Chandler TG12413 Zener Limiter
by: Adam McElnea
Audio Technology – Issue 55

The retro kings are at it again with the release of a compressor to die for – if looks are anything to go by.

Although a relatively young company, Chandler Limited has had considerable success with a variety of vintage ‘hybrid clone’ audio devices, such as channel strips, mic pres, EQs and compressor/limiters. Utilizing modified popular vintage circuits and at times original vintage components, Chandler has carved out a niche market and prides itself on producing pro audio equipment that is unmistakably musical, with a vintage flavor.

In celebration of Abbey Road Studios’ 75th birthday, Chandler’s chief concept and design man, Wade Goeke, in collaboration with ex pat Australian, Peter Cobbin (Senior Recording Engineer at Abbey Road), recently released the ultimate TG Limiter; the EMI TG12413 Zener Limiter. Based on vintage EMI TG circuits, the Zener Limiter is a modified hybrid design that borrows from the original 1968 RS168 Zener Limiter and 1969 TG12345 console. Known for their distinctive vintage tones, these EMI TG circuits were used by some of the greats, including the Beatles and Pink Floyd. Rather than just re-issuing the past, Wade has added more features and flexibility to the Zener unit, making it a more powerful device suitable for modern use. Let’s take a closer look . . .

The Zener is a well-presented unit that wears its ‘vintage heritage’ badge with pride. Furnished with the iconic EMI ‘chicken head’ knobs and two classy backlit Sifam VUs, the dual-channel 3U Zener looks well constructed and rather ‘sexy’ – in a retro kinda way. A peek inside reveals well assembled boards, hand wiring and gold-contact stepped switches in key areas. Gone are the early days of questionable Chandler quality; this unit is built to last with many high-grade components. New features added to the Zener Limiter include switchable hard and soft driving of the unit, 11-position attack (original units had a fixed attack), 21-position extended release, an on-board THD facility, frequency selectable side-chain facility (five frequencies from 30Hz-300Hz), and a new hybrid compression ‘Comp 2’ mode that’s designed to sit somewhere in between the two original Vintage settings.

For those die-hard vintage TG fans out there, you’ll be happy to know that the unit comes labeled with yellow and white markings on the controls. The white markings designate the original vintage TG control parameters while the yellow ones designate the new (expanded) parameters. A pair of large, blue hardwired bypass buttons for comparing compressed and uncompressed sounds round out the front panel.

Unlike many other compressor/limiters, the Zener doesn’t have a threshold as such, but instead is ‘driven’ by the input gain control and associated high/low input gain and impedance switch. When you want to drive the unit harder, just turn up the gain! This of course increases THD levels, fattens up signals and can result in THD amounts considerably larger than tape, without clipping. Look out fuzz police, here we come!

At the heart of the Zener’s tone sculpting abilities lie the compressor/limiter controls. The Limiter function was originally designed by EMI engineers to emulate the fast response curves of the beloved Fairchild 660, while the ‘Comp 1’ setting was EMI’s answer to the 2:1 ratio, slower Altec 436 compressors. ‘Comp 2’ is a new hybrid option that opens up the Zener to further possibilities.

Before putting the unit through its paces, I was lucky enough to track down an extremely rare original EMI TG Mastering console (there are only a handful in existence worldwide) to compare it against (many thanks to William Bowden for his tools and time). Obviously it’s important to determine if the Chandler unit does in fact sound like the original vintage EMI units. With a little tweaking we were able to get level-matched tests underway. Based only on the white-labeled original factory settings, I found the Zener in Limit mode to sound noticeably different to the original EMI unit. The Zener was a little leaner on the bottom, more modern and slightly two-dimensional sounding, while the EMI unit sounded a little more refined, slightly rounder with a definite vintage flavor – very musical. On the other hand, the Zener in Comp 1 mode definitely gave the EMI unit a run for its transistors with a noticeable low-end bloom, nice punch and musicality. Although there were minor differences, overall the units did seem to be in the same ballpark.

Fast forward to 2007, and let’s see what the distinctive TG sound (along with the additional bells and whistles on the new Zener Limiter); can do for you in the studio. Initially, I set up the unit in Limit mode and ran a selection of individual tracks as well as sub-grouped stems through the unit for auditioning. On transient-rich material such as picked guitar and percussive instruments, the Zener smoothed without flattening. However, the unit really excelled on drums, as there was an immediate improvement in the form of added attack, drive and plenty of transistor goodness. With a little tweaking of the side-chain facility, say 150Hz or even 300Hz, small-sounding drums became audio monsters with plenty of weight and new-found life. The additional attack and release parameters made further tweaking possible with exciting results.

There was plenty to like about Comp 1 mode. Bass and keys, especially digital synths, were definitely improved with the additional Zener drive and THD facility cranked up. On vocals I played around with all three modules and found the results to be okay, good if you’re looking for a certain rock flavor. However, the Zener would definitely not be my first choice on vox.

Now it was time to unleash the unit across the mix bus and/or in a mastering environment and a few anomalies soon became apparent. It’s imperative that the unit’s controls are set up identically for left and right channels, even when in ‘stereo link’ mode. The VU ballistics can be rather slow and (especially in Limit mode) can be compressing considerably more than the meters would have you believe. From a mastering point of view, gain reduction mostly happens in the 1-3dB range, whereas these VUs start at 4dB gain reduction. Finally, at times, some of the unit’s labeling can be quite difficult to read, thanks to the controls being in the way.

Quibbles aside, I decided the best setting seemed to be the Fairchild curve, so I switched back to limit mode, set up the side-chain to either 90Hz or 150Hz and shunted through a stereo source. The meters were barely moving but pumping was still very audible. With further tweaking of the attack and release times and a little less drive (to the point that the meters were virtually still), the mix began to ‘glue’ together. The Zener would definitely not be my go-to box on the mix bus unless I was specifically looking for the color it imparts, and/or the music demanded its driving attitude. Once again, definitely one for the rock dogs out there.

The TG12413 Zener Limiter is one of those devices that you either love or love to hate. It certainly has a distinctive, colorful sound based on a wonderful vintage ancestry. Heck, you even get the EMI stamp of approval on the front. However, the Zener comes with a rather hefty price tag, and in a market heavily populated by industry favorites it’ll face stiff competition. There again, if you’re in the market for a tracking compressor/limiter that sounds extraordinary on the drums bus, or if you’re looking for some funky TG flavor to add to your arsenal of colors, or maybe you’re trying to release the next Beatlesesque hit, then give the Chandler TG12413 Zener Limiter an audition, you may just end up loving it.

—Adam McElnea