Triode Triumph
"My invention relates to devices for amplifying feeble currents." Thus began the patent Lee de Forest left in the United States Patent Office in 1906. de Forest wasn't the first to invent such an amplifying device but he's considered to be the first who inserted three electrodes -- filament, grid and plate (not grid) -- inside a vacuum bottle or vessel as he called it. Hence triode.


Here's an extract from the back of a relevant T-shirt: "In a device for amplifying electrical currents, an evacuated vessel, three electrodes sealed within said vessel, means for heating one of said electrodes, a local receiving circuit including two of said electrodes, and means for passing the current to be amplified between one of the electrodes which is included in the receiving circuit and the third electrode."
Beukenhof's former monastery is situated in Biezenmortel, a 1.5 hour drive from Amsterdam to the south. From November 30th to December 3rd, around 80 enthusiasts from Australia, Austria, Belgium, Denmark, Finland, France, Germany, Greece, Italy, The Netherlands, New Zealand, Norway, Switzerland, the UK and the US
came together in this monastery to worship -- given the premises, not an overstatement -- Lee's invention and to explore the wonderful world of triodes both in theory and practice. The group has gathered six times before, first in Århus/Denmark, then in Langenargen/Germany. But this time was special. It was almost to the day 100 years ago when de Forest's patent had been granted.


And what better way to celebrate that than discuss the benefits of triodes in the peace of the monastery's library? Transformer specialist Manno van der Veen lectured on the operation of output transformers at very low signal levels, on the brink of human audibility. More as sub-plot to his presentation, he argued that triode amps and single-endeds in particular fare better than their PP rivals because less permeability is needed from the trafo. You'll be able to read more on his ideas shortly when his paper on the subject gets published by the Audio Engineering Society.


At some bleak point in history, tube manufactures abandoned power triodes and went for producing more efficient tetrodes and pentodes with extra grids. No need to worry, declared Tom Schlangen. One can coax very good performance from even some highly unlikely pentodes (such as those used in a TV apparatus) by triode strapping them. But what's the ideal way to do it? The operation has to be done in a controlled manner and Tom gave the audience some pros and cons. Tom's lecture is here.


Triode lovers are sensible people and not immune to acknowledging the downsides of their approach. Morgan Jones went through various scenarios on how instability will sneak into a tube amp and what might be the most feasible way to prevent the amp from oscillating in each case. Peter Miller provided a quick demo on how the high output impedance (measured at the terminals) of especially SET amps affects the sound of the system. For the purpose, he'd built a variable output impedance amplifier, a hybrid that allowed him to switch smoothly from a pure voltage source (0.5 ohm) to almost a current source (500 ohms). Unfortunately, the loudspeakers chosen for the demo weren't right for the job. The audience was split as to what to prefer. That doesn't undermine Peter's point one bit. Half a century ago it was a common practice to play with the output impedance (damping factor) in order to tune the bass output by a few decibels.


The keynote speaker of 2006 was Tim de Paravicini, a man in audio who hardly needs any introduction. Using his past designs (Musical Fidelity, Luxman, EAR etc.) as examples, Tim went against several conventions and prejudices of the triode cult. As was well known, he's not a great believer in any typical sound, be it from a tube of any sort or a transistor. All he believes in is execution and he made that perfectly clear. One of his examples was how to get perfect pentode performance from a triode configuration. In the course of his thought-provoking lecture, he covered many other interesting issues as well.


The second day got off the ground by paying tribute to Lee de Forest. First, Peter van Willenswaard from Stereophile shed light on the historical paths that lead to the birth of the triode tube. Then it was time for a short documentary produced by the organizers of the ETF 06, Guide Tent and Emile Sprenger. The film showed how de Forest's Audion tube from 1906 was newly produced in Philip's research laboratory and all phases of the production were carefully explained. The narrator was Guido Tent himself. Once the film was over, the audience had a chance to listen to a linestage built by Manfred Huber, in which these newly born de Forest triodes were put into action. And they worked! de Forest never really intended his tube to be used in an amplifier. As van Willenswaard pointed out, it was Western Electric who foresaw the potential of de Forest's invention after having bought the patent from de Forest. Later in the evening, a pair of de Forest triodes was sold in an auction to a lucky owner, another tradition of the ETF.


Gear
No amount of talk could replace the real world test - listening. As in earlier years, many great imaginatively built tube amps and phono stages were around. Each of them would have a special story to tell in terms of circuitry, tube selection (a fantastic variety of power tubes, e.g.), PSU and what have you. I'm no going into that however. Instead, I'll provide a pictorial overview. I'll start with what must the biggest phono stage my eyes have ever witnessed (the PSU on the left), and end with a tiny stripped non-tube execution that gave nice sound and music with Tentlab's CD player and a pair of two-way Ensembles.

One of the special features of this audio event is that everything that is brought for presentation arrives at the show place in parts - amps, speakers etc. Their assembly in plain view then kicks off the event. Equally many amplifiers are upside down as the other way round. Tool boxes are everywhere and the smell of soldering irons fills the air. Some amps will be ready for duty before the first participants are setting off, some won't.

Being triode lovers, the ETF folks rely on high-sensitivity speakers. This year Marco Henry's famous horns got company from huge bass balls driven by old Haflers. The music was sourced either from a laptop (via an Apple Airport Express modified by dB systems) or a Kenwood turntable for a relaxed and outgoing sound, with well-defined bass and good integration.

Haigner's BETA horns were experimented with on so many amplifiers combinations that I gave up keeping track of them all. Anyway, the sound was huge, transparent, and somewhat critical to where one happened to listen to them. Of other speakers one could pick up on were Ralf Raudonal's baffles whose PHY KM30s were commandeered by triode-connected tetrodes which Siemens once produced for the German Post Office only. Peter Stikking from Berlin had brought a small open-backed speaker with a ring of teeters on the top. They did need a sub. And so on.

Many speaker/amp combinations, including those not mentioned, did a good job of providing music with feeling, especially if the music had a certain quality, as it often had. Nonetheless, there were two unforgettable settings. One of them was built around the Telefunken O 85 A, a famous speaker from around 1960. The speaker incorporates 16 mid+ drivers shooting in all directions except backwards. Below them two woofers push the air in an acoustic suspension cabinet. The lowest 1/3 of the speaker hid a 30-watt tube amp. The speakers were fed from Alexander Krieger's preamp with a Micromega CD player as a source. The speaker may ignore the finest details but in exchange it offers extremely well-balanced, fresh and happy sound that doesn't lose its qualities even on massive music. A true ear opener.

Another one I liked a lot was Melaudia's replica of Altec's Iconic speaker from the 1930s using 802/416-8B drivers. Only one speaker, mind you - this system was mono as it should be. I'm probably listening to mono LPs more frequently than stereo but mainly from two speakers. That is fine if everything upstream from the speakers is true mono. But simple systems like this French one show that no second speaker is really needed if everything is matched up. (I didn't notice a mono equalizer though and that is mandatory really).

As always there was a shootout. It must have been the first time in the history of mankind that such a shootout was held in a big chapel. This time the object was DACs and CD players. 15 machines participated, many in the disguise of Marantz CD-40/50/60s. The loudspeakers for the shootout were good old Altecs driven by Guido Tent's power amps. The rules were the same as during earlier shows. A randomly selected pair is A/B'd blind, the audience votes, the winner advances to round two until there's only one component left standing. Outputs were measured and levels equalized. Two pieces of music were played per session, one classical, the other non-classical. Different music was played from one pair to another.

One should not underestimate the importance of this collective ritual. It's not dead serious. After all, ETF people are anything humorless people. It's not fully objective either. The playing order (A/B, B/A) and other factors seem to cause bias. And it's not about one piece being better than the other. No, it's about listening to good music without which the guys would not sit still over the three-hour period. It's about forcing the experts to meet the limits of their perceptive powers and providing material for endless speculations. And first and foremost, it's about setting an event horizon for next year's festival.