New Mark III's Build Up And Running- SWEEEEET!!!!

for Dynaco Mark II/III/IV and DIY PP monoblocks

New Mark III's Build Up And Running- SWEEEEET!!!!

Postby hilldweller » Sat Dec 15, 2007 6:33 pm

Just completed the second Mark III and now both are up and running. Very sweet sound as compared to my "Optimos Lateral Mosfet Solid State Power Amp" I have been running them for about 9 hours now. I had to rebias them two times as the tubes are breaking in. I Love these Poseidon drivers!!!! See pics,
http://hilldwellerstl.myphotoalbum.com/ ... me=album04 :) :) :)
I notice that the power tranny's get kind of hot, the output tranny's stay kind of cool. The Weber copper cap rects. are working out nicely allthough they get hot also. I am temporarilly driving these with a Carver C-4000 Preamp and an ADC SS-412X EQ. I am in the process of building a tube based preamp to drive these fine Mark III's. What an exciting project. I may delve into low power audio next. I was thinking of the AD-1 directly heated triodes for the output tubes. I will use this setup in my office. Yellow_Light_Colorz_PDT_11
Analog is Real! Experience it!
Digital leads to trans humanism. Not good.
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P Tranny heat

Postby logos47 » Tue Dec 18, 2007 4:39 pm

Yes, this is a classic issue for the MKIIIs. Yet the current draw of the Poseidon driver board is the same as the old 6AN8 original. It is tolerable, and better than some configurations which indrease the power demand. Small fans work. Other than that, a separate filament supply might help. Meanwhile, I have "voiced" my MKIIIs with a careful tube selection--to me and to the ears of the builders around here, the sound is "superb" in every way. Enjoy!
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Re: P Tranny heat

Postby Ty_Bower » Tue Dec 18, 2007 7:24 pm

logos47 wrote:Meanwhile, I have "voiced" my MKIIIs with a careful tube selection--to me and to the ears of the builders around here, the sound is "superb" in every way.

Oh, come on. You can't just tease us like that, and not tell us which tubes you chose. We promise we won't bid up the prices on eBay. :)

Besides the value of the C1 cap, did you end up making any other circuit changes (perhaps in support of a specific driver tube)?
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MK III tuberosis fetalis

Postby logos47 » Tue Dec 18, 2007 7:54 pm

Okay okay. Looks like you used AudioCaps as did I. Along with Fischer-Tausche (Authenticap) can cap replacements, all 20mf sections strapped together and additionsl caps (Sprague Atom) below for the output driver board. Lots of other little incidentals...if I can post a photo, I will.

Now, the tubes. Best of the lot are the GL reissues, (ll you have the same), although the JJ KT88s are killer, too. what I find really making a difference is the Sylvania triple mica blackplate 5751 (sq getter) sub for the 12AX7. In the 12AU7 spot are RCA 5814A blackplates--these, along with the GLs bring to the bottom an articulate, tight authority.

Now, I am using a thoroughly made over PAS 3, converted to a classic RCA linestage design. Here the tube is critical--I like old CBS-Hytrons from the 1950s and have two, a grayplate currently and a blackplate tube. These have stunning detail and texture. Interestingly, in the Poseidon 12AU7 position, they do not please me as much as the RCA 5814A--brilliant but a little less bass. That's it so far. I guess I've been leaning that where a tube is placed in the path makes a significant difference.

Don't laugh, but I am using stacked inverted Large Advent Speakers, re-capped, re-wired, and adjusted with virgin wool + latex slab. Our group is used to such things as Lowther, Martin Logan, EV Voice of the Theatre, custom Victor-Altec-JBL with acoustic lenses, etc. Everyone is absolutely captivated by the musical presence of this system. let me know what you find tube wise--your system is absolutely gorgeous!
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