Let’s face it gents, we are the thermionic green berets: a small group of dedicated fierce warriors ready to go anywhere and do anything to accomplish our mission. Because we are the vanguard of the audio revolution we know more about the edge of the audio arts for a good reason.... we are creating it. Because Karma rules, we, the throbbing phallus of the audio arts, are rewarded for our work. It is our job to question and challenge every conventional notion about design and continue to experiment. I remind you of my experiments with making interconnects and speaker cables with Radio Shack ultra-thin magnet wire and solid silver wire...which was exactly opposite of what everyone else was doing. So it is our job to question and experiment.

According to audio orthodoxy torroid output transformers don’t work . It is also well known that DHT SETs don’t work well. I also want to suggest that all vinyl systems don’t work well. So let us be skeptical about torroid OPTs, but the only thing we can trust is our heightened sense of music.

During the 1970s when I had to own every tube amplifier ever made, I bought a pair of Gotham Audio cutting head amplifiers just because they had the rara avis... torroid output transformers. Soon after that I was shown pictures of the David Hafler “never manufactured” torroid OPT Dynaco MkIVs, and that is the last I heard about torroid output transformers. Have you ever seen any tube amp with big round OPT? Probably not, because the orthodoxy is that torroid OPTs have a “family” of electrical problems that make them unsuitable for high quality audio.

Of course we all know how torroid power transformers and chokes have distinct advantages and are much appreciated.

In December I was contacted by Menno van de veen ( a serious Dutch thermionic techno-shaman who has written a great book on tube amplifier design available from Plitron and a dude I first made contact with at New York Audio Labs) who designs torroids of all sorts for Plitron Manufacturing in Canada. Menno was surfing the Triode Guild web site and wanted me to know that he had developed a new torroid OPT for single-ended circuits, and claimed that he had overcome many of the limitations of the torroid OPT  “orthodoxy” and believed that his new design had significant performance advantages. Was I interested? Which is like asking me if I would you like to take a shower with Cameron Diaz?  I suggested that he send me a pair of 5K models for 300Bs (Please remember that my hunt, as Guildmeister, is for the musical shadows that surround notes, and not power), and was informed that it would be a few months before the first were available, so I waited. Having owned a torroid output amp I knew that something potentially very colossally cool was coming my way.

I then emailed by thermionic techno-shamans around the world and asked if anyone had any experience with single-ended OPTs and no one had a clue...not even the lofty Sir Scott Frankland. In other words, Menno had created the first of its kind. By this time I received lots of technical papers from Menno explaining his breakthrough which was so technical that I didn’t understand most of it. According to Howard Gladstone president of Plitron, this SET OPT  has been a two year project.

What I find so interesting about Menno’s design work is that he wrestles with OUR   essential artistic paradox: to a serious audio engineer DHT-SETs don’t make any sense, and from their oscilloscope point of view they are right. To those who live by their ears, and not by their oscilloscope, DHT-SETs make profound sense because they produce such rich triode cream, and we wonder why engineers love their push/pull amplifiers. Don’t they want to cream more economically and dance naked in the stars?

But Menno is a righteous cool dude, and he recognizes that something is going on in the world wide craze for DHT-SETs, and is working to design a “better” OPT meaning.... wider bandwidth, more linear and one with better transient response, and one that interfaces with the speaker load with less variation.....recognizing the positively prehistoric nature of the circuits we love. Never forget this: When it comes to musical beauty YOU know best.


At 7:00 PM on December 14, 1999 I heated my soldering iron and put my custom 300B SET on the operating table, and in about fifteen minutes my “normal” output transformer was disconnected the Plitron unit rigged. The other amp stayed stock. My comparison was made with the KR 300BXL tubes.

I am so vain that I think this song is about me, but quite frankly it doesn’t take much on my system to discern differences in gizmos. After only listening for 30 minutes my initial impression is that Menno and Plitron have been very successful and.... the transformer hadn’t aged in yet, and I didn’t even experiment to find its “sweet spot”.

These are quickie responses: bass response like the Sun push/pull and the tonal quality of the Tamura iron. Better high frequency response and a very wide soundstage.

What I am asserting from my initial tests is that all of those who are insisting that torroid OPTs, and especially the ones for SETs, don’t work properly need a serious attitude adjustment....at least the Plitron design. So let me make the point plain: Menno’s design creates a unique aural matrix that is extremely creamy, but it is a completely different form of triode cream, and that is what is so exciting about it. Don’t ask me now to compare the micro to the macro cream or give you the details about the torroid cream’s harmonic or how wide it is. That will follow soon.

Let me tell you the bad news: these are big round mothers and probably can’t be fitted to your existing amplifier which means you have to build a new chassis to accommodate them.


Are torroid OPTs the answer to staying refined while using those higher current DHTs? Are torroids the secret of getting more of those push/pull aural matrix benefits without push/pull’s aural discombobularities? And what happens when we use the 2A3, and 45 with torroid OPTs?

And what about ‘REINVENTING PUSH/PULL”? What about a push/pull 300B amplifier with torroid OPTs?

How do these compare in quality to the new OPT designs that will be arriving shortly at Chez Gizmo?

More to come. And remember you heard it first from your dedicated servant Dr. Gizmo. Party On Righteous Dudes.

I have asked Howard Gladstone, President of Plitron and Menno to put together
a new “understandable” information package about their torroid OPTs and that will be available soon, so get on the waiting list.

For more information contact Plitron at their email address: techinfo@plitron.com
Web site: www.plitron.com