YBA 2 preamplifier
Finding a truly great, full-function preamplifier is a quest at which I have had only limited success. For a long time, I used an Audio Research SP-10 that I purchased back in the summer of 1984, but gave up on that fabulous device because, while its phono stage was (is) one of the greatest, it was too colored for CD use, and tube-replacement costs became unrealistic. The SP-10 gave way to a passive Mod Squad Line Drive Deluxe, which I enjoyed immensely, but which in turn was replaced by the inexpensive Melos SHA-1 headphone amplifier.
The Melos offers powerful bass reproduction, a wide, deep soundstage, and a very musically satisfying sound, at the expense of some upper-midrange forwardness and a lack of top-octave air; but its basic design means plugging and unplugging leads every time I want to tape a CD or make a DAT dub from an open-reel original. It also has much more gain than I need, meaning that its volume control has to be set at 10 o'clock or lower, where its inter-channel tracking is less good.
Such practical frustration led to me to write, a year or so back (footnote 2), that "The preamplifier is the heart of any system: every source signal passes through it, it has to provide all the source switching flexibility, control of signal level, and the ability to drive an arbitrary length of perhaps severely reactive interconnect cable. Yet compare any preamplifier (set to unity gain) with a length of wire and you will find that it has its own sonic character which interferes with the music to a greater or lesser extent." I further developed my theme: "It seems there is an inverse relationship with the number of functions a preamplifier performs and the accuracy with which it passes on the music unscathed...My wish is simple: Give me a full-function preamplifier that affects the music as little as a piece of wire. Oh, and design it to have a sensible amount of gain."
The YBA preamplifier, from Yves-Bernard André, a designer with a reputation for obsessive attention to detail, with its almost full set of switching functions and limited gain, appears to meet this wish.
The French YBA 2 is an attractive slim-line preamplifier, its blue-anodized aluminum front panel and chassis cover similar to those of the impressive YBA 2 HC amplifier that I reviewed in January (footnote 3). Though there is no mono switch, there are twin volume controls, obviating the need for a balance control. Though I generally don't like this, the control detents allow for easy channel balance. There is no source selector switch; instead, a separate front-panel toggle switch (each with four sets of contacts in parallel) is provided for each input: Tape, Aux, Video, CD, Tuner, and Phono. It might appear from this that more than one input could be selected at once. However, if more than one input is selected, the one nearer the top of the list above is given priority, the other muted. Nevertheless, YBA recommends not selecting more than one input at a time. A seventh toggle switch is labeled "Bypass": switching this both selects the phono input—no matter what input, if any, is actually selected—and minimizes the number of components in the signal path.
The YBA 2's phono stage is configured for MM cartridges. For use with low-output MC models, YBA supplies an optional transformer that plugs straight into the rear panel's phono RCA jacks. A small foot is screw-adjustable, to make sure that it takes most of the weight of the sand-filled module rather than the RCAs. (The input RCA jacks are on this unit's sides, which makes cable dressing a bit of a daunting task when you have mega-RCA connectors, like the WBTs or MITs, plugged into the adjacent CD inputs.) The large C-core power transformer is also housed in a separate module. This supplies 55V AC to the preamplifier chassis via an umbilical terminated in a three-pin XLR plug.
Looking under the YBA 2's hood, almost the entire available area is occupied by a printed circuit board with a ground plane on its upper side. At the center front of the chassis is a large encapsulated module for the line stage, with two physically large 4700µF, 63V reservoir capacitors on either side. There are, in fact, 16 such capacitors overall; with this much power-supply capacitance, the preamp remains powered for a good few minutes after the power supply is turned off.
Footnote 1: "The Final Word," April 1988, Vol.11 No.4, p.210.
Footnote 2: "As We See It," February 1993, Vol.16 No.2, p.5.
Footnote 3: Vol.17 No.1, p.113.