SMSL SU-1 Review: Budget DAC With Serious Performance

The SMSL SU-1 keeps appearing in budget desktop DAC conversations for good reason , it’s one of the more compact AK4493S-based options available, and the measurements ASR has pulled on similar SMSL hardware consistently punch above the budget tier. If you’re building or refining a desktop DAC stack and want to spend as little as possible without landing on a chip known for mediocre noise floors, this unit deserves a close look.

What separates a competent budget DAC from a frustrating one usually isn’t the headline chip , it’s the implementation around it. USB power handling, clock quality, and output stage decisions matter more than the spec sheet implies. Those are the areas worth examining here.

What to Look For in a Budget Desktop DAC

Chip Implementation vs. Raw Specs

The AK4493S is a well-regarded chip, and its presence in a unit doesn’t automatically mean the unit measures well. SMSL and Topping have both demonstrated that budget implementation can be clean, but owner reports across Head-Fi and ASR forums consistently flag that power supply quality and PCB layout affect noise floors as much as the DAC chip itself. A unit can carry a premium chip and still deliver audible noise if the surrounding design is careless. Verified buyer reviews citing channel imbalance or ground-loop hum at low volumes are worth treating as real signal, not edge cases.

The AK4493S specifically offers support up to 768kHz PCM and DSD512 , numbers that matter less in daily listening than the unit’s THD+N figures at standard 44.1kHz and 96kHz. ASR-style measurements showing low THD+N and a clean noise floor at those standard rates are the numbers to weight heavily.

Input Options and Desk Reality

A DAC that only accepts USB is fine for most desktop setups, but buyers who run a TV, a game console, and a PC from the same DAC will miss coaxial and optical inputs quickly. The SU-1 includes USB, optical, and coaxial , a meaningful advantage over bare-bones competitors that limit you to USB only. The practical upside is flexibility without buying additional converters.

That said, input count is worth nothing if the unit introduces jitter on coaxial or optical that USB avoids. Field reports on the SU-1 suggest optical and coaxial both behave cleanly, which matches the expectation for a unit in this segment built around a crystal-controlled clock architecture.

Output Stage: Single-Ended vs. Balanced

The SU-1 provides RCA single-ended outputs only. For the majority of buyers pairing this with a headphone amp like the Topping L50 or JDS Atom, that’s the correct output , most entry-to-mid-tier headphone amps accept RCA without issue. The balanced XLR path is a legitimate upgrade, but it belongs in the conversation only if your amplifier actually has a balanced input stage that benefits from the lower noise floor.

Owner consensus across DAC discussions is consistent: single-ended outputs from a clean-measuring DAC into a competent amp produce results that are genuinely difficult to distinguish from balanced in blind comparisons at this tier. The balanced step-up is worth pursuing once you’re running planar magnetics at volume into a proper balanced amp , not before.

Form Factor and Power Draw

The SU-1’s footprint is notably small. For a desk already hosting a headphone amp, a computer, and a monitor, that matters practically. Units in this segment vary from half-rack-width bricks to genuinely compact rectangles. The SU-1 lands at the compact end, USB-powered without a wall wart, which removes one cable from the equation entirely.

USB power dependency is a consideration if your PC’s USB ports are electrically noisy. Some buyers report improvement with a USB isolator or a dedicated USB power supply. It’s not a common complaint for this unit specifically, but it’s the standard caveat for any USB-powered DAC in the budget tier. Exploring the full range of dedicated DAC options before settling on form factor is worth the time if your desk situation has specific constraints.

Top Picks

SMSL SU-1

The SMSL SU-1 represents the AK4493S implementation at its most accessible price point, and the design decisions SMSL made around that chip are largely sensible. It’s USB-powered, compact enough to sit under a small headphone amp without looking awkward, and the three-input design , USB, optical, coaxial , gives it more flexibility than many competitors at the same tier.

Verified buyer reports across Amazon and Head-Fi forums point to a clean, quiet background with no reported channel imbalance issues at standard listening levels. ASR’s measurements on SMSL hardware in this segment consistently show THD+N figures that would have been mid-range territory three years ago. The SU-1 fits that pattern. Owner consensus on the optical and coaxial inputs is equally positive , no complaints about jitter artifacts or degraded performance versus USB, which isn’t universal in this tier.

The limitation worth stating plainly: this is a DAC unit only. There is no headphone output, no volume control, no integrated amp stage. Buyers who want an all-in-one solution should look at the Topping DX3 Pro+ or the FiiO K7 instead. The SU-1 is the correct choice when you already have a headphone amplifier , or plan to buy one separately , and want the cleanest DAC stage your budget allows without paying for redundant features.

For a Topping L50 or JDS Atom pairing, the SU-1’s RCA outputs feed directly into the amp’s RCA inputs and the chain works cleanly. The gap between this unit and a mid-range DAC like the Topping E50 is real on measurements but narrow in practice at standard listening levels with dynamic driver headphones. With planar magnetics , particularly the HiFiMan Sundara, which genuinely does respond to source quality in ways the HD600 does not , the mid-range step-up becomes easier to justify. For dynamic drivers and casual listening, the SU-1 is difficult to argue against at its price band.

Check current price on Amazon.

Buying Guide

Who Actually Needs a Standalone DAC

The case for a dedicated DAC unit rather than an all-in-one is strongest when you already own a headphone amp , or plan to buy one that lacks a built-in DAC stage. If you’re running a JDS Atom or a Topping L50, neither includes a DAC, so the SU-1 fills that slot cleanly without paying for features you won’t use.

Buyers who want a single box should look at integrated DAC/amp units instead. The standalone DAC path adds a cable and a USB port, but it also means you can upgrade either component independently later without replacing the whole chain.

Pairing the SU-1 with a Headphone Amplifier

RCA outputs from the SU-1 feed into the RCA inputs of most entry-to-mid-tier headphone amps without issue. The pairing with a Topping L50 or Magnius is the most commonly reported in owner reviews, and field reports on those combinations are consistently positive.

Planar magnetic headphones , HiFiMan Sundara, Monolith M1570 , are more source-dependent than dynamic drivers. The advice that planars “scale with source” turned out to have real content in practice: the gap between a laptop headphone jack and a clean DAC/amp chain is audible on the Sundara in a way it isn’t quite as obvious on the HD600. That doesn’t mean the SU-1 is wrong for planars , it means the step up from the SU-1 to the Topping E50 will be more noticeable on planars than on the HD600.

Understanding the Input Options

The SU-1’s three inputs , USB, optical, coaxial , cover the most common desktop source scenarios. USB handles your PC. Optical handles a TV or gaming console with an optical out. Coaxial handles CD transports and some network streamers.

Most buyers will use USB exclusively. The optical and coaxial inputs are insurance , genuinely useful if your setup evolves, and worth having even if you never use them. A DAC with USB only limits your flexibility unnecessarily when the cost difference between USB-only and multi-input at this tier is marginal.

When to Step Up to the E50 or SU-9n

The SMSL SU-1 handles standard 44.1kHz and 96kHz material cleanly. The step up to the SMSL SU-9n or Topping E50 is justified if you need balanced XLR outputs for a balanced amplifier input stage, or if you’re running the DAC into a high-sensitivity speaker amplifier where noise floor differences become audible.

For headphone use into a single-ended amp, owner consensus across DAC forums and Head-Fi threads points to the SU-1 as sufficient. The measurement delta between the SU-1 and the SU-9n is real but narrow under standard listening conditions. Spend the difference on the amplifier or the headphones before revisiting the DAC.

USB Power and Noise Considerations

USB-powered DACs draw power from the host device, which introduces a dependency on USB port quality. Reports of noise on the SU-1 are uncommon, but buyers running older PCs with electrically noisy USB implementations occasionally mention improvement with a USB isolator.

A powered USB hub with a clean external supply is the standard low-cost fix. Dedicated USB audio power supplies exist for buyers who want to go further, though the audible benefit at this tier is debated. The practical recommendation: use the unit as-is first, and address USB noise only if you hear a consistent hum or elevated noise floor.

Frequently Asked Questions

Does the SMSL SU-1 work without a separate amplifier?

The SU-1 has no headphone output and no built-in amplifier stage , it is a line-level DAC only. To use it with headphones, you need a separate headphone amplifier. Its RCA outputs connect to the inputs of an amp like the Topping L50 or JDS Atom. Buyers who want a single-box solution should look at integrated DAC/amp units like the Topping DX3 Pro+ instead.

How does the SMSL SU-1 compare to the Topping E30 II for desktop use?

Both units use competitive chips and measure cleanly at budget pricing. The SU-1’s advantage is its more compact footprint and USB power simplicity. The E30 II adds a remote and a display showing sample rate, which some buyers prefer for convenience. Field reports on both units across Head-Fi and ASR forums suggest performance is closely matched , the decision usually comes down to form factor preference and whether you want the display.

Will the SU-1 make a noticeable difference over a laptop headphone jack?

The gap is real, particularly with revealing headphones. Owner reports and ASR measurements confirm the SU-1’s noise floor is substantially lower than most laptop outputs, and the output impedance is better matched to low-impedance headphones. The difference is most audible with planar magnetics. With a forgiving dynamic driver like the Sennheiser HD600, the improvement is real but less dramatic than some buyers expect.

Does the SMSL SU-1 support MQA decoding?

Yes, the SU-1 includes MQA full decoding support. Whether MQA decoding matters depends on your streaming service and your position on the MQA format , it’s a divisive topic in the audio community, with ASR and others noting that MQA’s audible benefits over standard hi-res PCM are not reliably demonstrable. If you use Tidal and stream MQA content, the decoding is there. If you use Qobuz or standard FLAC, it’s irrelevant to your daily use.

Is the SMSL SU-1 good enough for HiFiMan Sundara or planar magnetic headphones?

The SU-1 is a competent pairing for the Sundara, though planar magnetics are more sensitive to source quality than most dynamic drivers. Owner consensus and field reports suggest the SU-1 feeds the Sundara cleanly without audible noise issues. The step up to a mid-range DAC like the SMSL SU-9n or Topping E50 will be more perceptible on the Sundara than on a dynamic driver headphone , but that’s a reason to consider the upgrade later, not a reason to dismiss the SU-1 as a starting point.