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October 2006
Superior Audio Equipment Review

conrad-johnson CT6 Preamplifier
Perhaps not quite Formula 1, yet very much in NASCAR territory.
Review By Rick Becker
Click here to e-mail reviewer.

 

 

 Anybody who has been around high-end audio for even a short time knows about conrad-johnson. They've been in the game since 1977. Their status is so legendary that I never thought I would ever review such a revered brand — especially considering the mediocre coverage I've given rooms featuring their components at the Montreal shows over the years. But the opportunity came along as part of a package deal. Spencer Clark, designer of the Aural Acoustics Model B loudspeaker, insisted that I review them with c-j equipment, since that was what he used in voicing the Model B. Who was I to argue? This prolonged the review process, since in effect I had to familiarize myself with the c-j gear in order to get a grip on how it differed from my own reference components. The short story is that the Model B is a terrific loudspeaker when used with the c-j gear and its review appears in the Superior Audio archives section.

 

conrad-johnson CT6 Preamplifier

 

The longer story is this review. The CT6 preamplifier is a descendant of the legendary ART preamplifier that is a major milestone in c-j history. Before the introduction of the Anniversary Reference Triode (ART) back in late 1996, c-j equipment was very conservatively styled, as was most high-end equipment at that time. The company's champagne anodized faceplates and the little "c" and little "j" were pretty much the extent of their visual branding. Of course, their equipment developed a great reputation for performance, build quality and factory support to back up the brand. The ART preamplifier kept the signature champagne finish and the little "c-j", but the performance and the styling broke the mold and catapulted the company to the forefront of contemporary audio design once again.

To say that the new CT5 and CT6 are trickle-down variants of the ART would be overlooking some serious engineering developments that have occurred during the intervening decade. Another audio journalist writers felt that the CT5 was almost the equivalent of his reference ACT2 preamplifier, the single box model that succeeded the two-box ART2 preamplifier and the original ART. I heard the CT5 along with the new LP140M monoblock power amplifiers at the Montreal show earlier this year, but for various reasons — room dimensions, loudspeaker compatibility and placement — did not feel it was among the Best Rooms. In fact, I was getting much better results at home with the more modest CT6 and MV60SE stereo amplifier in combination with the Aural Acoustics Model B.

From a styling standpoint it is clear that the CT5 is more expensive than the CT6 preamplifier, although as I write this, I still do not know the price of the CT6. With its slimmer, more straightforward design I will venture a guess that the CT6 falls in the $4000 to $5000 range. In place of the very attractive Half Moon Bay and two exposed tubes on the CT5, the CT6 has a series of slots cut in the faceplate that barely reveal the glow of the first of four in-line 6922 tubes. These twin triode tubes are linked in parallel (two per channel) to create a single gain stage that does not need feedback or buffers that would compromise the sound quality. Gain is a very healthy 26dB and maximum output is 15 Volts. Both figures are higher than the current top of the line ACT2 preamplifier. With only a single gain stage, the CT6 also inverts polarity of the signal — a feature that tripped me up more than once in the process of swapping multiple components under review. In normal installation you just need to be careful to switch the positive and negative leads of each speaker cable at one end or the other.

The large circular, black dial with orange CT6 logo and yellow LED digital readout of each channel tips us off to the microprocessor controlled volume and balance via remote control. Being "Old School," I never minded getting up out of the listening chair as it improves circulation and the flow of oxygen to the brain. But it is clear that our species is headed toward leglessness. The 100-step attenuator has increments of 0.7dB and all control functions are handled through the beautifully machined extruded aluminum remote control. In my system because of the differing output levels of my sources, the volume was typically set in the 20's for LPs and around "50" for CDs. Every two steps is a barely perceptible increase in volume.

The "off" mode is really just a "sleep" mode that shuts down the tubes for longevity while residual current keeps the solid state circuitry of the CT6 warmed up. When fully powered up, the signal is automatically muted and the orange "mute" LED flashes continuously for about 90 seconds until the tubes have warmed up sufficiently. It was somewhat frustrating to not be able to change the volume or source selection during this warm-up process. For example, if you were listening at a loud level the previous night, and wanted to listen at a lower level when you powered up again the next day, it was necessary to wait for the warm-up cycle to complete, then lower the volume, then select the tuner or hit play on the CD player. (The unit defaults to CD when you shut it down). A guy could burn his eggs in the morning with a protocol like that!

The remote control with a matching champagne finish was a serious tool, machined with crisp lines that emulated the crisp edges of the milled faceplate. Yet the edges were not so sharp that I feared scratching the leather of my listening chair. Four clear plastic feet were a nice touch to keep the remote from sliding around on the chairside table or scratching the top of a component. The volume and balance buttons were nicely differentiated and conveniently located in the middle of the remote. The other eight small buttons were identically sized and shaped. Three of them related to the video and surround processor loop, which I did not test. A fourth button was for the mute, which should have been more tactilely differentiated. The mute button also doubled as an On-Off switch. No arrangement of buttons is going to please everyone, but aside from the volume and balance controls, I pretty much had to have the lights on to observe and operate the remote.  To complicate matters, the arrangement of buttons on the remote does not correlate to the arrangement of the LED indicators on the face of the unit. Symmetry between the two would have been an elegant touch and facilitated learning the position of the buttons.

Since the remote had no backlighting or LED indication of what source had been selected, it was necessary to check the orange LEDs on the faceplate. At a distance of more than ten feet from the listening chair, the black silk-screened labels were not readable on the faceplate. But this was not an issue because of the other major drawback, which was more circumstantial. The only available slot in my rig to position the CT6 was directly in line with the right channel loudspeaker, obscuring my view of the volume readout and LED indicators. I'll never know if this was a plus or a minus, but it did require me to stretch my right arm out to the side to change volume or mute the signal, and stand up out of the chair to check the level.

If the preamplifier is close at hand by the listening chair and you leave the lights on while you listen, then all this would be a non-issue. In any case, with 26dB of gain and 15 Volts maximum output, locating the preamplifier at chairside might be a reasonable option. Lew Johnson cautioned against using long cables with a high capacitance, as this could mess up the micro timing and soften the highs, thereby throwing away some of the quality that they worked so hard to achieve. I use a 2-meter pair of Kharma Matrix 1.0 interconnects in my rig.

The other striking operational features are the clicking made by the microprocessor-controlled relays as you change the volume and the jiggle of the "floating" relay switches on the face of the unit. With music playing, from the listening position with the preamplifier ten feet away, this clicking was not usually noticeable. I'm well aware that this technology offers a cleaner sound and at some point I will have to evolve or die…possibly both. However, as a person who likes to listen in the dark, I am much more comfortable operating my CAT preamp with traditional volume and balance knobs and archaic switches to select the source. (I do turn on a light to change my LPs, lest you think I'm supernatural). I should also mention that selection of different sources with the buttons on the unit required cycling through a fixed sequence rather than direct random access to the desired component. Again, it would have been more elegant if the left button controlled the selection of the functions on the left column of orange LEDs and the right button controlled the right LEDs, but for some reason, it was just the opposite. Use of these buttons sometimes allowed a small "click" or "pop" through the system, possibly because I have lifted the ground on some source components. Out back, there are high quality, single-ended inputs (RCA) for an outboard phono stage, CD player, tuner, video and an auxiliary input, as well as the unity gain loop-through for a home theater processor. Dual single-ended outputs are provided to simplify bi-amplification or use of a powered subwoofer.

 

The Listening
I met Lew Johnson at the 2003 Festival Son Image in Montreal where he was playing his new Premiere 140 power amplifiers configured as monoblocks.  He was friendly and easy going, taking the time to point out some features of his new amplifiers without drowning me in technospeak. When I spoke with him on the phone in the process of setting up this review, he was much the same and over the course of this extended review period, he has been more accommodating than I would expect. Among his predictions was that I would find the CT6 to be better than my CAT preamplifier, an older Signature SL-1 Mk III model, not their current SL-1 Ultimate Mk 2. I assured him that I was open to the possibility. Although the box was stamped "Review Sample" it was evident that this was a brand new unit from the first production run. From the very first CD, it was clear that it had great potential. I burned it in with the accompanying MV60SE power amplifier and the Model B loudspeakers. Over time, I also listened to it with the Manley Mahi monoblocks and the Plinius SA-100 Mk III. And I listened to each combination with both the Model Bs and my Kharma loudspeakers. I tried it with and without various vibration absorbing footers. As good as the focus was without them, the footers made the CT6 even better, every time.

The MV60SE (pictured right) is a very good amplifier that worked superbly with the CT6 and the Aural Acoustics Model B loudspeakers. Its tonal balance is flat from treble down to the mid bass where it starts to roll off benignly. This complements the somewhat fat bass of the Model B and the music comes out smiling. With my Kharmas, which fare better with some extra emphasis in the bass, the MV60SE was not a good choice. With the CT6 driving my Manley Mahi monoblocks that have a tighter, more pronounced bass, the results were outstanding with the Kharmas. And with the CT6 driving the Plinius, which took firm control of the bass of the Model B, again I achieved great success — with both loudspeakers, actually. The important point here is to find an amplifier that works well with the strengths and weaknesses of your loudspeaker.

Ideally, we would all choose perfectly neutral components and the result would be beautiful music. But variables like efficiency, input and output impedances, amplifier dampening and loudspeaker dampening, cable capacitance, not to forget personal interpretation of "beautiful music," make the task more challenging. This involves the concept of system synergy that we hear so much about, but sometimes forget when we read a rave review or fall in love with a beautiful woman. (By the way, don't ever suggest to your significant other that he or she is perfectly neutral — go with the system synergy story and emphasize compatibility). Since the MV60SE has been reviewed numerous times, I'll set it aside here with the realization that I have nothing really to add to those reviews. It is every bit as good as they said it was.

Moving forward with the CT6, early on it became apparent that the CT6 had superior focus than the CAT Signature SL1 Mk III. It took me a long time to come to grips with that because I love the CAT so much, but eventually, the truth was undeniable. As I suggested above, the Boston Audio TuneBlocks and Sound Dead Steel squares increased the resolution even further. With the MV60SE and the Manley Mahis, this exemplary focus never became edgy or irritating. With the Plinius, being an older solid-state amplifier, the edges sometimes became a little rough on poor recordings, but overall it was still very good. With all these amplifiers, the result was more instant recognition of the lyrics, faster attack, faster decay, better micro-dynamic shadings, more tonal color, and an improved sense of the performance hall and room reverberations.  As Lew Johnson explained to me, the reason for this was due to their attention micro-timing in their circuit design. Things like the laser trimmed metal foil resistors and polypropylene and polystyrene capacitors make significant contributions to minimizing timing errors, as does the blanket removal of negative feedback circuits and buffers made possible by the use of a single gain stage. As you can see in the photo, many of the parts are of their proprietary manufacture and the circuit board is clean and uncluttered.

Another major improvement with the CT6 was the increase in transparency of the acoustic image. I've played with lots of components, loudspeakers and footers that improve the focus of the music, and improved focus certainly raises the "High" in "High End." An improvement in transparency has been more difficult to come by. The CT6 certainly improved the focus, but it was the increase in transparency, as if I had removed my sunglasses inside the performance hall, that really caused me to look up and watch the performance. I'm not talking about wiping a layer of grunge off my lenses that robbed me of some of the data, but rather like the stage lights were brought up a couple of notches and made it easier for me to see the performers. It also increased my aural depth of field — meaning the instruments and voices at the back of the soundstage were in better focus as well as more softly or delicately portrayed.

I won't get into whether it took me to the performance or brought the performance into my room — that's a Yin-Yang kind of thing. The performances were more present and compelling, with greater emotional connection, even with my compilation CD that I've heard a hundred times. I could see the sweat on Buddy Guy's face as he strung me out with his blues and feel the wailing of Neil Young's harmonica tugging on my heart strings. You certainly need focus to resolve the inner detail of the music and the timbre of the instruments, but without transparency, much of the emotion of a performance can pass unnoticed. The CT6 doesn't fry the performers in a spotlight leaving the performance flat, two dimensional and pale, but it lights the stage to a degree that all the music will be heard, for better or for worse. Song after song, I was hit with the conrad-johnson advertising theme: "It just sounds right," which is another way of saying kick back and "enjoy the music". My unconsciously tapping toe was the undeniable barometer. As I struggled to keep my reviewer's hat on I kept looking for shortcomings — the treble and the bass were the usual suspects — but didn't find any. The bass is solid down as far as my rig will go: the low 30s. And the treble, particularly with the Sonotex tweeter in the Aural Acoustics Model B, was smooth, focused, sweet and extended far above what I can still hear. The result is that the treble seems to go on forever. I suspect that this also impacts the sense of space with the CT6.

The revelation of venue and soundstaging benefited from the outstanding focus and transparency. We all know that, to a large degree, the image of soundstage is a construct of high quality stereo playback, rather than an exact replication of the experience of live music. With the CT6, I experienced what I prefer to call "realistic" imaging, rather than "pinpoint" imaging. Have you ever seen a musician as thin as a pin? They're very hard to spot. With the CT6, the musicians stand in a space that is commensurate with the human body and completely believable. Only with the occasional drum kit that is multi-mic'ed and stretched on the recording from stage left to stage right is the illusion broken. Because my rig is aligned with the long wall, the width of the soundscape was as good as it ever gets. The depth, because of the excellent focus, revealed excellent imaging all the way to the back of the soundscape with subtle shadings of volume and dynamics. Back-up singers were far away because of the volume, not because they were less well focused or were buried in the shadows for want of transparency. I've experienced greater depth, but it took more expensive SET power amplifiers to do it. I was not the least bit dissatisfied with what I was hearing with the CT6.

Hall sounds, too, were easily discernable, contributing to the sense of being present with the musicians. If anything, I heard more of the music from the recording than I could expect to hear at a live performance, depending on where I could afford to sit.  The microphones usually seem to get a better view of the music than I do. In making a final comparison with my CAT preamplifier, one additional feature stood out. The CAT presented the music with slightly more weight and body, sounding a little fuller at the expense of focus and transparency with my older model. I would expect the current model CAT to be better in both focus and transparency, but I've never heard one. Two things are for sure: there is a whole lot more "stuff" packed into the chassis of the CAT, not to mention its separate power supply, and it costs more like the CT5 than the CT6. I would count my blessings with any of these three preamplifiers.

 

Value
While I have heard the CT5 briefly, the show conditions were not optimal. The specs are very close, with the CT6 measuring slightly more THD at 0.25 percent, but then, we know better than to merely compare specs. The chassis of the CT6 has been obviously simplified, but the CT6 uses 6922 tubes just like the original ART. There is no question in my mind that this is a very fine sounding preamplifier. But sometimes manufacturers control technology and sometimes the winds of technology and cultural demands steer the manufacturers. We are living in an era of transition between stereo music and surround sound video performance.  The Composite Triode series of preamplifiers from conrad-johnson pays homage to both camps, being outstanding stereo preamplifiers capable of integrating with home theater. I was hoping for a line stage sounding this good that would be an incredible value at $3000. The addition of the remote control, pass through circuitry for surround sound and advanced technology necessitated raising the target. I made it nice and wide at $4000 to $5000 so I would be sure to look good. Bill Conrad passed the envelop to me... and the price is... Oops! $4500! Do I look too good?

I suspect at its list price it might still be a very good value. The question remains: How much worse could it be than the CT5, which is only a smidgen less refined than the top of the line ACT2? Maybe they should send me a CT5 to answer that question. Certainly, Messrs. Conrad and Johnson are astute businessmen and know that there are people willing to pay at each of the three levels of the Composite Triode series. But are they giving away the farm by offering too much audible quality in the CT6? Lew did his best to assure me the ACT2 and CT5 were a healthy step above the CT6, in a very elite performance group. The CT5 uses very expensive Teflon capacitors while the CT6 uses polypropylene capacitors with a polystyrene bypass. This amounts to small differences in temporal accuracy, which affects the things I talked about above. While the CT6 is a more noticeable step down in quality from the CT5, he said, it is as good as the best preamplifiers offered by most other companies. In an age that boasts of $13,000 six foot wide stainless steel refrigerators and $3200 espresso coffeemakers for the home, a $4500 preamplifier that contains most of the sound quality of their $13,500 model starts to look like a real bargain. And for those who cannot afford it, they have the PV15 line stage at $2800 or $3650 with built-in phonostage. In case you were wondering, a new separate phonostage for the CT series is in the works to replace the discontinued Premier 15.

Another, often overlooked element of a product's value is the ability and willingness of the company to stand behind the product. Not only does conrad-johnson offer a three year limited warrantee on parts and labor (tubes excepted), but they have been a major player in this game for three decades. In this age of Internet gossip, a company will not last long with a disgruntled customer base. You have no excuses on this count with conrad-johnson.

 

Summary
There were lots of things to quibble about with the ergonomics of the CT6, but I'm just not a remote control kind of guy, so your response may differ. It also doesn't have a phonostage, but I knew that going in. If I survive long enough, perhaps I will come to appreciate the convenience of a remote and become too feeble to lower a tonearm. But putting quibbles aside, what I can appreciate is the audible performance of the CT6. With its outstanding focus, temporal accuracy, sense of space, transparency and musical neutrality, there is little to keep me from giving it my highest recommendation except the fact it has two bigger brothers. Add the reputation for build quality, reliability and the track record for customer support and you have little justification for holding back. If you still need a reason to finally jump into tube gear, this is it. If you've got the courage to screw in a light bulb, you can handle changing the affordable 6922 tubes every few years.

On my bicycle ride this evening it occurred to me that the CT6 is a lot like a NASCAR racer. It's in the Big League. You have to push a few buttons and have some patience until it gets up to speed, but once there, the music flies high on the banks. But unlike the racer, which works primarily on Sundays, your music will fly any day of the week — anywhere the music takes you. Enjoy it.

 

Specifications
Type: Tubed stereo preamplifier

Tube Complement: four 6922

Frequency Response: 2Hz to 100 kHz

Maximum Output: 15 Volts rms

Gain: 26dB

Output Impedance: 850 Ohms

Distortion: 1.0V Output less than 0.25 THD

Hum and Noise: 100dB below 2.5 Volts

Phase: phase inverting

Dimensions: 15.5 x 19 x 3.315 (DxWxH in inches)

Total Weight: 19 lbs.

Warranty: three year limited warranty covering labor and parts

Price: $4,500

Warranty: 3 years parts and labor

 

Company Information
conrad-johnson design, inc. 
2733 Merrilee Drive 
Fairfax, VA 22031

Voice: (703) 698-8581 
Fax: (703) 560-5360
E-mail: service@conradjohnson.com
Website: www.conradjohnson.com 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

     
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