Radial ProD2 Stereo Direct Box: Eclipse Transformer Deep Dive 2026
Radial ProD2 Stereo Direct Box: Eclipse Transformer Deep Dive 2026
If you've spent any time running keyboards, synths, or laptop rigs through a PA system, you know the pain of ground loops, signal degradation, and that nasty high-frequency buzz that creeps in at the worst possible moment. The Radial ProD2 exists to solve exactly these problems — and it does so with a level of engineering that separates it clearly from the budget DI boxes cluttering up most stage pockets.
This isn't just another passive DI box. The ProD2 is Radial Engineering's purpose-built stereo direct box designed specifically for keyboards, digital pianos, laptops, and other stereo line-level sources. At its heart sit two Eclipse ETDB2 custom-wound transformers — and if you understand what that means for signal integrity, you already know why this unit commands respect on professional stages across Australia and worldwide.
Let's break down exactly what makes this unit tick, who it's built for, and whether the investment makes sense for your rig.
Understanding the Eclipse ETDB2 Transformers
The defining feature of the ProD2 — and frankly, the reason it exists as a separate product from Radial's other DI offerings — is the pair of Eclipse ETDB2 transformers. These aren't off-the-shelf components. Radial designs and specifies these transformers in-house, and they represent the sweet spot between the company's entry-level and premium transformer lines.
Here's why transformers matter in a DI box: a transformer-based (passive) DI provides galvanic isolation between the source instrument and the mixing console. This means there is no direct electrical connection between the two — the signal transfers magnetically across the transformer windings. This is your primary defence against ground loops, the single most common source of hum and buzz in live audio.
The ETDB2 transformers are engineered for wide bandwidth and minimal colouration. Where cheaper transformers roll off the high frequencies or introduce audible saturation at moderate signal levels, the Eclipse series maintains linearity across the full audio spectrum. For keyboard players running modern digital instruments with extended frequency response, this matters enormously. You're not losing the shimmer off your Rhodes patch or the sub-bass from your synth pads.
Transformer Specifications in Context
| Parameter | Radial ProD2 (ETDB2) | Typical Budget Passive DI |
|---|---|---|
| Frequency Response | 20Hz – 18.5kHz (±1dB) | 40Hz – 15kHz (±3dB) |
| Transformer Type | Custom Eclipse ETDB2 | Generic laminated core |
| Signal Isolation | Full galvanic isolation | Basic magnetic isolation |
| Low-Frequency Saturation | Minimal at rated input | Audible at moderate levels |
| High-Frequency Rolloff | Gradual, natural | Noticeable above 12kHz |
| Construction | MuMetal shielding | Basic shielding or none |
The MuMetal shielding on the ETDB2 transformers deserves a mention. MuMetal is a nickel-iron alloy with extremely high magnetic permeability, which means it's exceptionally effective at redirecting stray magnetic fields away from the transformer core. In practical terms, this means the ProD2 rejects electromagnetic interference from power transformers, lighting dimmers, and other sources of magnetic noise that are absolutely everywhere on Australian stages and in venues.
Complete Technical Specifications
| Specification | Detail |
|---|---|
| Type | Passive stereo direct box (2-channel) |
| Channels | 2 (stereo pair) |
| Input Connectors | 2 × 1/4" TRS (accepts TS also) |
| Output Connectors (Thru) | 2 × 1/4" TRS |
| Output Connectors (Balanced) | 2 × XLR male |
| Transformers | 2 × Eclipse ETDB2 custom-wound |
| Attenuation Pad | -15dB switchable (per channel) |
| Ground Lift | Switchable (per channel) |
| Merge Function | Stereo to mono summing |
| Input Impedance | Approximately 47kΩ |
| Power Required | None (passive design) |
| Construction | 14-gauge steel chassis |
| Dimensions | Approximately 130 × 85 × 45mm |
| Weight | Approximately 0.7kg |
Feature-by-Feature Technical Analysis
Dual-Channel Stereo Architecture
The ProD2 is essentially two independent DI channels in a single enclosure. Each channel has its own dedicated ETDB2 transformer, its own -15dB pad switch, and its own ground lift. This is an important distinction from some budget "stereo" DI boxes that share a single transformer or use a combined ground lift — with the ProD2, you have full independent control over each side of your stereo signal.
For keyboard players, this means you can run your left and right outputs with different settings if needed. Running a particularly hot synth on one channel while a more conservative digital piano feeds the other? Set the pad independently. Got a ground loop on only one side (which happens more often than you'd think with complex keyboard rigs)? Lift just that channel's ground.
The -15dB Pad: When and Why
The switchable -15dB attenuation pad on each channel addresses a real-world problem: modern keyboards and synthesisers often output signal levels significantly hotter than what a passive DI's transformer can handle cleanly. A Nord Stage 4, for instance, can push well over +4dBu from its line outputs. Without attenuation, you risk saturating even a quality transformer, which introduces harmonic distortion — pleasant in small amounts on guitar, not so pleasant on a clean keyboard patch.
The -15dB figure is well-chosen. It's enough headroom to handle virtually any professional keyboard's output without pushing the ETDB2 into saturation, while not so aggressive that you're killing your signal-to-noise ratio by forcing the console preamp to work harder than it needs to. If you're running consumer-level gear (laptops, phones, tablets at -10dBV nominal), you'll typically leave the pad off. For professional keyboards and synthesisers running at +4dBu, engage it.
Ground Lift: Your First Line of Defence
Every experienced audio engineer knows the ground lift switch is the first thing you reach for when hum appears. The ProD2's per-channel ground lift disconnects pin 1 of the XLR output from the chassis ground, breaking the ground loop that causes 50Hz hum (and its harmonics at 100Hz, 150Hz, and so on — Australia runs 50Hz mains, so that's your culprit frequency).
Having independent ground lifts on each channel isn't just a convenience — it's a troubleshooting necessity. Ground loops in stereo setups often affect channels asymmetrically, especially when your left and right outputs route to different stage boxes or snake channels that take different physical paths back to front-of-house.
Mono Merge Function
The merge function sums both stereo channels to a single mono XLR output. This is more useful than it might initially seem. Many smaller venues and pub gigs in Australia run mono PA systems, and rather than wasting two console channels on a keyboard that's only going to be summed to mono anyway, you can merge at the DI box and free up a channel. The summing is done passively and cleanly, maintaining proper phase relationships.
This feature also saves the day when you're short on XLR runs back to front-of-house. Rather than running two cables for a keyboard, merge to mono and run one. It's a compromise, sure, but in a pinch it works brilliantly.
14-Gauge Steel Construction
Radial's build quality is genuinely exceptional, and the ProD2 continues this tradition. The 14-gauge steel chassis is the same material thickness used across Radial's professional line. For context, 14-gauge steel is approximately 1.9mm thick — this is not a tin can that's going to cave in when a monitor wedge gets dropped on it.
The welded steel construction also serves a secondary purpose: it acts as an effective Faraday cage around the internal components, providing additional RF shielding. In an era where wireless microphones, in-ear monitor transmitters, mobile phones, and Wi-Fi routers are all pumping RF energy around every stage, this matters. RF interference manifests as clicks, buzzes, and in extreme cases, actual demodulated audio (yes, you can sometimes hear talkback radio through unshielded audio gear).
The I-beam internal structure that Radial uses — a feature they call "book-end" design — means the internal PCB and transformers are protected even if the chassis takes a direct impact. Radial famously drive over their DI boxes with tour buses in demonstrations, and while I wouldn't recommend testing this with your own unit, the point stands: this is equipment built for the reality of professional touring.
Real-World Performance Analysis
Keyboard Applications
The ProD2's natural home is between a keyboard and a mixing console, and here it excels. The 47kΩ input impedance is well-suited to the low-impedance outputs of modern keyboards and synthesisers. Unlike guitar DI boxes (which need much higher input impedance to avoid loading passive pickups), keyboard DI boxes need to handle line-level signals cleanly without colouration — and that's exactly what the ProD2 delivers.
Running a stereo keyboard rig through the ProD2, you'll notice the difference compared to budget alternatives almost immediately. The low end stays tight and defined rather than getting woolly and indistinct. High frequencies maintain their air and detail without the subtle dulling that cheaper transformers introduce. The stereo image remains accurate because both channels are matched — they use identical transformers from the same production batch.
Laptop and Backing Track Applications
For bands running backing tracks or click tracks from a laptop, the ProD2 is an excellent choice. Laptop headphone outputs are notoriously noisy — they share ground with USB ports, they pick up interference from the processor and display, and they're often unbalanced outputs running at consumer level. The ProD2's transformer isolation cleans up ground-borne noise completely, and the balanced XLR outputs can run long cable distances to front-of-house without picking up additional interference.
A common setup: left output carries the backing track to the PA, right output carries a click track to the drummer's in-ear monitor mix. The independent channel controls mean you can optimise each path separately.
DJ and Electronic Applications
DJs running line-level output from controllers or mixers into venue PA systems will appreciate the ProD2's ability to cleanly interface consumer-level gear with professional infrastructure. The ground isolation alone solves the majority of DJ-related noise issues that venue sound techs deal with every weekend across Australia.
ProD2 vs the Alternatives: Technical Comparison
| Feature | Radial ProD2 | Radial JDI Duplex | BSS AR-133 (×2) | Behringer DI20 |
|---|---|---|---|---|
| Type | Passive stereo | Passive stereo (Jensen) | Active (×2 units needed) | Active stereo |
| Transformers | Eclipse ETDB2 | Jensen JT-DB-EPC | N/A (active electronics) | Generic |
| Per-Channel Ground Lift | Yes | Yes | Yes | Yes |
| Per-Channel Pad | Yes (-15dB) | Yes (-15dB) | Yes (-20dB) | Yes |
| Merge Function | Yes | No | N/A | Yes |
| Power Required | No | No | Yes (phantom) | Yes (phantom/battery) |
| Build Quality | 14-gauge steel | 14-gauge steel | Machined aluminium | Sheet metal |
| Price Range (AUD) | Mid-range | Premium | Mid-high (×2) | Budget |
ProD2 vs JDI Duplex
Radial's own JDI Duplex is the ProD2's upmarket sibling, featuring Jensen transformers — widely regarded as the benchmark in audio transformer design. The Jensen JT-DB-EPC transformers offer marginally wider bandwidth and slightly lower distortion than the Eclipse ETDB2, but the real-world difference is subtle. In a blind listening test through a PA system in a live venue, most engineers would struggle to tell them apart. The JDI Duplex lacks the merge function, which is actually a practical disadvantage for some users.
The honest assessment: the JDI Duplex is the better unit on paper, but the ProD2 delivers 90% of the performance at a notably lower price point, with the added bonus of the mono merge feature. For most working musicians and sound engineers in Australia, the ProD2 represents the better value proposition.
ProD2 vs Active DI Alternatives
Active DI boxes like the BSS AR-133 require phantom power from the mixing console to operate. This introduces a dependency — if phantom power fails or isn't available, your DI doesn't work. The ProD2, being passive, works the moment you plug it in. No power, no batteries, no failure modes related to power supply.
Active DIs do offer some advantages: they can provide higher input impedance (useful for piezo pickups, not relevant for keyboards) and can include features like EQ or signal processing. But for keyboard and line-level applications, a well-designed passive DI like the ProD2 is technically superior in terms of reliability and noise performance.
ProD2 vs Budget Options
Budget stereo DI boxes from brands like Behringer serve the basic function but with significant compromises. The transformers (when present — some cheap "passive" DIs use resistive networks instead) saturate easily, introduce colouration, and don't provide the same degree of isolation. The chassis won't survive serious touring. And the switches and connectors are the first things to fail under professional use.
If you're gigging regularly in Australia — especially in the pub and club circuit where gear takes a beating — the ProD2's build quality alone justifies the price difference over budget alternatives. A DI box failure mid-set is not just an inconvenience; it can silence your entire keyboard rig.
Who Should Buy the Radial ProD2?
Ideal Users
- Gigging keyboard players running stereo rigs who need reliable, clean signal conversion night after night
- Sound engineers and hire companies building reliable DI inventories for corporate and live event work
- Churches and worship venues with permanent keyboard setups requiring set-and-forget reliability
- DJs and electronic performers interfacing consumer gear with professional PA systems
- Theatre sound departments needing dependable DI boxes for keyboard pits and playback systems
- Studios requiring clean stereo DI for tracking keyboards and synths
When to Look Elsewhere
- Acoustic guitar or bass guitar: You need a high-impedance DI like the Radial ProDI or J48 instead — the ProD2's 47kΩ input impedance isn't suitable for instrument-level pickups
- Ultra-premium applications: If budget is no concern and you want the absolute best transformer DI, the JDI Duplex with Jensen transformers is the step up
- Active source requirements: If you need features like input EQ, polarity reverse, or signal splitting beyond what the ProD2 offers, consider Radial's active options
Practical Tips for Australian Users
Dealing with Australia's 50Hz mains: Ground loops in Australia produce a 50Hz fundamental hum with harmonics. The ProD2's ground lift is your first solution. If lifting ground doesn't fully resolve the issue, check that your keyboard's power supply isn't sharing a circuit with lighting dimmers — a common problem in older Australian pubs and RSLs.
Cable runs on Australian stages: The balanced XLR outputs from the ProD2 can comfortably run 50+ metres to front-of-house without signal degradation or noise pickup. This is particularly relevant for outdoor festival stages and large venue setups common on the Australian touring circuit.
Heat considerations: Being a passive device, the ProD2 generates zero heat and has no temperature-related performance concerns. This is a genuine advantage for outdoor gigs in Australian summer conditions where active electronics can overheat.
Humidity and touring: The sealed steel construction provides reasonable protection against the humidity levels encountered in tropical Queensland or coastal NSW venues. Unlike active DIs with ventilation holes, the ProD2's sealed design keeps moisture away from the transformers and internal connections.
Technical FAQs
Can I use the ProD2 for a mono keyboard?
Absolutely. Just use one channel and ignore the other. You're not wasting anything — having a spare channel is useful when your setup changes. Many players start mono and eventually add a second keyboard or go stereo.
Will the ProD2 work with a guitar or bass?
Technically it will pass signal, but the 47kΩ input impedance is too low for passive guitar or bass pickups. You'll lose low end and the tone will sound thin and lifeless. Use a DI designed for instruments — the Radial ProDI or J48 are purpose-built for this.
Does the passive design mean signal loss?
All passive DI boxes introduce some signal loss through the transformer — typically around 1-2dB. This is negligible in practice and is easily compensated for at the mixing console's preamp. The trade-off is zero requirement for power and superior noise rejection, which is a net win for keyboard applications.
Can I run two separate instruments through the ProD2?
Yes. Each channel is completely independent. You can run a keyboard into channel one and a laptop into channel two with no interaction between them. Each has its own pad and ground lift settings.
How does the merge function affect the signal?
The merge sums both channels to a single mono output at the XLR. There is some level reduction when summing (approximately -6dB) which is normal and expected for passive summing. The console preamp compensates easily. Phase relationships between channels are maintained, so you won't experience cancellation issues with properly recorded or generated stereo content.
The Verdict: Engineering That Justifies the Investment
The Radial ProD2 occupies a smart position in the DI box market. It's not the cheapest option, and it's not the absolute top-tier — it sits right where most working professionals need it to be. The Eclipse ETDB2 transformers deliver genuinely excellent audio performance. The build quality is touring-grade without question. And the feature set — independent channel controls, -15dB pads, ground lifts, and the mono merge — addresses real-world needs that keyboard players and sound engineers actually encounter.
For Australian musicians and audio professionals, the ProD2 represents a piece of gear you buy once and use for decades. There are no batteries to die, no phantom power to troubleshoot, no firmware to update. It's a pair of precision transformers in an indestructible steel box, and it does its job flawlessly every single time.
If you're running keyboards, synths, laptops, or any stereo line-level source into a PA system, the Radial ProD2 is available now from MusiconStage — one of the smarter investments you'll make in your signal chain.
Need a reliable stereo DI that just works, every gig, no exceptions? Check the current pricing on the Radial ProD2 at MusiconStage and stop worrying about your DI box forever.