Updated October 2026 · status checked Oct 10, 2026.
Status in 2026
Drop, the store that sold the THX AAA 789, took its last orders on March 25, 2026 and closed on March 31, 2026. The brand was absorbed by Corsair. The 789 was a Drop product, so there’s no new-retail channel left. Every 789 you find now is used.
If you searched for the 789 because you want a clean, powerful amp, here’s what to buy new. The original review is below.
Buy Instead
The closest new replacement: rated at 6.4 W into 32Ω balanced, plus a DAC (dual ES9039Q2M), for about $299.
Uses THX AAA 788+ amp modules, 2 W into 32Ω from 4.4 mm balanced, DAC built in. Still sold on Amazon US for about $220.
If you want an amp-only box from a company that still sells direct: Schiit's $399 Asgard X.
| THX AAA 789 (discontinued) | Topping DX5 II | FiiO K7 | Schiit Asgard X | |
|---|---|---|---|---|
| Status | Discontinued (Drop closed) | Current | Still sold | Current |
| Price (Oct 2026) | Used only ($299 new) | ~$299 | ~$220 | $399 |
| Power, 32Ω (rated) | 6 W balanced | 6.4 W balanced | 2 W balanced | See Schiit |
| DAC built in | No | Yes | Yes | No |
| Balanced headphone out | 4-pin XLR | Yes | 4.4 mm | See Schiit |
Who should still buy a used 789: someone with a good DAC and 4-pin XLR headphone cables who finds one clearly below the price of a DX5 II.
Who shouldn’t: first-time buyers without a DAC, and anyone who wants a warranty.
Buying a Used THX AAA 789
- Confirm the power supply is included and matches the original rating.
- Test both headphone outputs and both inputs (XLR and RCA).
- Try all three gain settings at low volume and listen for crackles or a channel dropping out.
- Ask where it came from. Drop shipped in batches, so a seller can usually say when theirs was bought.
The Original Review
The Amplifier That Changed the Conversation
When Drop and THX released the AAA 789 in 2019 at $299, its measurements put many far more expensive amps to shame. Drop rated it at 6 W per channel into 32Ω from the balanced output, an SNR of about 136 dB and output impedance below 0.1Ω. Measurement sites, including Audio Science Review, rated it as one of the cleanest amps available at the time. It became the default answer for “the most transparent amp under $300.”
THX AAA: The Engineering
Conventional amps rely heavily on negative feedback to lower distortion. THX’s Achromatic Audio Amplifier adds feed-forward error correction: a correction stage senses the error and cancels it. The result is very low crossover distortion without the idle heat of a Class A design.
Connections
The 789 has balanced XLR and single-ended RCA inputs, a 4-pin XLR balanced headphone output and a 6.35 mm single-ended output, plus a three-position gain switch on the front. There’s no 4.4 mm jack.
Six Watts: Who Needed It?
6 W into 32Ω balanced is far more than most headphones need. For example, the HiFiMAN HE400SE and Sundara reach loud levels on a fraction of that. The point was headroom: the 789 stayed clean far below its limit, which helped with power-hungry planars like the Audeze LCD-2.
What “Transparent” Means in Practice
A transparent amp adds nothing you can identify. The DAC and headphones set the sound. Owners on r/headphones and Head-Fi consistently described the 789 as neutral, sometimes “lean” next to warmer amps. That’s what you’d expect from its measurements. If you want added warmth, a transparent amp won’t give it to you, and neither will the DX5 II.
Pairing Notes (Still Valid for Its Replacements)
- HiFiMAN Sundara / HE400SE: plenty of current. See the Sundara amp guide and HE400SE amp guide .
- Sennheiser HD 600 / HD 650: voltage to spare. See the HD 650 amp guide .
- Beyerdynamic DT 1990 Pro: clean, with a balanced cable option. See the DT 1990 Pro amp guide .
Verdict
The THX AAA 789 was the benchmark transparent amp for its price, and a used one is still a capable amp. But Drop is gone and so is the warranty path. Buy the Topping DX5 II for a current one-box replacement, or the FiiO K7 for a cheaper THX-based option. For a wider shortlist, see our best balanced headphone amps .
