Helm Audio Bolt is a portable MQA and THX-certified USB DAC/headphone amplifier dongle capable of PCM 32BIT/384kHz and DSD128. It is priced at $99.99
Disclaimer: The Helm Audio Bolt sent to us is a sample in exchange for our honest opinion in this review. We thank the team at Helm Audio for giving us this opportunity.
To learn more about Helm products reviewed on Headfonics you can click here.
Note, this 2-page review follows our new scoring guidelines for 2021 which you can read up on here.
It seems Helm Audio and THX are synonymous with each other and more so now. This next up for review item is another piece of gear that has the THX seal of approval that has been released by Helm Audio.
Back in August we took a look at their DB12 AAAMP and considered it a neat and versatile device. The rechargeable battery-powered line-driven amplifier had some THX tech in it and plenty of power for on the go scenarios but I stated that it needed a DAC.
I knew Helm Audio was going to try their hands on a THX Micro DAC because to me it was the next logical step up after the release of their in-line THX amplifier. So here it is and it is called the Bolt DAC.
The pitch of the Helm Audio Bolt is that it’s one of the less than a handful of micro dongle DACs to have been THX certified and they achieved a level in sound quality improvements compared to other similar Micro DACs by using a simple recipe.
Helm Audio physically isolated the DAC chip from the USB circuitry and used a three oscillator design which resulted in ultra-low harmonic, crosstalk, and crossover distortion.
At the heart of the Helm Audio Bolt is a Hyper Stream 2, Quad DAC Sabre 9281A Pro DAC/HPA chip with Sabre 32 technology. This chip supports synchronous and asynchronous sampling modes and could handle most formats out there.
Over its USB input, this chip is capable of handling up to sixteen channels and/or 8 inputs and 8 outputs simultaneously. This amount of power makes it possible to hardware render digital music formats.
On that note, since the Helm Bolt DAC internal chip and circuitry design have so much rendering power regardless of its micro tiny footprint, Helm Audio took advantage of that processing power and is using hardware rendering on this device.
For example, MQA is rendered by using software on the first fold, but then on the second and third fold, it uses hardware rendering. PCM and DSD are completely hardware rendered.
PCM performance is fully capable of handling up to 32 bit/384kHz sample rates. DSD capability is listed as being capable of sampling frequencies of up to 5.6MHz or DSD128. I can live with that.
I know most people are foremost concerned with power output specifications but the Bolt DAC has its power output listed in voltage and does not list the spec in watts. It has a listing of 1.1V when the device sees less than 150Ω. If the load rises above 150Ω then power output rises to 2 volts.
I wished there was a way of kicking the device to a constant 2-volt output all the time. I would rarely use headphones or IEMs of over 150Ω with this device. Perhaps this is done to keep the heat down to a minimum. At less than 150Ω the device does get warm and more so at higher than 150 ohms operation.
I am going to take an educated long-time audiophile guess here, use my spider senses to say the device feels as if the wattage is between 50 or 60mW. Another specification my ears are sensitive to is the signal-to-noise ratio and the Bolt has it at 120dB rated which is very good for a device of this type.
The frequency response is given as 20Hz to 20kHz. THD is listed as 0.0008% at less than 150 ohms and 0.0013% at over 150Ω. The listed specifications for the Helm Audio Bolt DAC are not bad at all on paper and read like specs for a good full-sized component, of course except for power output.
The Helm Audio Bolt has all its electronics components installed inside a small rectangular metal shell finished in a matte black with Helm Audio and MQA logos in contrasting white.
At one end of the shell is a gold-plated flush mounted 3.5mm single-ended headphone output jack which can also double up as a line-level drive. The jack itself has jack detect and moisture protection features.
On the opposite end is a black-colored paracord-wrapped cable that terminates to a USB-C male plug. Both ends of the cable have small black rubber grommet-style strain reliefs.
The entire assembly measures a little over four inches. Weight is at a very low 7.09g and all this in combination makes this unit highly portable. Bulk and weight have been kept down a bunch.
The single 3.5mm plug is a single-ended output jack and unlike the DB12 AAAMP the plug will accept a TRRS 3.5mm plug microphone-equipped cable but I could not verify if the microphone would work with the Bolt directly.
Although the Bolt DAC uses a modern-day USB-C plug it still works off a retro USB 2.0 port. I did use the Bolt DAC mostly with my desktop PC and it seems the speed of the 2.0 port was more than enough to feed the device and not cause any buffering or latency issues.
The USB input supports master and slave 32 bit PCM, DSD, DOP, SPDIF, and MQA formats. All signal processing is done on a 64-bit accumulator and a 32-bit process.
I do use smart devices but I am mostly a stay home PC guy and drivers worry me some but the Bolt DAC is completely a plug-and-play device at least on Windows 10. I checked the Helm Audio website for drivers or firmware updates and could not find any of the two. What I did find was lots of instructions on how to set up the dongle DAC.
However, I did not have to go through any of the website instructions on general use at all. I plugged the Bolt DAC into my PC and it just worked. I did set the sample rate and bit depth higher but that is it. I ran windows media, Foobar, and the lot with all the audio formats I had without issues or complicated setup procedures.
I know a large part of the PC community in my area so to them I often tell them to get away from the old-fashioned sound cards with sometimes buggy drivers and to just get something like the Bolt DAC. I was totally content with it performance-wise especially if you use IEMs or dynamic driver headphones that are fairly efficient.
And yet another versatility point of the Bolt DAC is that it can be used as a standalone line driving USB DAC. Just get a 3.5mm to RCA cable and feed that to a speaker amplifier RCA input section, or a headphone amp to cover hard-to-drive cans.
On the Android front, the same results were obtained. I mostly use Android 10 and to be honest, I’m not really an Apple products guy so my apologies but I did not test this device on an iPhone.
The Bolt DAC is specified to work fine on apple devices but you will need to source out a separate lightning adapter which is not included. Helm Audio should include one just to cover all bases out of the box.
On Android 10 I used Jet Audio, YouTube, Pandora, and even some Tidal with no issues. Every app and music format played along fine on the Bolt with no setup of any kind.
Packaging & Accessories
When you open the box you do not see the Bolt DAC, you see the black faux leather storage or carrying pouch, it serves both functions. The DAC is shipped inside the pouch. The box itself is matte black with a white-colored Helm Audio logo and a brief product description. The pouch inside the box is also black and has a debossed Helm Audio logo.
The Bolt DAC, the bag, a decent USB-C to full-size male USB adapter, and an owner’s manual are included. Simple and effective packaging like this works for me because the product sits comfortably inside and only a serious accident would damage the contents.
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