Ayre Acoustics V-3 power amplifier Page 2

"No one uses choke input filters anymore because they're just too expensive. But they have two big advantages—the first is that you get better AC filtration. The second is that an inductive choke resists changes in current—just as a capacitor resists changes in voltage—so it slowly releases current as its magnetic field collapses. This avoids that 120Hz spike of current going into the cap. Presumably, in a typical design, the capacitor filters this out. However, it's generating HF harmonics all through the audio band before it even gets to the cap, so garbage is radiated through the wiring and couples magnetically to circuits...you've got your own internal source of line noise—that's not a good thing.

"You need to learn how to size the choke correctly, but that's all been done—60 or 70 years ago, in fact. Engineering schools don't teach you about chokes anymore. My dad's college texts had all the formulae about how to apply chokes to a power supply—that's where I got that information. When you do it correctly, there's a continuous charge of current to the capacitor. It's not a battery—that'd be the only way to get constant current—but the charging current to the capacitor never drops below a certain point; you don't have that on-and-off charging current."

Hansen also emphasizes the advantages of fully differential balancing. The newly introduced Ayre preamp, the K-1, joins a mere handful of truly balanced preamplifiers (we'll go further into those advantages when we review the K-1). But Hansen feels there's an unexamined benefit from designing a power amp with common-mode rejection.

"One of the main advantages, one that never gets spoken about, is that power-supply perturbations—ripple, hum, hash, sag, all of that—are treated in the same way that common-mode rejection works on the signal. Fully balanced circuitry draws from the power-supply differentially, so it rejects common-mode noise. Now you're talking about something pretty darn special. If you've got circuitry that has 60dB of common-mode rejection on the power supply, then you're looking at a thousand-to-one reduction in sensitivity to what's going on in the power supply. Sixty decibels in terms of voltage is 1000:1! That's not an esoteric fact—it's indisputable.

"Here's a real-world example of how this affects sound: How many times have you heard someone describe a low-wattage tube amp by saying, 'But those are tube watts—that's like double the power of a solid-state amp rated the same.'? There's something to that—the output stage of a normal push-pull tube amplifier is balanced; it rejects the sag and all that stuff. Anything in common going into the center tap of the output transformer gets rejected.

"Well, think about the bi-filar winding of a transformer. You can get them wound to within 0.01%—that's your 1000:1 ratio again! That output stage will reject a 10% drop in voltage, or at least attenuate its effects by a thousand to one. So when you look at the performance of the power supply, there's an indisputable benefit from balanced technology. But—and this is a BIG but—you must have a fully balanced system from input to output. Not many people design that way."

Highest-quality parts
In the Krell KRC-HR and KPS-20i/l I had both a preamplifier and a CD player that were designed that way. I used them for this review, along with balanced runs of XLO Type 3.1 Signature and a bi-wire set of Straight Wire Gold. My analog front-end consisted of my Linn LP12/Armageddon/Naim ARO/Sumiko Transfiguration Temper/Naim Prefix/SuperCap rig. I used a full complement of Versalabs Red Rollers, Flat Rollers, Ground Blocks, and Wood Blocks, but not my usual supply of Shakti Stones—they made no audible difference on the V-3. I've heard the V-3 drive the Aerial 10T speakers at several shows, always to good effect, so I used them for the audition.

Watts my line?
From the get-go, I was impressed by the silence, dynamic ability, and natural sweetness of the Ayre, but initially I found it a tad soft on detail, especially transient attacks. This puzzled me because I had heard the amp at shows—under conditions far more onerous than those in my new listening room—and had heard a marvelous variety of textures and attacks. I rerouted wires, even though differentially balanced cables should be far less vulnerable to environmental influences. As I carefully ran an interconnect around an MIT Z-Stabilizer, a lightbulb went off over my head. The Ayre wasn't plugged into the Z-Stabilizer, but it was plugged into the same outlet as the MIT transformer. I wondered, Was the transformer loading down the circuit? I unplugged it and, sure enough, transient snap increased and detail was more tightly focused. I had a Z-Iso Strip and a Z-Isolator HC upstream on the Krell front-end, so I took them out of the circuit as well. Once again, I had gains in clarity and focus.

COMPANY INFO
Ayre Acoustics
2300-B Central Avenue
Boulder, CO 80301
(303) 442-7300
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