2A3 SETH S-240 Monoblock
||Two Dale metal film 100 ohms 1/4W in parallel
(one end to each grid pin on the tube socket)
||Holco metal film 43.5ohms 1/2W|
||Mills Wirewound 4.02K 12W|
||Mills Wirewound 12W 1K in parallel with|
Mills Wirewound 12W 750 ohm
||Black Gate "FK" 100uF /16V (optional)|
||Solen 6.8uF/630V (Sub Preference)|
||Black Gate "FK" 100 uF/100V|
||Solen 1.5 uF/630V|
||Cerafine 47uF+47uF/500V (Sub Preference)|
||MagneQuest "Peerless" S-240-A (permalloy version)|
||Hammond 374BX 375V-0-375V 175 mA |
(MQ MQR-060 excellent sub - C4 value to 1.8-2.0uF)
||Hammond 166Q2 2.5V CT 6A|
||MagneQuest BCP16 GC (used permalloy version)|
||MagneQuest EXO-173 PPS (used permalloy version)|
||Hammond 193H 5H 200mA 65ohms |
(MagneQuest MQ 04-002 excellent substitute)
||Hammond 193H 5H 200mA 65ohms|
(MagneQuest MQ 04-002 excellent substitute)
Step by Step Manual is here!
Yes, 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!)
This is an excellent manual but got so big, we had to lower the pic resolution a bit in order for the laggards with dial-up modems to not wring their own necks waiting. So Jeff and Pantheon Audio will give anyone that orders the Seth Iron Package from them a FULL HIGH RESOLUTION SETH 2A3 MANUAL CD FREE with the order. So get your Hi-Rez digital manual and the best i-rons this side of Neptune!
Can I have another A-MEN, BROTHER!??? Praise thy Pilsner and Sweet Quebecian Solder fumes!
To Download, right click Seth 2A3 Manual pic; select SAVE TARGET.
Don't have the latest FREE Adobe Reader? Go here.
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:
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.
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
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.