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09-28-2008, 06:59 PM
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#1 | |
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Senior Member
Join Date: Jul 2008
Location: Red Leicester
Posts: 785
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A Question About Valves
After a long time wondering whether to change my pre-amp valves, as I thought they could sound better, I decided to purchase 4 EH 12AX7s.
I was mightily impressed with their performance right away: much crunchier yet smoother and less harsh than the O/E Sovtek valves (even though they're both made by Sovtek) and a slight increase in volume too. That was about 2 weeks ago, today I turned on my amp for some Sunday noodling, only to hear a small drop in volume. Thinking it might be the pre-amp valves, I checked them and discovered that one has gone black at the tip where the others are a silvery. Is this normal? Could it be the problem, or does that lie elsewhere?  Whilst we're on the subject of valves; does anyone have any recomendations for 12AX7s and EL84s? Cheers for any input or advice. 
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09-30-2008, 09:02 AM
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#2 |
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Senior Member
Join Date: Sep 2005
Location: Islington / Crackney border
Posts: 19,996
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When Britain was an empire it was ruled by an emperor. When it was a kingdom it was ruled by a king. Now it is a country is is ruled by ..... Gordon Brown. |
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09-30-2008, 09:36 PM
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#3 | |
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Senior Member
Join Date: Apr 2005
Location: Lancashire
Posts: 14,072
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Quote:
And re your question - it depends. If there is sound coming out then the valve is still working ok, but being charred at the top does sound odd.
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10-01-2008, 12:01 AM
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#4 |
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Senior Member
Join Date: Feb 2008
Location: Wigan
Posts: 3,391
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JJ Valves
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10-01-2008, 05:18 PM
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#5 |
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Senior Member
Join Date: Dec 2007
Location: Peterboghorror on the Fens
Posts: 1,960
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NOS Mullard
 My very very private stash |
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10-01-2008, 07:13 PM
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#6 |
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Senior Member
Join Date: Feb 2007
Location: Belfast
Posts: 1,007
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Stick a tung-Sol in V1.
Seems more 3D than the EHs for me. i have EHs in the rest of my slots though.
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Im no Toob Amp Snob, Im happy with modellers - as long as Its my Axe-FX !! |
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10-02-2008, 09:02 PM
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#7 | |
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Senior Member
Join Date: Jul 2008
Location: Red Leicester
Posts: 785
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Cool- I'd been thinking about Harma Valves for the EL84s, so they're still a possibility. Anyone else tried JJ's? I've still got a couple of Mullards out of a Vox I used to own, but would they be ok to use with two other valves? Haven't a clue if they even still work.
I hadn't thought about mixing valves, so thats something else I might do. Any other suggestions?
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It's a hassle, you know, to make rocket-ships go to infinity Quote:
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10-03-2008, 12:26 PM
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#8 |
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Senior Member
Join Date: Feb 2008
Posts: 1,296
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The bit at the top is the "Getter Flash". Shiny means the vaccuum inside is intact. I was once told that white and powdery means air has got in. Black I'm not sure of, maybe the valve is failing for temperature-related reasons.
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10-03-2008, 03:04 PM
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#9 | |
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Senior Member
Join Date: Jul 2008
Location: Sunny Kent
Posts: 668
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Black is most likely due to poor lighting conditions.
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10-06-2008, 07:50 PM
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#10 | ||
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Senior Member
Join Date: Jul 2008
Location: Red Leicester
Posts: 785
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Quote:
Found a Mullard ecc83 in a drawer yesterday and it looks ok, so I may give that a try in place of the mysterious blackened valve.
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