If you are mixing or mastering on headphones, the single most impactful upgrade you can make — after choosing the right headphones — is how you power them. Most audio interfaces ship with headphone outputs that are, frankly, not fit for professional critical listening. They lack the current delivery, the headroom, and the low output impedance required for truly linear monitoring.
This guide distills everything we have learned through years of testing, measuring, and mixing on dedicated DAC/amp units. We will cover the science, bust a few myths, and give you concrete product recommendations at every price point.
Why You Need to Stop Using Your Interface Headphone Output
The headphone output on 98% of audio interfaces is current-limited. It may get your headphones loud, but loud and linear are two very different things. As Emrah puts it:
"We are not saying that you can never get sound out of them. We are talking about how punchy, how linear, how distortion-free the dynamics move. If you connect a less powerful amp and drive demanding headphones, you are simply hitting the red all the time." — Emrah Celik
The analogy is perfect: imagine driving a car at 120 km/h in third gear versus sixth gear. Both get you to the same speed, but one is straining the engine the entire time. That strain translates directly into audible distortion — coloured low end, shaved transients, and a loss of what Emrah calls "micro details."
Paul has tested this extensively with the track "Wild Thoughts" by Rihanna and DJ Khaled, which he uses as a reference for sub-bass linearity:
"If a headphone has too much distortion in the low end, or the amp doesn't have enough headroom, you'll hear the low end distorting on Wild Thoughts. That's my litmus test." — Paul Third
This matters profoundly for mixing. Distortion masks distortion. If your monitoring chain is adding harmonic distortion, you cannot accurately judge compression, saturation, or limiting decisions. You end up either over-processing or under-processing because you are hearing artefacts from your amp, not your mix.
Key problems with interface headphone amps
- ●Current-limited output — interfaces provide voltage (SPL) but not enough current for linear amplification, especially with low-impedance planar magnetics
- ●High output impedance — many interfaces have 10-50 ohm output impedance, causing frequency response deviations with dynamic headphones (rule of thumb: headphone impedance divided by 8 = max acceptable output impedance)
- ●Insufficient headroom — even at 85 dB SPL average, transient peaks need 20+ dB of headroom to avoid clipping and distortion
- ●EQ multiplies power demands — a 6 dB low-end boost can multiply the required power by 3-4x, pushing limited amps into distortion territory
Voltage vs. Current: Ohm's Law for Headphone Mixing
Understanding headphone amplification comes down to one fundamental equation: Power = Voltage x Current (P = V x I). That is Ohm's law applied to headphone amps, and it explains everything about why certain setups sound strained.
Voltage gives you SPL
Voltage is what gets your headphones loud. Higher impedance headphones (like 300-ohm Sennheisers or 600-ohm Beyerdynamics) need more voltage to reach a given SPL. Most audio interfaces have ample voltage on tap — this is the easy part of the equation and why people mistakenly think their interface "drives" their headphones just fine.
Current gives you linearity
Current is what moves the driver cleanly and accurately, and it is what 95% of audio interfaces lack. Low-impedance headphones — particularly planar magnetics at 16-32 ohms — demand significantly more current. When an amp runs out of current, it does not simply get quieter. It distorts. Transients get shaved, low-end becomes mushy, and you lose the micro details that are critical for professional mix decisions.
"Many reviewers base their conclusions on the SPL they can get. But there is a difference between getting loudness and getting loudness linearly — without distortion." — Paul Third
Why planar magnetics are especially demanding
Planar magnetic headphones use a thin diaphragm suspended between magnets. Moving that diaphragm accurately requires consistent current delivery. When an interface runs out of current, the driver cannot track the signal faithfully. The result: the sound gets thinner and thinner the more you turn up the volume. The low end compresses, transients lose their punch, and you are left mixing through a coloured, unreliable signal.
This is why Emrah tested the Audeze LCD-X on an Aronier at NAMM and immediately identified the coloured low end and shaved transients — the interface simply did not have the current to drive them linearly, even at moderate levels.
The headroom factor
We recommend calculating amp requirements based on 110 dB SPL peak, even though you will mix at 85 dB SPL average. The reason: transient peaks are fast and loud. A snare hit, a kick transient, a high-hat attack — these micro-detail peaks can sail well above your average listening level. If your amp cannot reproduce them cleanly, they get clipped, and you lose the information you need for critical mix decisions.
Do DACs Actually Matter? The Truth.
This is perhaps the most debated topic in audio. Videos claiming "DACs are a scam" have millions of views. The standard test — looping a DAC back into an ADC and null-testing — shows near-identical results. So does it matter? The answer is nuanced.
"In a headphone setup, the priority order is: headphones first, amp second, EQ third, then DAC. A DAC isn't the biggest bottleneck. But saying all DACs sound the same doesn't make sense scientifically." — Paul Third
The null test is misleading
Paul conducted his own tests — both the standard DAC-to-ADC loopback and a physical measurement using Room EQ Wizard with a measurement microphone pointed at a tweeter from 20 cm. The loopback showed virtually no difference. But the physical measurement told a different story: one DAC produced noticeably faster decay times than the other, resulting in better transient separation and clarity.
The key difference? The reconstruction filter.
Filters are where DACs differ
Nearly all modern delta-sigma DACs use digital reconstruction filters to smooth the output. These filters can be minimum phase (causing post-ringing), linear phase (causing pre-ringing), or various slow/fast roll-off configurations. In the digital domain, these differences are vanishingly small. But in the physical world — where speakers move air and headphone drivers have excursion — the filter characteristics interact with transients in audible ways.
Paul tested this directly with a Hifiman EF600, which has a non-oversampling (NOS) mode that uses an analog low-pass filter instead of the standard digital oversampling filter:
"The difference between oversampling and non-oversampling is very, very obvious. The transients are smeared, things get wider, the stage gets deeper, but it's not accurate. That definitely shows you the filter has a sound." — Paul Third
The bottom line on DACs
Modern DACs — even affordable ones like the Topping DX1 or an Apple dongle — have excellent conversion quality. You do not need to spend a fortune on a DAC. As Emrah notes:
"We are living in a legendary time for DACs. A $100 DAC today would have cost $3,000-4,000 twenty years ago. Even the cheapest sound cards today are good enough to work with as a DAC." — Emrah Celik
The amp is far more important than the DAC for mixing. Get the amp right first, and the DAC quality will follow naturally since most standalone DAC/amp units come with excellent DAC implementations.
Desktop DAC/Amp Recommendations by Tier
Every product listed below has been personally tested and used for mixing by Paul and Emrah. These are not theoretical picks — they are battle-tested units with verified measurements from Amir at Audio Science Review.
Budget: Topping L30 Mark II (Standalone Amp) — ~$130 / ~£130
If you already have an audio interface and just need a proper headphone amp, the L30 Mark II is the recommendation. It is unbalanced (single-ended, quarter-inch output) and connects via your interface's line outs using a TS-to-RCA cable.
Power: Approximately 3.4 watts at 16 ohms. That is more power than many balanced amps costing three times as much.
Output impedance: ~0.1 ohm — essentially zero frequency deviation with any headphone.
Paul and Emrah are emphatic: you do not need a balanced amp. The L30 Mark II measures better than many balanced options, and at this price, it will power 99% of headphones on the market.
"Balanced doesn't give you a better sound. It just gives you more power. And the L30 Mark II already has more power than most people will ever need." — Emrah Celik
Mid-Range: Topping DX5 Mark II (All-in-One DAC/Amp) — ~$220-300 / ~£220
This is the unit that changed the game. For under $300, you get a combined DAC and amp that outperforms units costing $3,000+. It replaced Emrah's RME ADI-2 DAC as his primary unit — a move that speaks volumes.
Power (balanced): 5.9 watts at 33 ohms, 4.5 watts at 16 ohms, 1 watt at 300 ohms
Power (unbalanced): 1.88 watts at 33 ohms — more than the Lynx Hilo 2 ($3,700) and the RME ADI-2 Pro FS
THD+N: -123 dB (class-leading; the Lynx Hilo 2 measures -117 dB)
Connections: 4-pin XLR, 4.4mm balanced, quarter-inch, XLR speaker outs, RCA outs, USB/optical/coaxial digital inputs, Bluetooth
"For the first time ever, we can say you have arguably the best quality DAC and amp you could ever hope for under £300. This is affordable for the first time ever." — Paul Third
The DX5 Mark II ships with Topping Tune software (now available on Mac and Windows), which provides onboard parametric EQ/DSP. You can import CSV target curves from AutoEQ, store multiple headphone presets, and switch between them via the included remote. You can even use it for speaker correction on the line outputs.
It powered Emrah's notoriously hungry Moondrop Cosmos — headphones that were clipping the Topping A70 Pro, A50 Pro, and distorting the RME ADI-2 at 70-75 dB SPL.
High-End / Endgame: FiiO K19 — ~$1,000 / ~£1,000
The K19 remains the endgame DAC/amp for those who need to drive absolutely everything, including extreme outliers like the Hifiman HE6SE V2 and Susvara. It features digital-to-digital conversion (DDC), meaning you can daisy-chain it with other DAC/amps in a multi-output setup.
For 99% of users, the DX5 Mark II covers everything you need. The K19 is for the rare cases where you are running the most power-hungry headphones on the planet and need the absolute ceiling of current delivery and headroom.
"For £1,000, the K19 can do everything. It can power everything you throw at it. But 99% of people won't need it — the DX5 Mark II is endgame for under £300." — Paul Third
The Stack Option: Topping D90/A90 Discrete
Paul's personal setup is a Topping D90 Discrete DAC paired with an A90 Discrete amp. He describes it as "arguably the most boring DAC/amp on the market" — and means it as the highest compliment. It is utterly sterile and transparent, which is exactly what you want for mixing. The A90 Discrete delivers approximately 16 watts at 16 ohms.
For those waiting, Topping has confirmed a DX9 Discrete is in development — an all-in-one unit with discrete circuitry and an estimated 10 watts of power, which would make it the most powerful DAC/amp combo on the market.
Portable DAC/Amp Recommendations
Sometimes you need to mix on a train, in a hotel room, or away from your studio. These USB-powered units need no external power supply — they run directly from your laptop or phone.
Budget: Topping DX1 — ~$80-100 / ~£70-100
Power: 250 mW at 32 ohms, 140 mW at 64 ohms, 45 mW at 300 ohms
Connections: 6.3mm and 3.5mm headphone outputs, RCA preamp output
It is better than most audio interface headphone amps. Driverless on Mac, plug-and-play. It will power around 80% of headphones — easy dynamic drivers, IEMs, and less demanding planars. It struggles with very current-hungry headphones like the Dan Clark Aeon Nanos at 16 ohms.
"It's one of the most used amps in my setup. Grab your MacBook, this DAC/amp, and your headphones, and you can go anywhere and continue to work." — Emrah Celik
Mid-Range: Chord Mojo 2 — ~$600 / ~£500
Power: 400 mW at 33 ohms, 70 mW at 300 ohms
Battery life: ~8 hours continuous use
Connections: Dual 3.5mm outputs, coaxial digital input, micro-USB
Built like a tank (made in the UK), the Mojo 2 features an FPGA-based DAC with excellent oversampling filters and one of the best crossfeed implementations available — useful for headphones with wide staging. It powers roughly 90% of headphones. The downsides: no balanced output, outdated micro-USB charging, and a colour-coded menu system that takes time to learn.
"It sounds incredible. The crossfeed is one of the best we have ever heard. But I'm waiting for a Mojo 3 with a screen where I can see everything and USB-C power." — Emrah Celik
Best-in-Class: FiiO QX13 — ~$200-250 / ~£200
Power: 900 mW balanced (desktop mode), ~480 mW at 16 ohms balanced, ~420 mW at 16 ohms single-ended
Connections: 4.4mm balanced, 3.5mm single-ended, USB-C
Features: OLED screen, onboard parametric EQ (10 bands, 7 user presets), desktop mode toggle, real-time power monitoring, carbon fibre construction
This tiny, pocket-sized unit has become both Paul and Emrah's portable endgame. In desktop mode, it activates all six internal amp stages, delivering power that rivals many desktop units. It drove Emrah's Moondrop Cosmos to decent levels — headphones that shut down far more expensive amps.
"Going from the Mojo 2 to this is like going from the 1970s to the future. The power, the screen, the workflow — I can do Dan Clark Nox with a bass boost on this little thing. It's the product of the year for pocket-size." — Paul Third
Recommendation Table
| Product | Price | Type | Best For |
|---|---|---|---|
| Topping L30 Mark II | ~$130 | Desktop Amp | Budget studio upgrade — pair with existing interface DAC. Powers 99% of headphones. |
| Topping DX5 Mark II | ~$220-300 | Desktop DAC/Amp | Best value on the market. Outperforms $3,700 Lynx Hilo 2. Onboard EQ via Topping Tune. Our top overall pick. |
| FiiO K19 | ~$1,000 | Desktop DAC/Amp | True endgame. DDC support. Powers the most demanding headphones including HE6SE V2 and Susvara. |
| Topping D90 + A90 Discrete | ~$1,200 (stack) | Desktop Stack | Maximum transparency. 16W at 16 ohms. The "boring" reference — Paul's personal daily driver. |
| Topping DX1 | ~$80-100 | Portable DAC/Amp | Budget portable. Better than most interface headphone outputs. Great with IEMs and efficient dynamics. |
| Chord Mojo 2 | ~$600 | Portable DAC/Amp | Battery-powered, tank-like build, best crossfeed. Ideal if you need battery power and don't require balanced. |
| FiiO QX13 | ~$200-250 | Portable DAC/Amp | Best-in-class portable. 900mW balanced, onboard EQ, OLED screen. Our portable endgame pick. |
What to Avoid
Studio-market headphone amps
The professional studio market has largely failed headphone users. The SPL Phonitor series measures terribly for the price. The Rupert Neve headphone amp loses linearity rapidly with low-impedance headphones — as little as 3 mW at 32 ohms before distortion rises. These units trade on brand prestige, not measured performance.
Relying on interface headphone outs for planars
The Audient Evo 16, for example, actually decreases power output as impedance drops — the opposite of what you need for planar magnetics. Many interfaces from major brands have output impedances of 10-50 ohms, causing frequency response deviations with dynamic headphones. Even the Lynx Hilo 2 at $3,700 maxes out its headphone amp quickly with demanding loads.
Daisy-chaining headphone outs
One user contacted Paul after buying a Topping L30 Mark II and complained it sounded terrible — he had connected it to the headphone output of his interface. Never feed one headphone amp into another. Always connect a standalone amp to the line outputs of your interface.
The "balanced is always better" myth
Balanced connections provide more power, but if an unbalanced amp has sufficient power and low noise, you will not hear a difference. Level-matched A/B comparisons between balanced and unbalanced on the same amp show no audible difference. Buy for the power spec, not the connector type.
How to Connect a Standalone Amp to Your Interface
The connection is straightforward:
- 1. Identify your interface line outputs — these are the TRS (quarter-inch) outputs you normally use for speakers.
- 2. For an unbalanced amp (RCA inputs): Use a TS-to-RCA cable from your interface line outs to the amp's RCA inputs.
- 3. For a balanced amp (XLR inputs): Use a TRS-to-XLR cable or adapter from your interface line outs to the amp's XLR inputs.
- 4. For a DAC/amp combo via digital: If your interface has optical (ADAT/S/PDIF) or coaxial output, you can send a digital signal directly to the DAC/amp, bypassing the interface's DAC entirely. Paul uses his ID48's ADAT out into the optical input of his Topping stack.
Important: You can feed an unbalanced signal into a balanced amp and still output balanced to your headphones. The amp's internal circuitry handles the conversion. This is confirmed in Topping's own documentation.
If your interface only has one set of line outs and they are occupied by speakers, you will need either an interface with additional outputs or a DAC/amp that accepts a digital input (USB, optical, or coaxial).
The Bottom Line
If you are mixing or mastering on headphones professionally, a dedicated headphone amp is not optional — it is essential. The good news is that it has never been cheaper to get reference-grade amplification.
Our three-sentence recommendation
If you want the single best value in headphone amplification today, buy the Topping DX5 Mark II. It outperforms DAC/amps costing ten times its price, includes onboard EQ via Topping Tune, and will power virtually every headphone on the market. If you need a portable solution, the FiiO QX13 delivers desktop-class power in a pocket-sized unit.
"It feels like Topping ended the game with this price range. I don't know how anybody else can compete. For $300, it's just crazy." — Emrah Celik, on the Topping DX5 Mark II
Invest in your monitoring chain. Every mix decision you make passes through your amp. Make sure it is telling you the truth.