Review – Helm BOLT DAC/Headphone Amp & DB12 AAAMP Mobile Headphone Amplifier

Interested in a small, tough, great sounding DAC/Headphone Amp that can decode MQA and DSD to boot? Look no further than the HELM BOLT DAC/Headphone Amp. For more oomph for your hard to drive headphones, pair it with the HELM DB12 AAAMP Mobile Headphone Amplifier.

The world is populated with portable DAC/Headphone amps, with the majority of them USB powered. They range from tiny, almost invisible, in the cable devices, to battery powered units the size of your phone. Within that frame, there are multitudes of wonderful devices. Into the fray steps HELM, with their BOLT DAC/Headphone Amp, and the matching BOLT DB12 AAAMP headphone amp.

Most of the time we never needed to reach for the DB12, as we found the output from the BOLT plenty powerful enough for just about any headphones or IEMs that we threw at it. From the Audeze LCD-1 open back planar magnetic headphones, Oppo PM-3 closed back planar magnetic headphones, HiFiMan HER-R10D Dynamic Headphones, Etymotic ER-4XR and newly released Etymotic EVO in-ear monitors, all were happily playing any genre of music at any level, including approaching hearing damage. It features something called THX’s AAAMP Achromatic Audio Amplifier technology, which we aren’t quite sure is, since “Achromatic” is a term normally applied to optics. Either way, it worked fine, and we always enjoy creative naming protocols.

When did we need the DB 12? Well, driving the OPPO HA-1 planar magnetic headphones, the bass response benefited from the extra horsepower, but most tellingly, it was when we watched movies, where the bass that normally a powered subwoofer pounds the room, that the DB 12 showed it’s forte. We liked the quality of construction, of the size and ease of use of the volume controls. It has a user adjustable bass boost, which came in very handy on some recent transatlantic flights, where no matter the claims, ambient noise always wins out. So, you need to overpower it. The DB 12 is up to the task, with a low noise floor, and THX certification. It has an integrated rechargeable battery, recharged through a Type-C port. HELM claims 8-hour battery life, which we found a bit conservative, as we managed 9 hours.

Moving over to the BOLT, it’s packed full of specs. The BOLT is an audio Swiss Army Knife that blends into your headphone cable. To cut to the chase, we really liked this unit. Sporting a “Premium shielded silver cable”, “Three oscillator design", and HELM states that the “DAC is placed in connector assembly for EMI isolation and reduction in crosstalk distortion.” Lastly, it’s “3.5mm analog output is soldered directly to the DAC printed circuit board to reduce high speed signal loss.”

So, what exactly is the HELM BOLT DAC? Well, it’s a USB-C DAC that is both THX and MQA certified and supports playback of PCM files with sampling rates up to 384 kHz, or DSD files with sampling frequencies up to 5.6MHz. According to the company the BOLT is a “perfect audio accessory for Android Phones, Computers” and we agree, most folks will use it for high-resolution audio playback with a phone or computer.

In terms of compatibility, we tried it with a Motorola Android phone, an Apple iPad, Apple Macintosh M1 14-inch 2021 MacBook Pro, and an older 15-inch MacBook Pro from 2017. It worked well with all of them, with various iterations of the Mac OS, iOS, and Android. It’s definitely a plus, when plug and play (PnP) works the way it’s supposed to.

Physically, it’s an inline design, a few inches long. With a standard gold plated minijack headphone jack, and a gold plated Type-C jack, and a small plastic box with a large MQA logo on one side and the HELM Audio logo on the other. One nice addition, which we wish was standard on all DACs, are lit indicators for operation. Magenta – MQA, Red – HD Audio, Blue – SD Audio, while we wish there was a bit more information, such as bit-depth, and sample rate, it’s helpful to know what’s going on in use.

How does it sound? Great, about how you would expect from an audiophile level product, which is to say it has a low noise floor, believable musicality, and neutral. The sound is open and airy, with no hint of restraint, and there is a nice palpable energy, especially when playing rock. Like the DB 12, it also sports THX's patented AAA Amplification technology. It’s tech specs include:

Output Level: 1.1 Vrms at <150 Ohms, 2 Vrms at >150 Ohms

Compatible Formats: PCM. MOA, DSD DoP

Connectivity: USB-C INPUT, 3.5MM OUTPUT

SNR: 120 dB

THD: +N% - 0.0008 at <150 Ohms, 0.0013 at >150 Ohms

Frequency Response: 20H7-20kHz +/-0.06 dB

Dimensions: Length 112 mm (4.4")

Width: 12.8mm (0.5")

Weight: 7.09 grams (0.25 oz)

Physical: USB Type-C Interface

Connection: USB 2.0 High Speed

PCM Sample Rates: 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz, 352.8 kHz, 384 kHz

DAC: ESS Sabre 9281Pro

As you can see from the specs it’s small, light, and the form factor relieves stress on ports. How does it compare to other units, such as the $200 highly rated EarMen Sparrow DAC, it’s half the cost, roughly $110, a bargain in that respect, although the Sparrow has other features to justify the higher cost. Our other low cost favorite, the Periodic Audio Rhodium DAC is under $50, but has half the output level, and no MQA. Sporting the well-regarded ESS Sabre 9281Pro chip as its core, the BOLT can handle DSD files with sampling frequencies up to 5.6MHz. Putting it all together, the BOLT really punches above it’s weight. So, much so that we brought it with us for our recent trip to Sweden.

The photo above of the Bolt was taken in Stockholm. When you travel, the last thing you need is any muss or fuss! And great sound takes the edge off of airport incompetence!

Like most HELM products, the BOLT represents a compelling package, great features, MQA & DSD compatibility, high level of build quality, and exemplary sound at an affordable price. Coupled with the DB 12 amplifier, there probably isn’t a headphone it can’t drive. We found it neutral, as in it worked well with any genre we tossed at it, and that’s how it should be in our opinion. The Helm BOLT DAC/Headphone Amp & DB12 AAAMP Mobile Headphone Amplifier come highly recommended.

Harris Fogel and Nancy Burlan, Posted August 3, 2022

Photos © Harris Fogel 2022

For more information on the HELM BOLT and HELM DB 12 visit: