Lunching With the 500 Series Roundup

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It''s a digital world, right? Not until our ears, acoustic instruments, and air pressure differentials are digital. Fact is, the “all-digital” studio has a lot of analog in it, starting with mic pres and ending at speakers.

But there might not be enough space, budget, or need to justify a rack that''s chock full o'' gear—so cue the 500 Series Lunchbox (trademarked by API) modules. Consider them analog plug-ins: Once you have a frame to hold them, you can mix and match modules to come up with the configuration your needs, tastes, and finances dictate.

These are not “lite” versions of bigger brothers. They don''t need a power supply, a large case to hold those power supplies, or in fact, a large case at all—which cuts down on price, without cutting down on specs. Sure, there might not be as many knobs and switches; or there might be, because some 500 Series manufacturers have discovered the joys of concentric controls.

It all started with API (thanks, API!), who created a spec, opened it to the world, and initiated the VPR Alliance standardization guidelines for 500 Series modules. The industry promptly adopted this protocol as a simple, easy way to create the equivalent of an outboard channel strip—but since its introduction, the Lunchbox has grown into a banquet of guitar processors, utility boxes, headphone amps, vintage re-creations, and even analog/digital converters.

Ready to check out the latest in the world of analog plug-ins? So are we . . . grab a menu, and let''s do lunch(box).

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The Workhorse is a more sophisticated, more capable, and more costly re-thinking of what a 500 Series rack frame should be. Rather than simply holding modules, the Workhorse puts increased emphasis on I/O and patching, additional module control, and internal mixing/monitoring.

Main Course: As expected, the Workhorse is compatible with 500 Series modules that conform to the VPR Alliance guidelines, and holds up to eight single-space modules. Four of the single slots can also accommodate two dual-slot modules. Although you''ll need Radial''s modules to take advantage of all of the Workhorse''s extra capabilities, the spec is open and already other manufacturers are designing modules that work in standard frames but also work in an “enhanced” mode with the Workhorse.

For example, although there''s rear panel I/O (standard XLR, paralleled TRS 1/4", and D-Sub), Radial modules bus to the internal 8x2 mixer for adjusting level, muting, and panning, as well as driving two sets of headphones through a macho headphone amp. (The outputs are isolated with Jensen transformers—cool.) Built-in switching sends one module''s output directly to the next module''s input, so you can create a series “channel strip” without patch cords; the standard API link function is also available for stereo modules. Furthermore, it''s possible to cascade Workhorses for up to 32 channels.

There''s a workaround with non-Radial modules for using the monitoring options: Use a TASCAM/Pro Tools D-Sub cable to connect the Workhorse''s D-Sub direct outs (which parallel the module outs) to the D-Sub Summing Mixer inputs. This input also lets you access the mixer for “out of the box” analog summing. A third D-Sub connector provides paralleled access to the module inputs.

Rear panel I/O includes a unique Radial feature, the “Omniport,” which provides access to a particular module function such as a key input, split output, insert (e.g., delay feedback loop for adding filtering)—or whatever the designers decide to stick in there.

Dessert: The Workhorse is clearly designed as a premium way to hold 500 Series modules, with performance, construction, component quality, design, and price to match. It''s built like a tank (all-steel construction), with a hefty 1.6A global power supply (100–240V). This reserves 400mA for the mixer/monitor, with the remaining 1.2A available for the various modules—that''s an average of 150mA per module, although modules can draw more than that as long as the total doesn''t exceed 1.2A. Note there''s no on-off switch.

There are less expensive, yet still effective, ways to get into 500 Series modules; but if you want to take the 500 Series experience beyond just putting modules in a frame and patching them into your system as needed, there''s currently nothing like the Workhorse.

The Check: $1,500; also available without the mixer (but it''s retrofittable) for $800

Reservations:Radial Engineering Workhorse product page

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Super-clean, transformerless, high-gain mic preamp and instrument direct input.

Main Course: This is not about “character,” but straight wire with gain—up to 70dB, with extremely low noise. There''s also an instrument direct in with a 2.5-megohm input impedance and thru for feeding an amp (or other audio input). The circuitry is based on their P8 preamp, but with what True calls “Type 2” circuit enhancements.

Although True claims “analog warmth,” I''d call it “analog sweetness” as there''s clarity and exemplary transient response, but without brittleness—if your ears are acclimated to digital, the pT2-500 represents what high-frequency response should sound like.

As to the DI, the minimal loading is ideal for some applications (e.g., that glassy, bright, single-coil Strat sound) but may be too bright if you''re going to subsequent pedals or amp sims. However, dialing back your guitar''s tone control slightly is a simple fix.

At the low end, the bass is both tight and full, and the clarity is similar to the high end. The pT2-500 excels for bass DI. You can trim incoming muddiness somewhat with the highpass filter, but it''s a gentle filter (down –3dB at 80Hz), so don''t expect to “brickwall out” rumble, handling noise, AC hum, etc. Other noteworthy features include gain control detents, four LEDs to indicate signal strength, two-stage gain switch, polarity switch, and +48V phantom power enable.

Dessert: The pT2-500 seems best-suited to acoustic instrument sources like acoustic guitar, percussion, strings, or anything else with major transients and significant high frequency content. I had great luck with feeding the piezo out from a Gibson J45 into the DI (although of course you can''t run a mic and the DI simultaneously), and had equally good results with bass. The mic input''s 5.5-kilohm input impedance is a little higher than normal, which seems to give more clarity with dynamic mics; past the hand-matched phantom power blocking caps, the circuitry is DC-coupled. The pT2-500 succeeds at providing neutrality with clean gain.

The Check: $749

Reservations:True pT2-500 product page

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This is very similar to the pT2-500, but optimized for dynamic and ribbon mics.

Main Course: The focus on dynamics and ribbons means there''s no +48V, and to make ribbon mics happy, the gain goes up to 76dB (with DC coupling and a 10-kilohm input impedance). Also, the low-frequency rolloff is much more developed than the pT2-500—a rotary switch chooses among an off setting and corner frequencies of 40, 80, 160, 280, and 400Hz. (According to the company, the rolloff is handled in a non-traditional way that doesn''t involve capacitors in the signal path.) While the higher frequencies may seem like a radical choice, in practice I was surprised at how effective the higher rolloffs were with voice—I wouldn''t mind having that low-cut filter in a box of its own.

Dessert: If you''re absolutely sure you won''t be using condenser mics, or can afford to specialize, the pT2-500D fulfills a unique need. That said, the pT2-500 does a credible job with all types of mics; if you could afford only one pT2-series preamp, the pT2-500 would be a better “general-purpose” choice.

The Check: $749

Reservations:True Systems site

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This simple, two-band program equalizer adds a gentle, unobtrusive boost or cut to the highs and lows, while adding a subtly warm character. Vintage compressors like the Pultec were often good at this sort of task (Purple Audio acknowledges the Lang PEQ-1 and Klangfilm RZ062 as inspirations); the LILPEQr brings this philosophy into the 500 Series world, with excellent build quality.

Main Course: The LILPEQr has only three knobs and two switches. The top knob handles high-frequency shelving, with an accompanying switch that chooses among three corner frequencies (5kHz, 10kHz, and “Air”). Another knob handles low shelving, with corner frequencies of 50, 80, and 160Hz. There''s also an overall level control with a twist—the bypass switch (which does relay-controlled switching) has two “in” positions. The first simply injects the post-input transformer signal passively into the tone control circuitry. The second position inserts a buffer between the input transformer and tone control circuitry, thus isolating the transformer and altering the tone somewhat. In this mode, the Level control is available as well, and the tonal quality seems very slightly brighter in the upper midrange. Although the tonal difference is in the “splitting hairs” category, options are always welcome.

Dessert: One obvious application is going “outside the box” to a compressor or limiter for mastering—LILPEQr can do appropriate EQ while staying analog; this really is a “kinder, gentler” equalizer that avoids any unnatural tonal quality. However, it''s not as kind to your wallet if you want stereo—you''ll need two of them. Then again, stereo isn''t the only game in town, and you''ll find LILPEQr helpful with vocals, drums, synths, guitar—pretty much everything that could use a little tone-shaping. This module may be simple, but it''s not simplistic.

The Check: $625

Reservations:Purple Audio LILPEQr product page

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If you have a Purple Audio Sweet Ten (their 500 Series, ten-slot frame), Moiyn inserts in slot 9 and provides an 8x2 summing mixer for modules in slots 1–8.

Main Course: The modules in slots 1–8 don''t have to be from Purple Audio; any 500 Series modules will work, and their XLR outs for the eight slots are still available. Moiyn''s transformer-isolated stereo outs terminate in slot 9''s two XLR outs, but there''s a Sweet Ten-specific function: An additional set of transformer-isolated stereo outs can jumper over to a Purple Audio Cans (their overachieving headphone amp) module in slot 10, without needing patch cables. The Moiyn mix bus is also accessible via its stereo input, which allows cascading multiple units if you''re into the analog summing thang.

There are no level or pan controls, but each channel has pushbutton switches to assign an input to the left, right, or both channels.

Dessert: Moiyn is of limited use in the 500 Series universe, as it''s Sweet Ten-specific. However, for those who do have a Sweet Ten, the ability to add on-board mixing simplifies the process of submixing and monitoring, while opening up the possibility of analog summing within a 500 Series frame.

The Check: $725

Reservations:Purple Audio Moiyn product page

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This transparent mic preamp features a DI input, and subscribes to the “clean and honest” philosophy instead of trying to add a specific character.

Main Course: Once you reach a certain level of excellence in performance, there''s nowhere left to go. You can''t get any quieter than the theoretical minimum noise level, and if you haven't loaded down a guitar pickup with a DI (the HV-35''s input impedance is 2 megohms), you haven't loaded down a pickup. The bottom line is that the HV-35 sounds excellent, with specs that are similar to other 500 Series preamps that embrace the “straight wire with gain” philosophy. This is not unexpected when you reach the performance limits of current technology, but you will find differences in terms of features.

Like the main input, the HV-35''s DI works in conjunction with the gain control to offer 15–60dB of gain, but also incorporates its –15dB pad into the circuitry. I found this essential for electric instruments with hot pickups, as 15dB of gain produced distortion. Interestingly, though—and this was a big surprise—overloading the DI input gave some useable distortion sounds. The best applications I found were single bass notes, and turning up drums for just a slight amount of clipping to shave off transients. This gave a bigger sound, without obvious distortion. I doubt that this is an intended feature, but of all the “wrong” things I tried with the modules I reviewed (like creating feedback paths—fun stuff!), this was one of the most useful.

Construction is very sturdy; unlike some modules, the sheet metal wraps around the back of the module, and the output impedance is lower than average (about 25 ohms). In ribbon mode, the HV-35 attains 70dB of gain and DC-couples the input to the gain stage.

Dessert: The HV-35 is extremely well-built, sounds great (actually, it''s more like it has no sound at all), and its DI is well-implemented. It accomplishes its goal of transparency, but also has the depth that''s the hallmark of a well-designed amplifier.

The Check: $799

Reservations:Millennia Media HV-35 product page

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I almost didn''t cover this, as it seemed too out of character to include a digital device among all these analog goodies. But that also makes it unique, so . . .

Main Course: The AD-596 provides eight channels of A/D conversion, using DB-25 connectors for the analog ins and digital outs. Resolution is 24 bits, with a choice of 44.1, 48, 88.2, or 96kHz sample rates. You can of course sync to AES, but the unit also has front panel word clock I/O.

Although I didn''t have any device capable of accepting all eight digital ins via DB-25 connector, Millennia Media provided a breakout cable so I could test individual AES outs (which I sent to Phonic''s Digital Console), as well as an input cable that brought Workhorse outs into the converter.

Frankly, the whole experience was pretty boring: The AD-596 was easy to hook up, worked without having to do anything other than make connections, sounded wonderful, and yes, fits in a standard 500 Series frame. The only real excitement comes from watching the peak indicator LEDs for the eight channels to see if they indicate clipping, and the fact that you can set the LEDs for peak hold as well as clear them—good for on-location recordings if you want to know whether there was an over when you weren''t looking. Another cool feature is what Millennia calls True-Lock-Clock, which basically means if the external clock goes away, the AD-596 switches over to its internal clock.

Dessert: I''m pretty sure this is the only digital 500 Series device, but it demonstrates the depth of the spec. Think about it: When used in conjunction with a frame like the Workhorse, you could have seven mic pres, send their outs through a DB-25 cable into the AD-596, then patch the AD-596 output into your recording device of choice . . . compact, portable, and comparatively speaking, inexpensive.

The Check: $1,500

Reservations:Millennia Media AD-596 product page

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Yes, it''s a mic pre; but the PowerPre has some interesting extras in addition to offering value.

Main Course: The circuitry is all-discrete, with a Hammond transformer-coupled output—a plus for those who like some iron in the signal path. Two ergonomically cool convenience features include a front-panel XLR jack, and recessed +48V switch that''s almost impossible to turn on accidentally. There''s a –15dB pad, polarity flip switch, and 150Hz high-pass filter that''s down –3dB at 100Hz.

One of the most useful features is the three-position “Vox” switch, although it''s for more than just voice. The Linear switch position is flat, Breath gives a slight high-frequency lift starting around 2-3kHz, and the Punch setting gives a bit of a low-end boost around 90Hz. This imparts more depth to voice, but also try it with open-back guitar cabs to hype the otherwise attenuated low end. These are subtle differences (it sounds like essentially passive circuitry at work), but they''re effective nonetheless.

The metering is above-average—a 10-segment meter instead of just a few LEDs. And if you use the PowerPre with Radial's Workhorse frame, you get some extras: You can tack on another +15dB of gain for 70dB total, and the Omniport provides a direct input for guitar, bass, etc. The input impedance for the DI is 150 kilohms, which will produce slight, audible dulling with some pickups (I''d rather see 220 kilohms or higher); but one welcome DI aspect is you can use the 15dB pad with it, so if you want to plug in a high-output unbalanced signal (e.g., synthesizer) you''re covered. However, the DI feature is more of an extra—Radial''s JDV Pre is dedicated to comprehensive DI functionality.

Dessert: The PowerPre is a fine example of a well-designed, low-noise mic preamp that can give a bit of “meat” or “air” to a signal, thanks to the transformer output and voicing EQ. As a preamp that''s capable of character as well as fidelity, it might well be your preamp of choice when you''re looking to flatter a signal source rather than just reproduce it.

The Check: $600

Reservations:Radial Engineering PowerPre product page

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Let''s go to a lunch place that does a smorgasbord, and check out three items of particular interest to guitar players.

Main Course: The JDX DI box offers two functions. One is a more traditional DI, which also includes 4x12 cabinet emulation. The idea here is you can plug into your pedalboard, plug the JDX into your recorder of choice, and get a realistic guitar + cab sound. The second option inserts the JDX between your amp and speaker, where it captures the sound they produce (and it really does; note the JDX is not a load box, but must be used with a “real” amp and speaker in this mode). Additional tone shaping, a ground lift, and phase invert button round out the feature set. However, the input impedance is 10 kilohms, so Radial assumes you''ll have something between the guitar and JDX (e.g., some kind of stompbox or buffer) to prevent loading passive pickups.

The EXTC is for using guitar-level boxes in a studio context. It takes a line-level balanced in, converts it to guitar-level unbalanced with transformer isolation, takes the output from the guitar effects, then re-converts that back to line-level balanced out. Extras include a blend control that combines the dry and processed sound, and a phase reverse switch. (Guitar effects sometimes flip phase, which matters in a blend situation.) When used with the Workhorse, the Omniport becomes a second, TRS send/receive loop for studio effects, and patches after the guitar effects loop.

Finally, the X-Amp is designed for re-amping. It takes a line-level in from a recorder, splits it into two paths, buffers each one, then sends each split through an isolation transformer to two outs suitable for driving amps. It''s simple enough, but the transformers and additional ground lift switches for the amps minimize a lot of potential hum and buzz problems. Furthermore, the Workhorse Omniport jack provides a true DI input for guitar with a 220-kilohm input impedance.

Dessert: These three modules show that the 500 Series concept doesn''t have to be limited to general processors like EQs and compressors; it can include specialty devices designed for a wide range of tasks. Without expensive cases, connectors, and power supplies, a company can produce relatively small quantities of modules and still come out ahead—which means we come out ahead, too.

The Check: JDX $350, EXTC $300, X-Amp $300

Reservations:X-Amp product page, EXTC product page, and JDX product page

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The Optical Disrupter is an unusual type of compressor that adds an overlay of second-order harmonics when hit hard, which is especially useful with bass.

Main Course: 500 Series boxes aren''t just about throwing a preamp, EQ, and compressor into a frame to create a channel strip; more companies are stretching the boundaries into the domain of unusual tone-benders—like the Optical Disrupter. This compresses asymmetrically, so that positive parts of the waveform are compressed, and negative ones aren''t. With light amounts of disruption, the signal basically sounds compressed, with a very low-level “buzz.” Turn up the disruption, and the sound becomes more distorted, courtesy of second-harmonic distortion components.

Light amounts of disruption work on just about anything. Heavy disruption sounds fabulous with bass, as the more percussive peaks get a crunchy sort of “growl,” while lower-level signals are “rounder” thanks to the compression. It reminds me a bit of Chris Squire''s bass sound on early Yes albums. Disruption can also add serious moxie to drum sounds, particularly analog (e.g., TR-808) drums. However, you need to find the fairly narrow sweet spot between no disruption and too much disruption, which neuters transients.

Operation is simple: Dial in the desired amount of disruption, then add makeup gain as necessary. With low-level input signals, push in the X4 button. Aside from that, don''t bring it into the bathtub with you and don''t eat it, and you''ll be okay. However, note there''s no wrap-around case—it''s just a circuit board and front panel.

Dessert: The input impedance is about 43 kilohms (balanced), so you''ll load down passive pickups if you go in directly; use a preamp or buffer first. Overall, the Optical Disrupter imparts a unique, creative sound (as befits a device that was discovered by accident!) and adds extra spice to a variety of tracks—although my first choices would be bass and drums.

The Check: $399

Reservations:XQP 545 product page

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The EQ5P resembles a channel-strip 4-band EQ—but “outside of the mixer,” and designed for a more vintage sound.

Main Course: The four bands cover 16Hz–1kHz, 50Hz–3kHz, and two bands for 500Hz–21kHz. The top band can switch between a highpass or boost/cut response; the pots are concentric types, with the outer detented pot covering gain from –15 to +15dB.

None of the bands have Q controls. Instead, the Q narrows with increased gain, and widens with less gain (“proportional Q”). If you think about it, that''s generally what you do with Q controls anyway. The science of it is that the EQ5P mimics the response of a properly loaded inductor/capacitor tank circuit; what this means in practice is that it''s easier to make adjustments, and the correlation between gain and Q sounds “right” with various types of material. The end result is EQ that straddles the line between a more gentle, character type of EQ (e.g., Pultec) and a traditional parametric. If you need to get a little more surgical, the three lower bands have buttons that change the response to a fixed 1/3-octave bandwidth.

All circuitry is discrete—even the op amp is made from discrete components—and there''s an output transformer for those whose audio diet lacks iron. However, note that the case is enclosed on only three sides (although maybe that''s just to force you to observe the component quality). Interestingly, the bypass button, which doesn''t bypass the unit as a whole—just the filters—produces no pops or clicks.

Dessert: The EQ5P isn''t a conventional parametric; I would call it more of a “tone control,” and that''s definitely meant as a compliment. As such, it offers something that''s different from the norm, but like a conventional parametric, is useable with a wide variety of source material.

The Check: $949.99

Reservations:Tonelux EQ5P product page

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While many 500 Series modules put traditional functions in a more compact package, the TX5C is a unique compressor design with some novel features.

Main course: Like on the EQ5P, concentric controls allow for more control in a smaller package. For example, the outer “output” control tweaks the auto-makeup gain function, while the inner control offers dry/wet balance for parallel compression—it''s great to see more compressors including this essential feature. Another concentric control combines Attack and Release. (An additional button slows the attack time to five times the current value, and a three-stage auto-release can, for example, allow transients to come in and out of compression faster.) The top concentric control combines Ratio and Threshold. All controls have a center detent.

My favorite concentric control can blend (not just switch between) feedback and feedforward compression. (Its outer control handles a link function, from 50 percent to 100 percent, for stereo applications.) Another interesting twist: Part of the ratio control goes into “overcompress” territory, where input signal increases don''t just increase less, but actually decrease. With percussive material, if you set the attack time longer than the initial transient and overcompress, you''ll get a “super-peak,” or in the case of previously-compressed material, can the ability to recover some degree of dynamics. Another cool feature is the sidechain''s Tilt control; this can weight the RMS detection toward highs to reduce pumping, or lows.

The unit also features a six-LED gain-reduction meter and front panel connections for a sidechain input and external input; construction is similar to the EQ5P (and yes, there''s an output transformer).

Dessert: I''m very picky about compressors, but this is a honey. It takes more effort to adjust than most, because there''s more to adjust. But, I couldn''t find any signal that didn''t sound good with it—the parallel compression was great for drums and program material, while the feedback/feedforward options can add very different characteristics with acoustic guitar. When used traditionally, bass and voice rocked.

The Check: $949.99

Reservations:Tonelux TX5C product page