At the conclusion of my review of the Sunfire 600~II Amplifier, I stated that Gary Leeds, President of Innersound, was sending me their new iPower 330 amplifier. This was the replacement of their ESL Mk II that had garnered such favorable reviews, not only in these pages (see my review of November 2002), but throughout the audiophile press. And so the story goes.

A Little History

Just about the time I finished my ESL-Mk II review, the aforementioned Leeds was so taken with Innersound's products that he bought the company. With an infusion of capital, new design talent, and marketing expertise, Leeds wanted to take some already excellent products, as well as creating new ones, and elevate them to a more prominent level in the high end. With his enthusiasm and commitment to sonic excellence, new products were launched, and they have been reported on favorably.

Physical Description

All construction and cosmetics appear to be a big improvement over the ESL Mk II. The clear anodized aluminum faceplate is sculpted from a one inch thick piece of solid aluminum with gracefully beveled edges, subtle blue LED channel indicators and company logo. The look is one of understated elegance and authority. The surrounding chassis metal is of substantially heavier gauge aluminum. All of these construction improvements are designed to minimize and eliminate resonance. It definitely passes the knuckle rap test. Ouch!

The rear panel has conveniently and widely spaced (much appreciated) WBT speaker terminals, an IEC power cord socket and provision for both single ended and balanced operation. There are two switches on the back panel; one is a standby switch (not mentioned in the rather sparely written manual) that keeps an idle current running in the amplifier. The other is a pure on/off switch that shuts everything down. The rear panel also contains a 15 amp, slow blow, AC line fuse and 10m amp internal power supply rail fuses. Additionally, there are also 8 amp, fast blow speaker protection fuses accessible at the rear panel. The manual does mention that if one uses an A.C. Surge protector and/or line conditioner, it is mandatory that it be able to produce a minimum of 1,500 watts. The manual describes using caution when switching on and off the power with the operation of both tube and solid-state preamplifiers. It suggests you leave your preamp on all the time. I wish the manual had more information on the internal construction and design of the amp. When queried, Gary Leeds emailed me the following information about the amplifier's design:

'The iPower 330 is a 330 watt (RMS into 8 Ohms) Stereo Amplifier that will deliver 660 watts per channel into 4 Ohms. The amplifier was designed to effortlessly drive complex loudspeaker load and is unconditionally stable into low impedance loads. The iPower uses 18 bipolar output devices per channel. The input stage is differential FET, followed by a single-ended Class A second stage, and fully complimentary bipolar output stage which is biased into Class AB operation. The iPower amplifier is based on the circuit topology of the award winning ESL Amplifier, however incorporates significant changes including a less resonant chassis, new bias control network and improved temperature tracking. The iPower continues Innersound's tradition of offering thermally efficient, cool running amplifiers. Power consumption is mere 3 watts at idle. In addition, a new custom wound, fully encased and shielded 2KVA power transformer and a novel DC/mechanical hum blocking circuit has been borrowed from Innersound's new flagship DPR series amplifiers. Remote turn-on capability has also been added.'

The basic architecture of the amplifier has remained with several key improvements (see Nov. 2002 ESL review). The first is a rather significant change to a regulated power supply, now with DC filtering. Secondly, the new and larger 2KVA transformer results in an increase in power output of 10%. The ESL was 300w/ch at 8 ohms and the iPower 330 has a power output of 330w/ch at 8 ohms doubling at 4 ohms to 660 w/ch and is said to be stable down to one third of an ohm.

Performance

When Innersound's Marketing Director, Wes Bender, kindly delivered the new amp, he said it needed burning in. I used a hundred hours with a continuous flow of a variety of music, including the XLO burn-in disc. Now I was ready for a serious listen. As you may have read, I had recently given the Sunfire 600~II a favourable review and was anxious to hear what this new amp could do. I used much of the same music to do my evaluation, along with some newly acquired CDs. I placed the amp on Soundcare Superspikes and replaced the stock power cord with my reference, Acoustic Zen's Gargantua II, later by AZ's newest power cord, the Absolute (review forthcoming). Another variable to add to the mix was the timely arrival of the Wasatch Ultama speaker cables (review also forthcoming).

My first impressions were extremely positive: smooth, quiet, utterly transparent and detailed. I was hearing a new clarity and articulation from old recordings. The amp's ability to resolve complex musical passages was remarkable. Words were more decipherable in background vocals, with greater soundstage depth. Voices had more focus and definition and inner detail. Guitars were more complete. What do I mean by that? Well, the finger on string details were very clear, and the body of the guitar, resonating as a three dimensional object in space, was truly palpable. Its location was clearly evident. Keith Ganz's playing on Music For People never sounded so present in my room as it did with the Innersound. All of this happened with a sense of delicacy when required and authority when demanded.

When listening to Patricia Barber, Diane Krall, Kate McGarry or Shirley Horn, I sensed, more than ever, real people were singing, not an electronic representation -- subtle vocal textures allowed more of the singers' emotions to come through. Listening to groups of singers was also very informative. When listening to Misty River on Misty River, Rising (a quartet of wonderful female vocalists I had the pleasure of meeting during CES 2004), it was so easy to hear their individual voices creating unique harmonies in combination with their wonderful instrumental facilities -- the musical parts made a strong impression. Listening to them perform on their CD with the iPower in the system, brought me back to the beauty and excitement of their live performance. Isn't that what it's all about?

Another strength of this amp is its excellence in speed and control. Huge transient attacks were handled superbly, without smearing. The iPower 330 grabs a hold of the music in a way that I've rarely experienced. In fact the amp does not glorify sound or romanticize -- there are no euphonics or colorations - just what is inherent in the recording, heard accurately and smoothly.

How Low Can You Go?

Bass performance was superb. Many good amps go deep with authority, but how many capture the body, timbre, and fingering of a bass accurately and with control? In my review of the Sunfire 600~II, I compared its bass performance with the Innersound ESL 300 Mk II and described the differences. It was clear that each had their own strengths and handled bass differently. The iPower 330 surpasses the performance of both and achieves a deeper, more authoritative bass than its predecessor and a more timbrally correct presentation than the Sunfire, with more definition and control. The opening cut, St. Louis Blues on Peter Cincatti's CD, On The Moon, opens with an acoustic bass line that was startling in its lifelike presentation. I had just heard him perform at the new home for Jazz at Lincoln Center at the Time Warner Center in NYC, and the Innersound's ability to get close to that live quality was enlightening. Another CD I often use as a reference is the gold version of RCA's Living Stereo, Rhapsodies with Stokowski. The first piece, Liszt's Hungarian Rhapsody No.2 has, in the opening moments, some wonderful cello and double bass section playing that you feel in your gut. This amp lets you hear and feel the powerful bowing viscerally.

High frequency extension was superb. Listening to the cymbal work, by Jack DeJohnette on Keith Jarret At The Blue Note was truly revealing. Each cymbal strike was clear from the stick hit to the 'sizzle' of vibration of the metal along the surface of the cymbal carrying into the atmosphere of the club. There was immediacy to the presentation that brought you into the live performance.

Flute presentation as heard on Telarc's wonderful hybrid SACD, Mozart, Flute Concertos, Symphony No. 41 with flutist Jacques Zoon, accompanied by Martin Perlman and the Boston Baroque Orchestra, was wonderfully reproduced with the Innersound in the system. This amp captured the flute resonating with air passing through the body of the instrument beautifully. The orchestra, performing on period instruments, sounded so clear, so complete and natural that I stopped reviewing and sat back with a glass of Merlot and let the music wash over me. And I'm only talking about the two channel, Redbook sound, not the SACD or multi-channel presentation. Down the road I hope to get my hands on another multi-format player to review the impact of its full SACD sound.

Colleagues Visit

Will this love fest end? As a reviewer it is necessary to keep some level of objectivity and I needed some input from several colleagues and friends just to see if I hadn't strayed too far from reality. Henry Wilkenson, a well-grounded colleague, came over, as well as dear friend and musician, Professor Terrence D'Altroy, an anthropology professor at Columbia University. Eric Ming, an audiophile hobbyist and tennis buddy, who builds his own equipment, became the third Musketeer of the group. They each brought over some reference CDs and the party started. As good as the Sunfire was, the overwhelming choice was the Innersound. I didn't need to say a word -- their words said it all and confirmed its excellence. Maybe the most telling was what Eric had to say. He brought over a live recorded blues CD of a group called Michael Hill's Blues Mob (Electric Storyland Live) -- he has seen the group perform many times and said that the Innersound produced the closest rendition to the live performance that he had yet heard. The lead singer's voice and the group's dynamics were right on. The Innersound captured the spatial environment of the venue as well as the excitement of the concert. Eric couldn't sit still.

I guess you know where I'm going with this one. This amplifier will not add or detract anything from the source. Any problems you might experience from your sound system will be coming upstream. It is flawlessly revealing and resolving. The Innersound ESL Mk II, before it was discontinued, was retailing for about $4000.00 US and received an Audiophilia 'Star' rating. The iPower 330, retailing for $5K US, has eclipsed it in every performance category. In fact, Innersound has produced an amplifier that will challenge those costing many more thousands. Therefore, I am recommending a 'STAR' rating be given to this amazing amplifier, with only the sparse manual subject to criticism.

Is this the best amplifier on the planet for the money? Words like 'best', in this context, are meaningless. Is there competition at this price point? Certainly, there is. Stay tuned. Of course, lurking out there is the Innersound's bigger brother, the DPR 500 Reference amplifier, a 500 w/ch behemoth amplifier retailing for a mere $14K US. Hopefully, I'll get an opportunity to hear it and report back.

[It is with great pleasure that we award The Audiophilia Star Component Award to the Innersound iPower 330 Power Amplifier. Congratulations! - Ed]