Toronto Audiofest 2019

The first thing I did at the Toronto Audiofest—after eating breakfast and attending some business meetings—was visit the Zesto Audio room, where I was hosted by Zesto Audio President and designer George Counnas. I was eager to hear the just-announced Leto Ultra vacuum tube preamplifier ($9995 US), which features—wait for it—tone controls.

For a while, tone controls had a bad rep in the hi-fi world. We were supposed to prefer minimalist, purist designs—and there is something to be said for simple. But, let's face it: I miss tone controls. I think a lot of people do. They're useful. The prospect of a new high-end tube amp that features them has much appeal. Hence my visit.

But let's be clear: These are not your father's tone controls—or your son's, either. Zesto calls it a "presence" control. There is no "bass boost"—indeed, there's no boost at all, at any frequency. What you can do is attenuate the high frequencies gradually, to a variable extent, starting from lower and lower frequencies as you turn the six-position control further counterclockwise.

When the "presence" knob is all the way clockwise, this filter is completely out of the circuit. Turn it up one notch, though—you can do it with a remote control, and the second is remembered from input to input—and the –3dB point is (IIRC) at about 10kHz. At that setting, the effect of the presence control is quite subtle. Turn it up all the way, for a –3dB point around 1kHz, and the effect isn't subtle anymore.

Such a tool would be most usefully deployed on problematic—overly bright—recordings. However, an LP of Ray Brown's Soular Energy, playing on a Transrotor Apollon TMD turntable with a Tri-Planar MK VII U2 9.8 tonearm bearing a Benz Micro Gullwing SLR cartridge, its low-ish output voltage fed into a Zesto Allasso step-up transformer and a Zesto Andros Deluxe tubed phono stage, there was no problem—the sound was good. But if you know this album, you know that Brown occasionally hits a high note hard, to startling effect, and on those notes there's a little bit of distortion. Turning the Leto's "presence control" up a couple of clicks tamed those high notes while having very little effect on the sound otherwise. The effect was similar on Mark Knoffler's guitar solo at the beginning of the live version of Dire Straits' Communiqué, from the album Alchemy.

In certain moods I'd prefer to listen to recordings like these with the presence control out of the system. But—to echo something George Counnas said in our conversation—if I was just relaxing, maybe with a drink, a click or two on the presence control might be just the thing. And there are, of course, albums—and especially early CDs—that need something to have their high ends tamed.

It would be wrong of me to imply that the presence control is all there is to say about the Leto Ultra preamplifier. It is a totally new design, with a whole new circuit. The Leto uses 12DW7 tubes—aka ECC832—in which one half is AX-7 and the other half is AU-7. Headroom was increased at the input and the output, and a new grounding scheme was employed.

Also in the system: Opera Callas Vida loudspeakers in walnut ($11,500 CAD/pair); Zesto Eros 300 class-A monoblocks ($27,000 CAD/pair), HRX racks and isolation bases, and all-Cardas cabling.