Conrad-Johnson MV60 power amplifier Page 2
The MV60 follows in the tradition of the MV75, MV50, and the MV55, which I reviewed in the October 1996 issue (Vol.19 No.10). Like those earlier amps, the MV60 has a single pair of EL34 output tubes per channel to deliver around 50Wpc.
The MV60 replaces both the MV55 and the Premier Eleven A power amps, and is now the only stereo tube power amp that Conrad-Johnson makes. The MV55 sold for $1995 throughout its production run, while the Premier Eleven A was last seen going for $3695. Split the difference and you're within 50 bucks of $2795—the MV60's retail price. I put the question to Tor over a plate of hanging beef.
"So what is the MV60—a MV55 goosed in price...or a Premier Eleven A for nearly $1000 less?"
He told me that you lose little, if any, transparency with the MV60 compared to the Premier Eleven A, and only a little power. The Premier Eleven A delivered 70Wpc from a pair of 6550 output tubes, while the MV55 offered a rated 45Wpc. The MV60 is rated at 55Wpc into 4 ohms, which is about the most juice that can be squeezed from a pair of EL34s.
Four ohms? Bill Conrad told me that most nominal 8 ohm speakers dip to 4 or 5 ohms, and that a transformer tap at 4 ohms will suit most speakers—which is why the MV60 is normally shipped from the factory set to deliver maximum power into a 4 ohm load. The amplifier can be wired—by Conrad-Johnson or your dealer—for 8 or even 2 ohms.
Another thing: Like the MV55, the MV60 can be wired in triode for possibly sweeter, softer sound, but less power. In triode, the MV60 is rated to deliver 25Wpc into your choice of 2, 4, or 8 ohms. This involves some soldering, which a dealer should be able to handle—or a unit can be ordered from the factory already wired in triode. You can't switch from ultralinear to triode on the fly. Being lazy, I didn't try triode.
I remember the MV55—not only because I reviewed it, but because I recommended it to a number of friends. Like the MV50, the MV55 didn't offer the last word in hi-rez, nor did it give the ultimate in kick-butt bass. Its midrange magic and musicality were superb, however. In my review, I talked about the amp's "harmonic richness" and "lushness." I also remarked that the MV55's appearance was somewhat "Spartan."
As Tor said, the MV60 is a step up from the MV55 without being a step down from the Premier Eleven A. Bill Conrad told me the same thing: "We felt we could equal, and in some respects better, the performance of the Premier Eleven A for significantly less money, and we had to do it."
The MV60 feels like a Premier. Weight tells some of the story, as it so often does in hi-fi. (The more a reviewer weighs, the better he writes.) The MV55 tipped the scales at 39 lbs, while the MV60 comes in at 48 lbs. That means the MV55 sold for $51.15/lb while the MV50 goes for $57.05/lb. The MV60 is about five times more expensive than "hanging beef" London broil from Otto, in East Fishkill.
And the MV60 looks like a Premier. In fact, if you pair it (as I did) with the Premier 17LS line stage, the looks of the pair match—even though the line stage costs $4495.
Gone are the cruddy plastic speaker binding posts that I invariably stripped. Gone, too, is the Spartan appearance. The MV60 looks much more elegant, with its faceplate fin rising to cover part of the tube cage at left. Funny thing about that fin, though—without the cage in place, it looks like a fish out of water. Might as well cage the tubes—they'll still get plenty of ventilation.
The MV60 has a total of eight vacuum tubes, though the rectification is solid-state—a good thing nowadays, as good rectifier tubes are hard to find. But remember—solid-state rectification does not put transistors in the signal path.
The incoming signals go to a pair of 12AX7 tubes (one per channel). These do some substantial voltage amplification and are used in parallel sections to lower impedance. (If you say so, Bill.) They're directly coupled to the tubed driver stage (one 6SN7 per channel), which provides additional voltage gain and still lower output impedance. Now, according to Bill Conrad, you have "good signal linearity to drive the output stage."
This driver stage is capacitor-coupled to the output stage (two EL34s per channel), and at this point the bias is set. As with other Conrad-Johnson tube amps, you're provided with a plastic wand with a screw tip at each end. You stick the wand through a slot on top of the tube cage, aim the tip into a well, and engage a screw. You turn the screw clockwise until a red LED lights up, then you turn the screw counterclockwise until the LED just goes out. Voil;ga—your bias is set.