Tube Preamp Reviews

• Replacing Tubes: While no other reviewer has mentioned this, I feel I must. Replacing tubes in the 7A is a big pain in the butt. The biggest problem is replacing any of the tubes in the right channel. Of the 7A's three chassis, both power supplies are in one box, the left- and right-channel circuitry in the remaining two. However, the left-channel box is fastened to and above the right-channel box. While getting at the innards of the power supply or left-channel circuitry is no big deal, access to the right-channel sockets is difficult enough that I advise having your dealer replace the tubes.

Sound: 7 vs 7A
The reviews of the 7 mentioned above presented a fascinating picture of the original Premier 7's sonic performance, areas of general agreement alternating with conflicting opinions. All of the earlier reviews praised the Premier 7 for its superlative soundstaging, ability to recreate spaciousness, and outstanding dynamics. My first concern was whether the 7A had done anything to impair these stellar attributes of the original 7.

Soundstaging: Prior reviews consistently praised the 7's soundstaging, especially its recreation of layers of depth. The 7A has lost none of this wonderful soundstaging ability. Listening to the superlative Athena reissue of Rachmaninoff's Symphonic Dances (ALSW 10001), the Dallas Symphony Orchestra occupied a wide, deep soundstage located around and behind my speakers. Clear delineations of different physical spaces were made for each orchestral section. There was no wander or vague positioning.

Results through only the line stage were identical, the must-have Chesky Test CD (JD37) verifying the 7A's soundstaging excellence. There was Bob Enders in the center, then halfway between the center and right channels; then coming out of the right speaker, etc. Yes, there were Bob and David Chesky just behind the speakers at center stage; then slightly further back, then still further back, etc. Soundstaging width and depth were excellent through either the line or phono stages; nothing whatever was lost in the revision.

Spaciousness: The second area in which the original reviewers agreed concerned the preamp's ability to recreate air, space, and ambience—those ever-so-critical cues of real musicians performing in real spaces. The combination of the Athena recording and the 7A was once again a marvelous illustration of this particular strength. There was a sense of actually being transported to the McFarlin Auditorium of Southern Methodist University, with a sense of space around the performers as well as a sense of the hall itself. The mixture of direct and reflected sounds, coupled with the decaying reverberations from the hall, transported me from my own listening room to the SMU campus.

Returning to the line stage with the Chesky CD, the sense of air and spaciousness on the test tracks was equally realistic. It became crystal-clear when sound segments were turned on or off. When a sound was naturally recorded in a real space, you could hear that space. On the "Viola Fora De Moda" track, all of the 7A's soundstaging, spaciousness, and dynamics capabilities came together to convey the performance's realism. The recreation of spatial information remained outstanding through the 7A's phono and line stages.

Dynamics: A third area of reviewer consistency related to the original 7's dynamic performance: in short, splendid. The 7A has lost none of this superb dynamic capability. Once again, the Rachmaninoff recording provided a wonderful illustration due to the recording's remarkable dynamics. The 7A was equally adroit at recreating the softest through the loudest passages. The most subtle volume shifts became audible and captivating. David Chesky's tambourine quickly answered any questions concerning dynamics through the line stage. The sound was very fast, very clean, and wonderfully dynamic. Whatever else may have been done to the 7A, nothing has been done to harm the original 7's marvelous strengths. Soundstaging, air/spaciousness, and dynamics were absolutely stunning. In these areas, Conrad-Johnson has indeed achieved their stated objective of assaulting the state of the art.

Prior Review Inconsistencies
Bass: Where the original reviewers disagreed on the 7's performance was in the area of tonal character. Starting at the bottom: HP felt the 7's lows were fabulous, with excellent power and articulation; JGH, however, thought there was a slight thinning out below 50Hz; and JA found a "tad too much bass energy." JA's measurements of the 7, however, showed it to be remarkably flat. The 7A does use polystyrene coupling capacitors (4µF). If the amplifier used has a low input impedance, there could be some softening of the deep bass as well as a slight phase shift. Given this interactive effect and the measured accuracy, it's likely that the bass anomalies heard by the different reviewers were attributable to the interaction between the preamp and different power amplifiers.

In my own listening tests, I found the bass performance first-rate. Deep bass was extended and powerful, midbass rich and dynamic, and upper bass was consistently clean and detailed. I formed these opinions listening to music, but tested them using a series of test tones from The Ultimate Test CD (Woodford Music, WM CD 1112). With my beloved ProAc Response Three speakers and my problematic-in-the-bass listening room, I had very strong and flat response down to 60Hz. I estimated the speaker's usable response to be down about 3dB at 40Hz. At 30Hz, the response was audible but significantly lower in level. More interesting, the 20Hz tone was audible, if just barely. Such results imply a tube-like attenuated bass. Fortunately, I also had the Kinergetics SW-800 Subwoofer System on hand (reviewed in Vol.15 No.3). With these monsters, the Premier 7A had absolutely no problem whatsoever in reproducing the 20Hz note as loudly as the 60Hz one. If you don't hear the deepest bass with the 7A in your system, there's something wrong in your system or listening room.

While bass performance with the 7A was indeed deep and powerful, it still exhibited vestiges of the character first identified by JA. While I'm sure that Tom Norton's measurements will show a flat response, there is a very minor trace of tube-like bloom in the mid- and deep-bass regions. A good illustration of this effect can be heard on the gone but not forgotten Toto IV (Columbia PC 37728). The bass was just a smidgen richer, rounder, and fatter than the rest of the frequency spectrum, where every other sound was pristinely clean and super-quick. This is not to say that the 7A has tube-like bass—it has a remarkably impressive bass that gives virtually no indication of tubes at all—it's just that the character of the bass is very slightly different from the rest of the frequency spectrum.

Midrange: JGH felt the 7 to be "essentially perfect" in the midrange; HP described the performance as having a "tan" coloration; SB felt the lower mids were warm, with a lack of midrange detail and an overall smoothing-out of sounds; and JA described the midrange as clean and detailed.

I had no problems tackling this mini-controversy, as my system is particularly adept at recreating midrange information. What I found was that what most of these reviewers described—with the exception of Stereophile's own JA—simply does not apply to the 7A. The 7A is, as John described, exceptionally clean and detailed through the midrange. In fact, it is in this region that the 7A deviates significantly from the traditionally warm "C-J sound."