With so much amazing boutique gear available these days, I have to confess that I don’t get all that excited when I hear about yet another expensive tube compressor being made in small numbers by experienced designers to quality standards that surpass every military spec known to modern society. Furthermore, I’d already prejudged the Rockruepel Comp.One because the units I’d seen sported a scantily-clad ‘50s-era pin-up babe on a swing, a design touch that conjures just about every stereotype about audio engineers that I’d like flushed out of my psyche. And then, despite my misgivings, I ran a parallel drum bus through the Comp.One and was completely blown away by the sound — just amazing.

This compressor is capable of making a number of distorted sounds that I’ve never heard out of any compressor, and it’s capable of beautiful, transparent level-control — and it’s capable of all kinds of sounds in-between. The Comp.One is an all-tube, variable-mu compressor with input, output, threshold, attack, and release controls for each channel. The two channels can be linked, which averages the settings between them. There is also a low-cut side-chain filter on each channel that cuts at either 45 or 60 Hz. Then there are two more settings that make the Comp.One really unique. The first is Amp Only, which allows you to use the tube stages without compressing, and the second is the Ruepel setting, which for lack of a better way of putting it, totally screws up the sound.

As a straightforward, stereo compressor, I was able to get the Comp.One to do pristine level-controlling for me on a whole mix. The sound is absolutely clear when being used subtly, with a really shimmery high-end and deep, solid bass. The high-end was particularly nice, as it sparkled but remained really smooth. Ride cymbals were especially articulate and smooth, and vocals sat down in the mix while remaining crystal clear. For me, the best mix-bus compressors are capable of gain reduction that doesn’t tug and pull at the high end, and the Comp.One is a champ in this regard.

Pushing the Comp.One into more aggressive settings reveals some time-relevant behaviors, which range from grabby, fast attack settings (the literature I’ve read claims it’s the fastest variable-mu compressor on the market) to subtler, rhythmic breathing effects. The attack and release behave predictably, and I was able to get the Comp.One to move and sway with the music pretty easily when the compression was more audible. When pushed a bit, it was really nice on stereo groups and parallel buses where some artifacts were a good thing.

I can’t say enough about how hi-fi and clear the compressor sounds when used in these more subtle ways on stereo material. The Comp.One always adds a nice layer of harmonic interest to the sound. I can see why mastering engineers are eating these up.

In Amp Only mode, the Comp.One becomes a tube-drive unit, and it does this amazingly well. As you drive into the tube stages harder, there is a natural saturation that slowly takes over and eventually offers up its own compression by way of saturation rather than actual compressor behavior. (Remember, the compressor circuit isn’t working in Amp Only mode.) My favorite use for this setting was on a drum bus, but I also ran an electric bass through it and got a very fat fuzz-tone without losing the bottom. And even at very saturated settings, the high-end sparkle stayed in place, which I found fascinating as many units roll off top and bottom end when you push them into distortion.

And finally, there is the Ruepel setting, which is an incredible leap into the realm of distortion and crunch. What was previously a really well-behaved and relatively transparent compressor becomes so raunchy that you’d guess certain sounds were being run through a distorted guitar amp with an intermittent short in the AC cable. I’ll do my best to explain why this is a good thing.

I was mixing an epic, genre-defying, nine-minute instrumental track for the band Pronto (Mikael Jorgensen of Wilco and his long-time collaborator Greg O’Keeffe —, and the core musical track was a beautifully screwed-up room mic that had been accidentally set near a PA speaker while tracking. This track holds jutting shards of distorted Rhodes piano, distant drums, probably some bass, and a ton of reflected echoes — a whole world in mono, born of a happy accident. The drum tracks I had, however, weren’t quite gelling with this oddly beautiful track, so I sent the drum subgroup out to the Comp.One and returned it parallel on the console. Pretty normal stuff, but when I popped the compressor into Ruepel mode and shortened the attack and release times, an evil, distorted, gating effect completely changed the sound of the drums, miraculously marrying it to the mix. I have never heard a compressor do anything like it, and it’s hard to explain just how messed up but great it sounds when you really push it.

I can imagine many of you thinking, “Who wants to put a $6500 compressor in the role of a distortion pedal?” But there is something to the sound of the Comp.One that — even when it’s destroying the signal — is so big, open, and powerful, that its particular brand of distortion can easily become the main sonic feature of a song. At its most completely screwed-up sounding extremes, it still maintains the full-range tonal nuance of the original signal. This is very hi-fi lo-fi.

Using the attack and release settings, you can also vary this chopping sound in really interesting ways. At the fastest settings, the beginning and end of a transient sound (say a snare hit) is sharply chopped on both sides. By lengthening the attack, you can soften the choppiness of the beginning of the sound, and by lengthening the release, you can soften the choppiness of the backside of the sound, such that the Comp.One’s attack and release knobs act like a set of ADSR controls. Again, I’ve never heard anything quite like it.

Interestingly, this most drastic aspect of the Comp.One has its roots in the variable-mu tube technology that has so often been heralded for its transparent nature. variable-mu compression operates by having the detector lower the bias voltage to the VCA tubes, which causes a gain reduction. Because the Comp.One has such a fast variable-mu circuit, in the overdriven Ruepel settings, these voltage changes are drastic and fast enough to create the quasi-gating effects mentioned above. It’s hard to remember that this same behavior, when mellowed out, generates some of the most open, transparent, and tonally satisfying compression I’ve heard. This wide range of behavior and sound is a testament to how well the designers, Oliver Gregor and Guido Apke, understand variable-mu circuits.

As I said, it takes quite a bit these days to make a high-end piece of gear stand out, and the Comp.One has done it in completely original and unexpected ways. The combination of extremely nasty and nuanced sweet sounds has me swooning for a piece of gear for the first time in a while. And, thankfully, you can order one without the pin-up girls on the meters, which is a great relief to me and some other people I know who prefer not to have the equivalent of semi-trailer mud-flaps staring at them when they’re checking gain reduction. Bravo to Rockruepel for their original vision and amazing execution. (€4450 EUR MSRP;

–Allen Farmelo,

Tape Op is a bi-monthly magazine devoted to the art of record making.

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