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Sonnect Audio Sound Bullet

Portable Audio Test Device By Hugh Robjohns
Published February 2022

As the XLR connectors protrude from the end, as well as hooking up to XLR cables, Sound Bullet can plug directly into equipment’s panel‑mounted connectors.As the XLR connectors protrude from the end, as well as hooking up to XLR cables, Sound Bullet can plug directly into equipment’s panel‑mounted connectors.

Every engineer needs portable problem solvers, and this offering from Sonnect Audio could become a constant companion.

No matter how well we maintain our audio equipment and how carefully we rig complex audio systems, sooner or later something won’t work as expected and the Law of Sod says it will be at the least convenient moment! Fast and efficient fault‑finding in a complex audio installation requires solid underpinning knowledge of the technology being used, a calm and logical approach, and some reliable test equipment. Of course, it’s that last element that’s so often absent when you really need it. To identify a broken cable you really need a cable tester. To identify a plugging or signal routing issue you need a signal generator and/or a signal level meter and speaker/earphones. And to spot which phantom‑power button has mysteriously managed to deselect itself when nobody was looking, you’ll need something that measures and indicates phantom power.

While I’m sure most of us have access to a decent cable tester, and a signal generator, metering, portable monitor speaker, and even a multimeter, this isn’t normally the kind of gear instantly to hand while rushing on stage or into the studio while everyone is staring at you to find and fix a problem. I’ve seen dozens of audio testing devices over the years, some more useful and usable than others, but it’s quite telling that the only one I’ve found useful, reliable, and convenient enough to carry with me everywhere for the last 30‑plus years is a home‑made Bright Eyes — a simple phantom power detector that can also be used to identify faulty XLR cables, which takes the form of a Cannon XLR plug on a keyring!

Sound Bullet

That’s why Sonnect Audio’s Sound Bullet was invented. David Scorteccia, a professional live sound engineer working in the UK, tried to find a comprehensive but convenient audio tester he could use in his day job and couldn’t find anything that met his needs. So he decided to design his own. Like most good ideas, the Sound Bullet was born out of a practical, everyday necessity. David needed something compact that he could carry with him easily to test mic cables, check for the presence of phantom power, and prove audio lines to and from the stage. Having identified these requirements, it took David four months to come up with his first working prototype.

Sonnect Audio's Sound Bullet portable audio test device.Of course, having a great idea is worth nothing if it can’t be turned into a realisable product, but David had an advantage there: his father owns an electronics manufacturing company in Perugia, Italy. As David used the prototype in earnest on a daily basis more ideas emerged for additional useful functionality and, with his father’s help, the design was refined and turned into a practical product which is now manufactured entirely in Italy. The PCB, metalwork and other components are all sourced within 100 miles of the factory, which also takes care of the assembly, testing, order fulfilment, and invoicing.

The Sound Bullet is a very compact yet surprisingly capable audio test system, measuring just 130mm in length and roughly 30mm square, housed in a metal box and powered by an internal rechargeable battery. It feels very durable and solidly put together, with male and female Neutrik XLR connectors extending from each end of the matt blue‑grey Nextel suede‑coated chassis, and both quarter‑inch TS and 3.5mm minijack sockets on the top. The protruding XLRs are key to the design, as they allow the Sound Bullet to be plugged directly into equipment without needing cables. Everything is controlled via a handful of buttons, switches, and a thumbwheel, all clearly labelled in white, and there are no screens or menus.

For fast problem solving on stage or in the studio the Sound Bullet covers four core functions: it is a simple signal generator (so it can substitute for a mic or DI box), a basic signal analyser (with metering and a monitor speaker), it measures phantom power, and it tests XLR cables. Its internal battery is charged via a micro‑USB port from any standard USB charger (a USB‑A to micro‑USB cable is supplied, but not a mains adapter), providing over two hours of continuous operation. In practice, as the unit is only switched on when it’s needed (via a recessed slide switch on the side), one charge will easily last a full day of PA rigging or studio sessions. When the battery reaches 20‑percent capacity the ‘Signal’ LED flashes three times every six seconds, and when it is nearing full depletion it flashes more urgently at 6 times every two seconds.

Each Sound Bullet ships with a fabric storage case (these are available in two different designs — see the 'Carry Case Options' box for more on this), a double‑ended jack plug adapter, a USB charging cable, and a well‑written paper manual.

As the unit is only switched on when it’s needed... one charge will easily last a full day of PA rigging or studio sessions.

Signal Generator

Exploring the testing facilities in more detail, the signal generator provides either a 1kHz sine‑wave tone or pink noise, chosen by pressing the ‘Sel’ button. The ‘Signal’ LED lights solidly when producing pink noise, but pulses slowly for tone, and its colour indicates the output destination (yellow for the default male XLR output, and blue for the quarter‑inch TS output — see below). The output level of both noise and tone is set by a miniature three‑way toggle switch at ‑10, ‑20 or ‑40 dBu (see the 'Generator Signal Levels' box). The tone levels are within a 1dB of the stated level, while the pink noise measured a couple of decibels low on the review model, but such minor technical inaccuracies are inconsequential for the intended applications.

A male‑to‑male TS jack adaptor is included, and this allows the Sound Bullet to be plugged directly into amps, stompboxes and the like.A male‑to‑male TS jack adaptor is included, and this allows the Sound Bullet to be plugged directly into amps, stompboxes and the like.On power‑up, the signal generator output is available at the male XLR as a fully symmetrical balanced output signal, while pressing the ‘To’ button re‑routes the output to a quarter‑inch unbalanced TS socket instead. A double‑ended jack‑plug adapter is included to convert the TS socket into a plug, allowing the unit to be plugged straight into a DI box, effects pedal, or stage amplifier to check those signal paths directly without needing an instrument cable, which is a nice feature.

Cable Tester

The Sound Bullet’s second function is as an XLR cable tester, and this mode is activated by holding the ‘Sel’ button down for two seconds, whereupon the Signal LED flashes white once every four seconds. With an XLR cable plugged between the unit’s two XLR connectors the integrity of each connection through the cable is tested individually by repeated presses of the ‘To’ button. A low (3.3V) DC voltage is applied to each of the female XLR’s terminals in turn and a set of six LEDs on the side of the Sound Bullet indicate the presence of the test voltage on each of the male and female XLR pins so that any missing, mis‑wired, or intermittent connections become immediately obvious.

The Sound Bullet cannot currently detect whether a cable’s XLR shells are linked to pin‑1 or not, and while many commercial cables have this link between the XLR shell and pin‑1 — as per the AES recommendation — in my experience this often results in unexpected ground‑loops, particularly when working with legacy equipment. For that reason, I have suggested to David that adding two more LEDs to indicate when pin‑1 is connected to the shell at each XLR would be a very useful, and fairly simple to implement, enhancement.

Phantom Power Checker

A common reason for non‑functioning mics and DI boxes is that phantom power isn’t reaching the end of their cable for some reason, and a simple check for the presence of phantom power can often resolve the problem in seconds. The Sound Bullet indicates the voltage on pins 2 and 3 of the male XLR (relative to pin‑1) with a pair of LEDs on the top of the unit.

If the phantom voltage conforms to the IEC specification (48± 4V) each LED illuminates solidly. Although some equipment struggles to meet the specs, especially when powering a lot of mics simultaneously, most mics and DI boxes will still function perfectly well with phantom power below 44V. So, very sensibly, the phantom power status LEDs flash slowly if the voltage is between 24 and 44 V and, in the more worrying event that phantom power exceeds 52V, the LEDs flash ‘in an alarming way’!


Often all that’s required for fault‑finding is to be able to audition a connection to confirm whether the right signal is on that cable. The Sound Bullet accommodates this requirement with a built‑in miniature speaker and 3.5mm minijack headphone socket (the speaker mutes when headphones are connected). Its volume is controlled with a thumbwheel on the side of the unit and it monitors signals connected to either the balanced female XLR or the unbalanced quarter‑inch jack socket (although the XLR seems to dominate if signals are applied to both at the same time). The volume control covers an impressive range, and I was able to monitor XLR input levels between about ‑65dBu and +20dBu just on the internal speaker (although I had to hold it to my ear for the quiet end of the range — earphones connected to the minijack output make it easier).

As the internal monitoring amplifier powering the speaker and headphone socket is permanently wired across the quarter‑inch socket, if the signal generator is routed to the jack socket its noise/tone can be readily auditioned too. It also means that the 3.5mm headphone socket can be used as a stand‑in sound source for a presentation laptop or other portable sound devices.

However, having the quarter‑inch socket as both an output (for the signal generator) and an input (for the monitoring) creates a technical dilemma. Ideally, the signal generator’s output impedance should be low, to drive long lines, but the monitoring input impedance should be high to avoid loading connected sources too heavily. David decided a low output impedance was the priority for the Sound Bullet’s typical applications, and a sound source plugged into the quarter‑inch socket ‘sees’ an input impedance of 610Ω. This is an unusually low input impedance and while some equipment won’t mind at all, others will respond with a slightly reduced output level and possibly some transient distortion — although neither are particularly significant if only testing for the presence of a signal.

Nevertheless, if an output signal needs to be auditioned more accurately there is a neat workaround: selecting the cable‑test mode disconnects the signal generator’s output circuitry from the quarter‑inch socket and then an input source ‘sees’ only the monitor amp’s input impedance of 12kΩ, which is high enough to keep any device’s line output drivers completely happy. (In case you were wondering, the XLR input impedance is a reasonable 5.9kΩ).

Where it’s not practical or necessary to listen to the monitored signal, the Sound Bullet also includes ‘signal present’ and ‘peak’ LEDs which illuminate at ‑25dBu and +10dBu, respectively, to give a very rough idea of received signal levels. Bizarrely, though, these only monitor the XLR input and don’t register signals connected to the TS socket at all. Although these are useful, it seems to me that what is more often required is confirmation that a signal is passing through a unit at unity gain, and the Sound Bullet’s combination of signal generator levels and metering LEDs is of no use in that respect. So I have suggested to David that perhaps he could add an extra tri‑colour LED which would indicate whether the input level is lower, the same, or higher, than the signal generator output. Again, this would be relatively simple to implement but would add worthwhile practical functionality. I’ve also recommended that the metering reflects the input to the speaker/headphones amplifier rather than just the XLR, although that may be a more difficult thing to engineer.


I am genuinely impressed with the Sound Bullet. It combines a plethora of pragmatic facilities while being easy to use and it covers all the common requirements for fast, efficient fault finding and system checking, whether on stage or in the studio. It is also conveniently sized, and is robustly built; it certainly feels rugged enough to survive life on the road. That it comes with a two‑year warranty is also reassuring, and I’ve been delighted with the designer’s very quick and positive responses to my queries and suggestions, which bodes well for the company’s future.

While €220$250 may initially seem expensive for a small device like this, the quality and functionality easily justify the price, especially given that this is a tool which will make the working lives of audio professionals easier — the Sound Bullet a very worthwhile investment for any serious ‘soundie’.

Generator Signal Levels

An audio test set that doesn’t generate the standard alignment level of +4dBu seems a little odd at first glance, but in the context of simple functional checking of equipment on stage and in the studio, +4dBu is actually a pretty hefty signal level — your ears wouldn’t thank you for sending a powered PA speaker pink noise at +4dBu!

The loudest output from the Sound Bullet is ‑10dBu, but this is a reasonable (and safe) level to check line inputs as it will register clearly the meters of most pro and semi‑pro equipment. The ‑20dBu option provides a notional instrument level, and is therefore ideal for checking DI boxes, effects pedals and guitar amps. It’s also useful for testing powered PA speakers without deafening anyone. And the lowest ‑40dBu setting replicates a typical dynamic mic’s output level, so is ideal for checking mic lines without having to turn console mic preamps down.

Carry Case Options

The whole kit and caboodle fits into a protective pouch, and a carabiner is supplied for easy attachment to belts, bags and so forth.The whole kit and caboodle fits into a protective pouch, and a carabiner is supplied for easy attachment to belts, bags and so forth.

The carry case supplied as standard comprises a pouch with a magnetically secured flap and a quarter‑inch socket on the side of the pouch to store the supplied adapter plug. A carabiner attached via elastic loops at the rear allows the case to be clipped onto anything appropriate, including a rigger’s belt, equipment bag, or whatever. It’s a neat, practical and versatile design, but when clipped to a belt it can move around which some users find undesirable. In response to customer feedback, an alternative design has been produced, which is identical except that the carabiner is replaced by a broad elastic belt loop. This variant ensures that the pouch sits flush against a user’s belt and stays tightly in place as the wearer moves about.

When purchasing directly from Sonnect the preferred type of case can be specified, while models bought from retailers come as standard with the carabiner version. Replacement cases of both types and spare jack adapters are also available from the Sonnect website.


There are few broadly comparable portable audio test units in current production. For example, Whirlwind offers the QBox, RDL the PT‑AMG2, and CTP both the TESTA and more elaborate dBbox3, but none of these match the convenience, compactness, practical feature set, or value for money of the Sound Bullet, in my opinion.


  • Extremely compact, and with a convenient carry case to ensure it’s always available when needed.
  • Carefully optimised range of audio signal, monitoring and testing facilities.
  • Easily rechargeable battery with a reasonable duration.
  • Responsive manufacturer.


  • One or two very minor weaknesses in the design, although they may well have been updated by the time you read this.
  • May seem a lot of money for a small box with lights on!


A very practical, well‑designed audio test device which will make any audio technician’s life considerably easier when it comes to system testing and fault finding.


€220 including Italian VAT (around £230 including shipping and UK VAT).

$250 plus tax & shipping.