Solid State Preamp Reviews

Editor: All of us at Ayre wish to thank Wes Phillips for his in-depth review of the Ayre KX-R preamplifier. It was clear from his writings that the KX-R brought him closer to the music than ever before. It was also gratifying to read that he preferred the KX-R to a highly regarded tube preamplifier. Although many people have been suggesting it for years, perhaps the time has come when a solid-state design has finally surpassed vacuum tubes in terms of sheer musicality. This truly represents a breakthrough for high-end audio design. And despite Wes's comment, I think it is safe to assume that much of this new technology will "trickle down" to less expensive Ayre products sometime in the future.

We also wish to thank John Atkinson for his thorough battery of technical measurements. The superb test results of the KX-R prove that it is simply not necessary to use negative feedback to achieve world-class technical performance. We were gratified that he agreed with our choice of gain structure for the preamp, and potential owners can rest assured that the overall gain of the KX-R is easily changed, should the need arise. One resistor per channel sets the overall gain, and it is mounted in a special terminal block so that no soldering is required to change it.

Unfortunately, we have to take our lumps for a firmware bug that surfaced in the test unit. With the sophisticated "fly-by-wire" control system, it is imperative that the controller always keep track of the position of the volume control. We have therefore developed a circuit that instantly detects a loss of AC power to the unit. At the same time, the power supply has enough reserve capacitance to continue operation for many tens of seconds after the loss of AC power. As soon as the AC power loss is detected, the position of the volume control is written to the controller's memory and all is well.

The problem was that this operation was not performed when the preamp was in Setup mode [art the factory]. So at some point, the preamp lost power while it was in Setup mode and the controller lost track of the position of the volume control. It turned out that when the volume was at the actual level of "60", the display read only "59". And when the display read "60" (or "Bypass"), the actual volume level was "1". (The volume control uses rotary switches with no end stops.) This explains the strange results noted in some of JA's measurements. We have corrected the firmware to prevent this problem in the future. Owners of current units can have the firmware updated (at no charge, of course) by their local dealer via the AyreLink port, without even removing the cover.

Finally, Wes called the KX-R "the eighth wonder of the modern world." We would tend to agree, but there is always the magnificent presence of Uma Thurman to contend with. She may just knock the KX-R out of that spot...—Charles Hansen, Ayre Acoustics