Conrad Johnson Premier 350 Amplifier
|Conrad Johnson Premier 350 Amplifier|
CJ’s assault on the state of the art
Mike Wright & H. Courtenay Osborne
[Follow Up by H. Courtenay Osborne]
No brag, just fact
For those of you who don’t remember, or didn’t know, there used to be a Summer CES held in downtown Chicago at the Palmer House Hilton Hotel, amongst other places. Then, like now, the shows were closed to the public so I, like many of my audiophile comrades used to “borrow” business cards from local audio shops in order to get credentials and get in to the show. Back then I was too awestruck to speak to manufacturers such as Jeff Rowland and Dan D’Agostino. These guys were the audiophile superstars who I had come to admire, so it was kind of intimidating to suddenly find myself in the same place with them. Instead, I would just smile, nod my head and walk on by, grabbing some of the freshly printed literature I collected from each room while resisting the temptation to ask these guys for their autographs.
Fast-forward about twenty years and here I found myself at this past Winter CES, and as an audio journalist no less. Well now it was my job to not only talk with some of these guys but in some cases to actually ask them to send me some of their megabuck masterpieces for evaluation and review in the pages of Stereo Times. Life is strange.
One of the people I remember most from those good ol’ days wasLew Johnson of conrad-johnson. Lew had always impressed me as one of the easier guys in high-end audio to talk to. So I quickly found the conrad-johnson room and decided to introduce myself. Having previously reviewed the CJ MF2500A amplifier I felt confident that I could approach Lew and chat with him, no longer feeling as much as an outsider stumbling upon a party that I was not cool enough to be invited to. I spoke with Lew and found him to be an engaging conversationalist.
We were having a friendly chat when he brought up the subject of a new amplifier that they were working on, the Premier 350. It’s the first solid-state amplifier in the “Premier” line and puts out a whopping 350 watts per channel. After Lew finished telling about all the great things he knew the Premier 350 could do, I simply shook my head and told him, “That’s a bold statement.” (I know what you’re thinking. That line was a lot cooler when Travolta said it in Pulp Fiction. Right?) Actually, I was just playing coy while waiting for him to offer to send me one for review. I had previously owned the legendary Premier Fives and spent a lot of time with many of the other Premier amps. I have always felt that they were great sounding tube amps, so just the thought that a solid-state amp just could sound superior to them did not register very easily with me. Lew never said another word. He just smiled. He asked that I check back with them in a couple months when a Premier 350 would be available for review. I did so and a few months later the amp arrived. As an appetizer for what’s to come, just let me say that Lew Conrad is not a man who is given to exaggeration but was stating what he felt was the absolute truth!
Looks can be deceiving
Having done a review of the surprisingly good CJ MF2500A amplifier, I expected the Premier 350 to be considerably larger, but when I saw the box that the 350 came in, I thought the amps would be of similar size and weight. Well, the dimensions are almost the same with the 350 only being a little over 1/4th of an inch deeper than the 2500A. But what I didn’t expect was that this puppy would be a whopping 28 pounds heavier! Trust me, I felt every last pound carrying that box downstairs into my listening room.
There really is nothing that stands out about the looks of the 350. It has the same elegantly styled champagne gold brushed aluminum faceplate that so easily identifies CJ. Whereas the MF2500A has a laser cut groove running from the top of the faceplate to the bottom, the 350 has one that starts from the top at one end of its ½” thick faceplate, then comes down and curves a few inches before traveling the width of the faceplate. The power switch is a 1” x 3” plate that matches the color of the faceplate instead of the large black one used in their more recent models. A small red LED comes on when the amplifier is powered up and that’s about it for the front. The rear of the amp has a set of gold-plated five-way binding posts and input connectors. One of the things I noticed on the back of the amplifier were four fuses. Seeing them led me to believe that there must be some serious power pouring through this beast and that the 350, would protect things before they got out of hand. This was confidence inspiring.
The other thing I noticed, and this really was a pleasant surprise, was that there was a detachable power cord. I had to take a look at the front of the amplifier and make sure that it said “conrad-johnson”, and it did. This is only the second CJ amp to make this design concession as for years CJ did not make the use of after market cords an option. The first time they did this was on the spectacular Premier 140 tube amplifier. The amplifier end of the power cord has a high current connector, further attesting to the care and design of the amplifier. The only sound the amplifier made on turn-on were two clicks that were about five seconds apart. The amp was always well behaved and there was never any hum or thump at turn-on or turn-off.
According to information provided on the conrad-johnson website, the Premier 350 uses what they call a “hybrid solid-state circuit.” It uses selected FETs in the voltage gain stage, because, like tubes, and unlike bi-polar transistors, they produce almost no strident odd-order harmonic distortion. CJ feels that the output stage of an amplifier must efficiently couple the high amplitude signal produced by the voltage gain stage to the loudspeaker system to assure the power and control needed to produce a musically accurate response. Bi-polar devices have been specified for the output stages of these amplifiers because they offer about 1/4 the output impedance of a MOSFET, resulting in much better control of the loudspeaker. This is most noticeable in faster, more solid bass response. CJ also uses “zero feedback” achieved by their unique auto-linear gain block for the voltage gain stage, which achieves low distortion with zero loop feedback by exploiting the symmetrical distortion properties of n and p channel FETs.
As complex as that all sounded it’s not just a lot of hyperbole but something that you really can hear. Since the proof is in the listening, then all I can say is they must be doing it right. I can’t tell you how many times I have read a manufacturers white paper or philosophy on circuit design, only to come away after listening to their equipment wondering to myself, “what the heck was I just listening to?” Thankfully, you won‘t have to try and understand what the design features of the Premier 350 are but you sure will hear them.
“the [350’s] percussive attack is fast and impactful. You not only hear but feel the percussiveness of sticks striking skins with the requisite speed needed to make the experience feel all the more lifelike.“
Getting down to it
I’ve been struggling for some time to find words to describe the sound of this amplifier and bypass most of the clichés. The Premier 350 is very neutral. It does have a wide, transparent soundstage and renders performers with a tremendous amount of focus and immediacy. But words like “bright”, “detailed”, “dark”, “tubey”, and “solid-state”, really do not apply here just as those terms don’t describe music in real life. The Premier 350 is dead-on neutral, neither adding nor detracting anything from the music. Sure, there was plenty of detail though in this case I’d prefer to call it accuracy. The performers had dimensionality, the highs were extended, sweet and airy and the bass was fast, deep and nimble. Those words, while helping to describe the sound of the 350 don’t really do justice to it. One meaningful attribute that I can confidently give to the 350 is “musical realism.”
The time I spent working on this review was about enjoying music and nothing else. Time and time again, my notes referred back to how musically real the 350 is. My ears kept telling me that the Premier 350 was the best amplifier I have ever had in my system. During the time that I played music, I felt confident and assured that the 350 was getting the best out of everything my system put forth. The 350 seemed take the components in my system to another level. Here are a few noteworthy examples:
Speakers: I replaced the Soaring Audio SLC-A300 with the 350 on the Von Schweikert VR-4.5s and the music had much more presence with deeper and more extended bass. These are areas where the Soaring does well. It also drove the recently reviewed Usher Audio 6371 loudspeakers with authority, routinely having some of my music-loving cohorts comment on how the stage width and depth and imaging were something extraordinary. The 350 also seemed to open up new sonic windows on my Martin-Logan Quests. These three very distinctive sounding speakers were given new life through this amp.
Digital: I had been enjoying listening to Opera Audio’s Consonance SACD 2.0 and Electrocompaniet EMC-1 CD players running through a Levinson no.36 processor and getting extremely good results. But when I inserted the Premier 350 into the system, it was like when all of the 1s and 0s that Neo saw in The Matrix finally came clear and really started to make sense. I may be a diehard analog man but this system increased my enjoyment of music by an order of magnitude that was surprising even to me.
Preamps: My Sonic Euphoria passive linestage was pressed into service with the CJ while I was having my Thor updated to Mark II status. At the time the Sonic had become my preamp of choice over the older Thor and was a very good match with the 350. But when the Thor came back it immediately established a synergistic brilliance with the CJ that was just jaw-dropping. I sat their stunned at this wonderful blend of tube and solid-state designs. Compared to the BAT VK-1000s, the 350 had much more … magic. There were a couple of times I had to pinch myself to make sure I was really hearing what I was hearing.
Interconnect: I started out with a very good cable (especially for the money) from Sonic Euphoria. I got steady improvement in presence and detail moving up to the much more expensive Virtual Dynamics Nite cables and I had still another level of improvement by stepping up to the excellent Blue Marble Audio cables (review to come). The Blue Marble cable was slightly more open in the highs but at the same time, more detailed and more dimensional. And further still, a sense of Nirvana was reached by inserting the Dynamic Design Platinum Series cables, interconnects, and power cords (review to come). The 350 used these hyper-detailed cables to dig out and flesh out every single audible nook and cranny. I got even more openness, more detail, more bass, more presence and more music! It was overwhelming. I thought I was going to faint.
With each and every component change, the sonic change was easy to hear. Whether it was an improvement or not, and above all, it was always m-u-s-i-c-a-l. I mean, the performances were not just on CDs or albums but were taking place in my room and stimulating my senses. Some of the music captivated me. Some had my toes tapping and some had me jumping up and doing the Macarena (Okay, scratch that last part). Vocal performances that I had previously just appreciated suddenly allowed me to also feel the passion of the singer.
In terms of the music
I really can’t figure out where to start, with all the great music I heard but I’ll try. The amount of detail the 350 presents you with is an assault on your listening capabilities. On Diana Krall’s Live in Paris[Verve], and Stan Getz’s Bossa Nova [Verve Jazz Masters 53] my listening room seemed to be housing the event. All of the hall sounds, small conversations, coughs, rustling and moving around on the stage, the timing of the musicians coming in before and after the singing starts, the interplay between the performers and theaudience, all were breathtaking. On Oliver Nelson’s The Blues and The Abstract Truth [Impulse] the track “Stolen Moments” features a solo with by Freddie Hubbard that was followed by Eric Dolphy playing the melody on his flute that sent a chill down my spine. The transient response of Hubbard’s rapid attacks on the trumpet brought a greater appreciation for his skill and technique. One of my favorite and most under appreciated pianists, along with Cedar Walton, has got to be Monty Alexander. On his album Echoes of Jilly’s [CCD 44796 Concord Jazz], the music comes from such a quiet background that the 350 puts forth that his playing is so easy and relaxed to get into. For a sense of timing and pace that the 350 presents, I like the solo piano playing of Sir Roland Hanna on his Tributaries – Reflections on Tommy Flanagan [IPO] CD. On “Body and Soul” and “Robin’s Nest”, the attack and decay of the Hanna’s piano are tuneful and easy to follow. The 350’s dynamic response is breathtaking. On Jacques Louissier’s Plays Bach [Telarc CD-83411] Andre Arpino’s drum solo on “Concerto in D Minor: Allegro”, the percussive attack is fast and impactful. You not only hear but feel the percussiveness of sticks striking skins with the requisite speed needed to make the experience feel all the more lifelike.
Power meets power
I was very fortunate to have on hand a very formidable foil in which to compare the Premier 350, that being the Balanced Audio Technology VK-1000 monoblocks. These amplifiers are 350 watts a channel and have enough power to drive just about any speaker that I can think of. My Martin-Logan Quests did not throw much of a load at either of these amplifiers and benefited from being driven by more than enough power to satisfying levels. The venerable VK-1000, though showing their age a little compared to the CJ, was still very enjoyable to listen to. The BATs were more than a match to the 350 in the bass department, having more weight than the 350, and it should. Were speaking of 270lbs worth of rompin’ stompin’ he-man amplifier versus the 350’s relatively demure 83lbs. However, the 350 was tighter and had more impact in the low end. The BAT was slightly better at shaking the room while the 350’s bass was more of an assault on the body (e.g. kick drums hitting you in the chest). I can’t say there was a clear winner in the “who’s got the deeper bass” category. But just the fact that it was close speaks volume about the 350. One thing was clearly evident about the two amp’s bass performance was the nimbleness of the 350. The bass was detailed and revealed a wealth of information through the 350. Don’t get me wrong. I’m not saying the BAT only had one note bass, it just did not convey everything that was going on in the lower registers as easily as the 350 did.
The midrange on both amps is very good but I had to give the nod to the 350 in this area based on how easily it pulled me into the performances that I listened to. The high frequency information advantage was clearly in the 350 camp. Simply, it was faster, more extended, with more information and detail. For example, cymbals that sounded good with the BATs, were even more lifelike through the 350. This is not a knock on the old BATs but more of a tribute to the Premier 350.
The Premier 350 is powerful and magical and allowed me to enjoy more music than any other amplifier I have had the pleasure of listening to thus far. I think my wife, in her infinite wisdom, summed it up best one evening. While walking through the listening room with a load of clothes, she stopped and asked me what I had done to my system, not long after I had inserted the Premier 350. She commented that it now sounded “really real”. Yeah. Now I can see why Lew Conrad was smiling when he talked about the Premier 350. You must hear this amp.
Follow Up By H. Courtenay Osborne
The first time I heard the Premier 350 was in reviewer Mike Wright’s system and to say that I was impressed would certainly be an understatement. It was immediately apparent that this amplifier is something special. I have heard many good power amplifiers over the years but not many that I would call exceptional. The Premier 350 is definitely in the exceptional class due to its outstanding sonic performance. This level of performance is the result of innovative engineering and most importantly knowing what music sounds like. More about these aspects as we proceed.
Conrad Johnson has enjoyed the reputation of making fine vacuum tube equipment for many years. The CJ sound has evolved over the years from what some might call “tubey” to neutral. One characteristic that seems to be a CJ hallmark is “dimensionality”; the ability to recreate the recorded event in three-dimensional space. Over the years CJ has made forays into the solid-state amplification game but never quite to this degree. The Premier 350 announces CJ as a builder of solid-state amplifiers of the first tier. There are some highly regarded builders of solid-state amps out there who have yet to build anything that sounds this good.
There has been a narrowing of the gap between tube and solid-state sound. Of course there are diehards that believe the two will never meet. It seems to be a game of trade-offs. Frequency extension or midrange magic, dimensionality or drive, tight bass or mid bass warmth, tonal accuracy or dynamics, detail or emotional involvement, and any other combination you can think of. Musical truth in the sense audio reproduction is not found in a type of sound but in the accurate reproduction of the recorded event. This is no trivial task. It is relatively easy to design amplifiers to reproduce pure sine waves with very low distortion. It is quite a different matter to reproduce musical signals which are much more complex. I know this from first hand experience being involved in analog circuit design for more than 20 years.
Designing an audio power amplifier to accurately reproduce musical signals is probably the greatest challenge to a designer. This is primarily because the amplifier has to faithfully deliver the musical signal to a speaker. Speaker loads can vary from being very simple (virtually resistive) to very complex (network of resistors, capacitors and inductors). It would be nice if all speakers presented a purely resistive 8-ohm load to the amplifier (so much for wishful thinking). The designer also has a choice in which electronic devices will be used to do the amplification. Will it be tubes, mosfets, fets, bipolars or any combination of these? Also there is the choice of using negative feedback (NFB). I know that there is debate about the use of NFB. Personally, I don’t have a problem with NFB. It is how you use it. If used incorrectly there will be problems. Then there is the issue of the power supply. The power supply plays a huge role in the performance of an amplifier. Surprisingly this is an area that is given little attention in many amplifiers due either to cost constraints or simply a lack of understanding. Clearly there are many choices to be made. Making the right choices is an art. This art is based in the understanding of technology and music and how to use the technology to serve the music. The Conrad Johnson design team is in an elite class of audio artisans based on my experience with the Premier 350.
Music? No Problem!
Clearly what struck me first about the 350 was how well it reproduced any kind of music. It didn’t matter whether it was classical, hip-hop, jazz, rock or R&B. Large or small-scale music, this amp delivered in spades. I was going through CDs and LPs like a madman. The listening experience was so involving that I didn’t get caught up in tube versus solid-state sound. The 350 was giving me the best of both worlds. It was only in the area dimensionality that I said to myself this must be a tube amp even though I knew it was solid state. The dimensionality of this amplifier is incredible. Tonal accuracy, the ability follow the music, and be moved by the music is high on my list of requirements for any piece of audio equipment. The 350 again delivers in spades. Perhaps you might be wondering about the detail, resolution and transient capability. No need to wonder, it’s all there, and there naturally. There is no exaggerated detail or presence due to aberrations in frequency response or amplifier instability. This is a very neutral amplifier which seems to be limited only by the ancillary system hardware and source material.
Einstein is quoted as saying “ Make things as simple as possible, but no simpler”. This is hard to do in practice. It requires skill, understanding and ability not to trivialize. The design of the 350 epitomizes this saying. When you look at the 350 you see a very well constructed black chassis with a tastefully designed gold anodized faceplate. There is nothing flashy about its exterior. The real beauty of this amplifier lies within. Looking at the amplifier from the front and working from right to left the layout is atypical of most stereo amplifiers. Behind the power switch on the right is a large power transformer, which contributes greatly to the total weight. The transformer is mostly enclosed in a metal shroud to prevent magnetic fields from radiating within the chassis and adversely affecting the amplifier circuitry. This transformer is not the typical toroid but an E-I core design with an electrostatic shield. This is significant from a powerline noise rejection standpoint. Transformers are basically bandpass filters. Ideally you want a power transformer to have a narrow passband, meaning pass the 50/60 Hz line frequency unimpeded and reject everything else. E-I core designs have a narrower passband than toroids thus better noise rejection. The electrostatic shield reduces the noise even further. What I am getting at is that a properly designed transformer can eliminate the need for expensive power cables and power line filters. I used the stock power cable plugged directly into the wall outlet for the entire review period and got excellent results. Behind the transformer are four large high-speed soft recovery diodes wired as a bridge rectifier mounted to a heatsink attached to the transformer shroud. These diodes produce much less high frequency switching noise than standard silicon diodes and are much more costly. The output of the bridge rectifier is feed to a bank of eight large electrolytic capacitors from which the output stage receives its power. Behind the capacitor bank is a printed circuit board that contains the protection and control circuitry.
Moving to the left is a large printed circuit board (PCB) that takes up most of the bottom area of the chassis. The majority of amplifier circuitry is on this PCB along with the regulated power supplies for the voltage amplifiers. The large number of CJ custom film capacitors caught my attention. These capacitors are used for signal coupling and power supply energy storage. The nice about using film capacitors in the power supply is their ability to deliver current much faster than electrolytics. What this means in terms of reproducing music is that transient information is not smeared or lost due to a slow responding power supply. The voltage amplifier power supplies use nothing but film capacitors after the regulator. The components used in this amplifier are first class. There is no need to do any tweaking. The thing that makes this amplifier unique is the relative simplicity of the circuit topology. The innovative voltage gain stage, which is composed of just two pairs of high voltage complimentary lateral mosfets and some passive components, is really slick. This is the heart of the 350’s great performance. The output of the voltage gain stage is then fed to output stage, which is basically a current amplifier, composed of complimentary bipolar power transistors known for their linearity. Finally to the extreme left of the amplifier is the large heatsink to which the power transistors are attached. The heatsink didn’t get very warm during use indicating good thermal design. I guess you would have to be an engineer to appreciate a lot this techno speak. The point to walk away with is that the Premier 350 is world-class amplifier due to CJ’s innovation and attention to detail.
The Conrad Johnson Premier 350 is one the finest amplifiers in the world for the reproduction of music regardless of price. Its construction and design should give the user many years of trouble free service. Kudos to Lew Johnson and the CJ design team. I highly recommend this amplifier to anyone who loves music.
Power: 2 x 350 watts per channel from 20Hz to 20kHz at no more than 1% THD or IMD both channels driven into 8 Ohms.
2 x 600 watts per channel into 4 Ohms.
Sensitivity: 1.0 V
Frequency Response: 20Hz to 20kHz +0, -.1dB
Hum and Noise: 100 dB below rated output
Input Impedance: 100 kOhms
Dimensions: 16.375D x 19W x 8H
Weight: 83 lb.
Conrad Johnson design, inc.
2733 Merrilee Drive
Fairfax, VA 22031
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