ATH-R70x, 470 Ω: the $76 dongle against the desktop DAC, and why 16 dB decides it
The R70x needs 2.73 V — more than a 250 Ω DT 770 and more than an HD 650. A FiiO KA13 on phone power delivers 1.22 V and lands 7 dB short; a Topping DX3 Pro+ delivers 7.6 V and finishes 8.9 dB above target.
Signal Chain Compatibility Matrix
Select gear and parameters for live gain, impedance and SPL calculations.
Input Equipment Setup
PASS: Optimal Signal Chain
Requires minimum +60dB of clean pre-amp gain. Most budget entry interfaces max out at +50dB to +56dB and introduce hiss at max pot. An inline preamp booster (Cloudlifter CL-1 / FetHead) is strongly recommended.
The interface preamp provides sufficient headroom.
$538
$405
-25%Tonal & acoustic characteristics: Flat, wide-range frequency response for clean music and speech. Smooth, warm acoustic character with air-suspension shock isolation.
Technical advisory: With +69dB max gain, the Gen 4 Solo can drive demanding dynamics like the Shure SM7B natively without requiring an external inline booster.
Physical Interconnect Topology
Shure SM7B
Direct Cable Connection (No Intermediate Box)
1x Shielded Balanced XLR Cable (3-Pin XLR Male to XLR Female)
Focusrite Scarlett Solo (Gen 4)
Host: Apple MacBook Pro (M1/M2/M3/M4)
No and yes: the KA13 reaches 103.0 dB against a 110 dB target, the DX3 Pro+ reaches 118.9 dB. Same headphone, same music, 15.9 dB between the two sources.
The ATH-R70x is 470 Ω at 98 dB/mW, which is 101.3 dB/V; in this catalogue only the 97 dB/V HD 600 asks for more voltage. A 110 dB peak needs 2.73 V. That is only 15.85 mW and 5.81 mA: the R70x is not a power-hungry headphone at all, it is a voltage-hungry one, and the two failure modes look nothing alike. The KA13 delivers 1.216 V into 470 Ω, so it stops 7 dB short — the volume control at maximum, the sound thin rather than merely quiet. The DX3 Pro+ delivers 7.598 V and has 8.9 dB in hand.
Why 470 Ω is not the point. Audio-Technica themselves warn on the Japanese product page that some sources will not reach adequate level. The reason is the pair of numbers, not the impedance: an equally 470 Ω headphone rated 105 dB/mW would need 1.22 V and the KA13 would drive it exactly to target. Impedance alone predicts nothing; impedance plus sensitivity predicts everything.
The pearl: the KA13's advertised voltage is not the one you get. FiiO's own parameter table gives two figures for the same 3.5 mm jack. On phone power it is >5 mW + 5 mW into 300 Ω, from which V = √(0.005 × 300) = 1.22 V. In Desktop Mode — second USB-C port fed from a charger — the same jack does 19.5 mW into 300 Ω, about 2.4 V. Most shop listings quote 2.3 Vrms without mentioning which mode it belongs to. Even at the Desktop-Mode figure the R70x would still be about 1 dB short of the 110 dB target, so the mode is not what saves this pairing.
What we can check, for once. Both sources publish an output impedance: FiiO says <1.7 Ω, Topping says <0.1 Ω. Against 470 Ω that is a ratio of 276 and 4700, far past the 8 the 1/8 rule asks for, so tonal balance is safe on both — the failure of the KA13 here is purely a shortage of volts.