Rhartt1234
223 posts
Feb 18, 2017
11:30 AM
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One of the power tubes on my Meteor lost its vacuum, aka went milky.
Should I buy a matched quad and replace all the power tube and get it biased? Or can get get by with just swapping in a new 6V6 s?
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tmf714
2996 posts
Feb 18, 2017
12:23 PM
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You should definitely replace all four- being the amp is cathode bias,theres no need to check it.
Last Edited by tmf714 on Feb 18, 2017 12:30 PM
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harpoon_man
193 posts
Feb 18, 2017
6:40 PM
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Tom: why replace all 4 on a cathode biased amp? Not saying you are incorrect; just for my education on amps.
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tmf714
2997 posts
Feb 19, 2017
5:10 AM
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Replace all for three reasons-
1. Reliabilty-if one went bad,more are sure to follow.
2. Sound-the 6L6,6V6 and KT series power tubes are the most important tube regarding sound in those amps that use them.
3. Bias-since it's a cathode bias amp,there is no "adjusting" or compensating for a weak or sub par tube.
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hvyj
3224 posts
Feb 19, 2017
8:20 AM
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I ain't no expert on tubes, but most specialty tube vendors sell power tubes in matched sets. As I understand it, power tubes of the same type will vary in current draw from tube to tube due to imprecise manufacturing tolerances. This being so, many tube vendors will "match" power tubes and sell them in sets so current draw is consistent from tube to tube. I think this affects the bias. So, I've always bought and installed power tubes in matched sets. FWIW.
Last Edited by hvyj on Feb 19, 2017 8:24 AM
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harpoon_man
194 posts
Feb 19, 2017
3:08 PM
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That makes sense. I was aware of matching sets for fixed bias but had not thought through the same issues for cathode.
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arnenym
405 posts
Feb 21, 2017
4:52 AM
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Meteor amps is extreme hot biased and if one tube left in the others is on the way.
That,s a good reason for change all 4 of them ;)
Buy a quad because they have a good balance.
Last Edited by arnenym on Feb 21, 2017 4:55 AM
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NiteCrawler .
350 posts
Feb 21, 2017
5:13 AM
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I installed 4 JJ,s a few yrs back as an upgrade to the stock Sovtecs upon recommendation.The originals did,nt go bad I just thought that it was time for the upgrade.BTW The only problem that I have had in the past is the rectifier tube going on me so I make sure that I carry an extra one with me when gigging.
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Rhartt1234
224 posts
Feb 21, 2017
9:47 AM
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I bought mine used and it came with JJ 6V6Ss. I was pretty happy with them so I guess I'll order a matched quad.
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tmf714
2998 posts
Feb 21, 2017
10:19 AM
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Great choice-they will continue to perform well for you I am sure.
Last Edited by tmf714 on Feb 21, 2017 10:19 AM
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hvyj
3229 posts
Feb 21, 2017
4:02 PM
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+1 on JJs. Btw, they have a new JJ 12AX7 called ECC83mg. I like it a lot. Very musical for lack of a better adjective.
Although matched power tubes are considered important, it is of no importance to get matched preamp tubes. Some people consider it a good idea to get a phase inverter tube with balanced triodes, but that's debatable, especially for harp.
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barbequebob
3391 posts
Feb 22, 2017
9:11 AM
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HvyJ is right about no need for matching on preamp tubes and every amp tech, especially reputable vintage amps say that as well, but with power tubes, ALWAYS buy matched sets because if one tube is weaker than the other, they'll wear down in regular gigging use much quicker. You may want to consider the reissue Tung Sol 6V6's.
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Sincerely,
Barbeque Bob Maglinte
Boston, MA
http://www.barbequebob.com
CD available at http://www.cdbaby.com/cd/bbmaglinte
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