HELM Audio BOLT DAC/Amp Review: A Brilliant Headphone Amp/Accessory For Your Phone or Laptop!









What We Dig

  • Great Build Quality
  • Crisp, Natural Sound
  • Easy to Use

What To Think About

  • Sound lacks a little depth and width

Helm Audio has been on a tear lately, producing an uninterrupted run of innovative portable audio gear for the last two years. They constantly seem to get the features/performance/price mix of their products right, making them attractive. A couple of months back, I took a look at their $199 HELM Audio DB12 AAAMP Mobile Headphone Amp, an analog-only portable amplifier that was one of the most powerful and transparent I’ve ever heard.

This time, I’m looking at their $99 BOLT DAC/Amp, an MQA compatible dongle DAC with THX-Certifed headphone amp section. It has a clean, balanced sound like the DB12, albeit not quite as clean or as powerful.

That said, comparing the two is really comparing apples to oranges because they are basically two different things. The DB12 AAAMP is an analog-only device made to provide additional output power to devices that already sound good, like a DAP with low output power. On the other hand, the BOLT is made to improve the sound of devices with inferior DACs, like many smartphones.

It can also be used as a high-quality dongle to add a headphone jack to phones that don’t have one, provided the phone has a USB-C connector. With popular phone manufacturers like Samsung removing the 3.5mm jack from their Galaxy phones, dongle DACs, which are basically an adapter wire with amp/DAC chips built-in, have become more ubiquitous, with more and more models popping up on the internet.

DAC/Amp dongles are a relatively cheap way to both allow the use of standard headphones with smartphones and improve their sound quality at the same time. They also work well with laptops. Due to their compact size, they’re effortless to transport.

I’ve had the chance to try out many of them, including the Zorloo Ztella, which I found to be a powerful little DAC/Amp for its size. It also has a detailed, open sound, which brings headphones alive. The only issue is that it tends to be bright on certain recordings, so careful headphone matching is necessary.

The BOLT and Ztella have identical specs and sound signatures, and while HELM Audio is tight-lipped regarding the DAC chip they use, I wouldn’t be surprised if it used the same ESS Sabre chip as the Zorloo product. That said, it’s the implementation of the chip that makes all the difference, which is why some manufacturers don’t like to disclose the exact one they are using.

At the end of the day, I found the BOLT to be a little less lively on the top-end than the Ztella, which may make it a better choice for those who are sensitive to treble. The BOLT also sounded more “real” (instruments, vocals) and richer than the Zorloo DAC. However, the Ztella’s boost on the top end does give it a more airy sound than the BOLT, and it also has a wider soundstage. They’re both great choices at $99, so your decision will probably come down to sound preference.

Other things worth mentioning are the BOLT comes with a pleather pouch for carrying, something the Ztella doesn’t have. Another thing to keep in mind is for an additional $10, the Zorloo can be purchased with a lightning adapter for Apple phones. The BOLT needs a $30 Lightning to USB Camera Adapter from Apple to work with iPhones.


The BOLT DAC/Amp looks to have a pretty sturdy build. It’s composed of Aluminium and soft-touch plastic, with a braided tangle-resistant cord. It’s super small, at less than four inches long, and only weighs about a quarter ounce.

Like I said earlier, it comes with a small pleather pouch for easy carry, and it also comes with an impossibly small USB-C to USB-A adapter for use with laptops. I used both with my HP Envy, and with either option, it was plug and play.

MQA compatibility comes standard, and there’s a small LED light that glows magenta when it renders an MQA track. The same LED also designates the sample rate. RED means above 48khz, and Blue means below 48khz.

Besides MQA, the BOLT also does PCM up to 384kHz, and DoP (DSD over PCM) up to 5.6MHz.

As far as output power is concerned, it uses an impedance matching scheme to match different headphones/earphones. That means it outputs 1V for headphones with impedances less than 150 ohms or 2V for impedances equal to or greater than 150 ohms. I wouldn’t recommend using the BOLT with a sensitivity rating much less than 100 dB /mW, or you may get mushy bass and restrained dynamics.

I really enjoyed the BOLT with the Andover Audio PM50 Planar Magnetic headphones (102 dB/mW), the Focal Elear (104db/mW), and the Sennheiser x DROP HD58X (104db/mW). The Hifiman SUNDARA at 94db/mW was a little too much.

THX Certification is the icing on the cake here, meaning the BOLT has to meet stringent standards for low-distortion.

Listening to the HELM Audio BOLT

For my sound test, I used the BOLT mainly with the Focal Elear headphone and a Moto G Fast Android phone with USB Audio Player PRO app installed. I listened to both TIDAL and local files thru UAPP, mostly hi-res.

Just a side note: I tried listening directly from the TIDAL Android app, but it wouldn’t play through the BOLT. This wasn’t fully unexpected, as many DAC/Amps don’t work with the TIDAL Android app. The only ones I’ve been able to use so far are the iFi DACs. It does work with the TIDAL desktop app on Windows 10. I didn’t try iOS.

If I had to sum up the BOLT’s sound with one word, it would be natural. While the lower highs are a little elevated, they are not bright per se. They actually add a nice level of clarity to the sound without being harsh. The upper mids also seem to have a slight boost, which gives percussion and vocals a nice full, realistic texture. The Bass seems pretty flat, just giving you the warmth the track needs.

Listening to “Midnight” by Khruangbin and Leon Bridges, I again impressed at how natural Bridges vocal was along with the drum hits. I didn’t get the separation or depth you would get with a more expensive DAC like the Audioquest Dragonfly Cobalt, but there was enough space and focus to hear the vocal front and center with the drummer behind him to the left. The guitar was panned off to the right.

The soundstage is a little narrow. The presentation was just out beyond my ears when I listened to Emily King’s Acoustic version of her song “Forgiveness.” However, I just loved the richness of the strings and Emily’s sweet vocal. This DAC really brings singers and instruments to life, with a clean, laid back sound that you can listen to for hours on end. This may be the cleanest sounding DAC I’ve heard at $99.

The Wrap Up

HELM Audio’s BOLT DAC/Amp is another great option for a dongle DAC/Amp at the $99 price point. Especially if you’re looking for MQA. The Zorloo Ztella may have a little bit more air and top-end detail, but it’s also a little bit bright with some songs and a little bit noisier than the BOLT. This makes it my new DAC recommendation for under $100. If you’re looking for a cheap compact device to improve the sound of your phone or laptop or just a USB-C adapter with a 3.5mm headphone jack, the BOLT is where it’s at.

Best Buys: 5 Marvelous MQA (Master Quality Authenticated) DACs…$99 to $799!

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