Apos x Community Gremlin

Gremlin Review - Amazing Entry Tube Amp with Room to Grow​

I'm reviewing this amp as part of the Bay Audio Enclave loaner tour. Included in the package were the base model with the Ray Tubes 12AU7 CORE and the Ray Tubes 12AU7 SELECT. I first tried an early prototype at the BAE HIFICON in July 2024, and I could already hear the potential in this diminutive little amp.

Design​

The bare-bones aesthetic, with a simple PCB, aluminum standoffs, and an acrylic sandwich, evokes an essentialist vibe—you can tell the development budget was spent on components rather than packaging. The green LED "ground effects," combined with the amber tube LEDs, make for a fun and exciting presentation that fits the amp’s namesake. You can turn the green LEDs off, but I prefer them on, as they beautifully illuminate the acrylic case. A red-colored potentiometer knob keeps the playful design going.

The packaging is quite premium for a product in this price class, using printed, coated cardboard and custom-cut internal foam. However, I would have preferred something simpler—like what Schiit uses, with recycled cardboard and standard external shipping boxes—so that an extra $5-10 could be allocated toward ergonomic improvements, which I’ll discuss next.

Ergonomics​

The amp arrives fully assembled, ready for plug-and-play use. I appreciate the flexibility of having dual 3-pin XLR and 4.4mm balanced inputs, along with 4-pin XLR and 4.4mm balanced outputs. Swapping a small jumper to toggle the green LED is simple enough, and the front power toggle switch is a great convenience—something all tube amps should have.

This amp uses an external power supply brick with a standard IEC power cord, which I prefer over the bulky wall warts that other amps in this class tend to use. However, tube rolling requires unscrewing the top standoff nuts to remove the acrylic roof. Instead of small round-top nuts, taller knurled thumb nuts (like these) would make tube swaps much easier.

The volume pot knob is a small, lightweight piece that should be replaced with a heavier, solid metal knob—something like the brass knob on the special edition NITSCH Piety. The $5-10 savings from using more basic packaging could cover these metal components, significantly improving daily usability. The small rubber feet provide adequate grip and cushioning, and I like how the clear rubber matches the clear acrylic.

DAC Pairings​

Being balanced-only is fine because if single-ended input/output options were included, this would be a very different product—costing significantly more and likely performing worse. Selecting the right DAC is a big part of this amp's value proposition. I see two primary customer types for this product:

1. Those with a limited budget and/or desk space, looking to explore their first tube amp.
2. Enthusiasts with a diverse collection of amps and DACs who want to add a fun little piece to their setup while leveraging tubes they already own.

If you're just starting your tube journey, I recommend pairing the Gremlin with a simple dongle DAC that has balanced outputs. I picked up a Fiio KA3 off eBay for $45 because I wanted an ESS-based DAC with 4.4mm balanced output and PCM 768 kHz + DSD512 capability for upsampling. I made an adapter cable for this setup using a male 4.4mm connector leading to dual 3-pin XLR outputs. I chose dual XLR to keep the DAC/adapter compatible with my other balanced amps, but you could also use a simple male-to-male 4.4mm cable.




I also tested the Gremlin with my Chord Hugo TT2 via dual 3-pin XLR to evaluate how it scales with a high-end DAC and to compare it with my other tube amps—a DIY Aegis and a Feliks Euforia Evo.

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Sound Impressions​

Chord Hugo TT2, CORE 12AU7 Tubes​

I started with the stock Gremlin and CORE tubes connected to my Chord Hugo TT2's XLR outputs, listening for almost four days straight. Right away, I noticed how much power this little hybrid tube amp has. I never had to turn the volume past 8-9 o’clock with my 32-ohm HFA Dahlia dynamic driver headphones, and only around noon with the more power-hungry 300-ohm Sennheisers and ZMF Caldera Open.

The sound had that characteristic tube bloom and softness but also retained the impact and speed of a decent solid-state amp. Everything sounded spacious and thick, with deep-reaching bass. It was hard to believe that this level of performance was possible at this price. At higher volume levels, distortion was noticeable, but that's expected from a tube amp in this category.

Chord Hugo TT2, SELECT 12AU7 Tubes​

Swapping to the SELECT tubes resulted in a significant jump in resolution, soundstage width/depth, and layering—while retaining the tube bloom, softness, and impact. This is a $150 upgrade, so I expected a major performance boost, and the Gremlin delivered. At higher volumes, distortion was significantly reduced, and the amp maintained composure even with complex layering and staging. If you have the budget, this upgrade is absolutely worth it.

Chord Hugo TT2, PSVANE Horizon 12AU7-AT​

For $55 (available here), these new production tubes offer a more affordable upgrade if you can’t spring for the full Ray SELECT tubes. The Horizon tubes improve resolution and detail almost to the same level as the SELECT tubes, but they sound slightly thinner, with less body and fullness than both the CORE and SELECT tubes. While I still preferred the SELECT tubes overall, the Horizon tubes were my second choice over the stock CORE tubes. They also performed better at higher volumes, making them a solid intermediate upgrade.

Fiio KA3, All Tubes​

Switching to the Fiio KA3 DAC, I didn't hear as drastic a change in the amp's sound. The KA3’s ESS DAC delivered its signature highly detailed sound, with a clean and balanced presentation. I used HQPlayer upsampling for PCM 768 kHz and DSD512, and I enjoyed both. PCM had more detail and layering, while DSD offered a smoother and more intimate sound.

For a budget, compact setup, I highly recommend this dongle DAC with an adapter cable. I also ran it with the Topping HS02 USB isolator to eliminate USB noise and achieve a pitch-black background. While a high-end DAC does improve the sound, this $180 all-in setup ($120 amp, $45 DAC, $15 adapter) is tough to beat.

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Summary​

I don’t have extensive experience with entry-level tube amps, but I firmly believe the Gremlin offers terrific value—both in its stock form with CORE tubes and with the SELECT upgrade. This amp has a lot of room to grow in terms of DAC pairing, tube rolling, and potential DIY chassis mods.

I briefly owned the Schiit Vali 3, which is another great product in this category. The Vali 3 has more DAC flexibility with its single-ended design, but the Gremlin benefits from its balanced circuit, delivering a cleaner and more powerful presentation.

My recommendations for improvements:

• Switch to simpler recycled packaging (like Schiit Magni) to free up budget for ergonomic upgrades.
• Replace the top nuts with knurled thumb nuts (like these) for easier tube swaps.
• Use a heavier volume knob for a more premium feel.

Apos should be proud of this product. It’s an affordable, accessible, true audiophile amp. I hope it gains a community of modders and enthusiasts who explore its full potential.

Disclosure: Received Gremlin from APOS for a loaner tour.

My chain is spotify playing from my PC to a Gustard U12 then a BiFrost 2/64 connected to the Gremlin via its balanced input.

Starting with the "core" set of ray tubes, this amp has plenty of punch and power. It has a lovely musical tubey sound. It's not terribly detailed but the sound signature is full and warm. Sound has a bit of a congested nature and instrument separation is a bit tough as everything sounds too full and hard to pick apart the details. The sound signature itself though is right up my alley. It is wonderfully warm with an emphasis on the mids and mid bass.

Changing over to the "select" ray tubes and the detail really jumps. It's very significant. The amp is still warm but it loses the "fullness" it had and instead you get a lot more detail and instrument separation is clear. I much prefer this sound profile. The bass detail increases which makes it sound more punchy. Of course, the detail extends across the mids and treble as well. Vocals clear up and the treble sounds less grainy. The price also jumps considerably.

Connectivity wise, the limitation for only balanced inputs is a bit rough I think for the budget market. I think the majority of budget DACs with this small form factor will likely have RCA outs. It makes it a bit difficult to pair. I like the balanced outs though, I think getting a balanced cable is a much easier ask.

For $120, the gremlin feels unbeatable. I can't think of anything else at this price point which is as enjoyable. Jumping up to $300 though and I still think it's quite a great value. I did compare this amp to my DIY project ember from garage1217. At the time I build that amp, the price was comparable as I recall. I feel like they really are at the same level but the project ember gives you selectable impedances, more tube compatibility, and a large power range. This shows for harder to drive headphones like the Sierra. Nowadays, the ember (even DIY) is $20 more without the tube. I think they both make a case for themselves. The gremlin and ember both sound amazing and I really couldn't pick one over the other. They actually sound very similar to me. The ember just ends up costing more with more features. If you don't need those features, then the gremlin is the better pick. I recommend the gremlin in both forms. I think the $120 version is a budget king, while the $300 version with the upgraded tubes would be my preference but the tradeoff for detail is a significant jump in price.