My comparison of the Svetlana 12ax7 vs. the JJ ECC83S vs. the ART DI/O's Penta 12ax7a:
(tested with the MG Head OTL in OTL mode, Ei EL84's, HD580's, and Clou blue cable from an ordinary CD source)
Svetlana 12ax7 (from Triode Electronics):
Where did my highs go? Vocals, snare drum hits, and harpsichords sound a bit fuzzy in an unclear, muddy sort of way. Bad. Where's the spark? The energy? The dark character of the Sennheiser 580's seems to accentuate this problem.
Otherwise, the tube does a good job with bass and midrange notes, making the lower octaves sound satisfyingly full. This tube throbs with low-end vitality. I like that.
Of the three, the Svetlana is the most microphonic of the bunch. If I tap the case, or the DESK for that matter, I can easily hear it. I guess this can happen with tubes from any company, so it matters little.
JJ ECC83S (stock tube w/MG Head OTL):
The JJ is the Yin to the Svetlana's Yang. They are total opposites. Female vocals and high notes have enough sizzle required to deliver satisfying snap. BUT... the midrange is murk-city. The notes tend to run together and flatten out. Bass is noticeably weaker, too.
Overall, the JJ's presentation seems like an improvement over the Svetlana at first because the highs initally stand out. This quickly becomes boring due to the lack of bass and midrange punch. It's a tad lifeless. Too dull for me. My girlfriend noticed too.
Penta Labs 12ax7a (pulled from my ART DI/O):
Hey you ART-heads... try sticking that spare tube in your MG! The Penta is a re-labeled Chinese tube that actually sounds OK. It's the compromising middle child of the bunch: highs that snap, mids that don't run together, and bass that almost keeps things interesting... almost.
OTL vs. transformer...
I used to agree with the general consensus that transformer w/no feedback sounded best. After spending a week with the MG, I find myself plugging into the OTL jack 99% of the time.
Wrapup:
With my equipment, all of these tubes are lacking. The Svetlana narrowly beats the Penta for first place, but that isn't saying much. Each of these tubes falls short in at least one critical way. I'll try some 5751's as soon as possible. Actually, I bought most of acidtripwow's remaining stash. Updates to follow.
Concerning the EL84's...
The Ei EL84's and JJ EL84's are almost totally interchangeable to my ears. The Ei's *slightly* favor bass octaves and the JJ's *slightly* favor the high notes. Because of this, the JJ's sound best when mated with the Svetlana. They help the Svetlana make the most of its limited top end.
Whether you select the Ei or JJ EL84's, you can't go wrong. Both are better than the stock Sovtek tubes.
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