Helm Bolt DAC/Amp Review – Sweet Dreams Are Made Of This
Pros — Balanced, natural sound with good tone colour without sharp edges; great haptic and build; small & light.
Cons — Fixed cable.
In this Article
Executive Summary
The Helm Bolt is a very small and light MQA certified portable DAC/amp that excels in terms of its organic/natural reproduction.
Introduction
The source-operated dongle dac-amp has experienced a huge upsurge recently. Originally designed in 2012 to convert your phone into a high-quality digital analog player (dap) and first able to do so in 2016, the market is currently flooded with tens to hundreds of such devices – which makes it is essentially impossible for a single person to keep the overview.
Prices range from a handful of dollars to $400 with a crowding in the $80 to $150 range. The Helm Bolt fits into this sweet spot.
Helm is a young British-American company that specializes in portable devices from headphones/earphones to amplification.
The Bolt is the company’s sole portable DAC/amp that works with a phone, either alone or in combination with the Helm DB12 AAAMP amp. It appears to be a popular item as it is always sold out. Many favourable reviews of the unit exist already, so I would like to put it to my ultimate test.
Specifications
| Dac Chip: ESS Sabre 9281A Pro (dac + amp) |
| Output Level: 1.1 Vrms at < 150 Ω 2 Vrms at > 150 Ω |
| Compatible Formats: PCM, MQA, DSD, DoP. Visit mqa.co.uk for more information. |
| Connectivity: USB-C input, 3.5 mm output |
| SNR: 120 dB |
| THD+N%:0.0008 at < 150 Ω, 0.0013 at > 150 Ω. |
| Frequency Response: 20-20,000 Hz |
| PCM Sample Rates: 44.1, 48, 88.2, 96, (176.4, 192, 253.8, 384 kHz MQA) |
| LED: Blue SD Audio <= 48kHz – Red HD Audio > 48kHz – Magenta For MQA |
| THX certified |
| Product Page: https://helmaudio.com/products/boltdac |
| Tested at: $99 |
Visit mqa.co.uk for more information.
Physical Things and Usability
The box/s content is rather spartan: Helm Bold, USB-A adapter, and pleather storage case.
The dongle comes with a fixed USB-C cable, which is great for connecting to an Android device or a newer Mac, and, with the USB-A adapter, to a Windows computer. But using the Bolt with an iPhone requires the Apple camera adapter, which doubles the “snake” in length. Since the enclosure of this 8 g dongle is very small, the whole construct is effectively just an extension of the earphone/headphone cable.
The housing is made of metal and feels premium. The cable is cotton-shielded against outside interference and the strain reliefs on both ends could be a bit longer and sturdier.
The Bolt has no physical controls and is operated through its host device. It is completely plug-n-play, and does not even need a Windows driver.
The enclosure features a small LED that changes colour with playback rate/type: Blue SD Audio <= 48kHz – Red HD Audio > 48kHz – Magenta For MQA.
Headphone output level automatically detects headphone impedance and sets level accordingly: 1V for < 150 ohms, 2V for >= 150 ohms, which corresponds to low gain and high gain. The device is plug and play, there are no Windows 10 drivers needed.
Amplification and Power Consumption
The Helm Bolt drives all iems I have thrown at it, but it reached its limits with the 300 Ω Sennheiser HD 600. For large cans, Helm offers the Helm DB12 amp [product page],which can be used in series with the Bolt. The DB12 adds a constant 12 dB gain, and a 6 dB bass boost (if selected).
I my 3h battery drain test of several dongles, the Dragonfly Black and Red had the lowest consumption on my iPhone 5S, the Helmo Bolt consumed about a third more, which placed it in the midfield. But it could have done far worse than that….see the detailed results. I would call the Bolt’s battery consumption ok but not outstanding.
I tested the power consumption of several portable headphone amps connected to my iPhone 5S. The conditions were as identical as possible: 3 h test, volume calibrated to 85 dB ± 0.5 dB white noise with Dayton microphone, no sim card, BT off, no other apps open; network on, 32 ohm Blon BL-03 iem, Genesis’s Supper’s Ready (from the Seconds Out album) played in an endless loop.
The iPhone’s battery was fully charged at the start of the test and the remaining charge was measured thereafter. The result is shown in the table below. Since the tests were performed at different times and considering the ongoing battery deterioration, the results have to be seen with a grain of salt.
Sound
Equipment used: Macbook Air/iPhone SE first generation; Sennheiser IE 400 PRO, Meze Rai Solo, JVC HA-FDX1; Sennheiser HD 600.
The Helm Bolt has an organic sound with a good tonal colour. It is not warm and not neutral, that is not dark and not analytical, but it strikes a balance between the them. The presentation is clean and lean (in a positive way), think of slimline – as opposed to fat and congested.
The Bolt is not the bassiest dongle, which keeps the vocals up front. Midrange is clean and clear with a tinge of warmth. One of its biggest qualities is the very pleasant, well-rounded, smooth, appealing top end. It works well with most earphone/headphone signatures and, in particular, helps taming shouty ones.
Compared to the $10 Apple audio adapter or the $10 VE Odyssey HD, the Bolt sounds much more refined and it is more powerful. The $50 Shanling UA1 features the same SoC and almost identical specs. Both therefore feature principally the same sound signature with one big difference at the top end: the Shanling is much scratchier/grainier in the upper midrange and lower treble. Helm must have applied effective filtering.
The Shanling UA1 is also a tad bassier which pushes the vocals back. The Bolt’s bass is tighter and cleaner, it has a more open sound with a wider stage, and it is a tad more dynamic.
Scaling up to the $200 AudioQuest DragonFly Red. The Red is punchier, bassier, fuller bodied with bigger staging and more midrange clarity and depth. Bolt is more relaxed, softer on the attack and has the lesser separation, but is sweeter in the treble.
Using the Bolt as a preamp and adding the Helm DB12 as an amp opens up the stage substantially, however takes away from the note weight. The sound is fluffier, bigger, “inflated” like a balloon. But since both devices have fixed cables, this combination can create some cable chaos in your pocket.
Concluding Remarks
The Helm Bolt is a fine sounding dongle which I like a lot. It may not have the strongest amplification but it has a very refined sound. It sticks out of the crowd by its small size and weight and convinces by its natural sonic reproduction. The Bolt has played any iem well for me I had thrown at it. It is a quality product and I am not surprised it is always sold out. It is a serious contender in the $100 segment.
Until next time…keep on listening!
Disclaimer
The Helm Bolt was supplied by Helm Audio for my review – and I thank them for that.
Our generic standard disclaimer.
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