Grado SR80 on a Chord Mojo 2: what $650 actually buys when 2.1 V was already enough
The SR80 needs 0.776 V. Mojo 2 publishes 5.2 V at 300 Ω and 4.24 V at 30 Ω — 126.5 or 124.7 dB depending on which point applies. Neither number is the reason to buy it: the 0.06 Ω output impedance gives a damping ratio of 633 where the rule asks for 8.
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)
A $175 open-back headphone that needs 15.85 mW, plugged into a $650 portable DAC. The level question was settled two hundred dollars ago; the interesting number is somewhere else.
The SR80 is 38 Ω at a clearly labelled 98 dB/mW — 112.20 dB/V — and needs 0.776 V for a 110 dB peak. Chord publishes 5.2 V RMS at 300 Ω for the Mojo 2, which puts the SR80 at 126.5 dB SPL, +16.5 dB. That is more headroom than any listening situation can use, and a plain DragonFly-class dongle at 2.1 V already delivered +8.6 dB.
The pearl: Chord publishes two operating points, and together they show that "maximum output" is not one number. The spec line reads 600 mW into 30 Ω (4.2 V RMS) and 90 mW into 300 Ω (5.2 V RMS). The higher voltage appears at the higher impedance — which looks backwards until you see what limits each case: into 30 Ω the amplifier runs out of current, into 300 Ω it runs out of volts. For a 38 Ω load the 30 Ω figure is the relevant one, so the honest reading is 4.24 V and 124.7 dB, +14.7 dB. Every single-number "max output" spec on any other product page hides which of these two you are being sold.
What the money buys, in one figure: 0.06 Ω. Against the SR80's 38 Ω that is a damping ratio of 633, where the 1/8 rule asks for 8 — a factor of 79 in hand. It is worth putting that next to the Audient EVO 8's published <50 Ω, where the same 38-ohm-class headphone lands at a ratio of 0.8 and the divider eats several decibels. Output impedance is the specification that separates these two devices; the volts do not.
The rest of the chain. The iPhone 16 Pro connects over USB-C, and the Mojo 2 runs on its own battery, so the phone's 4.5 W port carries data only and the level above does not depend on the handset. The SR80's 3.5 mm plug goes straight in. One caveat on the headphone side: Grado's store page lists this model as SR80 with a 20 Hz–20 kHz response, which does not match the SR80x datasheet — the numbers here come from the page we cite, so check your own box before reusing them.