Buckeye Amps PuriFi 1ET9040BA Monoblock Reviewed

The Buckeye Amps PuriFi 1ET9040BA Monoblock is an audiophile power amplifier I’ve been really eager to review. I am a fan of the neutrality and low distortion of today’s best Class-D amplifiers (learn about the audiophile trend here), and also of their low weight and minimal heat emissions or energy usage. When the latest high-powered amplifier modules became available and Buckeye released their finished amplifiers, I thought this could be a winning combination. 

The Buckeye 1ET9040BA Monoblock is based around Purifi’s second-generation high-power amplifier module. As usual for Buckeye Amps, the amp’s model designation is simply the module identifier (Purifi 1ET9040BA) and the number of channels (one; two monoblocks are required for stereo). The review samples included Buckeye’s optional power supply upgrade, which raises the retail price from $1,195 to $1,295 each and provides better efficiency and slightly more output at two ohms. While $2,590 a pair is significant to most of us, it is on the low end for first-rate monoblocks. Buckeye’s Web site states: “Our commitment to providing the most advanced amplifier technologies at prices that are accessible to every enthusiast remains our main goal. Audiophile for the masses.” Please join me as we see how this new amp lives up to that commitment …

What Makes the Buckeye Amps Purifi ET9040BA Monoblock So Special? 

• The ET9040BA output module powering this amplifier is a new design by engineer Bruno Putzeys, who for decades has led much of the progress in Class-D amplification. His 2024 article, “Life on the Edge – A Personal Perspective on the Past, Present, and Future of Class D Audio Amplifiers,” is down to Earth, humorous at times, and well worth reading. It’s on the Secrets of Home Theater and High Fidelity website.
• Noise and distortion specs of the Buckeye 1ET9040BA Monoblock are superlative. The amp’s signal-to-noise ratio (140 dB) and low distortion (< 0.0001 percent, 20 Hz to 20 kHz at 400 watts into four ohms) place it in the top tier of audiophile amps in objective performance. 
• Frequency response is flatter and more extended than ever. Eyeballing Purifi’s spec sheet, response is ruler flat from 20 Hz to 40 kHz, down perhaps 0.1 dB at 50 kHz, and not down a full decibel until about 80 kHz. This is approaching the extended frequency response of GaN FET Class-D amps (learn more here). It’s my impression that such extended, distortion-free bandwidth is an important factor separating outstanding power amplifiers from those that are merely excellent.
• The Buckeye 1ET9040BA Monoblock is a powerhouse, specified at 375 watts output short-term into eight ohms, 750 watts into four ohms, and 1,400 watts into two ohms. According to Buckeye, short-term here means about 10 continuous seconds, well beyond what any sane home music program might require – or most speakers could withstand. With that power and vanishingly low output impedance, these amps should exert a firm grip on almost any audiophile speaker, including power-hungry ones considered difficult loads. 
• The Buckeye 1ET9040B Monoblock has unsurpassed load independence. Its flat frequency response remains flat, no matter what speaker it drives. The amp can’t change a speaker’s own response, but because it doesn’t interact with the speaker’s impedance pattern, you hear your speakers as designed, not an unpredictable set of speaker-amplifier interactions.
• Switchable gain (15.5, 20.5, or 25.5 dB) in the input circuit allows better gain staging in most systems. Gain staging is simply reducing amplification of noise by managing gain of each step in the audio path. Running a preamplifier near maximum volume reduces noise introduced by its volume control and keeps any background noise (say, from the power supply) minimal, compared to the signal. With the preamp providing higher gain, the power amp can be set to lower gain, so noise in its input is amplified less. I wish every amp had this feature. 
• The Buckeye 1ET9040BA Monoblock is light and compact. Monoblocks are often best placed by each speaker, thus short speaker cables can keep damping factor high and frequency response flat. Because each amp measures only 10.0 by 13.5 by 3.5 inches and weighs just seven pounds, fitting them by your speakers is a cinch.

Why Should You Care About the Buckeye Amps 1ET9040BA Monoblock? 

This amplifier is about sound first and foremost, without elaborate casework or flashy/costly meters. The only luxury is the monoblock form factor, which is incrementally a little more costly than two channels in a single chassis.

You can spend more – a lot more, if you like – but the objective performance of the Buckeye 1ET9040BA monoblock is unsurpassed in any meaningful way by any amp on the market now. I love that it delivers transparency and honesty, rather than extra sparkle or sweetening because, to me, in the long run, neutrality wears best. Subjectively, the amps remained clear, immediate, neutral, and relaxed on demanding program material, from harpsichords to electronica to orchestral music. This, then, is an amplifier for someone who wants outstanding sound and who will be pleased, rather than self-conscious, to have acquired it economically.

Some Things You Might Not Like About the Buckeye 1ET9040BA Monoblock

• The power switch is on the rear panel. It’s more convenient in front, especially when gear is going into a rack. Still, if the amps are put on stands near the speakers, as monoblocks often are, a rear-mounted switch is a trivial inconvenience.
• The rear-panel connections are crowded, with binding posts close together and the XLR input jack directly beneath them. A little more space would be a treat, especially for reviewers who are constantly connecting and disconnecting. It’s hard to imagine this being of more than minor importance to a more typical owner. 

Listening to the Buckeye Amps Purifi 1ET9040BA Monoblock … 

The Buckeyes were fed by my Anthem STR DAC/preamp, and occasionally by a Topping DX9 DAC/preamp for a different perspective. Impressions were consistent across preamps. Speakers were my long-term reference Janszen Valentinas, run without subwoofers to exercise the amps full-range. The source was an Auralic Aries G1 streamer, fed through my LAN by a Roon server (learn all about Roon from Brian Kahn here).

Putting on “VeLDÁ” (a song of modern flirtation and lust) from Bad Bunny’s album DeBÍ TiRAR MáS FOToS, I was immediately impressed by the scope and clarity of the sound (24/44.1, Qobuz). A wide soundstage extended beyond the speakers left and right, and the illusion of depth was strong. Percussion was clean, the bass line was strong and tight, and the vocals had the clarity that is a strength of the best amps. A lot is going on in this mix, many instruments and a lot of strong dynamics, and it all was well-sorted by the Buckeye amps. Reverb tails were quite long, defining a spaciousness probably added electronically in production. Whatever instrumental line I chose to follow, the amp’s clarity made that easy and natural. 

When the Byrds’ album Sweetheart of the Rodeo came out, it almost made country music cool – the influence of Gram Parsons, no doubt, combined with excellent musicianship all around (16/44.1, local file). Listening to Parsons’ beautiful “Hickory Wind,” once again, I was taken in by a wide soundstage and colorful sound, with each voice and instrument shining with individuality. Sonically, this is a dated commercial recording, but the beauty and sincerity of the playing and singing came through as well as I’ve heard, and I found the music especially engaging. The Buckeyes’ clarity made it possible to follow every word of the lyrics and every instrumental line without straining. I expect this level of finesse from much more expensive power amplifiers. 

I’ve been enjoying the album The Astounding Eyes of Rita, featuring Tunisian oud player Anouar Brahem, on the ECM label (24/96 Qobuz). (An oud looks like a fretless mandolin, with a more mellow tone.) The track “For No Apparent Reason” is easy to listen to, yet it repays focused attention with emotional depth not obvious in casual listening. As with many tracks I played through the Buckeyes, the soundstage was wide and airy. Depth also was convincing, typified in this track by percussion placed stably in the rear left, seemingly feet behind the speakers. The clarity and subtlety of sound highlighted the interplay among musicians, and each instrument’s individual characteristics were clear. For example, I could hear clearly that the reed instrument was a bass clarinet, not a saxophone. 

In many other familiar tracks, the timbre reproduction, airy soundstaging, dynamics, image stability and clarity of the Buckeye monoblocks continued to impress me. 

Will the Buckeye Amps Purifi 1ET9040BA Monoblocks Hold Their Value?

Although Buckeye Amps is a small business, they have gained recognition for offering objectively excellent products at lower price points. Their amplifiers have gained many favorable objective and subjective reviews like mine of the Buckeye Amps Hypex NCx500 Stereo Amp. Buckeye keeps active on social media, including for customer support. With all that, audiophile interest is high, and I expect that used Buckeye products will attract plenty of attention on the used market. 

What is the Competition for the Buckeye Amps Purifi 1ET9040BA Monoblock Amplifiers?

Few other amplifiers offer as much power as the Buckeye 1ET9040BA monoblocks at a similar price point. Thus I’ve included some that offer less power, or are priced higher, or both. (Prices may vary due to tariffs or manufacturer adjustments.)

If you want high power but don’t need this much, Buckeye also offers amps based on the second-generation Purifi 1ET6525SA module. That module, the successor to the widely admired 1ET400A, is specified at 230, 450, and 510 watts into eight, four, and two ohms, respectively. Finished amps are priced at $875 per monoblock, $1,150 per stereo amp, or $1,550 per three-channel amp.

Another company serving value-oriented audiophiles is Schiit. The Schiit Tyr monoblock amplifier ($1,599, sold direct) is described by Schiit as a “monstrous, old-skool, crazy heavy, over-the-top mono … amplifier.” It’s specified at 200 and 350 watts into eight or four ohms; it weighs 55 pounds.

The NAD C298 Stereo Power Amplifier ($2,999 – buy at Crutchfield) uses Purifi 1ET400A modules, excellent performers still. It’s rated at 185 and 340 watts per channel into eight and four ohms and, when switched to mono operation, 620 watts into eight ohms. The NAD adds several useful features: RCA and XLR inputs, continuously variable input sensitivity, and extra line outputs that can be used for subwoofers.

Buckeye sells internationally, but readers outside North America may also wish to investigate makers closer to home. We can’t give a complete list, but here are three with amps based on the 1ET9040BA: In the UK, Nord Acoustics makes the Nord Three Mk II Monoblock (£1,200 and up), with choice of op amps in the input circuit and other options. In the European Union (Slovenia), Apollon Audio offers a monoblock in their Premium line that includes balanced and single-ended inputs and a handsome custom case (€2,995). I owned an early pair of Apollon monoblocks and was quite pleased. In Australia, March Audio’s Model P801 features a custom power supply and a milled aluminum case (AUD $3,000 and up).

Final Thoughts on the Buckeye Amps Purifi 1ET9040BA Monoblock …

As a reviewer, I am at a loss to explain why theoretically perfect amps sound slightly different from one another, but to my ears, they often do. I’ve heard excellent amplifiers in Class(es)-A, A/B, D, and H, and I think the Buckeye Purifi 1ET9040BA Monoblock is up there with the very best, without most of the cost. Besides their extraordinarily low noise and distortion, I suspect that the flat, extended high-frequency response subtly improves the treble in the audible range, and the extremely high power increases the sense of openness.

The Buckeye Amps 1ET9040BA Monoblocks are a fantastic tool for deep music listening. They are dead quiet, dynamic, open, clear, and neutral, with extended, non-irritating treble. Those qualities drew me deeper into the music and seemingly into the musicians’ worlds. I would recommend these amps to audiophiles who have more money to spend, or who have more demanding/expensive loudspeakers. This is a bargain of an amp and a killer performer, and that is a brilliant combination.