If you’ve spent any time around me—or around my absurdly overstuffed drawer of vintage glass—you already know where this is going. I’m a tube-sound guy at heart. Yes, the measurement crowd will remind you that solid-state amps test cleaner, flatter, and closer to whatever passes for perfection these days. But tubes do something different. They add warmth, dimension, and harmonics that turn audio gear into an instrument, not a calculator. Art isn’t supposed to be ruled entirely by spreadsheets anyway.
I’ve spent decades chasing that feeling, writing more articles on tube amps and tube rolling than my accountant or my wife would prefer. My tube stash rivals actual storefronts, and I’ve joked more than once about getting a full back tattoo of a 12AT7 with “born to burn out” wrapped around it like a banner from a questionable ‘80s biker movie.
And this is exactly why the $120 Apos x Community Gremlin Tube Amplifier had my attention from the minute it crawled out of the lab.
That’s why it always stings a little when someone asks me for a budget recommendation and I end up steering them toward solid-state gear. Not because it’s bad—far from it—but because affordable tube gear is usually priced out of reach for newcomers who just want a taste of that glow, that harmonic sweetness, that unmistakable “music over math” charm. Tubes aren’t cheap, and the good ones definitely aren’t.
Apos Audio clearly heard the same frustration from their own community. They asked what people actually wanted, not what the spec sheet evangelists said they should want—and the answers lined up almost perfectly with my inbox. There’s a big group of listeners who love tube character but don’t love the typical tube-amp price tag.
So Apos partnered with Geshelli Labs, a brand that already knows how to deliver high-value, great-sounding gear without the boutique markup, and the result is a pair of products built directly from community input. The first is the Gremlin Amplifier—small, affordable, unapologetically fun—and the second is a matching DAC designed to feed it properly. It’s the kind of collaboration you get when a company actually listens instead of assuming.
Gremlin Build: Hawkins Lab Hardware, Minus the Hazmat Suit
The Gremlin shows up in a box that looks like it missed its cue from Stranger Things—matte black, muted red lettering, and just enough eerie minimalism to make you expect a Demogorgon trading card inside. Instead, you get the manuals up top, and beneath them the amp nestled snugly in a foam cradle with the Apos Ray Core Series 12AU7 tubes already installed. No mystery goo, no flashing red lights—just proper protection on all sides. Under that sits a separate box holding the laptop-style power supply, because even tiny monsters need to eat.
The amp itself is comically small—5 inches wide, 3.25 inches deep, and 2.5 inches tall—and unapologetically barebones in the best possible way. There’s no typical enclosure here; instead, you get clear Lexan plates on the top and bottom with stainless standoffs at the corners. The whole interior is on display like some Hawkins Lab science fair project, tubes glowing proudly while air moves freely across the chips.
Up front, everything is simple and practical: a power switch, a 4.4 mm balanced output, a 4-pin XLR, and a volume knob. Around back, it keeps the same no-nonsense vibe with dual 3-pin XLR inputs, another 4.4 mm input, and a barrel connector for the power brick. That brick looks like it was pulled straight from a classic ThinkPad—AC cord on one end, rectangular converter in the middle, and the DC plug on the opposite end. No frills, no drama, just the essentials to bring this little creature to life.
Gremlin Internals: What’s Hiding Under the Lexan
Being able to see everything under the Lexan makes tracing the signal path from XLR input to XLR output almost laughably easy. No mystery box, no hidden gremlins—just a clean, fully balanced Class-A circuit laid out like someone actually expected enthusiasts to look at it. The design is a true hybrid: tubes handle the preamp duties while solid-state op-amps manage the output stage. That approach keeps output impedance low and ensures the Gremlin plays nicely with everything from sensitive IEMs to full-size 600-ohm headphones without wheezing.
The Class-A topology also explains the laptop-sized power brick. Class A doesn’t sip power; it chugs it, because the output devices conduct current for the entire signal cycle. That’s why Class-A amps are still the gold standard for linearity and why they tend to run warm even before you press play. This wasn’t a cost-cutting move—it’s a design decision that puts sound quality at the front of the line.
Specs back that up. The Gremlin delivers 1.25 watts into 32 ohms and has enough voltage swing to drive 600-ohm headphones with comfortable headroom. Frequency response is rated from 20 Hz to 50 kHz, with a signal-to-noise ratio of 100 dB and channel separation measured at 104 dB at 1 kHz. For an amp this small, transparent, and intentionally simple, the engineering is surprisingly serious.
What immediately catches the eye when you look across the Gremlin’s circuit board is the pair of jumpers sitting between the outer tube socket and the 4.4 mm input. Those little switches aren’t decorative—they let you swap between the default 12AU7 family and the 6922 family, the two most common small-signal tube lineages on the planet. If you’re even mildly tube-curious, this is a gift. If you’re like me and have enough tubes to qualify as a fire hazard, it’s basically an invitation.
I won’t go deep into tube rolling here—there’s a separate article coming for that—but the Gremlin’s compatibility list is impressively wide. On the 12AU7 side, you can roll everything from the standard 12AU7, 12AU7A, and 12AU7W to ECC802, E82CC, 5814A, 6189, and half a dozen military variants. Flip over to the 6DJ8/6922 camp and you can run ECC88, E88CC, 6922, 7308, and the ever-popular 6N23P. Between those two tube families, you’re looking at well over 200 variants for the 12AU7 alone, plus another 40+ for the 6922 crowd. Translation: if you can’t find a tube that fits your taste here, the problem isn’t the amp.
Still, start with the stock tubes. The included Apos Ray Core 12AU7s are legitimately good—not “included for convenience” good, but “you’ll need to spend money to noticeably beat them” good. The optional Select upgrade tubes ($207 more) are a step up in channel balance and low-volume consistency, but the Ray Cores are strong enough that I stuck with them for this review.
Apos x Community Gremlin Listening Impressions
One thing to know up front: the Gremlin is all balanced, all the time. There’s no single-ended safety net here. You get a 4.4 mm TRRS input and dual 3-pin XLR inputs, but since the design isn’t switchable, you should only hook up one source at a time. For this review, I paired it with DACs that make sense in the same price orbit—Khadas Tone 2 Pro via XLR, the iFi Zen DAC Signature 2 via 4.4 mm, and the Apos Merlin DAC also via XLR.
On the headphone side, I threw a little bit of everything at the Gremlin. Sensitive in-ears like the Apos Rock Lobster stayed quiet—no hiss, no tube hum, no ghostly Stranger Things interference between tracks. At the same time, the Gremlin had enough muscle to drive full-size classics like the AKG K240 Sextett and the 600-ohm Beyerdynamic DT-990 without breaking a sweat.
The only model that really pushed it past its comfort zone was the notorious HiFiMAN HE-6. The Gremlin could get it up to listening levels, but headroom was tight and big dynamic swings collapsed faster than a Demogorgon after a round of Steve Harrington’s bat therapy.
Everything else — Audeze LCD 3, Audeze MM 500, HiFiMAN Susvara Unveiled — was handled with far more authority than I expected for something this small. Unless you’re running low impedance planars with the sensitivity of concrete, you’re in safe territory.
The tubes absolutely add warmth, giving most tracks a more euphonic tone than what you’ll hear from something like the Schiit Magni or the JDS Labs Atom 2, which are the Gremlin’s most obvious rivals in this price bracket. Tube rolling only reinforces that point. Depending on what you drop into the sockets, the Gremlin can swing noticeably warm with something like a Mullard or Valvo, or land closer to neutral with options like Telefunken or Tesla 6922s. In other words, the character you get is heavily shaped by the tubes you choose.
The stock Ray Core 12AU7s sit comfortably in the middle. They add a gentle warmth without sliding into the syrupy smoothness associated with classic Mullards, and they avoid the drier, more matter-of-fact presentation you get from many Telefunken tubes. It’s a balanced, engaging baseline that makes a lot of sense for a community-built amp like this.
I ran the Gremlin through a wide mix of genres, and for the most part it punched well above its size. The only real criticism is that on certain tracks, that added touch of tube warmth isn’t necessarily a benefit. Some music is meant to sound unforgiving. A prime example is the mechanical grind at the start of The Prodigy’s “Mindfields”—it loses a bit of its bite. Industrial metal can suffer the same fate. Marilyn Manson’s “Beautiful People” should have that sandpaper edge, and the Gremlin smooths it slightly depending on the tubes and source chain.
The DAC you pair with it matters too. The iFi Zen DAC Signature 2, with its Burr Brown chipset, leans warmer, and when combined with the Gremlin it doubles down on that coloration. This was the combo where I first noticed “Beautiful People” losing some of its serrated energy.
Switching to a cooler, more neutral DAC like the Apos Merlin brought back much of the intended aggression. Harsh tracks still weren’t quite as jagged as they are on solid state competitors, but the balance was far better and the Gremlin held its own without dulling the attitude.
After going through well over a hundred tracks across genres, I ended up with only two songs where I preferred one of the competing amps. Two. That means roughly ninety eight percent of the time, the Gremlin came out on top. For something this small, this affordable, and this community-driven, that’s an impressive hit rate. It also doesn’t hurt that it’s cheaper than one of the competitors and offers fully balanced connectivity—something the lower priced rival can’t match.
The Bottom Line
The Gremlin isn’t the perfect starter amp, and that’s mostly because it’s balanced only. A lot of mainstream headphones still ship with single ended cables, so newcomers may find themselves buying adapters or replacement cables before they even get to hear the thing. The good news is the landscape has changed—detachable cables are now the norm, balanced aftermarket options are everywhere, and you no longer need to break out the soldering iron just to join the club.
For anyone already in the hobby, though, the Gremlin is an easy recommendation. If you own a pair of headphones with a detachable cable, have been curious about tubes, or want to try a true balanced setup without draining your bank account, this little amp makes a strong case for itself.
It’s one of the least expensive fully balanced Class A hybrids on the market, and when paired with the Apos Merlin DAC you can build a complete balanced system for less than what a lot of single ended stacks cost. Add in the ability to swap between the two most popular small signal tube families ever made—6922 and 12AU7—with decades of variants from around the world, and the tuning possibilities open up fast.
Apos and Geshelli clearly listened to their community, and the result is a tiny amp with real personality, serious engineering choices, and far better performance than its size suggests. I still don’t know why they named it the Gremlin, because in daily use it behaves a lot more like a well fed Mogwai—unless you pair it with a warm DAC after midnight, in which case things do get a little Stranger Things around the edges.
Pros:
- Great price for a fully balanced Class A hybrid amplifier
- Compatible with both 12AU7 and 6922 tube families (huge rolling options)
- Stock Ray Core tubes offer a well balanced, musical baseline
- Mild tube warmth adds a pleasing, more euphonic presentation
- Very quiet with sensitive IEMs, yet powerful enough for most full size headphones
- Compact footprint with open Lexan design that shows off the internals
- Community driven design built in partnership with Geshelli Labs
- Pairs well with neutral or cooler DACs for flexible system tuning
- One of the least expensive ways to build a full balanced stack (with the Merlin DAC)
Cons:
- Balanced only input and output limits plug and play compatibility for newcomers
- Some genres that rely on sharp, industrial edges can sound slightly softened
- Warm leaning DACs can compound the coloration
- Not the best match for notoriously hard to drive planars like the HiFiMAN HE 6
- Requires tube purchases to fully explore its tuning potential
Where to buy:
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