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2008-04-06, 00:40
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Senior Metalhead
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Join Date: Jan 2007
Location: ny
Posts: 242
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help: preamp tubes
i just got a peavey rock master preamp. it came with the original stock tubes, which were marked "12ax7a".
i bought a matched quad of sovtek 12ax7lps to replace them.
with the new sovteks, there is about 40% decrease in overall volulme. if i put in one of the old ones, or a JJ in place of one of the sovteks, the volume returns to full.
what could the problem be?
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2008-04-06, 02:34
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Pirate Lawd
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Join Date: May 2004
Location: Hanger 18
Posts: 6,520
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You might have got a bad sovtek tube. Is it just the one tube?
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2008-04-06, 02:37
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Senior Metalhead
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Join Date: Jan 2007
Location: ny
Posts: 242
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there's 4 of the sovteks. i might have to label them and try by process of elimination. is there an easy way to test them individually?
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2008-04-06, 03:08
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Pirate Lawd
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Join Date: May 2004
Location: Hanger 18
Posts: 6,520
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Just replace them one at a time to find the bad one. It shouldn't take very long to find it.
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2008-04-06, 03:31
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Senior Metalhead
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Join Date: Jan 2007
Location: ny
Posts: 242
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ahhh there was a bad one, you were right. it was substantially quieter than the rest, but it was still putting out sound. thx
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2008-04-06, 03:58
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Post-whore
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Join Date: Dec 2004
Location: Toronto, Canada
Posts: 1,816
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be CAREFUL with those lps's. If they crash in a cathode-follower stage, they'll burn out some shit in your amp... simple trifle shit like resistors and stuff, but if you dont know what is going on, it will seem like your amp is dead and you'll have to take it into a tech which makes me want to 
And also, preamp tube matching is pointless, because they're cathode biased.
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Originally Posted by Dahmers Fridge
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2008-04-06, 05:12
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Senior Metalhead
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Join Date: Jan 2007
Location: ny
Posts: 242
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good to know re the matching. i really have no clue, that's just how they were listed in the auction.
they definitely sound weird. even with the 3 working ones + a stock, there's something strange going on. idk maybe i got ripped off and they are shitty tubes.
i had one lps in my engl 530 and it sounded great. that's why i ordered some for this the rockmaster. but with this rockmaster, the old stock tubes sound better it seems.
should i order some EH and compare? aside from a single JJ, i don't have any others to compare with.
fucking annoying. it was $40 for the sovteks.  |
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2008-04-06, 17:26
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Pirate Lawd
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Join Date: May 2004
Location: Hanger 18
Posts: 6,520
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Sometimes tubes need a few hours of use before they sound right if they are new. If you got these from Ebay then there is no telling what condition they are in electrically. Certain tube testers can tell you if they are good but those are expensive.
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