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Analogue Tube AT-1 Compressor: New/Old School Fairchild-Style Limiter

I first bumped into Simon Saywood at an AES in San Francisco when he was showing off his then-brand-new Fairchild 670 copy, the AT-101. It became instantly clear that Simon was not into this just to make yet another copy of a classic. Being one of London’s top maintenance engineers, Saywood takes great care and pride in researching how the original units behaved and which components were responsible for the sonic character. In his designs, he sticks as close to the original specifications as possible, yet improves where possible and appropriate. I test-drove the AT-101 when it came out on an Elliott Randall session. Needless to say, I couldn’t wait to hear how the AT-1 was going to compare and what it would bring to that infamous Fender Strat.

First Glance

The AT-1 is impressive. It is 19 inches wide, six rack units tall, and weighs 44 pounds—this is not a small unit. The front panel is a lovely brushed matte black with the same control knobs as the stereo AT-101, but in mono. It gives the user control over input level, threshold, attack and release times, bypass and external input. And, of course, it wouldn’t be a true Saywood Analogue Tube without one big mother of a VU meter.

It is recommended that the unit be kept more or less freestanding in order to provide airflow. Taking a peek around the back will make this very clear. The AT-1 has 12 tubes poking out of the back (6386LG, 6084, 5651, 12AX7, 12BH7, 6BL7, 6L6GTA, and GZ34). Drawing around 110W of power, the unit gets quite hot.

Geek Speak

The AT-1 was designed and developed to perform and operate like the Fairchild 660. Gain reduction control is achieved by using a double triode gain reduction amp and push-pull amplifying stage to produce a high-voltage sidechain. This design makes for a very natural sound, low distortion and no audible thumps or pops, even under severe limiting conditions. The AT-1’s attack time can be set at microsecond level so that it can catch short transients in the material. The release time is adjustable from 0.3 to 25 seconds across six click stops. Two of these six release settings have automatic functions dependent on the program material, offering fast recovery for quick peaks and longer recovery times for high-level material. All the Time Constant values are exactly the same as on the original 660 and 670 units. Like its 660 ancestor, the AT-1 uses a single independent feedback limiter and was designed for use in regular line-level circuits, like the mix bus and channel inserts.

This unit is not just half of the stereo AT-101. The mono unit has its own character and, like the 660, sounds and behaves differently compared to its stereo counterpart. A few of the main distinguishing features that set it apart from the stereo unit are the valve PSU and attenuator control. It is a tapered step attenuator, remade exactly the way it was back in the ’50s. Some of the new features are the stepped AC Threshold control, making it easy to recall, and when you’re stereo linking two units (or more for surround), this control boasts a neat one-percent accuracy per step. The AT-1 also comes with an external key input, which you can easily engage with the key switch. This splits up the gain reduction and AC threshold circuitry, allowing you to access the compressor’s sidechain when you require de-essing or ducking.

The AT-1’s attack times range from .2 to .8 milliseconds and the release positions give you the choice of 0.3, 0.8, 2 and 5 seconds, in addition to the two automatic function program settings. Depending on the DC threshold setting, the AT-1 will provide ratios from 1:1 to 1:20. In addition to the original tapered step attenuator for the input gain and the time constant switches, it has a 21-step AC threshold, a continuous DC threshold control, the bypass that switches the AT-1 completely out of circuit, the bright green external input switch, stereo link and the metering switches. The inputs and outputs are all transformer-balanced and on XLR connectors wired with pin 2 hot for Europe and pin 3 hot for the U.S.

In the Studio

I wanted to hear this unit on Elliott Randall’s Strat and hear how it compared to the stereo version. I put up a dynamic and a ribbon on the cab and strapped the AT-1 across the dynamic channel, straight to disk. The mic went from an ultra-clean preamp into the compressor and into the DAW. No electronic detours. We both know the amp and the mic really well. The resulting sound was humongous. Generally, I blend a little of the ribbon in to supply some warmth and roundness. What happened here was that the dynamic combined with the AT-1 was perfect. What’s more, it did not kill the use of the ribbon—it actually made the ribbon and the dynamic signals gel together even better. I decided to drive the input stage quite hard and had it compressing very gently. The AT-1 smoothed out any little level jumps, and Elliott’s signature volume swells just leapt out and sang.

Just before we hit the red button, I did one of my favorite things with the Analogue Tube units. I hit the bypass and had the artist play, then slung the unit into circuit, unannounced. Seeing an artist’s face light up and get inspired by the sound they’re hearing must be the biggest compliment to the unit and its designer. Well, that and the exclamation: “Oh my God, I want one!” (That would be me shouting that.)

By now I was seriously vibe-ing on the AT-1 and wanted to hear more. I subsequently tried it on various vocals—high and screaming female vocals, funky male vocals and really dark, husky male vocals. All of them blossomed, and hearing the results back in the headphone mix made the singers perform significantly better.

Finally, I had a bass in an EDM track that was flatter than a pancake. The source sound wasn’t very exciting. The moment I hit the insert and had the AT-1 across it, with plenty of gain driving those tubes, that bass came out bigger than a house. The track started pumping, and all the bottom end of the song just glued together.

This is an excellent replica of the original Fairchild 660 in shape and function, and it makes me think back to tape. It looks like an original, it sounds like an original, it’s cheaper than buying an original today, and it’ll require a lot less maintenance. Every studio should have one.

Wes Maebe is a UK-based recording, mixing, mastering, and live sound engineer. You can check out his work at

Product Summary

COMPANY: Analogue Tube


PRICE: $11,500

PROS: Well laid layout. Puts out an amazing sound.

CONS: Price. Transformer noise if freestanding in small room.

Try This

It is important to let the AT-1 warm up for a while; 20 minutes is recommended. However, I did a take after 20 minutes and then the same after 30 minutes and the same again after an hour. It sounded best after an hour. Vocals: Don’t drive the unit’s input too hard, unless you want that fuzzy tube distortion as an effect. Have it set to gently squeeze the peaks, and you’ll get a nice warm in-your-face vocal that’ll pop out of the mix. Kick: Yes, even on a kick it’s really nice. Have a fast release and quite a bit of gain, and you’ll end up with a pumping, round kick. I like using it like a parallel compressor, too. Route kick and the snare to it, use a nice EQ to boost the lows and highs, and mix that in with your kit.