McIntosh C2200 preamplifier Page 3
Surprise, surprise—the C2200 was so quiet I thought I was listening to my Purest Sound Systems 500 dual-mono passive unit. I heard no noise at all through the line-level inputs, even with the volume cranked way up. (Of course, I heard some noise when I selected the phono input, but not much.)
Larry explained the C2200's silence: It's the microprocessor-controlled post-attenuator stage. He believes that the C2200 is the only tube preamp that has one.
"Under normal listening levels, the C2200 is essentially a straight wire. The post-attenuator is working full blast and you're listening at 12dB down from unity gain. If you need more gain to blast the house apart, then turn up the volume and the post-attenuator starts being gradually removed. This allows us to get high volume out of the preamplifier, if you need it, but low noise under normal listening conditions. By reducing gain, the post-attenuator reduces noise. That's what makes the C2200 so quiet."
"You're an old-timer, Sam..."
"Well, you're probably old enough to remember preamps that had output attenuators. There were individual volume controls for left and right channels and then a master volume control. The master control set the overall gain of the preamp, and it was used to add gain only if necessary. In the C2200, a microprocessor does this automatically and you don't have to think about it. As you turn down the volume control, the microprocessor reduces gain."
The digital display reads from 0 to 100, but there are actually 214 volume-control steps. "You can set the volume in half-dB steps." From your easy chair, of course. If you turn the volume up or down very slightly, it might not show on the display.
"A lot of thought went into the volume control," said Roger. "We used to have a certain taper that we used for our mechanical volume controls. As we introduced electronic volume controls, we made the action linear through a long range. But there wasn't much action at the lower end. Linear all the way through wasn't really desirable, so we changed the way it works. That's the beauty of software: we build in the taper, or curve. The C2200 basically duplicates the old mechanical volume control."
"That's right," added Larry. "The volume-control curve was developed over the years to come on very quickly. What we did was replicate the mechanical action with software so that the same rotation gives you the same result. For instance, if you go to the three o'clock position on the C2200's front panel, the volume will be as loud as it would with a mechanical control."
"The advantage of the software is we are able to maintain the half-dB resolution," Roger pointed out. "This would be impossible with a mechanical control."
As I said, the C2200 sounded quiet—almost as if it weren't there. Compared to my Purest 500 passive preamp, the C2200 imparted more oomph, more body to the sound. Yet at no time did the Mac seem to color the sound—to roll off the highs, for instance, or fatten the bass. It did not add extra warmth. The C2200 seemed neutral without being clinical. Another thing: the C2200 did not impart any tube glare, a problem with some tube preamps I've heard over the years. It did not overly brighten the sound.
I went back to the Purest 500, using the Rega Jupiter CD player into the Musical Fidelity A324 DAC. I felt that the C2200 enhanced the presentation, giving the sound more body, as I said, and taking off some of the otherwise transistory edge. In a well-designed preamp, tubes tend to be harmonically restorative.
Roger had said that I could get my tube sound from the C2200 and bang for my buck from solid-state. That's true to some extent, and maybe more so with McIntosh gear than with other brands. Mac solid-state power amps, after all, have transformer-coupled output stages: they're built like tube amps.
There was certainly no penalty in terms of noise.
"Our goal was to make a tube preamp and have it be as good as solid-state," Roger told me. What's actually happened, I think, is that McIntosh has made a tube preamp that exceeds what, for $4500, would have been possible in a solid-state design. But I couldn't get Roger or Larry to admit that.
"In the past," said Roger, "there have been problems with a tube preamp hooked up to a transistor power amp. You had to turn on your preamp, wait for it to warm up, and then turn on your transistor amplifier. Your amplifier was ready to go before your preamp was."