Buy the SSL 2+ MKII if anyone ever records with you: two mic preamps at 64 dB and two independent headphone outputs is the combination that makes a two-person session work. Buy the Audient iD4 MKII if you record alone and want the cleanest channel at the price — -129 dB(A) EIN and 0.0017% THD+N are tier-above figures.
Both have two headphone outputs — only one has two mic inputs
This is an unusual pairing, because the iD4 MKII is one of the very few single-input interfaces with two headphone outputs. That is genuinely useful: you can record yourself while someone listens alongside you. What you cannot do is record that second person, which is the limit.
So the question is whether your second person talks or just listens. If they talk, the SSL is the only one of these two that works, and it is not a close call. See best 2-channel audio interfaces for the wider field.
Choose the SSL 2+ MKII if
- You record with a co-host, a guest or a musician. Two preamps and two headphone feeds is the whole requirement.
- Your microphone is low-output. 64 dB clears an SM7B where the iD4's 58 dB is marginal.
- You want the Legacy 4K switch, which is a real top-end lift with a little harmonic character — not a marketing mode.
- You want four line outputs, for instance to feed monitors and a separate headphone amp.
Choose the Audient iD4 MKII if
- You record alone and will continue to. One excellent channel beats two good ones.
- You want the published noise figures. -129 dB(A) EIN and 0.0017% THD+N are what you would expect a tier up, and Audient publishes both.
- Your microphone is a condenser or a hot dynamic where 58 dB is plenty.
- You want the smaller footprint and the lower price.
Gain: 6 dB apart, and it matters at the margin
64 dB against 58 dB. With a condenser, irrelevant. With an SM7B at -59.0 dBV/Pa, the SSL is comfortable and the iD4 is at the edge — it will reach the level, but with the knob near the top. The iD4's exceptional EIN partly compensates, because a quieter circuit at high gain is exactly what you want. But it does not fully close a 6 dB gap.
What else you need to buy
- SSL 2+ MKII: a second microphone and a second set of closed-back headphones, if the point is two people. Two-person podcast setup.
- iD4 MKII: possibly a booster if you pair it with a very low-output dynamic.
Both interfaces in detail
SSL 2+ MKII
Top pickSolid State Logic · Two headphone outs and a console voicing
Buy it for the second headphone output if you record with anyone else in the room — that single feature is worth the premium. For solo work the 2i2 gives you more gain for less money.
Why it is here
- 64 dB of gain clears an SM7B without a booster
- Two independent headphone outputs is the feature that makes a two-person recording workable
- The 4K switch is a real, usable top-end lift rather than a marketing mode
What it costs you
- Costs meaningfully more than a 2i2 for 5 dB less gain
- Four outputs are wasted if you only own one pair of monitors
- Larger footprint than the rest of this group
Audient iD4 MKII
Audient · The best-sounding single preamp here
The right box if your mic is a condenser or a hot dynamic and you want the cleanest single channel at this price. If you are buying an SM7B, 58 dB puts you straight back into booster territory.
Why it is here
- -129 dB(A) EIN and 0.0017% THD+N are numbers you would expect a tier up
- The Class A preamp is the same circuit family as Audient's consoles
- Two headphone outputs on a one-input box, which is unusual and useful
What it costs you
- 58 dB is not enough for an SM7B without a booster
- One mic input only
- No onboard DSP or voicing
If neither: the third option
If you want maximum gain and two inputs for less money, the Scarlett 2i2 at 69 dB beats both on that specification — it just has one headphone output. And if two people is really three or four, an interface is the wrong category: RodeCaster Pro II vs Zoom PodTrak P4.