Soyuz Launcher with a Shure Beta 57A: 26 dB from a transformer, and the same unwritten phantom question
The Beta 57A needs 52 dB on an iD4 MkII and the interface has 58, so the Launcher is a tone decision rather than a rescue. Soyuz publishes 26 dB and phantom operation, but not whether phantom power reaches the microphone.
Short answer: the Beta 57A does not need this booster on an iD4 MkII. Buy it for what a transformer does to a signal, not for the 26 dB.
The numbers. At 85 dB SPL the Beta 57A's −51 dBV/Pa sensitivity puts −57.8 dBu on the cable. The iD4 MkII clips at +12 dBu, so a −18 dBFS take needs 52 dB — and the iD4 MkII has 58 dB on its own. With the Launcher's +26 dB the interface's share drops to 26 dB, which is a real improvement in preamp noise terms but not a rescue. Point the Beta 57A at a snare or a guitar cabinet at 100 dB SPL and the requirement falls to 37 dB without any booster at all.
What Soyuz publishes. The Launcher is described as boosting “your gain by 26dB”, built around a hand-wound transformer rather than a plain FET gain stage, and running on phantom power. What the page does not say — like Klark Teknik's and Radial's — is whether that phantom power continues past the box to the microphone plugged into it. With a Beta 57A the question is moot: a moving-coil dynamic needs no power. With a condenser in front, the specification simply does not answer, and this site marks that state rather than guessing at it.
The gem. Shure's own spec sheets give the Beta 57A and the Beta 58A the same sensitivity, −51 dBV/Pa (2.8 mV), and the same 150 Ω output impedance. The difference between them is the grille — a hardened instrument grille against the ball — not the cartridge output. So every gain figure on this page transfers unchanged to a Beta 58A, and any advice that treats the 57A as the “quieter” one of the pair is describing a difference that Shure does not publish. That is unusually convenient: one gain plan covers both microphones in your case.
What to do: Beta 57A → Launcher → iD4 MkII mic input, +48 V on for the booster, interface gain around 26 dB. If the reason you are considering the Launcher is level rather than tone, save the money — the iD4 MkII already has six decibels more than this microphone asks for.