Berning TF-10 preamplifier Page 2
As usual, it is necessary to add that many listeners aren't going to like this. Apart from those audiophiles who don't know what live music sounds like anyway, many will find that the TF-10 doesn't do as good a job of complementing other aberrations in their systems as well as does the Blotzblotz Mk-XVII-k preamp. But audiophiles who are seeking the most accurate components they can get—and particularly those who admire the quickness of transistors but prefer the musicality of tubes—will find the TF-10 to be the answer to their prayers. Like the Infinity HCA, this seems to represent the best of all possible worlds.
The Berning's stiffest competition is of course the similarly priced Audio Research SP-6A—generally acknowledged thus far to be the best preamplifier money can buy. We borrowed an SP-6A from a subscriber for a brief time, and can report that the difference, while not dramatic, was unmistakable. The ARC was quite a bit brighter, a little warmer in the lower-middle range, not quite as tight at the bottom, and not quite as open at the extreme top. It had somewhat more high-end texture (very subtly rough by comparison) than did the Berning, and tended to reproduce surface noise a little more conspicuously. In short, we would say that, whereas the SP-6 had all of the attributes of the very best tubed components, the Berning seemed to have all the attributes of the best tubed and solid-state components with none of the shortcomings of either.
Can the TF-10 be improved upon? Well, it could have lower phono-preamp noise. Our sample measured 58dB of S/N relative to 5 millivolts input—enough to be audible at high volume-control settings when no disc was playing. Perhaps another design will better the TF-10 in detail or inner definition, but there is so little room for improvement there that we can't conceive of this being "obsoleted" within the foreseeable future.
What about tube life, though? How long will a TF-10 continue to deliver this level of performance? Tubes, after all, are known to have a finite life, and can be expected to deliver progressively impaired performance for many months prior to their outright failure. They also continue to become harder to get and higher in price, making routine periodic replacement an increasing problem. The TF-10's designer, David Berning, expressed his conviction that all tubes in the TF-10 should be "good for at "least 20,000 hours." These are industrial-quality tubes, rated at 10,000 hours under normal-use conditions.
And they are not being operated "normally." Heater voltage in the TF-10 is lower than the rated 12 volts (virtually guaranteeing double the heater life), and normal operating currents are far below the manufacturer's rated values. The tubes don't even get hot; just warm to the touch. In fact, after four hours of operation on a hot day, there is less heat coming from the vents at the top of the unit than comes from most transistor-only preamplifiers (and far less than from class-A transistor designs). We have no way of verifying Berning's optimistic estimate of tube life, except to say that the tubes in the 1710 appear to be "coasting," which has always contributed to extended tube life. Even assuming that the tubes only meet the manufacturer's minimum-life expectancy, 10,000 hours works out to over 13 years of life, assuming 2 hours of use per day. That's longer than most transistors can be expected to last. And of that 13 years, at least eight years represent the peak-performance life of the tubes. That kind of overkill should be reassurance enough to anyone considering the purchase of a device using "old-fashioned tubes."
The vacuum-tube, incidentally, does not seem destined for imminent demise. The old, familiar 12AX7 may well be on its way out, but industrial-grade tubes with lower noise and distortion are in widespread use throughout the world in military electronic devices which would cost far more to replace than to keep retubing. As long as that situation continues, those tubes will continue to be readily available to manufacturers, if not to your local RadioShack. (The Soviets, for example, have used more powerful rocket engines than we had, and thus never had the need to miniaturize as much of their onboard electronics for reduced weight.)
This, then, has to be considered the state of the art preamplifier as of now. Now, how about a cheaper version of it that most audiophiles can afford?