Conrad-Johnson MV60 power amplifier Sam Tellig May 2003
I reviewed the Conrad-Johnson MV60 almost a year and a half ago, in the January 2002 Stereophile (Vol.25 No.1). This stereo power amp came with EL34 output tubes, as had its predecessor, the MV55. But the MV60 also replaced C-J's Premier Eleven. In fact, it uses the same power supply and output transformers as the Eleven. There are circuit similarities, though the Eleven used more powerful 6550 output tubes.
Tube buffs know both types well. The EL34 is known for its midrange magic. As Lew Johnson, of Conrad-Johnson, puts it, the EL34 is "seductively sweet." (I've used words such as "palpable" and "dimensional.") The EL34 is a real workhorse, too—the best examples are robust and reliable. The tube is available, currently in production, and economical.
The 6550 is known as a less "romantic" tube—less dark than the EL34, more sharply focused, more resolving, but perhaps a tad less dimensional.
Of course, much depends on the particular make of EL34 or 6550 tube; and even more, perhaps, depends on the particular amplifier design. I've heard EL34s sound like 6550s, and vice versa. But, in general, the two tube types seem to have distinct characters.
As I said, Conrad-Johnson chose the EL34 for the MV60—partly for reasons of economy, partly because the US-made GE6550, long favored by C-J, was no longer available in significant quantities. C-J continues to use the Sovtek EL34 in the standard MV60, which continues to be available for $2795.
But in the MV60 I wasn't so sure about the choice of the EL34 tube type. I had nothing against the Sovtek EL34, which sounded splendid in the old Conrad-Johnson MV55 and in my son's vintage Marantz 8B, the very amplifier that I lusted after while in college but couldn't afford. Even with EL34 tubes installed, the MV60 seemed to exhibit more of a "6550" sound—more brightly lit, more resolving, more dynamic and authoritative than the MV55. The MV60 was less warm and fuzzy, more detailed and sharply focused.
Now, Conrad-Johnson offers people a choice: the same amplifier with different output tubes. The MV60 with Sovtek EL34s for those who prefer this tube, and the MV60SE (for "Special Edition") with Svetlana 6550Cs from my wife's native city of St. Petersburg. The MV60SE retails for $2995.
"I'm a big fan of the Svetlana 6550C," Lew Johnson told me. "I feel it provides most if not all of the positive attributes of the EL34 in the midrange, and most if not all of the traditional attributes of the 6550 in terms of added weight, extended highs, and greater dynamics. The midrange is where the EL34 may have had an advantage in the past. But the 6550C has that kind of full-bodied midrange that I'm looking for while retaining the virtues of the 6550."
Customers who bought an MV60 can have their amp turned into an MV60SE for the cost of the new tubes, a labor charge, and shipping both ways.
"These models are exactly the same, except for the change in output tubes," Lew emphasized.
"Why can't I simply switch output tubes?"
"The 6550C wants to see a higher idle current than the EL34, so the amplifier has to be set for a higher bias voltage. But everything else about the amplifiers is the same—same transformers, same parts. Nothing changes but the output tubes and the bias voltage setting."
The rated power goes up...slightly, on paper. While the regular MV60 is specced to deliver 55Wpc into 4 ohms, the MV60SE is rated at 60Wpc into 4 ohms. "The figure for the MV60SE is very conservative," Lew told me. My listening bore this out. The MV60SE sounded much more powerful than 60Wpc.
As standard, both versions are supplied with the speaker terminals wired into the 4 ohm transformer taps. According to Lew, many nominal "8 ohm" speakers actually dip to 4 ohms or below. However, the amplifier can be wired into the 8 or 16 ohm taps, by the dealer or at the factory.
The MV60 is unusually flexible. Not only can you turn an MV60 into an MV60SE, but you can order either as a mono amp—or have it made into a mono amp with about double the power.
Tor Sivertsen, of Conrad-Johnson, lives nearby. He brought over a Premier 16LS Series 2 line-stage preamp. "You're going to love this," he chortled, with his Norwegian lilt and Scandinavian cheer. "I want you to have the best possible sound."
I used my reference Quad ESL-988 electrostatic speakers. My main digital source was a Musical Fidelity NuVista 3D CD player. For analog, I turned to my Ortofon Kontrapunkt B cartridge in an SME 309 tonearm on my AR ES-1 turntable. Phono stage was an AcousTech PH-1P.
Too bad I no longer had a standard MV60 for side-by-side comparisons; but I remember the amplifier well, having lived with it, on and off, for almost six months.
While the EL34 tube certainly does have its midrange magic, the 6550C seemed better suited for the MV60. Perhaps it's the output transformers, with their wider bandwidth than the transformers used on the old MV55. Maybe it's the bigger power-supply transformer. For whatever reason, the 6550C seemed more at home in the MV60—or MV60SE—than the EL34. Only the output tube has changed, remember; but what I heard was a significant, not a marginal, improvement in sound quality. What a difference a tube made!
The SE version gave me better dynamic contrast. Louder passages sounded louder—so-called "macrodynamics"—while subtle shadings were more apparent—so-called "microdynamics." I noted greater bass extension and authority. I heard a wider, deeper soundstage—a more generous spatial presentation. The amp just sounded bigger. I especially appreciated this while playing Klaus Tennstedt's performance of Mahler's Symphony 1 (EMI 5 74182 5, with Symphony 2). I twice heard Tennstedt conduct this work in concert; with the MV60SE, those experiences were almost re-created. The bass extension and authority were especially impressive for what is, after all, a modestly powered tube amp. The MV60SE sounded like 100W or more. The MV60, as I recall, sounded more like its rated 55Wpc.
I felt that the SE version sounded more open and extended in the highs, without excessive brightness or tube glare. I heard increased low-level resolution compared to the regular version. The sound of the MV60SE seemed more delicate, refined, and, above all, assured. In addition, I heard at least as much "midrange magic" with the MV60SE as I had with the MV60.
As far as I can tell, the MV60SE's only disadvantage is the higher price and the higher cost of re-tubing the amp. A set of replacement 6550Cs costs about twice as much as a set of EL34s.
With only a few days left before deadline, I took the MV60SE downstairs to our living room and used it to drive the Triangle Magellan speakers using Musical Fidelity's A3.2CR preamp and the NuVista 3D CD player from my listening room. The harmonic presentation was superb—convincing and immediate—as was the low-level resolution. Bass extension and definition were very good for a modestly priced stereo tube amp. But the Plinius SA-102 solid-state amplifier clearly surpassed the MV60SE in this regard, as did Conrad-Johnson's own solid-state MF2250A, as I expected.
I appreciated the sweetness of the sound, especially with Corelli's Violin Sonatas Op.5, performed by violinist Andrew Manze and harpsichordist Richard Egarr (Harmonia Mundi HMU 907298.99). Do tubes do something for truth of timbre or what?
For those with deep pockets, Conrad-Johnson will soon introduce a new "statement" product: the Premier 14 monoblock amplifier. Yes, it will use Svetlana 6330C tubes. There's something to be said for a big, powerful mono tube amp—the sweep, the drama, the dimensionality. But you might get close with a pair of mono MV60Ses.
The sound quality of the MV60SE was such that you might consider Conrad-Johnson's Premier 17LS line-stage preamp ($4495), or even their 16LS Series 2 line stage ($8295). The MV60SE seemed limited only by its modest power.—Sam Tellig