April 2025

World Premiere Review!
Class D Audio Premium GaN 6.0 Balanced Amplifier And Terry Audio EI 30A Balanced Power
Two great high-fidelity audio products that offer truly great value.
Review By Paul Schumann

   One of the advertising slogans that makes me the most suspicious is the statement that something is "new and improved". Usually, it means that a company updated the packaging, with little or no change on the inside. The worst scenario is when a significant change is made but for the worse. For those of you old enough to remember the New Coke, you know what I mean.

Part of the high-end audio business is updating one's products periodically to maintain public interest. I'm not saying this is wrong or right, it's just how it is. I know most audio manufacturers are tinkers by heart, so they always see room for improvement. While much audio technology is well-established, some areas are rapidly changing. One of those is the implementation of gallium nitride (GaN) devices.

Just under a year ago, I heard the Class D Audio's Mini GaN 3 amplifier at the inaugural Southwest Audio Fest 2024. I was impressed with its combination of great sound and affordable price. This led to my in-home review of it a few months later. As I was completing my review, Tom mentioned that he had an upgraded version of the Mini GaN 3 he was working on. He asked if I would be interested in reviewing it when it came out. I immediately said yes because I had enjoyed the Mini GaN 3 so much. Time flies because before I knew it, the new amp arrived at my home.

A Few Technical Detail
When I notified Tom of Class D Audio the Premium GaN 6.0 had arrived safe and sound, he explained to me that this amp was a completely new design, utilizing new GaN devices and a new circuit design. He didn't elaborate, and I'm sure the technicalities of it would be above my geologist brain. I do know that when I took the Premium GaN 6.0 out of the box, it had the same compact dimensions and sturdy feel as its predecessor. The outer case is a new design with new color schemes. My review sample was cherry red and looked snazzy. The layout of the Premium GaN 6.0 is identical to the Mini GaN 3.0 with a power switch in front and connections in the back. Just like Mini GaN 3.0, the Premium GaN 6.0 weighs in at only five pounds. If you have a smaller stereo cabinet like me, you have to appreciate it.

Over the past few months, I have been digging deep into vinyl and exploring the world of streaming, but I realized that my CD collection has been feeling ignored. While I do have a nice vinyl collection, most of my music is still on compact disc. The recent additions of the FiiO R9 and the Kimber Kable D60 digital interconnects have taken my CD playback to new heights. This led me to plop in some shiny silver discs that I hadn't experienced in quite a while. Since I've been dealing with a lot of stress lately, I decided to play some butter-on-the-brain albums to keep my anxiety down while writing this review.

Enjoying Great Tunes
When it comes to chill, nothing may top K.D. Lang's Ingénue [Sire - 9 26840-2]. This is a giant album that made K.D. a household name and does a tremendous job of showcasing her effortless singing style. While Ms. Lang had been considered a country artist, Ingénue was a genre-warping effort that refused to be categorized. That's why it sounds just fresh now in 2025 as it did when it came out in 1992. As soon as I hit the play button, I knew I was in for a special treat. I remembered it being a good-sounding album, but I was immediately blown away by Ingénue's spectacular sound. One track that stands out is "Wash Me Clean". Listening to it with the Premium GaN 6.0, K.D.'s vocals were beautifully rendered with effortless dynamics. The acoustic guitar also sounded incredibly natural and the bass was deep and tuneful.

Another track that was a revelation was "Still Thrives This Love". The construction of this piece is simply brilliant. Set to a samba rhythm, it opens with mandolin, acoustic guitar, piano, drums, and bass. Lurking in the background of the first two verses is a clarinet. After the chorus, an accordion, full-blown Clemmer clarinet, and strings are added to the mix to add a tango feel. At each chorus's end, K.D. holds a note that starts at pianissimo (p) and effortlessly crescendos to a double forte (ff). I had similar experiences with other songs on Ingénue. With the Premium 6.0 GaN amp, it was a joy to rediscover this album.

Another oldie I pulled out was Sting's The Soul Cages [A&M Records – 75021 6405 2]. This was Sting's third album and it explored his feelings after his father's death. The first song," Island of Souls", echoes Sting's bleak childhood growing up in a shipyard town. To set a timeless mood for the song, Northumbrian pipes open with a mournful melody emerging from the mists of time. The Premium 6.0 GaN amp perfectly captured this haunting introduction to a dark album. On "Mad About You", the mandolins were strikingly clear and wild reverb on the electric guitar. If you have any questions about the bass reproduction of the Premium 6.0 GaN, I could feel the impact of the gong at the end of this song in my toes.

On the album's final cut, "When the Angels Fall, " the catharsis in Sting's vocals bleed through. Throughout this album, Manu Katche's drums are perfectly captured. Listening to this CD with the Premium 6.0 GaN, it is obvious that his drumming is the glue that holds this album together. His drums and cymbals cut through on every track and were clean and dynamic with the Premium 6.0 GaN amp.

I do have quite a few pop, rock, and jazz CDs, but the lion's share of my collection is classical music. One of the great classical CDs I stumbled upon was William Walton: Orchestral Works [Arte Nova Classics – ANO 391240]. This collection features "Scapino, a Comedy Overture", "Siesta", and his "Symphony No. 1". I picked this CD up at a resell-it shop in the basement of my in-laws' senior living facility. Hey, for a quarter, how could I pass it up? These orchestral works were performed by the Orquesta Filarmónica De Gran Canaria under the direction of Adrian Leaper. If you've never heard of this orchestra before, neither had I. Located in the Canary Islands, they play in the stunning Alfredo Klaus Auditorium, which has a large window overlooking the Atlantic Ocean.

The acoustics of this auditorium are reportedly excellent due to its hexagonal shape. Even though this CD is from a budget classical label and performed by a little-known orchestra, the performances and sound are stunning. The Premium 6.0 GaN amp showed off what I like about this album. Firstly, the sound stage has amazing depth and width. You can hear the acoustics of the Alfredo Klaus Auditorium in this recording. The strings sound luscious, the horns have just the right amount of bite, the woodwinds are filled with those woody overtones, and the percussion is startlingly dynamic. If you are a fan of 20th-century classical music, you will love this disc.

Premium 6.0 GaN Amp Versus The Mini GaN 3
So now to answer the big question: how does the Premium 6.0 GaN amp compare to the Mini GaN 3 I listened to last year? The Premium 6.0 GaN amp is very similar to the Mini GaN 3 in its personality. Where it excels in the retrieval of musical details. Tones are richer, instruments and vocals are clearer, and acoustic cues are more apparent. I recently had the pleasure of having the Hegel H400 Integrated in my home. How does the Premium 6.0 GaN compare to it? The big difference was in terms of refinement. The highs are a little more sparkle. Instruments and vocals are more precisely located in the aural matrix. This is what one has to keep in mind, a Hegel amplifier is significantly more expensive. The Premium 6.0 GaN amplifier is, Dollar-for-Euro, such a great deal. If you are looking to purchase high-end audio separates but worried about breaking the bank, the Premium 6.0 GaN is the amplifier for you.

EI 30A Balanced Power And Isolation Transformer
Last spring at SWAF 2024 I visited Marshall Terry's room several times during the show. On the last day, Marshall performed a quick A-B comparison to demonstrate the merits of his EI 30A Balanced Power and Isolation Transformer and I was impressed. I was inclined to review it ASAP, but Marshall wanted to improve its cosmetics first. Reluctantly I said I would wait. A few months later, Marshall reached out to me and told me he decided to forgo any upgrade to the appearance of the EI 30A. Since Marshall is here in Austin, I was able to drop by his home and pick one up.

When I arrived, Marshall gave me a tour of his one-man shop. Then I spied to the side of the room the EI 30A. It looked so cute sitting there perched on its four wheels. I just had to pick it up. But just like certain toddlers, the EI 30A is much more hefty than it looks. As soon as I lifted it, I understood why it had wheels. The EI 30A tips the scale at 50 pounds. As I carried it out to my car, I mentioned to Marshall that I wanted to add a spot where you could connect a leash. That way you could tow it around to where you needed it.

Once I lugged the EI 30A out of my car and into my living room, I was able to get a good look at it. The heart of the EI 30A is an E-I 30-amp stacked lamination transformer. This is the part that converts the normal 120 VAC to a balanced 60-60 VAC. There are industrial-grade plugs attached to heavy-duty power cords for input and output. For safety reasons, Marshall added a Line Guard installed in line with both balanced output phases – a 30A dual GFCI (ground fault current interrupter) protector. If there is any current imbalance between the two balanced power pins (ie, a fault in a piece of equipment or a power cord), the GFCI trips immediately to both phases and stops power from the main power cord. Then it must be manually reset via the front of the Line Guard GFCI.

So do you use the EI 30A? Just plug in an outlet, and plug the power strip for your system into the female plug for the EI 30A. I didn't have room for the EI 30A to be close to my system, so I got a 12 ga extension cord to make the connection to the power strip. Marshall did warn me that switching-power supplies do not work well with balanced power, so I plugged the Pass B1 Korg Preamp wall wart directly into the outlet. To evaluate the EI 30A I used the Mullard 3-3 amp paired with the Korg B1 preamp.

Listening to the Terry Audio EI 30A with my system, I realized I have been thinking about power supplies all wrong. I always considered them as an accessory. The EI 30A made such a dramatic change in my system, that I consider it as a component just as valuable as an amplifier or a DAC. If you are looking to upgrade your entire system without changing its personality, you might want to check out the EI-30A.

Specifications
Type: Solid-state Class D power amplifier
Frequency Response: 20 Hz to 20 kHz (+/-0.5dB)
Power Output: 150 Watts (400W Peak) @ 8 Ohms (250W at 4 Ohms)
Power Supply: Full GaN Powered LLC Resonant Converter
Input Sensitivity: 2 VRMS
THD+N: 0.006% @ 8 Ohms, 1 kHz, 1 W Power
Input Impedance RCA: 100kOhm
Input Impedance XLR: 100 kOhm
Voltage Gain: Adjustable – 26dB, 28dB, and 32dB
SNR/DNR: 108 dB (Unweighted), 110 dB (A-weighted)
Dimensions: 9.75″ X 7.5″ X 2″ (WxDxH)
Product Weight: 5 lbs.
Price: $875

Terry Audio Balanced
Type: Balanced Power Supply 
1:1 Power Transformer Rated at 5kVA (40W at 120V) 
Spec'd by Terry for 30A for best audio practice 
Pure copper windings 
Dual electrostatic shields between primary and secondary 
True center-tapped secondary for balanced power, center tap referenced to ground 
Chassis, electrostatic shields, and center tap reference tied internally to ground, reference to power ground pin
Epoxy, stone, and resin cast transformer to guard against all elements and to damp magnetic vibrations
Price: $3150

Company Information
Class D Audio
California

E-mail: sales@classdaudio.com 
Website: ClassDAudio.com

Terry Audio
Austin, Texas
Website: TerryAudio.com