 80Hz respectively, while the mid-band peaking filter can effect similar gain changes across a usefully wide 150Hz-7kHz range. Given that TL Audio suggest using the Fat Track's EQ for stereo bus processing, I'd have liked to see some kind of stereo link switch here. As it is you'll just have to line up the two processors as best you can by eye and ear.

A switchable insert point is provided between the EQ and fader, using separate balanced connections for send and return, and the former is half-normalled, so you could potentially use it as a pre-fader alternative to the direct out. Although there is an EQ bypass switch, I would personally have liked the option to move the insert point to between the high-pass filter and the EQ — the most logical insertion would be a compressor, and pre-compression EQ is trickier for most people to set up, in my experience. While we're on the subject, if the signal chain had been 'preamp, filter, insert, tube, EQ' you could have filtered out subsonics before they hit the tube, and you would then also have had the option of a non-tube-flavoured recording via the insert output. As it is, you'll have tube sound on everything, whether you want it or not — and on this point I share something of the concern Hugh Robjohns expressed in his SOS January 2007 review of the M1 Tubetracker.

After the feed to the direct out, each recording channel can be routed through a pan control to the Fat Track's stereo mix bus, whereupon it appears at three separate outputs: the main balanced XLRs, a pair of unbalanced jacks, and an unbalanced stereo TRS tape-out jack. The single mono aux bus is fed post-fader and post-mute via a separate FX send control, and there is also a dedicated stereo FX return input feeding the main mix bus directly through the FX return control.

DO8 Multi-channel ADAT Interface

The DO8 interface option can be installed into the Fat Track's rear panel and offers four channels of A-D conversion and eight channels of D-A conversion. The converters are 24-bit/96kHz capable, and there is Word Clock I/O too. Via ADAT lightpipe connections, you can stream audio post-fader from each of the recording channels and from the main mix outputs to a suitably equipped soundcard for recording, and can feed eight channels of audio from the computer directly to any of the 10 mixer channels. No card was shipped with the review unit, but its operation appears to be fairly well thought-out. That the price of the D08 (in the UK) adds roughly 50 percent to the overall system cost might raise some eyebrows, particularly of those who must also budget for an ADAT interface for their computer, but it's worth pointing out that it would rather defeat the point of a box like the Fat Track to compromise its sound with sub-standard A-D and D-A conversion, particularly if you're summing or mastering your entire mix through it.

Summing & Monitoring

The Fat Track's four remaining stereo inputs (A, B, C and D) offer nothing more in the way of control than a +4dBu/-10dBV sensitivity switch by the input sockets and a larger, grey rotary fader, and these channels can be sent to the main mix, if required, using the Main switch. The remainder of the controls govern the four sets of monitoring outputs, which comprise two headphone sockets and two pairs of speaker outputs. The Artist headphone output simply receives the main mix through a dedicated level control.

The mix feeding the rest of the outputs is configured using the A, B, C and D buttons, which can be pushed down in any combination to monitor a post-fader mix of the respective stereo returns — and if all the buttons are up then the main mix bus is monitored by default. The Producer headphone output again has a separate level control, while the large main Monitor Level knob affects both the Main L/S and Alt L/S outputs. A final pair of buttons enables you to decide which of the two sets of loudspeakers is active and mutes the monitoring completely.

On a product at this price point I was rather disappointed not to see a mono-sum switch, and I suspect that many people will find the absence of talkback facilities even more tiresome. I can only assume that TL Audio's market research has suggested that their target customers are mostly recording and monitoring in the same room, so don't need talkback.

There are a number of different ways you might actually use the Fat Track in a computer studio. At the writing stage, you could monitor the outputs of your computer alongside those of a few hardware synths and sound modules, recording the synths into the computer alongside any acoustic sources or DI'd instruments as tracking progresses.

At mixdown, you could use all 10 inputs for summing the mix in the analogue domain through the unit's second dual-triode, which is strapped over the main mix bus. Hugh was peeved at the lack of mix-bus insert points on the M1, so it's a pleasure to report that a switchable pre-fade insert point is provided here for your favourite esoteric mix squisher. Alternatively, if you happen to think summing's a load of old cobblers, you could use the four returns to reference your mix against three other stereo sources — in which case you might pass your mix through the recording channels on its way to your master recorder before routing the recorder's playback output to the appropriate stereo return.

Session Impressions

This is by no means a budget product, so it's good to feel that you're getting your money's worth even before you switch the thing on! The industrial metal construction hefts like a crate of beer, despite having a footprint no larger than an open copy of SOS, and the frame is surprisingly deep, standing a good six inches off the desk at its highest point. Punch a switch and it gives a satisfying click; grab a control and it travels beautifully smoothly and with a reassuring resistance.

Each of the two mic/line channels includes a switchable insert point, which is post-EQ but pre-fader, as well as a post-fader direct output.Each of the two mic/line channels includes a switchable insert point, which is post-EQ but pre-fader, as well as a post-fader direct output.Plug the Fat Track in, make it sweat, and you'll find that the sound amply lives up to the promise of the first impressions, delivering technical excellence with all the trappings of tube loveliness: smoother high end, rounder transients, that fraction more stereo interest, and a low-end thickness that really brings bass instruments alive. The preamps were quiet and clean when I wanted them to be, and warm and fuzzy when I didn't, allowing each of the half-dozen mics I tried to shine in their own unique ways. The EQ is tracking-processing as it should be, delivering broad tonal changes with musicality. While some musicians might feel a semi-parametric design to be somewhat inflexible, to my mind they're missing the point of a tracking EQ — the pickier settings are best left to the mix engineer. In short, the sonics here are the main reason to buy the Fat Track, and the unusual combination of features helps improve the price/performance ratio considerably — you could pay a good chunk of the Fat Track's price for a decent two-channel valve DI or multi-channel valve summing box alone, for example.

With all that taken into account, though, any potential purchaser needs carefully to think through whether the Fat Track will actually meet their operational needs effectively. Besides the aspects of the design I've already touched on above, my main concern is to do with setting up monitoring while overdubbing, and stems from the fact that deselecting any of the returns from the main mix also defeats their feed to the monitor matrix. To see why this is a problem, let's imagine you're recording a guest vocalist. For zero-latency monitoring you'd have to switch off software monitoring in the DAW, to avoid phasing between the direct and latency-delayed vocal signals, but then if you switched the Producer headphones to monitor anything other than the main mix (in other words, exactly what is appearing at the Artist headphones output) you'd not hear the vocal you were recording.

If you used software monitoring instead, disconnecting the recording channels from the Fat Track's mix bus and monitoring the vocal coming back from the computer, the engineer could at least monitor without any reverb arriving at the FX Return inputs, by monitoring the stereo returns directly through the monitor matrix. However, there'll still be no straightforward way to create an independent cue mix for the singer, which seems to me a pretty basic requirement.

If the designers had simply fed the monitor matrix from before each return channel's Main switch, none of these problems would occur, because the engineer could create whatever mix he or she liked and listen to it through a stereo return disconnected from the main mix bus. As it is, though, this kind of proper cue monitoring is, for the Fat Track, currently the stuff of dreams.

Fat Is Beautiful

Despite my various operational quibbles, there can be no denying that this is a classy-sounding piece of kit that delivers a lot of different DAW support functions. What's more, it does so in a format which, while not exactly cheap, is comparatively cost-effective when considered against the alternative of putting together this feature set at this quality level using a combination of other equipment. Can you name another standard mixer design at this kind of price point that offers premium valve processing and instrument inputs? Which recording channels include built-in bus mixing? Which monitor controllers incorporate two fully-featured valve recording channels? The Fat Track really seems to be in a market of one.

However, great-sounding and innovative though this unit undoubtedly is, customers with this much cash to splash might justifiably feel entitled to expect proper talkback and cue-mixing facilities from any ostensibly one-box solution. Although I'm fairly confident that its formidable price/sound ratio will convince many musicians immediately to part with a stack of their hard-earned, I think that the less impulsive potential purchaser might sensibly bide their time a little to see if TL Audio (or, indeed, their competition), can come up with a future product combining this level of valve sonics with a more well-rounded feature set. 


I really can't think of anything that could be considered a direct alternative to the Fat Track, although there may well be other suitable products, depending on which features of the Fat Track you require.


  • The sound of the valves and EQ is marvellous.
  • Forward-looking 'one-stop-shop' feature set for high-quality tracking, summing, mixing, mastering, and monitoring with your computer-based DAW.
  • Optional multi-channel ADAT interfacing.


  • The cue-monitoring options are frustratingly limited.
  • There are no talkback facilities.
  • There's no way to bypass the unit's valve stages if you want to record something more neutrally.


The Fat Track's sound is good and will doubtless sweep some people off their feet all on its own, but more practically minded producers may find that this unit omits some operational features they can't live without.


Fat Track £1174; D08 ADAT card £586. Prices include VAT.

TL Audio +44 (0)1462 492090.