Highland Dynamics: BG-2 tube compressor

When it comes to checking out new recording equipment, we all bring expectation biases. Some really want to believe that the latest truly is the greatest, while others are skeptical of the new and novel (particularly when it appears someone has tried to fix what isn't broken). Despite striving for even-handedness, I'm somewhat solidly in the latter group, and can admittedly be pretty ambivalent toward (and critical of) new products that don't actually seem to address new problems. When I was offered the Highland Dynamics BG-2 to review, my first reaction was to wonder whether the world really needed another high- end variable-mu tube compressor. Would it show me anything that a myriad of industry standards didn't already have covered? Despite my skepticism, the BG-2 quickly overcame my bias against it, and I was within a day inquiring about Tape Op policy on purchasing demo units. In the end, we actually bought two. I'm not sure I've ever been as quickly and favorably impressed with a piece sent to me for review. 

The BG-2 has roots in a couple of historic designs, chiefly an EMI-modified Altec compressor that's storied in Beatles lore. After some more-literal early recreations, designer Bryce Gonzales re-imagined some key aspects of the design. The biggest: a modified threshold gives finer control over the compression while a powerful RCA-style dual-6V6 output amp replaces a puny 6CG7-based original, increasing output level and headroom. 

The BG-2 is part of a family of tube compressors, often called variable-mu designs, that are engineered around what's called a "remote-cutoff" tube. As with all remote-cutoff tubes, the voltage gain (or mu) of the new-old-stock GE 6BC8 in the BG-2 can be manipulated by varying the tube's bias. Unlike a typical tube, which will shut down and stop conducting entirely if given too much bias (a condition called "cutoff"), a special control-grid geometry allows remote-cutoff tubes to conduct under a far wider range of bias voltages (and signal swings), enabling a wide range of gain behaviors. If we add a circuit capable of responding to the level of incoming audio, we can make a control voltage that follows the input level. Summing this control voltage with the tube's bias will make the tube's gain characteristics respond to the input dynamically, reducing gain as the input signal gets louder. This variable-mu (or "variable gain") strategy, when implemented well, results in gentle, intuitive leveling. 

Getting the obligatory feature rundown out of the way, the BG-2 has continuously variable input and output controls, two- position attack and six-position release switches, a nice Simpson meter, a two-position input-impedance switch, and the ability to choose "American" or "British" negative-feedback characteristics. A link switch gives stereo flexibility, and while compression can be switched off (allowing use as a mic or line amp), I did wish for a full bypass. I'd also be happier if the meter calibration trimmer were front-panel accessible and if the meter were illuminated, but any other feature I'd want from a variable-mu compressor is present and accounted for. 

Mechanically and visually, the unit's quality reflects its price point. Sonically, it even exceeds expectations. My first impression was just how much gain reduction could happen without the audio getting destroyed. My second impression was that even when you do crush signal to the point of pumping and distortion, you're left with a sound that, while highly (and familiarly) stylized, still is fundamentally as pretty-sounding as it is aggressive. Sometimes even excellent compressors can get sibilant or congested when pushed to the extreme, but this one seems immune to bad behavior. 

As a result, the BG-2 is a uniquely effective, forgiving and superior-sounding compressor in a vocal tracking chain. With powerful vocalists (especially those having more spontaneity and dynamic range than mic technique), a compressor capable of sounding this good under massive gain reduction can help protect you from the unpredictable, and that alone will justify the price for many. Simply put, it's easy to use; margin of error is wide, but the ability to dig in and mine for nuance is deep. 

Though reluctant to pull the patch from the lead vocal channel, I did try the BG-2 on other stuff with success. I unboxed it the morning of an EP recording for British pop artist Phil Gibbs, so we dove right in, using it to track a wartime Gibson SJ acoustic behind a Neumann U 67 and 80-series Neve console preamp. It stayed patched in the whole day, moving over to guide vocal only after all acoustic tracks were finished. If it hadn't been such an instant and clear "yep," we never would've committed so immediately. Clicking the release control down from fastest to second or third fastest, the BG-2 impressed us on a bass that had lots of long, sustained notes; the soft knee of the longer release created a bit of extra note length in a very natural way. Truly, I liked the BG-2 pretty much anywhere I'd normally reach for a variable-mu tube compressor. 

About a week in, the BG-2 was already in-demand at our studio, bouncing from room to room, garnering remarkable consensus. Some raved about its ability to level a lot without pumping or pinching, thereby allowing a vocal to sit lower in the mix but still command lead-vocal importance. Others touted its ability to slam room mics on drums without getting gross, in part due to impressive clarity and focus in the low midrange. Multiple engineers thought it even more forgiving than our Retro 176 tube compressors [Tape Op #66], my previous champion of leniency, because no matter what we threw at the BG-2, we couldn't make it get bad-weird. 

Many of us were particularly impressed with the sheen of American mode, so about that American/British switch: Gonzales verified my hunch that it's largely a negative feedback selector. British mode employs the greater amount of negative feedback used in its EMI/Altec ancestor, while American mode has less, more like a vintage RCA compressor. Perhaps as a consequence, the British character is a bit damped, smoother, and more polite overall, but transitions into clipping more abruptly. American mode on the other hand seems livelier, more brilliant, and has a very gradual, natural onset of harmonic distortion when pushed. In a departure from the overall immediacy of the BG-2, the two relative characters must be learned over time to be fully exploited; a level difference of a few dB makes it difficult to A/B the two without volume-level prejudice. For whatever reason, I found myself staying in American mode a lot at first, though British was especially nice on a particular electric bass. As familiarity continues to mount, I expect to gain an even richer handle on the relative merits of both. 

I'd like to emphasize again that the BG-2 has a gestalt good enough to overcome what is for me an ingrained, difficult-to-articulate mistrust of things that appear to attempt "best of both worlds" in any way. I'm especially leery of things that seek to bring modern refinement to an overall vintage sensibility; too often such hedges-of-bets just feel character deficient, as though they lost their soul somewhere on the journey between revivalism and innovation. Until I tried it, I feared the BG-2 might be another such neither-nor to throw on the pile, but it's not. It's different — its own thing. Even more than that, it's just really, really good.