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2A3 SETH S-240 Monoblocks All Triode Push-Pull DIY Fun;
or How I ruined my summer...

See 2A3 SETH parts and Circuit

SETH 2A3 S-240 Monoblock
Step by Step Manual

To download Seth 2A3 Manual, right click and select SAVE TARGET ASYes, while some say miracles don't exist, others don't need to see divine intervention; some just need to see something so improbable, that even divine intervention seems more likely. But alas, miracles DO exist as evidenced by Pantheon Audio's Dr. Jean-Francois Lessard's TEARING APART of one Seth Monoblock to rebuild and take shots of the process! And amazingly enough, we now have a nice simple PDF package, albeit a huge one (over 6.45MB), with pics and step by step documentation!

Yes, can I get an AMEN BROTHER!?

Yeah, well a simple, "that looks great Jeff" will suffice (A-MEN, brother!)

The Official SETH BUILD BEER!  Can I have another A-MEN, BROTHER!??? Praise thy Pilsner and Sweet Quebecian Solder fumes!

View Seth_2A3_s240_Manual_v1.pdf.
To Download, right click Seth 2A3 Manual pic; select SAVE TARGET.

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Note, this document is also available in MS Word.

Belle Gueule, The Official Seth Build Beer -
Responsible for Jean-Francois AGREEING TO this in the first place! SKOAL!

Dr. Jean-Francois Lessard finally gets his AC working.

OK, so this is pretty late but according to Dr. Jeff, the results are worth it, or so he says. He is planning to send it down to the NC coast for an audition so we don't have to only take his word for it. Based on my listening time with his other projects, I would say it's a no-brainer. Jean-Francois describes the project below:

For now, some insight on the design to come. Phase splitting is achieved by an MQ EXO-173 PPS. The OPT is a MQ "Peerless" S-240-A. The driver is simply resistor loaded. I tried some elaborate pentode/MOSFET constant current source applications as well as a choke load approach. In the end, a simple resistor proved to sound really good and end up cheaper and much easier to do (yet Jeff ended up going further with the excellent BCP-16NiGC grid choke)

The driver is the venerable 6C45-Pi. Not usually my first choice but an appropriate one considering the comments long ago from a certain Gary Dahl, this in relation to driving a pair of 2A3 through a EXO-173; seems the PP configuration will require a driver with cojones, for lack of a better word. Since you can get 40 mA from the 6C45-Pi with no sweat, it turned out to be the final choice. With this configuration, the amp is quiet as a tomb and sounds VERY nice.

Of course, there's the politically correct tube rectification which ain't too bad for sonics either. I'm running it now with 5U4G but GZ34 are OK too. Ditto with a 5R4

See the 2A3 SETH PP Parts List

I'm warning you guys, don't expect something really elaborate as a circuit with this amp. This amp was designed with the write up of a"how to build a..." article in mind. This kind of article usually destine itself to rookies in the DIY Audio world so I had to keep in mind simplicity of design and building plus a relatively low building cost. All this while achieving excellent sonic results. In this actual case simple just became simpler than I initially thought.

So what is left between now and the time the article is online... Simply dismantling one of the amps and rebuilding it while taking pictures of the whole process.

Well, when I read this last sentence, I had to suppress an audible groan. So all that's left is simply dismantling one of the amps and rebuilding it while taking pictures? In Quebec-Lessard time this might just equal the new Happy Holidays Christmas/Hanukah 2A3 Project! I'll make sure this doesn't happen...I want to hear the beasts before the leaves fall. Take a look at the menu at left for the iron deals as well as a few surprises.


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