DT 770 Pro 32 Ω on an Audient EVO 8: the 1/8 rule, finally with numbers on both sides
Audient publishes <50 Ω of output impedance. Against a 32 Ω headphone that is a ratio of 0.6 where the rule wants 8, and the divider costs 8.1 dB of level. No DT 770 version comes out clean here: 32 Ω and 80 Ω flag damping, 250 Ω runs 1.7 dB short.
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)
Most of this catalogue has to say "output impedance not published". Audient publishes it: <50 Ω. So for once the rule can be applied instead of quoted.
The EVO 8's headphone output is rated at +10.1 dBu into 600 Ω, which is 2.48 V. The DT 770 Pro 32 Ω needs 0.897 V for a 110 dB peak — that looks like a large margin. It is not, because a 50 Ω source and a 32 Ω load form a voltage divider: 32/(32+50) = 0.390, so only 0.968 V arrives. Result: 110.7 dB SPL, +0.7 dB of headroom, and a damping ratio of 0.6 where the rule wants 8. Verdict: damping risk.
The divider costs 8.1 dB. With an ideal 0 Ω source the same 2.48 V would give 118.8 dB. That is the number worth carrying away: the output impedance is not a footnote about tone, it is also most of a volume control. And it takes the most from the lowest-impedance headphone, which is the opposite of the usual intuition that low impedance is the easy load.
The pearl: on this interface there is no DT 770 version that solves it. Move up to 80 Ω and the level barely changes (110.6 dB, +0.6) while the ratio only reaches 1.6. Move to 250 Ω and the divider costs just 1.6 dB — but now the voltage requirement has risen to 2.506 V and the output falls 1.7 dB short of target, verdict too quiet. The damping problem improves with impedance and the level problem worsens with it, and on a 2.48 V output they cross in a place where neither is solved. That is a property of the source, not of the headphone, and no amount of version-shopping fixes it.
Two honest caveats. Audient's figure is "<50 Ω", an upper bound, so the real device may sit lower and both numbers improve; the bound is what can be checked, so the bound is what we use. And the 2.48 V is specified into 600 Ω — essentially open-circuit next to 50 Ω — which is exactly the condition in which the divider arithmetic above applies. If you own an EVO 8 and want the DT 770 with it, the fix is a separate headphone amplifier fed from the line outputs, not a different impedance version.