VTL IT-85 integrated amplifier Page 2
Luke concurred. "To me, that's the key in biamping. Because most people would say that to 'really' biamp, you need to use a crossover in front of the amps and let the amps see only the frequency that they are going to be amplifying, and not rely on the speaker's crossover to provide the impedance to those frequencies. But to me, the biggest deal of biamping is that you've got an amp that's having to grapple with a bass driver—it's the amount of current that a bass driver is trying to suck out of the amplifier, and modulating its B+ (high-voltage) supply. If your B+ rail sags under full power, then the onset of distortion is much lower, because the amp is effectively limited in the amount of power it's able to deliver.
"It's also limited in the current capabilities of the output stages. Usually what happens when the B+ sags or dips is you hear it in the top end; you hear it in the high frequencies—that's when you hear the distortion the soonest. You're talking frequencies from the bass to the top, where the amp runs out of gas when the bass driver is trying to suck all this current out of the amplifier. But in horizontal biamping, the top amp doesn't feel that; even though it sees the bass frequencies, it's not trying to drive a big bass driver—so the top amp is driving only the tweeter, which isn't very demanding. The system has a whole lot more headroom."
Even without invoking its biamping capabilities, the IT-85 is loaded with features for a standalone integrated. The top part of the chassis houses the amplifier section, and its descending-staircase faceplate echoes VTL's signature design motif. The lower section of the chassis, with its concave front panel, houses the preamp section. From left to right are a manual input selector, a headphone jack (this fine-sounding feature derives its signal from the binding-post output, and a headphone/speaker-selector switch. Then there's the remote-controlled volume knob, a Processor/Amp In switch (for disconnecting the preamp stage should one wish to use the power section alone, as in a home-theater rig), a mute switch, an IR receiver window, the On/Off rocker switch, and a green Status LED.
The back-panel juts out of the chassis at 45 degrees, making access to the speaker terminals much easier for those using heavy-duty speaker cables. And VTL has finally replaced its stupefyingly nonstandard 3/8" binding posts with its own milled-brass, gold-plated 7/16" design—a true five-way that accepts bananas, praise the Lord. Also on the back panel, in addition to the protective fuses, are VTL's own high-quality, gold-plated RCA inputs, clearly labeled.
Double Your Pleasure
Listening to the IT-85 as a standalone unit, I was struck by its midrange sweetness and smooth top-end extension, qualities I would normally ascribe to the Svetlana output tubes. Even more impressive was the gradual onset of gain as I brought up the volume past midnight. Some amps, such as the VAC Avatar, reach their peak volume in a hurry, after which it seems there's no place to go. But the IT-85 had a uniformly tapered character that sounded quite natural and refined to me, unlike the sense of loud, louder, LOUDEST you get from some potentiometers.
VTL's output transformer is optimized for a 5 ohm loudspeaker, whereas most of the amps I've evaluated have taps for 4 and 8 ohms. "We didn't want to tap the output transformer," Luke Manley explains, "because we wanted a more efficient current transfer. We wanted to utilize the whole of the secondary of the output transformer, so it's set at 5 ohms, which covers the majority of speakers."
I mention this because, right out of the box, my first impressions of the IT-85 driving my Joseph RM7si Signatures was that it wasn't putting out quite the power (60Wpc tetrode into 8 ohms) its rating suggests, compared to the VAC Avatar (which also uses EL34s and is rated at 60W Ultralinear). Initially I also found the Avatar's no-feedback design to confer a touch more openness to the midrange compared to the IT-85, perhaps a byproduct of Manley's use of negative feedback to tidy things up. ("Some 6 to 14dB," he allowed vaguely during one of our phone conversations.) However, as I pushed the Avatar up to and beyond its limits, the sound took on an upper-midrange/lower-treble glare that could prove fatiguing. The IT-85, on the other hand, remained dead quiet as I turned up the juice; more tellingly, its tonal balance remained constant and natural regardless of gain-stage level, and the harmonic spectrum didn't change—the depth of dimensionality and dynamics became more immediate.