+28dB of clean gain. Zero extra cables.
Your dynamic mic isn't broken.
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Four engineering decisions that separate the GainTube+ 28 from budget boosters and bulky stompboxes.
A matched Class-A JFET stage adds 28dB before your interface preamp, enough to bring an SM7B or PodMic to broadcast level with the knob in its quiet range.
Rated at -128dBu EIN. In editorial testing on a Scarlett 2i2, the measured floor dropped from -71.2dBFS to -86.4dBFS.
Boost mode keeps phantom DC away from dynamic and ribbon capsules. Flip the recessed switch and condensers get their 48V as normal.
Male-to-female barrel design plugs directly into your mic or interface. No extra cable, no box on your boom arm.
Inside the aluminum shell, matched JFET transistors give your dynamic mic a steady high-impedance load and add +28dB of low-noise gain, all powered by your interface's phantom supply.
Connect it to your interface's XLR input or your mic's output, plug your existing cable into the other end, and turn the gain knob back to around 11 o'clock.
A recessed selector keeps 48V away from dynamic and ribbon mics in Boost mode, or passes it through for condensers. Gold-plated pins and a spring-loaded latch keep the connection tight.
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Inline +28dB Class-A FET Microphone Preamp with 48V Phantom Pass-Through
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$89.99 $179.99 Free Tracked Shipping (5–7 Days) Included
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Who it's for: Podcasters, streamers, voiceover artists, and anyone on remote calls using a low-output dynamic or ribbon mic with a USB interface or mixer that has 48V phantom power.
What it fixes: Quiet levels, audible hiss at high gain settings, thin-sounding dynamic mics, and having to press your lips against the windscreen to be heard.
What it needs: An XLR mic and an interface or mixer with 48V phantom power. It doesn't work with USB-only microphones or 3.5mm inputs.
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The thick anodized aluminum shell blocks hum and digital ticking from PCs, monitors, and Wi-Fi routers on a crowded desk.
With 28dB added up front, your gain knob can sit around 11 o'clock, well below the hissy top of the dial.
Plug it in, put on your headphones, and listen. If the hiss doesn't drop, return it within 30 days for a full refund.
Cosari GainTube+ 28Standard Competitors
| Feature | Cosari GainTube+ 28 | Standard Competitors |
|---|---|---|
| Clean gain added | +28dB Class-A JFET | +25dB typical |
| Extra XLR cable needed | No, plugs directly in | Yes, for box-style units |
| 48V pass-through for condensers | Yes, selectable switch | Usually no |
| Size and weight | 98 × 21mm, 78g | Box on desk or boom arm |
| Price | $89.99 (50% off) | $149 plus cable |
Swipe left for steps 2 and 3
Plug the GainTube+ 28 into your mic's XLR output or your interface's input, then connect your existing XLR cable to the other end.
Switch on phantom power, then turn your interface gain back to about 11 o'clock, roughly half where it was.
Sit back comfortably and talk. Your voice comes through fuller and louder, with silence between the words.
I honestly thought my Shure SM7B was defective because I had to crank my Scarlett 2i2 gain knob to 95% just to get a usable signal, and the background hiss sounded like Niagara Falls. Clicked the GainTube+ 28 straight into Input 1 on my desk, backed the gain knob down to 11 o'clock, and my raw recording floor is completely silent now. Best upgrade on my desk.
I almost spent $150 on a Cloudlifter plus another $25 for a second XLR cable before finding this. It clicks directly onto the back of my broadcast mic right on the boom arm, clears the tight yoke bracket without touching the thumb screws, and adds virtually no weight so my arm doesn't sag. Locking collar has zero wobble when I swing the mic out of the way.
As a full-time audiobook narrator recording in a treated walk-in closet, hitting ACX -60dB RMS noise-floor compliance on a dynamic mic used to force me to run heavy iZotope RX passes that took the life out of my voice. With the GainTube+ 28 inline, my raw files pass ACX check straight out of the preamp.
Being able to leave this plugged into my interface and flip the recessed 48V pass-through switch when I swap from my dynamic vocal mic to my small-diaphragm condenser for acoustic guitar is brilliant. Every other inline barrel I looked at blocks phantom power completely and forces you to crawl behind your desk to unplug it.
The biggest difference over the budget $39 inline booster I returned last week is the bass response. That cheap one rolled off my lows and made me sound like an AM radio caller, whereas the GainTube+ 28 kept all my natural chest warmth intact while giving me effortless headroom.
My studio desk sits inches away from a dual-monitor gaming PC and a Wi-Fi 6 router. My previous inline preamp picked up a faint ticking EMI buzz whenever my GPU spun up. This thick anodized aluminum housing blocks all of it—dead quiet even during heavy streaming loads, and Twitch chat noticed within five minutes.
Before adding this to my Shure MV7X, if I leaned back more than two inches from the foam windscreen my volume dropped off a cliff. Now I can sit back comfortably in my chair during two-hour podcast sessions and still hit -12dBFS cleanly without straining my voice.
The recessed 48V pass-through toggle requires a pen tip or paperclip to flip, which took me a second to realize, though I get why Cosari recessed it so you never fry a ribbon mic by bumping it accidentally. Audio quality is phenomenal and saved me from dropping $350 on a new interface.
I used to own a FetHead that had slight play in the XLR barrel and popped in my headphones every time I adjusted my boom arm. The tolerances on this Cosari collar click in tight with zero wiggle. Plugged it into my PodMic, turned on 48V, and got instant broadcast presence.
Took literally ten seconds to set up: unplugged my XLR cable from the front of my UA Volt, clicked the GainTube+ 28 in, plugged the mic cable into the back of it, and pressed the 48V button. Dropped my interface gain knob by half and wiped out all the preamp hiss.
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Yes. The barrel is 21mm wide and cleared the yokes on both mics in our testing. If your mount is tighter, plug it into your interface's XLR input instead. Performance is the same either way.
No. It's a male-to-female inline barrel, so it sits between your existing cable and either your mic or your interface.
In Dynamic Boost mode, the GainTube+ 28 uses the 48V to power its JFET circuit and keeps DC voltage from reaching your mic. Switch to pass-through only when you're using a condenser mic that needs phantom power.
Any XLR interface or mixer with 48V phantom power, including Focusrite Scarlett, UA Volt, Audient iD and EVO, Behringer UMC, PreSonus, Motu M2, GoXLR, and Rodecaster units.
No. It runs entirely on your interface's phantom power. Press the 48V button and it's on.
It's rated flat from 10Hz to 50kHz (±0.5dB), so it adds level without EQ coloration. Many dynamic mics sound fuller with it because they see a steadier load than a budget interface provides.