PPA Technical Notes: Why Valencia Drives Tungsten (and Serene) So Well
Understanding voltage, current, crest factor, and why “easy to drive” doesn’t mean what you think.
The Orchard Audio × Z Reviews Valencia is an unusual headphone amplifier. On paper it’s a compact, fully-balanced Class-AB power amp with up to 17 W into 32 Ω, ultra-low output impedance, and enough gain to double as a small speaker amp. In practice, it has built a reputation for doing something that looks almost contradictory:
- It drives “notoriously difficult” headphones like the Modhouse Tungsten Double-Sided beautifully.
- It also reveals just how much performance is left on the table with supposedly “easy to drive” planars like the Kiwi Ears Serene.
This article explains why that happens, in a way that’s useful both for engineers and for music lovers who just want to understand whether their amp is actually doing the job.
“Easy to Get Loud” vs. “Easy to Drive Well”
In headphone forums you’ll often see people describe a product as “easy to drive” based on two things: impedance and sensitivity. If the numbers look modest and it gets loud from a phone, the conclusion is usually that the headphone is easy to drive and doesn’t need a serious amplifier.
The reality is more nuanced. A headphone can:
- Be easy to get loud (high sensitivity) but hard to drive well (demanding current, back-EMF, dynamics).
- Or it can be hard to get loud (low sensitivity) but electrically polite and relatively easy for a stable amplifier.
To show why this distinction matters, we’ll look at two very different loads: the Kiwi Ears Serene and the Modhouse Tungsten Double-Sided, and how both behave on the Valencia.
Inside the Valencia: Why It’s Not a Typical Desktop Op-Amp
At a glance, the Valencia looks like many solid-state amps. The important difference is in how the stages are split and powered:
- Input stage – Fully balanced, with ESD protection and its own filtered ±12 V supply.
- Gain stage – A fully balanced discrete gain block running from independent, linear-regulated ±34 V high-voltage rails¹ with substantial reservoir capacitance (1000 μF per rail).
- High-current buffer stage – Twenty-four OPA1622 devices in total (each containing two amplifier channels), providing forty-eight output buffer channels arranged equally across left and right. These serve purely as high-current buffers, not voltage-gain devices.
The key point is that the voltage-gain stage is not limited by op-amp rails. The discrete stage runs on far higher linear rails than typical IC-based headphone amps, while the OPA1622 array provides clean, stable current delivery into the load. This is why the Valencia can deliver:
- Up to 17 W into 32 Ω.
- Clean, high-voltage swing into high-impedance headphones (≈23.5 Vrms, 66.5 Vpp).
- An extremely low output impedance (< 0.02 Ω from 20 Hz–20 kHz).
Valencia’s Output Impedance: The Amplifier’s “Grip” on the Headphone
Bench measurement of Valencia’s output impedance (Zout), showing ~18 mΩ across the audio band.
The bench measurement above shows Valencia’s output impedance staying around 18 milliohms across the audible range. That has three major implications:
- No frequency-response shifts from the amplifier itself, even on complex loads.
- Excellent damping – the amp can control the driver rather than being pushed around by it.
- Low distortion under dynamic, real-world signals, because the amplifier isn’t fighting wild impedance swings.
In other words, Valencia is designed to be a neutral, low-interaction source. It lets the headphone be the headphone.
Modhouse Tungsten DS: “Hard to Drive” on Paper, Polite in Reality
Headphones.com impedance measurement for the Modhouse Tungsten Double-Sided.
The Modhouse Tungsten Double-Sided has a reputation for being extremely hard to drive. The facts from Headphones.com’s impedance measurement tell a more useful story:
- Nominal impedance of around 160 Ω.
- Impedance is almost perfectly flat from bass through treble (≈156–165 Ω).
- EPDR (effective peak dissipation resistance) bottoms around 114 Ω.
- Phase is mild (≈–12°), indicating low reactive behavior.
Electrically, that makes Tungsten a high-impedance, low-reactance load. From the amplifier’s perspective, this is relatively easy: you need voltage swing, but not extreme current, and the load doesn’t do anything strange as frequency changes.
This is why a well-designed Class-AB amplifier with good voltage rails and low output impedance — like the Valencia — is such a strong match. Tungsten becomes a question of:
- Can the amplifier provide clean voltage peaks?
- Does it remain stable and low distortion when pushed?
- Does it have low enough Zout to avoid tonal shifts?
On all three counts, Valencia performs extremely well, which is why listeners consistently report that Tungsten sounds “pretty damn close to the best it can” on this amplifier.
Kiwi Ears Serene: Easy to Get Loud, Harder to Drive Well
Now contrast Tungsten with the Kiwi Ears Serene, a large-format planar magnetic headphone whose official specifications are:
- Driver: 72 × 89 mm planar magnetic.
- Impedance: 50 Ω ±15% @ 1 kHz.
- Sensitivity: 102 dB ±3 dB (0.179 V at 1 kHz).
- Lowest resonant frequency (F0): 130 Hz ±20%.
- Rated power: 10 mW, max power: 20 mW.
- THD: < 3%.
On paper this looks “easy”:
- Moderate 50 Ω impedance.
- Very high sensitivity (102 dB at only 0.179 V).
- Only ~0.57 V needed for the rated 10 mW.
In practice, Serene behaves very differently from Tungsten — and this is where the notion of “easy to drive” breaks down.
Why Serene Is Electrically Demanding
- Planar behavior – Nearly resistive impedance means current draw increases directly with signal level. The large diaphragm needs strong instantaneous current to control bass and fast transients.
- Low F0 (130 Hz) – The driver stores more mechanical energy in the bass region and reflects it back into the amplifier as back-EMF. A weak amp here sounds soft, veiled, or congested.
- High sensitivity only guarantees loudness – Serene will get loud on almost anything, but loudness isn’t the same as clean transient response, low distortion, or stable imaging.
Small dongles and portable DAC/amps can bring Serene to high SPL, but they typically run out of instantaneous current and headroom on complex music. The symptoms are familiar:
- Bass loses definition and “punch”.
- Treble becomes grainy or splashy.
- Dynamics feel compressed.
- Staging collapses into a flat, forward presentation.
On a high-current, low-Zout desktop amp like Valencia, Serene transforms:
- Bass tightens and extends cleanly.
- Transients snap into focus.
- Vocals and instruments separate instead of clumping together.
- Stage gains width and depth.
- Listening fatigue drops as distortion from under-driving disappears.
So while Serene is genuinely easy to get loud, it is not trivial to drive well. It exposes the difference between “the amp can make sound” and “the amp can actually control the driver.”
Music Is Not a Sine Wave: Crest Factor and Time Matter
Most power and voltage ratings are taken with steady sine waves into fixed resistors. This is great for consistency, but it doesn’t describe how music behaves.
Real music has crest factor — the ratio of its peak level to its average level:
- Electronic / heavily compressed pop: 6–8 dB.
- Rock and mainstream pop: 9–12 dB.
- Jazz: 14–16 dB.
- Classical / orchestral: 18–24 dB or more.
This means that for most of the track, your amplifier is operating at a fraction of its rated continuous power, with short bursts of higher voltage and current on peaks. Those bursts last for milliseconds, but they define how alive, dynamic, and natural the music feels.
An amplifier like Valencia is engineered for exactly this reality:
- Stable high-voltage swing into high-impedance loads like Tungsten.
- High peak current delivery for more demanding planars like Serene.
- Fast recovery and low output impedance so the driver (not the amp) defines the sound signature.
In other words, it’s designed around music as a time-varying signal, not just static test tones.
Putting It All Together: Why Valencia Works So Well with Both
Once you look at the electrical behavior instead of just the headline numbers, the picture becomes clear:
Devices at a Glance
The table below compares the two headphones and the amplifier in terms of how they appear on paper versus what they actually demand or provide in a real system.
| Device | Impedance & Behavior | What It Looks Like | What It Actually Needs / Provides |
|---|---|---|---|
| Kiwi Ears Serene (headphone) | 50 Ω planar, high sensitivity, low F0 (~130 Hz) | “Super easy to drive, works on anything.” | High instantaneous current, low Zout, fast recovery from back-EMF. |
| Modhouse Tungsten DS (headphone) | ~160 Ω, flat impedance, low reactance | “Extremely hard to drive, needs huge power.” | Clean voltage swing, low Zout, stable performance into high impedance. |
| Valencia (amplifier) | Class-AB, high-voltage discrete gain stage + high-current buffer, Zout ≈ 0.018 Ω | “A small power amp with no volume knob.” | Exactly the mix of voltage, current, and stability needed to maximize both Serene and Tungsten. |
The short version is:
Serene is easy to get loud but hard to drive well.
Tungsten is hard to get loud but comparatively easy to drive cleanly.
Valencia’s architecture happens to line up beautifully with both demands:
- It has the voltage headroom to make Tungsten come alive without strain.
- It has the current delivery and control to show what Serene is really capable of.
- Its ultra-low output impedance and stable time-domain behavior ensure that in both cases, what you hear is the headphone — not the amplifier fighting the load.
Conclusion
If you only look at headline numbers like impedance, sensitivity, and a single “watts into 32 Ω” rating, it’s easy to come away with the wrong impression about both headphones and amplifiers.
The Modhouse Tungsten DS is not as terrifying a load as its reputation suggests, and the Kiwi Ears Serene is not nearly as effortless to drive well as its sensitivity figure implies. The Valencia sits in a rare sweet spot: a compact, carefully-engineered Class-AB design with the voltage, current, and control needed to do justice to both.
For listeners, that means something simple: if you own either of these headphones — or anything similarly demanding — the Valencia isn’t just capable of making them loud. It’s capable of letting them sound the way their designers intended.
Technical Appendix: Voltage, Current, and Load Behavior (click to expand)
1. Maximum Voltage Swing2
Most desktop headphone amplifiers use op-amps as both the voltage-gain stage and the output stage. Because op-amps typically run from ±12 V to ±18 V rails, their maximum undistorted voltage swing is limited to roughly 7–12 Vrms. This is why so many IC-based desktop amplifiers plateau around 18–20 Vrms regardless of their published wattage into 32 Ω.
The Valencia is architecturally different. Its fully discrete voltage-gain stage and its paralleled OPA1622 buffer array are powered from independent ±34 V linear regulators2. Because the OPA1622 devices are used strictly as current buffers rather than voltage-gain elements, they are not the rail-limiting factor the way op-amp output stages normally are.
These rails allow the Valencia to reach:
- 23.5 Vrms clean swing
- ±33.25 Vpeak
- 66.5 Vpp
This voltage headroom is the primary reason the Valencia performs exceptionally well with high-impedance headphones like the Modhouse Tungsten DS, which demand voltage far more than current.
(A light aside: if your amplifier’s voltage ceiling is the same as the voltage limit of the op-amp at the heart of the circuit, it may be worth reconsidering your conclusions before declaring universal limits.)
2. Maximum Current Capability
The Valencia’s output stage is designed around high instantaneous current delivery. The twenty-four OPA1622 packages provide forty-eight buffer channels, sharing load gracefully and maintaining low distortion even under dynamic conditions.
The specified maximum output current is:
- Imax ≈ 1.2 A
Into common low-impedance loads:
- 32 Ω: P = 17 W → V = 23.3 Vrms, I = 0.73 A
- 16 Ω: P = 10 W → V = 12.6 Vrms, I = 0.79 A
- 8 Ω: P = 7 W → V = 7.5 Vrms, I = 0.94 A
These numbers show that Valencia’s limiting factor into low impedances is current, not voltage. This is exactly what we observe in bench tests: distortion rises at the ~1.1–1.2 A knee, consistent with the modeled output envelope.
3. Tungsten: A High-Impedance, Low-Reactance, Voltage-Dominant Load
Using the impedance curve measured independently by Headphones.com for the Modhouse Tungsten DS:
- Nominal impedance: ~160 Ω
- Minimum EPDR: ~114 Ω
- Phase: ≈ −12° (very low reactance)
Required voltage for high SPL on Tungsten can be written as:
$$ V = \sqrt{P \times R} $$
At 1 W into \(160\,\Omega\): $$ V_{1\text{ W}} = \sqrt{1 \times 160} \approx 12.6\ \text{V}_{\mathrm{rms}} $$
At 3 W (extremely loud): $$ V_{3\text{ W}} = \sqrt{3 \times 160} \approx 21.9\ \text{V}_{\mathrm{rms}} $$
At 5 W (borderline unsafe): $$ V_{5\text{ W}} = \sqrt{5 \times 160} \approx 28.3\ \text{V}_{\mathrm{rms}} $$
Valencia delivers ≈23.5 Vrms clean into these load ranges, which covers realistic listening levels and musical peaks with headroom to spare. Once crest factor is considered, continuous voltages above 20 Vrms are rarely needed in music.
4. Crest Factor: Why Music Doesn’t Stress an Amplifier Like Sine Waves Do
A sine wave at 20 Vrms is 20 Vrms continuously. Music isn’t.
Typical crest factors:
- Electronic: 6–8 dB
- Rock/Pop: 9–12 dB
- Jazz: 14–16 dB
- Classical: 18–24 dB
This means the average musical voltage is far below the peak musical voltage. Peaks last milliseconds. Amplifiers like the Valencia are designed to deliver these cleanly:
- Discrete high-voltage gain stage → clean transients
- High-current buffers → stable control under back-EMF
- Low output impedance → prevents FR shifts and reactive distortion
5. Why Tungsten Sounds “Pretty Damn Close to the Best It Can” on Valencia
Once we combine Tungsten’s impedance behavior with Valencia’s voltage and current profile, the reason becomes clear:
- Tungsten demands voltage → Valencia supplies it cleanly.
- Tungsten does not demand extreme current → buffers stay in their linear region.
- Tungsten’s impedance is flat → Zout ≈ 0.018 Ω prevents tonal shift.
- Music requires peak voltage, not continuous voltage → Valencia’s rails deliver peak dynamics effortlessly.
The result? A pairing that is electrically sound, musically responsive, and very often close to optimal.
And if someone confidently tells you “all headphone amps max out around 20 volts,” you can smile politely and refer them to the math above.
¹ This line was updated from the original article to incorporate information provided by Orchard Audio regarding Valencia’s ±34 V regulated supply rails for both the gain stage and associated output buffers.
² Technical Appendix updated with information provided Orchard Audio, in response to this article regarding Valencia’s ±34 V regulated rails, which enable its 23.5 Vrms / 66.5 Vpp maximum clean swing. The original article referenced generalized bench measurements prior to these confirmed values.