September 2000

conrad-johnson 17LS Vacuum Tube Stereo Preamplifier
The legend continues...
Review By Steven R. Rochlin

  Any true music loving audiophile worth their salt knows about the great products from conrad-johnson. It all began during the mid-seventies where two economists friends, who were avid music lovers, joined forces. Specifically, Dr. William Conrad and Dr. Lewis Johnson felt that the then available equipment left much to be desired. After much research and development came a commercially produced conrad-johnson preamplifier that immediately brought critical acclaim as makers of great sounding vacuum tube gear.

Fast forward to 1996 where their introduction of the Anniversary Reference Triode (ART) preamplifier garnished more positive ink than any other preamplifier of its time. Garnering a few Product of the Year awards, many of my reviewer buddies were buying it up like kids in a candy store! While the ART preamplifer was not cheap, no one who heard it could deny the magic it brought about in a music reproduction system. The ART's massive dual-mono, two-chassis design was very costly to manufacture and therefore was, sadly, too expensive for low fundage guys like myself to buy. Today, nearly four years later, the musical magicians Dr. William Conrad and Dr. Lewis Johnson have brought what they feel is extremely close performance to the ART yet in a single chassis unit costing considerably lesss. Enter the Premier 17LS preamplifier.

Using the same single-active-stage composite triode tube (four 6922) circuit as in the ART, the musical signal is very pure. The entire amplification circuit is a single active stage using no buffers or feedback. During an e-mail exchange with Dr. Lewis Johnson he brought about more light to the state-of-the-art circuitry and construction of the Premier 17LS:

"There are two reasons that it is important that a preamplifier have a relatively low output impedance:

1. The output impedance of the preamp should be not more than 1/10th of the input impedance of the power amp(s) it is connected to in order to avoid degradation of performance due to overloading the preamp's output stage. (Most amps range in impedance from 20kohms to 100kohms. A few are as low as 10kohms. Below that is irresponsible).

2. The output impedance of the preamp forms a low-pass filter with the capacitance of the interconnect cable (rolling off the high frequencies). The 3dB down point of this filter is inversely proportional to the product of the source resistance of the preamp and the capacitance of the cable. Accordingly, the lower the source resistance of the preamp, the wider range of types and lengths of cable the preamp will work well with.

Even high-conductance triode tubes (such as the 6DJ8 and 6922) would normally have too high an output impedance. The traditional solution is to add a buffer stage (cathode follower) to the circuit. What we have done instead is to construct a composite triode made of several sections of 6922. Each doubling of the number of sections reduces the output impedance by a factor of two. The ART uses 10 sections... the Premier 17LS uses 4. In the case of the 17LS, the resulting output impedance is about 800 ohms.

An important feature of this circuit is that it uses no negative feedback of any kind (there is neither loop feedback, nor local feedback). The result is a temporal accuracy that we think is unique to this approach.

The rest of the circuitry includes three discrete power supply regulators (an input regulator followed by separate regulators for left and right channels), and the switching and control circuits. Note that the power supplies use polypropylene and polystyrene capacitors exclusively (NO electrolytics in the audio circuits or related power supplies).

The control circuit is interesting in its own right. Level control is effected by microprocessor selection of combinations of discrete Vishay resistors via sealed relays. Way better than a traditional potentiometer."

With such great heritage and unique design, the Premier 17LS should be among those great preamplifiers that will set a new standard in their price category. Hmmm... let us find out shall we?

Looking Good
The preamplifier has the same attractive champagne colored front panel as seen on other top-line conrad-johnson products. Installing the tubes inside the top center of the chassis is easy. Simply remove a few screws, place the four 6922 tubes in their sockets and then the cool tube dampeners. One great additional feature of this unit is that it includes unique tube dampening devices. These are small reddish-brown colored silicone rings to help reduce air-borne microphincs from adversely affecting the music reproduction. Two of these rings go around each tube at 1/3 and 2/3 the distance from the top of the tube. As for nasty EMI noise, carefully chosen materials and circuitry layout help to reduce/eliminate such problems. As conrad-johnson is a very mature company, consumers such as myself expect and receive top quality parts, circuitry layout and overall build quality. 

As seen above, the buttons from the left to right are as follows: Power, Source, EPL, Volume Down, Volume Up and Mute. EPL stands for External Processor Loop for those of you with analog equalizers and/or who choose to use external processors. The small lights above the left buttons allow you to see the operational status while the yellow numeric display to the right permits you to easily see the volume level for the right and left channels. The Premier 17LS also comes with an impressively hefty twelve button wireless remote control. Input selection, volume, balance, and muting can be selected via the remote control. It feels good to sit back and adjust the volume. rarely, but some recordings also require small adjustments of the balance and here is a great additional feature the remote also offers. Of course when the phone rings during one of my long listening sessions i can turn down the music, or mute it as necessary.

The Quest
Needless to say, upon received my log-awaited review sample it was within minutes unpacked, owner's manual read, and hooked into my reference system. It has been a while since i listed my system so here we go:

Here in Dreamland we use a custom digital disc transport, 100% silver wired Audio Note DAC 5 Special Edition, VOYD turntable with silver wired arm, Clearaudio Insider Reference Gold cartridge and various Wavelength amplifiers or the 47 Labs/Sakura Systems Gaincard. Loudspeakers were mainly the Avantgarde Acoustic Uno Hornspeakers, though i was also lucky enough to have the new Reference 3A minimonitors during the last week or so. All interconnects were Kimber all silver KS-1030. Loudspeakers cables were the excellent Nirvana S-L Series. While i have dedicated electrical power and grounding, the use of the professional-grade Furman Sound IT-1220 is magical in that it balances the power and seems to lower the noise floor and cancel out electrical noise. Before i forget, the Premier 17LS, like many other cj preamplifier products, inverts the phase of the signal. Therefore my easy solution was to reverse the positive and negative leads to the loudspeakers.

Why invert the phase? It saves the additional circuitry needed for yet another stage to invert the signal for "proper" phase output. Most preamplifiers add more circuitry in the signal's path to insure proper output phase. conrad-johnson (wisely) would rather have less in the signal's path and therefore users can simply invert the phase of their speaker wire as necessary. This easily and properly insures the correct signal phase is produced in their music reproduction system. And how does all this sound...

It has Begun...
I really do not want to spend too much time writing about the breaking in. While the dynamics were fairly impressive and the bass deep, the lowermost frequencies seemed a slight bit disconnected from the upper bass notes. Worse still, the extreme upper frequencies (over 7.5k or so) seemed to be a bit rolled off. It was not muffed sounding, just not seamlessly extended. Well, the unit was literally new, cold and right out of the box. After a week the bass was wonderfully integrated and deep. In fact the lowermost frequencies were among the best defined i have ever heard. Alas, the highs did open up a bit but still did not have that magical ease and extension i just knew was missing. After two weeks of break in the Premier 17LS it finally reached the point where the highs were glorious. Adding yet a third week to break in and the highs, in fact the whole musical spectrum, set into a glorious sound that...

Gather The Flock
After three long weeks (seemed like forever to my eager ears) the preamplifier was really singing. The highs were not just incredibly extended, they seemed to go on and on forever! As the unit is rated with the ability to reproduce frequencies over 100kHz, this should be more than enough for even the "dog eared" audiophile. The ease at which cymbals shimmered to the way bells and xylophones cut through sounded incredibly effortless. There was never any coarse sound or listening fatigue. Components that are harsh, augment the upper midrange/highs or are brash can easily and quickly lead to short listening sessions as ear fatigue and headaches would be the result. Images truly floated in a three-dimensional space.

Speaking of space, the Premier 17LS could throw a soundscape as best one could wish for. Layers and layers of depth were presented as the hall's acoustics seemed to have transformed my listening room into whatever was on the recording. Like the best of them, front right and left staging was beyond the loudspeaker positioning. In my room this seemed to be about two feet to the right of the right loudspeakers and two feet left of the left speakers. Very few components, or systems for that matter, can reproduce such feats. When it does happen it is simply magical!

The midrange, while very impressive from the start, was made whole as after three weeks the entire musical spectrum came into focus. Because of great dynamics (which i cover shortly) coupled with smooth and well resolved tonality, vocalists seem to have such an amazing thereness that it is scary. Scary in that, given the right recording, can sound so real you can close your eyes and feel you could reach out and touch them. Chesky Records compact disc of Laverne Butler No Looking Back (JD91) is a good example. Track seven titled "Isn't It A Pity" is a must-listen for any audiophile who wants to truly hear some of the best, most transparent female vocals on compact disc.

As for male vocals, get some soul in your roll and grab a copy of Mapleshade's Electric Blues Doctor Live! by Drink Small (Mapleshade 01832). In fact Drink Small's legendary guitar work on this compact disc will make you think there is really a guitar head unit/speaker in your room! Vinyl junkies such as myself will quickly grab our direct to disc recordings. The sadly no longer pressed RCA 45rpm vinyl of Beethoven Piano Sonata No.23 in F Minor, Op.57 as performed by Ikuyo Kamiya on the famous Bösendorfer piano (RCA RDCD-4) will truly, and i do mean truly, test your system's overall capabilities. From the lowermost notes of the left hand to the twinkling of the right hand's upper keys. And dynamic attacks? WOW! If your system can not reproduce the truly dynamic attacks of this vinyl record then this disc will tear your system to shreds.

Need i tell you how well the lower notes were reproduced? The conrad-johnson Premier 17LS does not have that overused audiophile phase "slam" per se. To me, slam seems to mean more of a single-note or few notes bass attack. All those irritating 1.21 jigawatt car stereos that thump down the street have slam. Impressive? i think not. The 17LS has incredible dynamic attack capabilities no matter if it is a drummer's cymbal, a sax blast, or bass guitar wallop. Back to the quality of bass notes...

From acoustic bass as on the aforementioned Laverne Butler disk to the piano attacks as played by Ikuyo Kamiya, the preamplifier seemed untrippable. Even when i was in a more, um, rowdy mood when the music by rage band The Prodigy was on my turntable came through clearly. In fact i heard more inner levels of music that ever before with the possible exception of my home-built passive preamp using the DACT attenuator. Because the volume of the Premier 17LS is adjusted by a microprocessor that selects various combinations of discrete Vishay resistors via sealed relays, i can understand why only my fave pure passive could come close to this active preamplifier. WARNING: Using purely passive preamplifiers can be a trying experience as impedances need to be carefully dealt with. Since the Premier 17LS offers great gain and low output impedance there are no problems using it with virtually every system on the planet.

So you must be asking yourself "Is Steve saying the conrad-johnson Premier 17LS preamplifier is perfect?". Alas, nothing is truly perfect, but we really get close here in my humble opinion. The bass might use a tad bit more oomph, but if this would come at a cost of the incredible resolution then i would leave things as they are now. Dynamically, the unit is scary good. Still, i seem to miss some of the teeny tiny ultra-small microdynamics. Very small scale dynamics are reproduced in my system. It is the very last bit that i wish could be squeezed out. The more than three times more expensive conrad-johnson ART preamplifier does this effortlessly, as it should. Of course who knows what may eventually happen while the unit has been here a few months, maybe in a year those very teeny tiny bit of small-scale dynamics will appear as the tubes and other parts age.

As i know many owners of the conrad-johnson ART preamplifier, two of them have some experience with the Premier 17LS. One of them felt that the unit under review here is about 80% or so of the legendary ART while the other feels it is more like 90-95%. Given that the ART retails at $14,995 and the Premier 17LS retails at $4,495 it seems, relatively speaking, you get quite a large amount of the top-shelf sound with a more, eh hem, bargain pricing.

The Triumphant Ending
It appears the great hearts and souls at conrad-johnson have done it again! Outstanding music reproduction that can easily bring musically emotional tears to your eyes or make you dance for joy. Ah, the glories of music! So here i sit thinking to myself "Myself, how the heck am i going to be able to afford this preamplifier?" Hmmm... sell my soul to rock and roll? Nope... did that years ago. Sell off some of my rare vinyl? NO WAY! i guess i will need to get a second, part-time job and work ever harder. The Premier 17LS is well worth it. The only real problem i foresee is finding more time between jobs to... Enjoy the Music.

Specifications
Tubes: four 6922

Tube Life: two to three years with normal use

Gain: 26dB

Inputs: five stereo inputs plus two stereo External Processor Loops (tape loops) all via female RCA jacks

Output: two stereo pair via female RCA jacks

Frequency Response: 2 Hz to more than 100 kHz

Maximum Output: 15 V rms

Hum and Noise: 100 dB below 2.5 V output

Distortion at 1.0V output: less than 0.25% THD or IMD

Phase: inverts phase of all inputs at main output

Output impedance: less than 850 ohms

Wireless Twelve Button Remote Control Included

Dimensions: 15.25D x 19W x 3.75H inches

Net Weight: 21 lbs.

Price: $4495

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

Voice: (703) 698-8581 
Fax: (703) 560-5360

E-mail: custserv@conradjohnson.com
Website: www.conradjohnson.com