LaChapell Audio: 583S mk2 tube preamp

Let's paint a picture. If you are new to painting, let's paint by numbers. If you have been at it awhile, let's explore and start mixing our own colors and use more than just a paintbrush to apply it.

Now, in the hands of a novice, even the best paintbrush and the finest oils in the world are likely to yield strictly two-dimensional results. But as practice continues, and you fritter away more of your evenings with Bob Ross, you start to realize that those trees you've been painting straight-green have an incredible rainbow of light and dark shades and tones. As with the visual arts, the practice of recording audio operates on a continuum of growth, revealing more and more as time goes on. As the ear develops, we desire more colors to paint and more tools to put those colors on canvas. The newest offering from LaChapell Audio is a mic preamp in the 500-series form factor that opens up a wide spectrum of shading and coloration for your sonic landscapes.

The original 583S was the first tube mic preamp designed specifically for the 500-series and was based on LaChapell's flagship 992EG circuitry in single-ended form [Tape Op #65]. It was a double-wide unit, but the new 583S mk2 is a single-slot module. As more and more excellent 500-series modules become available, space in the 500-series frame is at a premium, and leaving room for another module is a welcome thing. Designer Scott LaChapell said this about the 583S mk2:

"The opportunity to offer a high-end vacuum tube solution for this frame size, something everybody had said was an impossibility, was appealing to us. We wanted to crack that nut. It also gave us the opportunity to offer a LaChapell preamp in the $1000 range."

And now, esteemed readers, you likely are about to learn something new:

"The key factor was our DC-to-DC converter. Taking a ±16 V supply (standard API lunchbox power supply) and converting it to 250 V for the 583S is not terribly difficult. But going from 16 V to 250 V quietly gets pretty tricky. We take the ± rails and convert up to 250 V, but to be VTR certified, you have to fit into the 130 mA per slot requirement.

"The 12AX7 doesn't have just one voltage requirement. It also has a filament that requires 12 V and pulls 150 mA, so the question was, how are we going to satisfy both the filament and plate voltages and stay within 130 mA? The solution was to be very creative in spreading out the current between the ± rails. So essentially, when the 12AX7 is pulling 150 mA, it's satisfying that current requirement from both rails simultaneously. This helped us to properly power the tube with 250 V for the plate supply and 12 V for the filament.

"A 12AX7 tube will indeed work at 100 V on the plate, but it will not perform or sound like a 12AX7 (per RCA/GE 12AX7 power requirement standard). The gain tube in the 583S is operating under the same power conditions as the input gain tubes in a LaChapell 992EG."

All of this power conversion is happening within the module itself and poses no risk to your current 500-series rack or its stock power supply.

The 583S mk2 has a Cinemag CMMI-10 input transformer and a Jensen JT-11 line output transformer, and the usual features of 48 V phantom power, polarity reverse, and a -20 dB pad. The 1/4'' DI defeats the transformer automatically for hi-Z inputs. The unit has an internal gain of +72 dB, a frequency response of 10 Hz-50 kHz, and a maximum output of +26 dBu.

Out of the box, the module looks and feels like a solid piece of machinery. It has a nice heft, and everything about it showcases a no-compromise build. The two aluminum knobs (for input and output) have a great feel, are detented in micro increments, and are just more evidence of the beautiful craftsmanship that went into the design and build of this unit. Also, almost as "proof" of the tube, these knobs get warm to the touch after the unit has been on for a while. For sedentary reptilian engineers, this is also good for getting the blood flowing. All switches for 48V, polarity, and pad are solid. Layout is simple and clean, and all functions are easily accessed. The module even has a small handle at its base to ease installation and removal. There is one small light on the unit labeled 250V that indicates that the internal voltage converter is receiving proper DC power from the rack to operate the tube.

I had a recent session with Baltimore singer/songwriter and ukulele-slinger Victoria Vox, and I was anxious to put a pair of 583S mk2 preamps into action. The first deployment was on kick and snare. I somehow expected the preamps to sound a bit wooly and soft, but man was I wrong! There was an absolute deliverance of power and tone. I loved being able to drive the tube on the input stage to dial in the right amount of grit and hair onto the individual sources. The bottom was nice and round, but plenty of punch, clarity, and focus was maintained. With my subwoofer on, the low-end content on the kick was simply massive. As I had done with the kick, I found the sweet spot for the snare drum by balancing the input and output stages for the right amount of tube color and smack.

It went on and on from there. I used the preamps on ukulele, horns, vocals, and bass. Each time, the results were impressive. From clean and sweet, to dirty and tough, the 583S mk2 made the cut. Married with different mics, the preamp offers a color palette that is essentially endless. There was not one thing I thought was a mismatch for this preamp.

The DI input sounded great too, bringing additional vibe to synths, bass, and other direct sources. One particular example of really leaning on the tube was when we recorded a Rhodes through the DI. In this particular case, we were caught in the middle of the Rhodes feeling like the right tonal choice for the song, but thinking it was sounding a little soft and a bit too blended into the track. Instead of going to the Wurlitzer, I just pushed the Rhodes into a bit of overdrive using the input knob on the preamp. Listening back, you'd swear it was tracked through an amp - only it wasn't noisy! And this is really the magic of this device. Having the opportunity to shape the tone and aggressiveness of a source makes this a very powerful tool. Another visual reference - think of being able to raise the hair on a dog's back with the turning of the input knob. When you increase the tube drive, the sound gets more aggressive, and conversely, when you reduce the drive, things get smoother and tamer. Also worth noting is that the 583S mk2 is extremely quiet. From the cleanest to the most aggressive of sounds, the preamp delivered pure tone and very little noise.

I like to think of recordings as sonic visual images, and a tool like the 583S mk2 opens up a whole range of color gradations and possibilities. Don't misunderstand me. This is not a box with a billion knobs, buttons, switches, menus, and submenus. What it is, is a very simple and straightforward device that is deceptively deep in the range of tones it is capable of achieving. From very pristine and crystal clear on a source like acoustic guitar or vocals, to additional grit and meat on an overdriven electric guitar, the 583S mk2 delivered every time - with beautiful results.

I love things that just simply do their job as intended, and produce excellent results without me needing to endlessly tweak or hijack a session while I search for the magic. I selfishly just want it to be there at my convenience every time. That is why I so enjoy this mic preamp. Plug it in, and it delivers from note one. As we progressed through the Victoria Vox session, I began to lean on it more aggressively to provide tonal colors where I would typically rely on EQ. Saturation of some tones contrasting with the punchy clean of others created the "mix picture" as we were tracking, and logically informed each successive step.

As a mic preamp with broad sonic possibilities, exhibiting excellent build quality, sized for a single 500-series slot, and priced under $1000, this unit should not be overlooked. If you'd like to start painting better sonic images with more interest and depth, the LaChapell Audio 583S mk2 would be a beautiful addition to your collection.

($945 street; www.lachapellaudio.com)