Fosi audio DS1 Dongle-DAC/Amplifier

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Video version of this review.

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Build & Design

The first thing you'll notice when taking this thing out of the box is that it's an absolute unit at 37.9 grams, minus the cable.
For it's size it feels incredibly robust, weighty, instilling confidence that it will survive more than a few drops over it's lifetime.

Edges and corners are only ever so slightly chamfered, so it doesn't feel sharp, but it plays strongly into the brutalist aesthetic, with it's asymmetrical raised plug hole mounds and straight lines, which helps this dongle stand out in the sea of curved, smooth aluminium and plastic alternatives.

Like many other dongles it also has two different coloured sockets, which at the very least can be considered an easy visual way to distinguish between the 3.5mm and the balanced 4.4mm.




The position, brightness and colours of the lights are not obnoxious, but we'll talk more about the colours later.

The USB-C socket provides a reassuringly tight grip on the cable, which in of itself feels like it might be the least robust element.
Perhaps I'm wrong about these twisted 'rope' type cables, but I am concerned about their longevity.
In the end, I think you can be forgiven for believing that USB cables like this are more like consumables, akin to ear pads, which will eventually wear out, break and need replacing in the future.

I'm more in the camp that believes cables should be built to spec for their purpose and extra effort should be made for a cable that potentially may involve many journeys in pockets, being involved in miniature tug of wars between a mobile phone and a headphone cable and potentially many hundreds of plugging cycles.
I hope this one does last, but I'm not yet convinced.
In any case, the presence of a detachable cable rather than a hard-wired cable is always welcome and preferable.

Also provided is a USB type A to C adapter which has the same plastic finish as the cable connectors, but finished in black instead of the grey of the cable.



The volume buttons are symmetrical, making them difficult to differentiate in some situations, particularly on-the-go if it’s in your pocket. So you may need to actively remind yourself that volume up is on the USB side, and volume down is towards the audio sockets.
If used with a laptop, the dongle is very likely to be orientated in the 'correct' or ‘intuitive' direction for volume controls with volume up at the top.
To give credit to Fosi - these buttons have a very satisfying tactile click when pressed, which is always appreciated as each click changes volume by 1 increment out of over 60, but holding the buttons will also slide the volume up or down faster.

As a final side-note, the dongle does get a little warm to the touch after a while but it never reached an uncomfortable temperature.

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Functionality

So let's talk about the LED colours and what they mean.
I found them all relatively unintuitive, so some reading of the manual is required to learn what each colour indicates.



Flashing Red or Yellow indicates the stream is in UAC 1.0 mode.
All other constant LED colours are in UAC 2.0 mode which is preferable, mostly because flashing lights are annoying.

For Most users with a library of mp3s and 16 bit FLAC files, get used to seeing Red and Yellow, as they will most likely have a sample rate of 44.1 and 48kHz.
If you have a library of 24 bit FLACs with a higher sample rate, you will likely see Green and Cyan, and those with DSF files with very high sample rates can expect to also see Blue and Purple, once the DSD format decoding automatically kicks in.
So, if your library contains all of these file types, it may become confusing learning what all these colours mean.

Finally a blinking white light means you've reached the lowest or highest volume.

Each sample rate bracket has two modes: High and Low Mode.
This is actually not a high or low gain mode.
It is in fact a setting you should chose depending on the headphone that you plug into it: Low Mode being for a low impedance headphone, between 16-150 ohms, and High Mode for headphones between 150 and 300 ohms.
The DS1 will however not chose the mode automatically. The only automatic change is the LED colour based on the format being streamed.



To switch between Low and High mode, you're supposed to press both buttons simultaneously, but I found that holding down any one button and pressing the 2nd button after a short delay works better.
The High and Low modes are designed to lower the distortion and are are optimized for the two ranges of headphone resistance previously mentioned.

I think in the end, the High and Low Modes are likely not going to be a significant or defining feature for many users.

One thing users will have to take into consideration is that the maximum power of the dongle can only be unleashed with the use of a balanced 4.4mm cable.
The 3.5mm already provides a really good amount of volume, but the balanced 4.4mm output can very easily give you hearing damage if you're not careful.

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Measurements

The DS1 does not seem to impart any tone to the recording and remains perfectly neutral.
I measured a Sennheiser HD650 seated in exactly the same position with several amps and DACs in quick succession and found that the DS1's frequency response was no different to the others.

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Sound

So how does this amp sound?
It's an amp.
It doesn't make any noise of it's own unless you drop it.
So don't worry about it.

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Comparisons

Compared with my trusty old NFB11.28TXO I was very pleasantly surprised with how well this dongle performs with all kinds of headphones and IEMs.
It is strong enough to adequately drive a Hifiman HE-500 even out of the 3.5mm socket, and does an equally good job of supplying power to planar IEMs like the KZ HBB PR2.
I couldn't detect any obvious reason to pick a more powerful amplifier over the DS1 under normal listening situations.
Most of the dynamic headphones I tested also posed no challenge.
I had to turn the volume up significantly higher for my AKG K501, but it was still below 50%, just to give you an idea of how much headroom this little dongle has.
But of course, even at 100% volume this dongle is nowhere near powerful enough for my hard-to-drive vintages like the Pioneer SE-700.



The DS1 is honestly making me start to question some of my more expensive purchases, but for obvious reasons I won't be using this dongle with my hard to drive vintage headphones, which is already way beyond where you would normally draw the line with any dongles.
No amplifier is designed to output maximum volume all day long, and of course using it on higher volumes with hungrier headphones like full sized planars will also lower the headroom and theoretically increase distortion.
So compared to larger desktop amplifiers, it's better to stay reasonably well within it's recommended specs, but most users of course will not be powering their Hifiman HE-6 or Pioneer SE-700 with this dongle.

It's also worth mentioning that there is absolutely no background hissing or audible distortion at the maximum volume.

Also, aside from the obviously higher power of the 4.4mm balanced output, I didn't hear any obvious reason to use this dongle exclusively with balanced cables.

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Conclusions

This little dongle is capable of powering most common headphones very adequately, while decoding some of the highest quality audio formats around today.
Putting aside any of the design features that may come across as unintuitive or a require a learning curve; in it's purest form there is nothing to strongly dislike.
For minimalists or frequent travellers, this could very easily replace a full sized desktop amplifier, permanently.

I can easily give this product a recommendation based only upon it's audio quality and high power output, but I still have some reservations about the LED colour choices and the USB cable.

If like me you enjoy brutalist design and seemingly endless portable power, this is one dongle worthy of consideration.

The review sample was kindly provided free of charge in exchange for an honest review.
I didn't receive monetary or any other kind of compensation and I don't use affiliate links.
The price of the DS1 is $75.99 and you can order it from the Fosi Audio online shop.

Fosi Audio were kind enough to offer a 10% off promocode: CAR10DS1 for the readers of this article.

Fosi Audio

Fosi Audio might be unknown to you as it was to me so in order to get acquainted with them you can read the following information as derived from their website.
"An audio equipment company with a focus on HiFi sound, Fosi Audio was founded in 2017 by a team of engineers and music lovers with the objective of delivering high-quality audio products. After years of research and development, they have mastered the art of miniaturizing HiFi sound and bringing it to any space, big or small. Fosi Audio’s range of products includes speakers, amplifiers, headphones, turntables, and other hi-end audio equipment.
Their goal is to make audiophile-grade sound accessible to everyone and to further the advancement of music technology."
Further information is available here.



Fosi Audio DS1

The Fosi Audio DS1 is a compact sized USB-DAC dongle that uses the ES9038Q2M DAC chip from ESS technology.
The amplification is handled by dual RT6863 op-amps by Ricore, in a fully balanced configuration, with a 120mW/32Ω(SE) and 220mW/32Ω (BAL) of power output while an auto detection system will switch to high gain mode for headphones with an impedance of 200Ω and above.



Built-in is also an independent jitter and phase noise active crystal oscillator for accurate audio reproduction.
From a technical point of view the Fosi Audio DS1 is pretty much identical to the FiiO KA3 or the Hidizs S9 Pro but it is the least expensive of the three.
It has both balanced (4.4mm) and unbalanced (3.5mm) headphone outputs and supports sampling rates up to 32bit/768kHz PCM, DSD512 but no MQA decoding while it is compatible with Android/iOS/Windows/Mac without the need to install any drivers.



Design and build quality

The rectangular chassis is made from a tin alloy and it has a rather interesting design with the rounded headphone plugs protruding from the main body.
The DS1 is built like a tank, it is relatively compact sized and not bigger than the competition but at 38g, is quite heavier from the FiiO KA3 which weighs 17.5g or the 23g of the iBasso DC06.
Except for the hardware volume control buttons there is also a notification LED that will light red for PCM and blue for DSD when in normal gain or yellow and magenta when switched to the high gain mode.



Accessories

The DS1 comes with a type-C to C cable of typical quality with aluminum plugs and a USB A-C converter.



Listening impressions

The DS1 was left playing music for about 100 hours prior to listening tests.
For the evaluation I used various earphones and headphones like the FiiO FDX, Penon Vortex, Sennheiser HD660S and Focal Clear Mg among others.
The DS1 is dead silent without background noise or electromagnetic interference from the mobile phone.
Power output is among the best for a USB-DAC dongle and it didn't have any problem driving all the full sized headphones mentioned above.
The following impressions include a comparison with the FiiO KA3.



Don't let the humble price fool you, the DS1 offers a stellar sound performance that is on the same level with the competition like the FiiO KA3 and the Hidizs S9 Pro.
A reference linear frequency response with great transparency, crystalline clarity and excellent technicalities.
Regular readers will know that the ES9038Q2M is my favorite ESS DAC chip when implemented right and this is something that can be said for the DS1 as the implementation is truly good, at least as good as it can be for a passively powered USB DAC dongle.
It has the typical ESS fidelity and mirror-like source transparency but at the same time it manages to sound quite musical and engaging without artificiality or as giving the impression of a clinical and boring sounding DAC.
In that respect it is slightly more organic and analogue sounding than the FiiO KA3 with a touch fuller and weightier texture from the bottom to the top of the frequency range.
The bass is fast, tight, controlled and impactful with excellent definition and some great layering.
There is plenty of harmonic variety, especially in the critical mid-range which is distinguished by the colorful tonal palette and the fine articulation both for the vocalists and the instrumentalists.
The frequency integration is very good, the sound is blended and cohesive without too much of the accustomed ESS treble prominence.
The DS1 is one of the smoothest sounding ESS based DAC dongles I have tested with minimum digital glare and without too much brilliance.
It is still airy, detailed and open sounding with plenty of energy and a sparkle but it manages to sound controlled and realistic without making the notes become thinner than the ideal.
The DS1 is good sounding from both the balanced and the unbalanced outputs but the latter offers a slightly more expanded and wider soundstage with better holography and sharper imagining.



The DAC is music and headphone agnostic as it pairs well with everything and yields a very enjoyable listening experience with all types of music and all headphones, even brighter ones without sounding unforgiving and punishing.
Listening to all sorts of classical music was a real joy and the overall performance reminded me more of a mid range DAP rather than an entry level priced USB DAC dongle.



In the end

The Fosi Audio DS1 was a well hidden gem that has fortunately surfaced from obscurity and is trying to get the place it deserves in the overcrowded USB DAC dongle market.
It has an entry level price but it packs an advanced circuit design that is usually found in much more expensive competitors and it combines excellent sound performance with great power delivery, dual headphone outputs and hardware volume control.
The only real drawback is the increased weight but for the asking price, honestly I wouldn't care that much.

Test playlist

Copyright - Petros Laskis 2023.

Disclaimer:

• Fosi Audio sent this unit to me in an exchange for an honest, unbiased review. Rest assured that this review will be free from any form of bias/s as much as possible.
• I have not tested this with MQA files or MQA streaming since I don’t use MQA at all.
• The following remarks and observations shall be made and owned only by me.
• No monetary compensation is/was involved before, during, and after the period of creation of this review.
• I have only tested this with earbuds and IEMs and earbuds.
• Your mileage may (and always, will) vary.

Burn-in time: 5-10 hours per day, 10 days.

IEMs/Earbuds/Source used:

• Celest Pandamon
• Etymotic ER3SE
• Cat Ear MiMi Pro
• NiceHCK EB2S 4.4
• VE Monk Espresso
• VE Asura 2.0
• VE VE Monk V2s
• Shaytan Customs’ Lamia
• Tinhifi C3
• Non-HiFi smartphone (Infinix Note 12 G96, Teclast T-Pad)
• Desktop PC, Laptop.
• Local Files via Foobar, YouTube Music, Deezer, and Qobuz with UAPP.

Setup configuration: Fosi Audio DS1 paired with phones/laptop/pc.

Essential Product Specifications:

• Frequency response: 20Hz-20kHz (±0.5dB)
• THD+N: SE: 0.0006%(32Ω); BAL: 0.001%(32Ω); S/N: ≥120 dB
• Recommended headphone impedance: 16-300Ω(SE); 16-300Ω(BAL)
• Dual headphone outputs: 3.5mm single-ended and 4.4mm balanced headphone jack;
• Power Output: 3.5mm - 120mW(SE); 4.4mm - 220mW(BAL)

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Sound signature:

• The Fosi Audio presented itself as a neutral, clean-sounding DAC. It greatly avoided major colorations to the sound and is evident when paired with Etymotic ER3SE. There is a bit of an additional tinge of warmth (but not as much as when compared to the Ifi Hip DAC or the likes) to the sound to keep things from sounding too clinical, but it is very negligible, depending on the gear paired with it. Despite not being too technical, it still showed the technical capabilities of my IEMs and earbuds. Interestingly, it also managed to add a bit of body to the Asura 2.0 when paired with it. In general, the Fosi Audio DS1 delivers the power the IEMs or earbuds need when paired. I never experienced "underpowered" instances throughout my tests.

Build Quality:

• Sturdy—that is the first thing that came to mind when I held the DS1 in person. It is literally solid and hefty. It might be too heavy for some. If I’m going to compare it to other dongles, my guess is that it would be as heavy as an Ifi Go Bar. The volume buttons are really satisfying, as they are tactile and crisp. Adjusting the volume via the hardware volume buttons adjusts the device’s software volume as well.

Device Compatibility:

• It is literally plug-and-play. There is no need to install any proprietary drivers, regardless of what device you are going to pair with it.

Battery Consumption:

• The DS1’s battery consumption is average. It is nicely proportioned for the power it delivers. It lasted around 5–7 hours on my smartphone and tablet.

Power and volume:

• The volume here was mostly handled by the device itself, and the DS1 will base the volume on what volume you were at last time. Here are some IEMs and earbuds I have tried with their respective listenable or loud enough volumes:
• Etymotic ER3SE - 20/100
• Celest Pandamon - 16/100
• VE Asura 2.0 - 25/100
• NiceHCK EB2S 4.4 - 16/100
• Most IEMs - 14/100
• Earbuds - 25/100

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Comparisons!:

VS the VE MEGATRON

• The VE Megatron is more powerful when compared, but lacks cleanliness when compared to the DS1. There is a perceivable noise floor on the MEGATRON, whereas the DS1 does not have one. Both contribute the same lack of coloration to the sound of the paired gear. The MEGATRON seems to emphasize the midbass just a little bit, while the DS1 exhibits a tinge or warmth to the mids. Both are well made in terms of build quality. The DS1 is smaller and has volume buttons, while the MEGATRON is complete with the essential ports but lacks the physical volume buttons that the DS1 has.

VS Tempotec Sonata HD V

• The Tempotec Sonata HDV looks more elegant as it is a literal glass sandwich, while the Fosi Audio DS1 aims for a more robust, sturdy, all-metal, industrial design. In terms of sound, both share the same level of minimal coloration but are quite different in terms of where they are leaning. The DS1 has a tinge of warmth, while the Sonata HD V seems to emphasize the upper frequencies a bit. The DS1 is also more powerful and has a 4.4mm BAL port and volume buttons, which the Sonata HD V does not have.

Pros:

• A powerful, relatively neutral sounding USB DAC.
• Clean, detailed sound.
• Slight tinge of warmth to the sound makes it not too clinical (subjective).
• Free from any perceivable noise floor.
• Minimal battery consumption compared to the power it can give.
• Hefty, solid build quality.
• Excellent device compatibility - literally just plug and play.
• Very tactile, hardware volume buttons.
• DSD support is always a good treat.
• 3.5mm SE and 4.4mm BAL ports makes it very versatile.
• Very competitive and might be the best dongle I’ve encountered under 80 USD (obviously subjective).

Cons:

• DAC gets warm to touch on long usage. (subjective).
• Might be too hefty to some people (subjective).
• A pouch would be a treat for everybody (a nitpick).

The Fosi Audio DS1 truly is a hype-worthy dongle! I must say, if we’re talking about practicality, you will be more than fine with this dongle throughout your 100-200 USD IEM, earbud, and maybe even headphone journey. I did not experience any major flaws or issues with this dongle, up to the point that the only things that I found were only nitpicks. It’s that good for a dongle. The Fosi Audio DS1 is my top USB DAC recommendation under 200 USD as of Q1 2023!

Who is the Fosi Audio DS1 for?

• For those people who want an all-rounder, fairly powerful dongle .
• For those people who want a bit of warmth to their listening sessions.
• For those people who want a robust usb dongle on-the-go.

Why should you not buy the Fosi Audio DS1?

• None, actually. This might sound shilly, but if you have the budget and do not have a proper source, buy the Fosi Audio DS1.

Thank you for reading!

Non-affiliated links here: https://www.amazon.com/dp/B0B5ZR9GFJ/
https://www.fosiaudio.com/product/headphone-amplifier/ds1-dac-headphone-amplifier/

Additional Photos Here:

I would like to thank Fosi Audio for providing me the samples for review, my opinion is my own and I am not paid or influenced in any way.
https://www.amazon.com/dp/B0B5ZR9GFJ/
https://www.fosiaudio.com/product/headphone-amplifier/ds1-dac-headphone-amplifier/

Lets get started with the package its simple and inside is the DS1 a cable and a USB-C to USB-A adapter. Construction of the DS1 exceeds my expectations it is robust with an all-metal build, the device itself is little but feels solid in the hands. there is both a 3.5mm and a 4.4mm headphone output.
The DS1 adopts ESS Technology ES9038Q2M DAC Chips supporting DSD 512 and 32Bit/768kHz PCM, features best-in-class specifications and high-power outputs capable of supporting the most demanding of headphones with impedance above 200Ω with the 4.4mm balanced output that can support up to 240mw output.


Impressions: The DS1 sounds clean, with good details, transparency and natural tonality with a hint or warmth and musicality making it very pleasant. In A to B testing, it provided a louder and better sounding presentation than the stock DAC chip included. It has a fair amount of air and openness, and soundstage is accurate and above average in width and depth. headphones tested with the DS1 were the HiFiman HE x-4, the Fostex T20rp, Dekoni Blues, 1More Triple and Philips X2HR to name a few, IEM use were the Moondrop Kato, Sonic Memory SM2, NF NM2 plus, the Kinera Hodur and Moondrop Aria SE.

The DS1 is an exceptional value in my opinion, it offers a noticeable improvement at a good price to performance ratio.