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VALVE Magazine Online!
October's Meeting
By Dan Schmalle From VALVE Issue 11, November 1994
October's meeting was another packed event at Classic Audio, with a few folks left standing. A couple of new members joined after the meeting, and I'm sure that o couple more folks who are starting to attend regularly will do so soon. We're really starting to grow! I'll try to schedule half or so of our meetings on the Seattle side from now on. If you live on that side of the water and would be interested in hosting a meeting and showing off your system, let me know.
We got right down to the demo at hand because of its length. Dave brought the McIntosh MC40 described last month and we fed it directly with a generic Japanese CD player with a volume control. It it turn fed a JBL speaker. Everybody agreed to listen one more time to the good old Wagner Without Words CD. We're all learning it pretty well now and know what details and nuance to listen for, so in spite of the repetition, it seems to be a good choice for this group.
The tubes that showed up for the comparison
were pairs of the following:
6L6G - Sylvania
6L6GA - Sylvania
6L6 (metal) RCA
1614 - RCA
5881 - Tung Sol
6L6WGB - Phillips (Sylvania)
6L6GC - RCA
6L6GC - Sovtek
KT-66 Mullard
5962
807 - RCA, in Myron's cool adapters
807W - Sylvania, ditto
All tubes were matched for transconductance and all types except the 5962 and Sovteks, which Dave brought, tested within 10% of each other, around 5500 micromhos on my TV-10B/U tube tester. Each pair was plugged in, warmed up very briefly and auditioned with the same two tracks of the CD (4 & 5).
I might as well admit my screw up on this comparison right here. The MC40 was chosen because it was freshly redone and had no bias or balance pots to mess with. Unfortunately l failed to notice that it has a plate and screen voltage of 470 VDC. The MC40 was designed to use 6L6GC1s. This is the only tube of the group rated for such high screen voltage, so every other tube in the test was really being misused.
Surprisingly, only a couple of types really fell apart under the strain, those being the 5962 and the 807. The 5962 made scratchy arcing sounds on peaks, and the 807's put out these scary pops at seemingly random intervals. Mike mentioned having the same problem when trying 807's in a Mac MC30. We were, however, able to draw some conclusions about the other tubes in spite of their torture.
The 6L6G and GA both gave OK, slightly soft and mushy presentations, with the GA slightly better. The metal tubes were less than impressive, with the 1614 giving a slightly brighter presentation than the 616. Once again please remember that these tubes were all being pushed beyond the limits of their screens, some by as much as 200VI.
Moving on to the more modern tubes, I was surprised to find that I liked the most holy KT-66 least of all. It seemed a bit bass shy, and not as punchy as the others. Perhaps this is good, as there ain't no more anyway. Enough with the stuff we didn't like. The really cool sounds started happening when we plugged in the 5881 's. Good highs, good dynamics, and pretty good bass. Ditto the Sovteks, with even better bass and dynamics. I'd say these are a best buy right now. Dave really liked Sovteks. He had these in the amp when he came to the shootout, and left with them back in there afterwards. My personal favorites were the 6L6GC1s and the 6L6WGB1s.
The 6L6GC1s had great punch and lots of upper detail without being too harsh. I had come to use this particular pair as the tubes I plug into any 6L6 amp I have in the shop, and this test proved that they really did sound a little better than others I had lying around. f think most people in the room really sat up and took notice at the Phillips 6L6WGB1s, though. They had the smoothest, least 'pentodey' presentation and handled transients better than any other tubes. Most realistic and least strained would be appropriate descriptions as well. Don't ask me where to find these. I got four from Eric a long time ago, and promptly broke one. If he has one more, I claim first dibs. If he has more than one, I doubt he'll want to let them go!
Actually the results were promising in terms of the high scoring of the more readily available tubes. 6L6GC's and to some extent 5881's are still findable, and the Sovteks are both reasonably priced and plentiful.
Someday next year we'll redo this test with a more appropriate amp. In the meantime, don't get too hung up on funky old tubes with high price tags and big globes. Try the more reasonable and modern tubes too. You may get a nice surprise!
-- Dan
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