HHB Radius 5 Fat Man 2 Tube Mic Preamp and Compressor Review

The HHB Radius 5 Fat Man 2 like its predecessor, the Radius 3 Fat Man is certainly one of the more distinctive-looking pieces of gear on the scene. Comprising

The HHB Radius 5 Fat Man 2 — like its predecessor, the Radius 3 Fat Man — is certainly one of the more distinctive-looking pieces of gear on the scene. Comprising a single-channel mic preamp, DI input, and compressor, the Fat Man 2 offers a novel and compact alternative in the burgeoning market of front-end processors oriented toward the personal studio. Its portly personality is rounded out by a plethora of compression presets tailored for many common studio sources. Here's the skinny on the Fat Man 2.


For a fat guy, the HHB Radius 5 Fat Man 2 doesn't take up much space. The chunky chassis is a compact half-rack wide, letting the unit sit close at hand on a table or on another work surface. A single Fat Man (or a pair) can also be rackmounted in an optional three-space rack tray ($79) available from HHB.

The Fat Man 2's top panel, which slopes downward from front to rear, is made of perforated steel, thus providing breathing room for (and a nice view of) the unit's ECC83/12A×7A tube. Although the Fat Man 2 is advertised as a tube preamp, it is important to clarify that the preamp section is a hybrid design utilizing a solid-state front end followed by a secondary tube stage.

The upper half of the Fat Man 2's front panel is devoted to a round VU meter, status LEDs for compressor (green) and AC power (red), and logos screened on the standard HHB purple background. The bottom half is the business end of the unit, where the circuitry and controls are located. Six rotary knobs span the Fat Man's middle. The red Input-Gain knob is marked +16 at its counterclockwise extreme and +60 at the fully clockwise position and has a detented center position marked +38; the detented center also functions as unity gain for line-level input (marked as 0 dB). Beneath the knob, line-level gain is marked as -20 to +20. The next knob, moving right, is the off-white Output-Gain control (marked -• to +15), which has a nondetented 0 dB indication at the 12 o'clock point. Next is the gray Makeup Gain knob, which ranges from 0 to +20 and has intermediate markings at +4 and +12. (According to the Fat Man 2's manual, which is thorough, the aforementioned numerical gain values represent decibel measurements.)

The large gray Program knob beneath the VU meter lets the user select 1 of 15 compression-parameter presets: five for vocals; two each for acoustic guitar, electric guitar, and bass; and one setting each for snare, kick, loop, and keyboards. When the unit is in Program mode, all other compressor controls are disabled (though the Input-Gain control does let the user increase or decrease the signal strength relative to the fixed threshold level, thereby affecting the onset of compression).

Also provided is a Manual Compression setting. When in Manual mode, the Fat Man 2's compressor parameters can be manually adjusted by means of two black continuously variable knobs, Threshold and Ratio, located to the right of the Program knob. The Threshold knob is marked +10 to -20 (dBu), with intermediate marks at 0 and -10; the Ratio knob is marked 1:1.5 to 1:30, with intermediate marks at 1:3 and 1:10. In Manual mode, three two-position button switches at the bottom of the front panel (marked Knee, Att, and Rel) control knee characteristics (hard or soft), attack (slow equals 5 ms; fast, 0.5 ms), and release (slow equals 1.5 seconds; fast, 0.2 seconds).

Five other button switches — labeled Source (Instrument Gain), 48V On, HPF On, Comp On, and Meter — control, respectively, the input source (Mic [Hi] or Line [Lo]), 48V phantom power, a 90 Hz highpass filter, and the VU meter mode (output or gain reduction). Note that the Source switch also determines the appropriate gain mode for either source: mic or ¼-inch DI input (located on the lower-left corner of the front panel). As described in the manual, the DI input always feeds into the main signal path whether or not mic or line is selected; the gain selector basically allows line-level padding for samplers or stringed instruments with high-output pickups. Finishing out the unit's front panel is a round AC power switch.

The Fat Man 2's feature-rich front panel is logically laid out and fairly easy to negotiate. The Compressor On light proved an especially handy feature. I did miss, however, having a phase-reverse switch and an indicator LED for phantom-power status.

The Fat Man 2's rear panel provides a balanced XLR mic input, a balanced ¼-inch TRS line input, and a balanced ¼-inch TRS line output (see Fig. 1). There is no XLR output. A standard IEC power cable connection is also located there, but the unit lacks a provision for AC voltage switching or fuse replacement.


I put the Fat Man 2's mic preamp to work on a variety of sources during a daylong recording workshop. The unit provided plenty of gain in all situations. There were no noise problems, except for an inexplicable click that occurred just before the input-gain pot reached its +60 dB maximum.

When paired with a Sennheiser e602 mic, the unit delivered a nice low end on kick drum, and the resulting track worked well in the mix, even though it was a bit shy of upper-end clarity and attack. The Fat Man 2 also complemented electric basses (patched directly to the unit's DI input and through a Manley tube direct box to the mic input). An Epiphone jazz guitar sounded good through the unit's DI input, though the instrument's healthy output level produced grainy distortion at the Mic (Hi) setting. Switching to the Line (Lo) position eliminated the grunge, and though it raised the input gain close to maximum, it still yielded clean, crisp tones, without undue noise or muddiness.

Paired with an Oktava MC 012 small-diaphragm condenser, the Fat Man 2 gave a solid, chunky sound to an acoustic guitar. But after some close comparison, I preferred the extended highs and faster transient response of a more accurate solid-state pre on this instrument. In general, the HHB is not a particularly airy or detailed mic pre, and therefore it would not be my first choice for percussion, piano, or any delicate acoustic sources.

Interestingly, on the mix of diverse vocalists in the session, the unit's somewhat veiled high end proved sometimes a strength and sometimes a weakness. With some female singers, for example, the Fat Man 2 helped soften the etched highs of the Neumann TLM 103 mic I was using, giving good results. But on softer or underconfident vocalists, the HHB preamp sounded a bit dull and didn't help the vocal track cut through, particularly in a dense mix.


I gave the Fat Man 2's compressor section a good workout on a diverse range of instruments. Overall, when applying compression to average +4 dBu microphone signals from the unit's preamp, the programmed settings were less than subtle and often drastic. On kick drum, for example, engaging the appropriate compression preset resulted in extreme, heavy-handed squashing of the signal. Similarly, engaging the loop preset on a full-spectrum music mix (line-level in at unity gain, averaging 0 VU) produced wild pumping and dramatic fluctuations in level.

One remedy for this problem is to lower the signal relative to the threshold by lowering the preamp's input gain. However, it is then necessary to raise the output or makeup gain to get a usable level to the recorder. Once the gain was properly adjusted in that manner, the gentler presets were almost perfect for acoustic guitar, vocal, and bass compression. In a hybrid tube circuit, such gain changes can also produce subtle variations in the sound of the mic preamp, making A/B comparisons a difficult proposition. Picky engineers wanting to avoid changing the gain structure may find it easier to switch into Manual mode, duplicate the preset parameter settings illustrated in the manual, and adjust threshold and other controls to taste.

During a mixing session, I tried the Manual mode on a previously recorded tenor-saxophone track. The resulting compression was easy to hear, but it seemed a bit hard and aggressive, even with mild parameter settings (soft knee, slow attack, fast release, and low ratio). For this application, the slow attack time (rated by HHB at 5 ms) still seemed too fast and unforgiving. Additionally, an A/B comparison of the Fat Man 2 on a channel insert revealed that the sax lost some of its upper-end clarity and air when processed through the Fat Man 2. A trombone track was similarly dulled when patched through the unit, even with minimal gain reduction.

In other sessions, another engineer and I noticed that the Fat Man 2 tends to distort when compressing sustained bass-guitar notes, especially in the Bass 2 program. That is a fairly common problem with most compressors; however, it seemed worse than usual with the Fat Man 2, even when the unit was set for moderate amounts of compression and Slow release time. Fortunately, I didn't notice distortion problems on more percussive bass parts. Still, I preferred to dial in my own gentler settings (in Manual mode) to mitigate potential distortion artifacts.


As a mic preamp, the Fat Man 2 is true to its moniker — it imparts a noticeable low-end thickness to most sources. Although the preamp lacks the high-end clarity of some upscale designs, it is still a useful alternative to the preamps found in most budget mixing consoles.

I was less impressed by the performance of the Fat Man 2's compressor, particularly some of its preprogrammed settings, which are extreme. But it certainly has a worthwhile range of functional dynamics — some of the gentler presets are quite good — and those in search of subtler compression can always employ the Manual setting.

Overall, I'm amazed at how much control and flexibility HHB packed into the newest member of the Fat Man family. The Fat Man 2 is a solid, convenient, and quite affordable module that, despite the name, has a lot of muscle on its frame.

Myles Boisen is a guitarist, producer, and composer and is head engineer and instructor at Guerrilla Recording and the Headless Buddha Mastering Lab in Oakland, California. He may be reached by e-mail atmylesaudio@aol.com.


Radius 5 Fat Man 2
mic preamp/compressor



PROS: Compact. Affordable. Well featured, with a worthwhile array of preset dynamics controls. DI input with Gain Makeup switch. Compressor On LED. Mic preamp is a useful alternative to budget mixing-console preamps.

CONS: Slight loss of high-end clarity. Compression presets tend to be excessive and lacking in subtlety. Noticeable distortion on sustained bass notes. No phantom-power status light. No phase-reverse switch. No XLR output.


HHB Communications USA
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Radius 5 Fat Man 2 Specifications

Inputs(1) balanced XLR (mic); (1) balanced ¼" TRS (line); (1) unbalanced ¼" TS (instrument)Outputs(1) balanced/unbalanced ¼" TRSOperating Level+4 dBuInput Gain Range±20 dBOutput Gain Range+15 dBMaximum Input Level (input gain @ 0 dB)+6 dBu (High); +26 dBu (Low)Maximum Output Level+26 dBu (balanced); +20 dBu (unbalanced)Hum and Noise (compressor in and all gain controls @ 0 dB)-75 dBVFrequency Response20 Hz-20 kHz (+0, -1 dB; line input @ 0 dB gain or mic input @ 40 dB gain)Total Harmonic Distortion0.5% (typical) @ nominal level, 1 kHzSignal-to-Noise Ratio80 dBThreshold+10 to -20 dBRatio1:1.5-1:30Attack Time0.5 ms or 5.0 ms (switchable)Release Time0.2 sec or 1.5 sec (switchable)Kneehard or soft (switchable)TubeECC83/12AX7AMetermoving-coil VU; monitors output or gain reduction (switchable)Dimensions8.4" (W) × 5.2× (H) × 8.3" (D)Weight5.5 lb.