Manley Laboratories' SLAM!

By Barry Rudolph

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Mix Magazine "Compression And Compressors"


SLAM!The SLAM! (Stereo Limiter And Mic pre) defies categorization, combining an updated version of Manley's stalwart ELOP opto-limiter with a new FET-based brickwall limiter and two Class-A preamps with mic and DI inputs. The $6,000 SLAM! is a superanalog approach to louder-sounding recordings.

Construction is to Manley's excellent standards. There are two Lundahl mic transformers, two more feeding the FET limiter section and four Manley-made line I/O transformers. Caps are Wima and Multicap; the resistors are mostly 1% metal film; and some two-dozen relays handle audio switching. The external PS has a large, 16-pin, mil-spec connector. My review unit included the optional $2,500 Anagram Technologies Quantum AD/DA converter board.

The mic preamp uses a 12AT7 for 99% of the voltage gain with an FET in series with the tube's cathode. This design self-corrects for drift and tube changes, and capitalizes on the complementary characteristics of tubes and FETs by canceling out each other's inherent weaknesses. The new ELOP optical limiter circuit differs from the original Manley ELOP. A conventional op amp and transistor-current amplifier driver are used for better control, wider voltage swings for flatter response and faster action.

Below the large, lighted Sifam VUs and ladder LED peak meters are switches for meter modes, limiter in/out and stereo-linking, and a power switch that's dangerously close (for Mr. Clumsy here) to the other controls. Although calibrated in 1dB steps, my only wish is that the LED meter was twice the size and double the resolution.

The input knob adjusts levels of +4dB line sources and/or the DAC's output. This control usually runs straight up at 12 o'clock with +/- 20 dB of range; but for mic or DI sources, it operates like a standard gain knob. Likewise, the output control operates at unity gain (normally around 12 o'clock) and also has a +/- 20dB range. Unlike a makeup gain control on a compressor, the output does not go to zero for fade outs or muting; it's more like a master output-level trim.

The ELOP limiter has only a single control: threshold. Fully CW at +26 dB is off, and it ranges to +6 dB. ELOP's other control is the SC (sidechain) Filter switch. It has three positions: flat (no sidechain filtering); a 100Hz, 6dB/octave HP filter; and a 200Hz corner frequency position that also adds +3 dB at 4 kHz. Great for mixes where hot kick and bass levels would otherwise cause pumping, the 100Hz position provides more limiting, better control and makes your mix louder. The 200Hz position is best for recording or mixing vocal tracks, and its 4kHz boost causes a subtle de-ess action. The 200Hz roll-off allows more limiter depth with less-errant gain reductions caused by "p" pops or other LF plosives.

The FET limiter has attack/release/threshold controls. Attack has three positions: moderate (10 ms), fast (1 ms) and very fast (0.1 ms). The 11-position release control varies from two seconds to 10 ms. Medium release times in the 50ms to 200ms range provide for maximum loudness. The threshold control ranges from +26 off to +6 dB. All controls on SLAM! are interactive: Every parameter change affects the other settings. Increasing the speed of attack will cause more frequent gain reductions, and overly fast release times can cause LF modulation distortion; listen before committing to a superfast release setting. A clip-release position simulates an overdriven electronic distortion that could work for guitars or synths.

SLAM! accepts audio from the DAC output (if your unit is equipped); a rear-panel Neutrik Combo jack line input; DI from a dual-impedance, 1/4-inch rear-panel jack (30 dB more gain than line); and mic (60 dB of gain), with or without polarity flip and/or 100Hz highpass filter.

One quirk: Both balanced line and mic inputs share the same XLR jack. To prevent accidental application of phantom power to a line source, the phantom switch is also on the back panel. Other rear connections include a TRS balanced DAC output, an unbalanced 1/4-inch -10/ +4dB output jack and two rows (one for each channel) of six TT patchbay jack/inserts. These are send and return paths to both the opto and FET sections to insert external EQ (or whatever) to these limiters separately. Other TT jacks let users link multiple units for multichannel or surround audio.

Swiss-based Anagram Technologies' optional AD/DA converter plugs into SLAM!'s rear panel and provides digital I/O. The DAC asynchronously up-converts a digital signal to 192 kHz using a high-speed SHARC DSP chip running 40-bit, floating-point software. This results in near-zero jitter, thus reducing audio "time smear." The DAC converter analog output is then routed through SLAM! for peak limiting and returned to the Quantum ADC, sampled at 192 kHz, while a second SHARC down-converts to 44.1/48/88.2/96 kHz. Future designs will include 192kHz capability when the connector issue is finalized--an easy upgrade, as the converters are already running at 192 kHz. User choices include 16/20/24-bit wordlength; dither and noise-shaping on/off (only if you are not 24-bit); Word Clock and Super Clock inputs; and three filter settings to "personalize" the sound.

Setting up a limiter is more critical and time-consuming than using a compressor. A lead vocal with 5 dB of limiting can sound louder than 10 dB of constant 1.5:1 compression, where the compressor raises quieter sections but lets fast, distorting peaks hit your A/D converter. The limiting ratio of SLAM!'s ELOP goes to a maximum of 10:1 and it's soft-knee- and program/drive-dependent. The FET limiter starts at 5:1 and gradually climbs to 8:1 with a maximum, practical gain-reduction depth of 15 dB! Because the ELOP can do about 20 dB of GR, the two combined offer a total gain reduction of 35dB gain.

For all recorded sources, I used tracks and mixes from a Pro Tools|HD3 rig and a large Nuendo PC. I began with both the ELOP and FET threshold knobs set to max CW, or +26 dB. I used a 1kHz tone to set input and input-level controls to 0 dB. The controls are a little touchy at first, and I wish there were separate bypasses for both the ELOP and FET sections.

I used SLAM! on every imaginable audio source. On live kick drums, it's a godsend. You can record full digital levels and not be concerned when the drummer plays a little harder and (normally) goes into digital clip; the drummer won't with SLAM! in the way. I used the Medium and Fast attacks on drums. The VF setting was so fast that the percussive edge is rounded off too much. Lower threshold settings and VF work well for things like guitars, vocals and bass, although the ELOP section usually controls these sources very well without the FET limiter.

I tested the mic preamp section using a Lawson 47 condenser. With loads of gain, the mic preamp has a lively, open and clean sound with excellent dynamic range, most noticeable in the quieter and subtle moments. I was listening to both speaking and singing vocals on-mic. The Lawson's owner never heard his mic sound so good. He always thought it sounded a little muffled, and now considers his regular preamp the reason.

Next, I recorded a 9-foot Yamaha grand piano using two DPA 4011 cardioid condensers. I liked the mic preamp's "tube-y" sound for a round and sweet tone, even on this bright piano.

The 1/4-inch DI input is dual-impedance: Plugged all the way in, it's 100k-ohm; half-way out, it's 10Meg ohm. My bass player (and I) preferred the 10M position for its more open and clear sound from his Fender P Bass pickups. I used both the ELOP and FET sections to limit the bass. Wow! I have always had trouble with recording bass (to digital) when the player 'slapped' or 'popped', causing immediate overs. Analog tape would take care of these peaks; digital doesn't. I set the ELOP to clamp most of them without killing the rest of the performance's dynamics. At a slower release and a fast attack, the FET section brickwalled the rest.

Full analog-based mixes that you want to be loud benefit the most from using the ELOP and FET together. I use about 2 to 6 dB of ELOP limiter on certain rock songs (which consist of mostly compressed individual tracks) and then added up to about 2dB peak limiting from the FET. My average loudness came up anywhere from 3 to 7 dB, but my peak level was about the same: around 1 to 2 dB below digital full-scale. I could go hotter, but the filters in ADCs require 1 to 2 dB of headroom and you may want your mastering engineer to have some room to work, too.

Mixes from a Nuendo PC were fed using the Anagram ADC/DAC. The limiting process is the same as using the analog inputs, except that I was able to take in a session running at 44.1 kHz and output a 96kHz mastered stereo mix. If you output the same rate as the session, then you'll have to use a master word clock. I could add 3 to 6 dB of loudness and still love the overall sound quality. I could have added more, but you start to trade off good music fidelity for just "louder."

SLAM! is the ultimate analog front and back end for any recording studio. With the Anagram Quantum option, I could cleanly record tracks with a pair of clear, Class-A mic tube preamps with minimal peak limiting using the ADC, and then master the final mix using the DAC/ADC path and the modern-sounding ELOP/FET combo. All of my clients want this process for louder mixes, and SLAM! gets there with a gorgeous sound and a minimum of sonic mangling.

Manley Laboratories, 909-627-4256,

Barry Rudolph is an L.A.-based recording engineer. Visit his Web site at: WWW.BARRYRUDOLPH.COM

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