Emerald Physics EP600.2SE Power Amplifier written & YouTube review

The world of ultra high-power amplifiers falls into two categories: Solid-state beasts that require shipping crates to transport, or the Mohammed Ali Class-D with its light on the feet twenty-first century design. Now, while I’ve been endlessly enthralled with the monstrous power of Nelson Pass and other designs, the price tag was beyond what I could ever afford. Three years ago I found the first high power Class D amplifier that I found truly musical, the Peachtree amp500. It has been a fine pairing with my Magnepan .7’s along with its newer sibling, the GaN400.

Watch the YouTube video review

In August, I was sent by Internet-direct seller Underwood HiFi, their new Emerald Physics EP600.2SE amplifier. The fifteen pound, 17” wide, 13.8” deep, 4.2”, high cabinet comes in a satin black anodized finish. The front panel consists of a runway level bright blue LED set over a round chrome power button. Two traditional VU meters are placed dead center. The right side has a simple toggle switch that when in the up position engages two vacuum tubes, more on that in the next paragraph. The overall look is what I would call “Minimalist Steam Punk”, as the VU meters are lit by the golden hue of the tubes. The top panel has two sections of diagonal ribbed vents. Moving around to the back, the left side holds the two gold-plated RCA inputs as well as XLR. The right side holds the stacked (by channel) binding posts with a nice amount of space between them. Finally the power cord receptacle. The tops and sides of the case are 1/4 inch thick metal. While I've never been one to stack gear on top of an amplifier, it could handle some serious weight.

Lifting the hood reveals the blending of old and new technology. The topology shows two JJ E88C vacuum tubes, one for each channel. The tubes are allowed a few seconds to light up before becoming active. This type of protection circuitry is well known to designers. Once active the sound is then fed into the IcePower 1200AS2 Amplifier Core chips. The power output is 600wpc into 8 Ohms, and 750wpc into 4 Ohms, with the capability of 1250w for rare dynamic moments. The amplifier's design is the work of Dr. Viet Nguyen and his team. The manufacturing process is spearheaded by Mark Schifter. To understand more about the topology, I suggest a visit to the EP600.2SE web page.

Listen to the Music

Hooking the EP600.SE into my reference system between the Parasound P5 preamplifier and either the LSA Signature 80’s, or Magnepan .7’s, the sheer power of this amplifier is immediately noticed. The ability to pull out additional lower bass detail is palpable. Taking a listen to “The Chain” by Fleetwood Mac, the bass drum contains micro details on top of the powerful punch. The reverberation of bass notes in Dire Straits, “The Man’s Too Big, The Man’s Too Strong”, can be felt in the chest, even at under 80db in my small listening room with no subwoofer.

The bass experience for me with the tubes engaged is the additional depth of the bass notes. Best described as a sponge expanding when water is added.  Flipping the toggle switch between the Tube & Solid State modes (yes, a bit of an interesting word choice since the EP600.2SE uses Class D amplification) reveals this subtle, yet noticeable difference. I would be remiss not to mention that the VU meters require some seriously loud listening to get moving. In my case it was above 85db powering the Magnepans that finally got the needle dancing.

To be fair, music, speakers, and room acoustics will play a significant role in whether, as well as when a user will engage the tubes. In my primary listening room, (which is undergoing the first two of three acoustic improvements) engaging the tubes is definitely the better option, no matter the speakers as well as 90+% of the music I enjoy. In a former home, the difference would be more balanced from a physical space perspective. 

When paired with the original Totem Acoustic Model 1’s, the EP600.2SE Tube mode was the hands-down winner, as the speakers’ naturally bright top end truthfully needs the tempering nature of the glowing filaments to maintain acoustic balance with Class D power.  With speakers that are more reserved in the upper registers, for example Aperion Audio, along with some British brands, Class D only may become the preferred choice. Once again, having the option is key, much like when choosing sampling modes with DAC’s.

Shifting to vocals, the EP600.2SE finds the depth where the unique resonances of each artist lay. This detail only increases as the artist’s age. Mark Knopfler has developed a whole new layer to his almost tavern-style singing in the past decade or so. The thrust of the amplifier allows for this characteristic to be in full bloom.  Take a listen to his Down The Road Wherever album, each track is imbued with the decades of time.

Female vocalists such as Diana Krall, Lucinda Williams, and Mary Chapin-Carpenter benefit the most from the exceptional horsepower of the EP600.2SE. While the beauty of a pure soprano note is nicely presented by various artists, the mezzo-soprano and alto ranges that really shine from this amplifier. With all that power, large symphonic pieces fill the room. The LSA Signature 80 standmount speakers thrive and replicate the concert hall recording space when juiced by the EP600.2SE. This is especially true with Deutsche Grammophon recordings. 

Compared to the Peachtree amp500, the EP600.2SE puts the extra 100wpc to good use, it's the difference between the punch of a light-heavyweight boxer to that of a heavyweight, there is just more impact. One wouldn’t think at this level of power it would be that noticeable, though it was a bit less-so when the tubes were not engaged. Therefore, the natural properties of tubes do influence the final sonic experience. Interestingly enough, Peachtree used to include a tube in their integrated amplifiers some years back, but removed them in favor of greater clarity.

Moving to a battle with a vintage solid state Adcom GFA-555ii, the sound differences are quickly and regularly spotted. The Adcom exudes a graininess across the frequency bands, though for being less than half the watts-per-channel provides some 85% of the sheer bass frequency rate of the EP600.2SE. The Class D + tubes do bring the overall sonic signatures closer together. A Parasound A21 amplifier would be an interesting comparison if one was in my collection.

For a final tilt, the EP600.2SE was put against Peachtree's GaN400 amplifier. For those that don’t know the Gallium Nitride is the newest in Class D design, providing a very noticeable solid-state-like sound. This was a fascinating comparison even with the 350wpc difference at 4 Ohms powering the Magnepan .7’s (I did have to increase the volume one remote button press to even out the volume level with the GaN400). Without the tubes in the signal path the GaN400 had a smoother, more natural presentation, no surprise. The EP600.2SE produced more impactful bass, as expected. Once the tubes were engaged, the warm richness especially with the cello in the Piano Guys rendition of “Rockebel’s Canon”, as well as “Begin Again”, was the difference-maker. This was a lucky, fun comparison, and a decision for those that are shopping will come down to personal taste. 

Final Thoughts

The EP600.2SE is a perfect example of the value that Class D amplification brings to the audio market. For $1999 with a three-year warranty, it delivers ridiculous levels of horsepower that easily drives traditionally difficult 4 Ohm speaker loads such as Magnepan without stress. In a small to medium-sized room, I sincerely doubt one would claim a subwoofer is still needed. Mine has been gathering dust since the EP600.2SE arrived. Most importantly, across the entire frequency spectrum, the vacuum tubes add a wonderful level of lushness and vibrancy to the music. For those of you who crave power on a smaller budget, get your ears on the EP600.2SE. I’m looking at what excess gear to sell, as this Emerald Physics EP600.2SE has found a home!


Manufacturer/Distributor: Underwood HiFi

Website: www.underwoodhifi.com

Phone: 770-667-5633

Associated Equipment

Parasound P5 Preamplifier

Denafrips Ares II DAC

Technics SLJ2 Turntable

Adcom GFA-555ii Amplifier

Peachtree amp500 Amplifier

Peachtree GaN400 Amplifier

LSA Signature 80 Speakers

Magnepan .7 Speakers

Totem Acoustic Model 1 Speakers

Celestion si Stands

Shunyata Venom Cords

Audio Art Interconnects & Cables