So, Russ...How does it sound.... - diyAudio
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Old 5th March 2010, 02:47 AM   #1
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Default So, Russ...How does it sound....

....the "Beta" Simple P-P that is? I never had an amp with small power tubes like EL 84's, and I'm pretty used to my main system that uses KT88's in 70 watt monoblock configuation.

My Simple SE is also enjoying the KT88's, although Ty Bower has me interested in trying some Russian 6P3S-E's.

Curious too about the differences in sound between EL84's and the 6CW5.

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"The Cat"
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Old 6th March 2010, 10:32 PM   #2
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I only listened to it for a short time before taking it back in the shop. It seems that one of my EL84s is bad. I ordered a new quad of JJs to try so we'll take it from there. The good channel measures pretty well, but it wants some feedback.
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Old 6th March 2010, 11:26 PM   #3
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Waveform of the channel with the bad tube.
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Old 6th March 2010, 11:45 PM   #4
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I hope this "bad tube" thing isn't contagious among Tubelab builders. I mean yesterday, my Russian 6P3S-E's arrived. Out of a quad, 1 was DOA!
Perfect sine wave, eh?
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Old 6th March 2010, 11:51 PM   #5
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I dunno...I bought them some time ago but never used them until now. The DC operating point of all four seems fine but obviously one has low transconductance. Good argument for the uselessness of tube matching, at the very least.
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Old 7th March 2010, 03:11 AM   #6
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Quote:
I dunno...I bought them some time ago but never used them until now.
Which brand are they. I got 12 more JJ's and 2 "Groove Tubes" at the Orlando Hamfest. I haven't tried any of them yet. Maybe I should.

Quote:
Curious too about the differences in sound between EL84's and the 6CW5.
There isn't any big obvious difference. I am running the exact same (not the same kind, the same pair) of OPT's with both tube types in my test amp (same amp used for both tube types, with external power supply). I hear a bigger difference between Amperex 6CW5's and GE 6CW5's than I hear between Amperex 6CW5's and Amperex EL84's.
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Old 7th March 2010, 03:58 AM   #7
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Quote:
Originally Posted by tubelab.com View Post
Which brand are they. I got 12 more JJ's and 2 "Groove Tubes" at the Orlando Hamfest. I haven't tried any of them yet. Maybe I should.
Sovtek EL84M (supposedly 6P14P-EV).
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Old 7th March 2010, 11:52 PM   #8
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Default JJ woes....

Seeing as how JJ tubes were mentioned in this thread, there's currently a lot of discussion over at the Tube Asylum about JJ failures and general lack of quality. Tubes Asylum
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Old 8th March 2010, 01:21 AM   #9
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The thread you pointed to discusses the problems with JJ's OCTAL tubes. This has been discussed here too, and unfortunately it does appear to be true. Many Simple SE builders have witnessed 5AR4's that delf destruct on power up. One builder blasted two of them on power up, but the third lasted for years. Other builders have seen EL34's with red spots on the plates and glowing grid wires.

These issues are indicative of poor tolerances during assembly. If the tube was assembled properly it should not glow when operated within its maximum ratings. If the tube is operated beyond its ratings to provoke glow, the glow should evenly distributed along the plate with equal glow on both sides. Any hot spots are indicative of uneven current flow, caused by sloppy assembly.

Unfortunately it seems that bad batches of tubes seem to show up from all of the current production vendors. I bought some "Winged C" EL34's that positively sucked, 2 out of 4 wouldn't work at all, and the other two had problems. I suspect that the bad batches that should have been destroyed find their way back into distribution. Ebay buyers beware!

That said, The JJ 9 pin tubes haven't seen the same issues.....yet. I asked a tube seller that I trust for some EL84's that I could lean on. He said that the JJ's had the lowest problems, so I bought 4 (about a year ago) I have indeed hammered them pretty hard, with no issues, and all 4 of them match fairly well. I recently got 12 more from the same seller, but I haven't fired them up yet.
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Old 8th March 2010, 02:01 AM   #10
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I have high hopes for the JJs. There aren't many other choices other than Sovtek and it's relabeled reissues (Mullard, etc). I've had problems with JJs octals. Blew up a few 5AR4s until I ended up with two that seem to work well. One has been in the SSE since I built it. The other issue was a quad of KT77s. Two of them had cathodes that slid down out of the mica and shorted against one of the strap in the bottom of the tube. I arced a Chinese 5AR4 a few times before I pinpointed the problem. I was able to smack the offending KT77s hard enough to move the cathodes back up and then they worked. I got them exchanged and these have been fine (in the ST70). Oddly, that Chinese 5AR4 still works just fine.
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