What is the Denon/Exemplar DVD-2900 universal player?
The Denon 2900 is apparently a much sought-after player for modification. At its retail price of approximately $1K, it represents great value but many folks see more potential in it than the folks at Denon have extracted. I can think of at least a handful of well-known specialty shops that offer modifications for it and do so at various levels and stages. Only briefly, I have heard two of these before, one of which has been extensively reviewed by our own Chip Stern. I was not personally taken by what I'd heard: Good but not delicious is how I would describe those versions. Given the hype that preceded them, I would say that I was disappointed. Had John's unit not been specifically recommended by others who own and know what really first-rate digital playback sounds like, the truth is I wouldn't have been interested in Exemplar's version either. Neither the stock player nor the modified forms which I'd heard before would have encouraged me to expect anything more from the Exemplar version. Was I ever in for a surprise.

Just what is the Exemplar version?
Here it is in a nutshell. Tucker upgrades the rectifiers for the analog section and the caps in the power supply to Blackgates. He changes the clock on the main board to a Tent Engineering clock powered by one of his own shunt regulators on the main board. On the analog board, he adds shunt regulation to the digital and analog power supplies for the DSD chips and upgrades more caps to the ubiquitous Blackgates. He then adds a high-voltage power supply to feed the new tube output stage. The new tube stage is an actively loaded, shunt-regulated cathode follower said to provide good low-impedance drive. The output tubes are Amperex 7062s, which increase RedBook output to 3 volts, 50% higher than the industry standard. This makes the player a favorite with audiophiles who prefer passive preamps. I am not among them.

Other than adding holes for ventilation, Tucker makes no changes to the chassis.

And just who is John Tucker? Reclocking, adding Blackgates to the power supply... these are very familiar mods. Tube analog output stages? Less familiar but still not unusual. What's distinctive about the Exemplar is the emphasis on shunt regulation and active loading, two approaches championed by John Tucker not just in the Exemplar universal player but in his products in general. Like many audio designers/manufacturers, Tucker got hooked early in life modifying speakers in his preteens years and moving on to playing with old tube gear by his teens. He was the school sound engineer in high school and received most of his hands-on electronics training in the military. Further developing his expertise during a 15-year stint at the Johnson Space Center, he began designing gear of his own while continuing to modify the work of others. This is where the DIY life began in earnest. Like many DIYers, John had visions of someday taking his ideas to

market in a serious way. After a move to Washington, John fell in with three other figures who were to play an important part in the development of his electronics and speakers: Dennis Boyle of Chimera Labs; John Camille (he of near-legendary status among the DIY crowd); and Jeff Markwart. Jeff and John developed the Exemplar horns, a project that first came on the scene in two issues of the much lamented and lost Sound Practices. The speaker itself was loosely based on the Altec A-5 and went out of production when those drivers were discontinued. The Altec drivers are available once again and so too are the Exemplar horns. I will have a pair in for review sometime in the spring of 2005, yet another 6moons first [below at VSAC 2003 - Ed]!

From 1996 until the latter's death about four years ago, the two Johns -- Tucker and Camille -- worked extensively on shunt regulation and active loading, neither of which were much in use in audio at the time. John left his full-time job in the software industry in 2000 to start Exemplar Audio in earnest. He's since advanced the design and use of shunt regulation and active loading. These two techniques are distinctive of all of his electronics and have caught on with several other designers and the DIY scene for which he offers upgrade boards through Dan Schmalle's Bottlehead Corporation.

A word about shunt regulation and active loading. Both are aimed at tightly controlling the operation of tubes. Active loading aims to control current through the tube while shunt regulation is a form of parallel tube voltage regulation and an alternative to the common series regulation. It is far more costly in general because it doubles the current requirements on the power supply. Properly implemented -- which seems no small feat judging by the number of failed attempts at constant current source preamplifier designs -- active loading and shunt regulation control current and voltage behavior of tubes, allowing them to perform optimally over their entire life.