3dzapper Posted February 18, 2007 Share Posted February 18, 2007 I've had Shannon Parks DIY Poseidon boards with Jensen PIO coupling caps running for about a week now. The population and building of the boards is rather easy. With care, a first timer could complete the task in a couple of nights. I bought all the resistors and small parts in accordance with DIY's great bill of material included in the documentation just substituting the Jensens for the metalized poly caps and Uncle Ned's plate resistor values. I also eliminated the biasing circuit on the boards as I had already incorporated an individual biasing scheme in my original build. The only caveat I have for a newbie is to make sure to heat sink the leads on the constant current device in the driver stage as it is easy to damage solid state devices with too much heat. OK, now for the juicy part. I tested for DC and oscillation, which were fine then I hooked them up to the Juicymusic Blueberry Extreme. I turned everything on and the SOUND! WTF did I do to my amps!!! It was that bad!! After a few minutes, things settled in and the sound became better and better and better until it reached the 72 hour mark from where it has remained the same. Running NOS RCA 5963 and black plate 12BH7s and GE 6550s the sound is much smoother and more musical than the stock Mark IIIs from which the transformers were donated, the previous Triode Electronics boards and the "other boards" I initially used in both triode and ultra linear modes. The dynamic punch is less than the Triode boards but then, the Triode boards over exaggerated the punch of a kick drum to a rather unpleasant startlingness. The bass is warm and tight, the mids while not as silky as DHTs are excellent. The highs are clear and pleasant and extend well beyond my hearing. All in all, I highly recommend the Poseidon boards for anyone planning an upgrade to some Dynaco Mark IIIs or a bottom up build using aftermarket transformers. Fini, Robert, did you build up your's yet? Rick PS: I want to try a set of the Valve Art KT-88s Craig has raved about but I can't right now. I've spent my allowance getting ready for this years archery tournament season. Quote Link to comment Share on other sites More sharing options...
Deang Posted February 19, 2007 Share Posted February 19, 2007 Click your heels together three times and repeat after me: There's no such thing as break-in, there's no such thing as break-in, there's no such thing as break-in. I've turned it into a nice Gregorian Chant that I sing for the first 20 hours after I install a new network so I can't hear the caps settling down. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 19, 2007 Author Share Posted February 19, 2007 Do I gotta wear these? Quote Link to comment Share on other sites More sharing options...
anarchist Posted February 19, 2007 Share Posted February 19, 2007 Hey Rick,Glad to see you got them built and I was waiting for a review from you with the jensens. I have had the boards built for a while now - less the coupling caps. I think I have finally decided to use the Auricaps in them - maybe... I just recently built the SDS boards and built them with 41/90/90/90. Right now, I am waiting to pick up a 12bh7, 5751, and 5ar4. Again, choices. Once I secure the tubes, I will crack the amps back open and install everything. The 5ar4 will be Mullards. No question. I am interested in opinions on the "best" 12bh7 and 5751. I am leaning towards Sylvania 5751 or Raytheon 5751 and the RCA or Sylvania 12bh7. You have any thoughts on variants? Anyone else? Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 19, 2007 Author Share Posted February 19, 2007 I have the RCA blackplate 12BH7s in. From what I read, they are the best. There aren't a lot of choices in this tube designation. Definately not like 12AX7s or 12AU7s. Rick Quote Link to comment Share on other sites More sharing options...
mike stehr Posted February 20, 2007 Share Posted February 20, 2007 "Right now, I am waiting to pick up a 12bh7, 5751, and 5ar4. Again, choices. Once I secure the tubes, I will crack the amps back open and install everything. The 5ar4 will be Mullards. No question. I am interested in opinions on the "best" 12bh7 and 5751. I am leaning towards Sylvania 5751 or Raytheon 5751 and the RCA or Sylvania 12bh7. You have any thoughts on variants? Anyone else?" I never really listened to 5751 compared to a 12AX7, I have with 7025. Isn't the 5751 more or less a 12AX7 with less gain, like 70 as opposed to 100? Here's a GE JG-5751, from a Lambda DC PS. I would think they would make a good driver tube, or gain stage. I dunno...me I'd just be more concerned about having good strong tubes. Then once the amp is up and operating optimum, do the tube rolling thing. Quote Link to comment Share on other sites More sharing options...
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