DECWARE / High Fidelity Engineering Co.

A U D I O... P A P E R


 MAY 2009
by Steve Deckert


Thanks to the creative mind of Mr. Hazen, my top solder guru, we have stumbled into a modification that can be applied to most Decware amplifiers. In all the years of typical mods and tweaks, we have never come across a more dramatic improvement in sound quality. It eclipses all of the usual attempts to make something nearly perfect even better. Things like; cryo treated tubes, coupling cap or resistor upgrades, silver wire, tube dampers etc., etc. The mod actually improves the coherency of true pentodes to a degree that you wouldn't even think it's the same tube.

There are two unique pentodes that can be found in many Decware amplifiers.  These are the Russian 6P15P-EV and the EL34.  What makes these pentodes different from other tubes is that the suppressor grid is not internally connected to the cathode. These two tubes can be wired as either pentodes or triodes.  And the suppressor grid can be manipulated.   

From the RCA transmitting tube manual on air-cooled tubes from 1938: 

In all radio tubes. electrons striking a positive electrode may, if moving at sufficient speed, dislodge or "splash out" other or secondary electrons. In diodes and triodes, such secondary electrons produced at the plate usually do not cause any trouble because no positive electrode other than the plate itself is present to attract them. These electrons, therefore, are eventually drawn back to the plate. In tetrodes, the screen (operating at a positive potential) offers a strong attraction to secondary electrons when the plate voltage swings lower than the screen voltage. This effect limits the permissible plate swing for tetrodes because the major portion of the space current then goes to the screen rather than to the plate. The plate swing limitation can be substantially removed when a fifth electrode, known as the suppressor, is placed in the tube between the screen and the plate. Such five-electrode types are called pentodes.

The suppressor in a pentode is usually connected to the cathode, or to a low positive or negative voltage, depending on the tube application. Because of its negative potential (in any case) with respect to the plate, the suppressor retards the flight of secondary electrons and diverts them back to the plate, where they cause no undesirable effects. Thus, in pentodes, the plate voltage may swing below the screen voltage."

Even though it is stated that diverting secondary electrons back to the plate causes no undesirable effects, we have found this to be somewhat false with respect to sound quality based on the rather dramatic improvement that results from modifying HOW the spray is diverted back to the plate. 

Consider this; a piece of wire connecting the suppressor grid to the cathode sounds familiar, but replacing the wire with a non-polarized film cap creates a condition that makes the tube sound better. You hear a dramatic increase in clarity. This kind of clarity can only be from better linear timing with less delays from shifting phase angles throughout the frequency spectrum, or so one would think based on the resulting sound. Phase angles are largely a factor of the amplifier design more so than the tube itself, however, when the tube is inserted into the amplifier, they become one in the same. It can only be assumed that by manipulating the suppressor grids potential against the cathode that we have improved how the tube functions based on what we're hearing. We're still discussing theory's to explain exactly what is happening that would remove hardness and smearing in the playback.  Certainly it has been an eye opening experience to the importance of the suppressor grid and its effect on the sound.  Over a piece a wire, the film cap has several components, AC, DC, it's size and rate of charge, and may even have a damping effect on the grid itself.


Can be read here:  Christmas Comes Early Mod Part II



The result of doing this is an improvement in coherency that has to be heard to be believed. On our first test we took a well seasoned SE34I (EL34 based single ended triode amp) and found the difference to be larger than any single thing we could have done. For example, pure silver-wound output transformers would not have made as big an improvement. Switching the coupling caps to V-Caps or Audionote would not have made as big a difference. Spending hundreds on N.O.S. tubes would not have made as big a difference nor would any anything else I know of. The midrange being always the first to reveal true success was simply unbelievable.

The next test was to see what happened on our pentode wired EL34 push pull amp called The TORII MK II, and again the same results were observed. The final test was to do our original Zen Triode amp with the Russian 6P15P-EV tubes, and again, simply amazing. In every case an increase in performance was seen and dynamics improved with head shaking improvements in clarity and imaging.

To bring the point home, during the test on our Torii MK II, one channel was done and tested on a single speaker against the stock channel. Starting with the stock channel, as you might expect when listening to only one speaker, the sound seems to come directly out of the speaker. When the modded channel was tried, the single speaker virtually disappeared. Any time you can make a single speaker disappear you're on to something.


After hearing what we had done to the above mentioned amplifiers with this mod we could only look at each other and say that "Christmas came early this year (it's only MAY)!"

So we're calling it the "Christmas comes early mod" or CCE mod for short. As of May 2009 all Decware amps that use either of these tubes are manufactured with this mod standard.


Steve Deckert

NOTE: This mod can be done on The Torii Mk II and all of the Zen Triode amplifiers except for the Mini Torii. Cost is $100.00 plus return packing and shipping.

If you would like to get the Christmas comes early mod, just pack your amp so it can't be damaged and fill out the RA form here on the web site. Print it out and include it with your amp. We will contact you a few days after it arrives.



Decware is a trademark of High Fidelity Engineering Co.
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by Steve Deckert