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  1. #1
    Eruption
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    12.31.69 @ 04:00 PM
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    Hi guys, I need new preamp tubes (and was thinking about replacing the powertubes pretty soon too). I replaced them last time with Sovtek 12ax7s and they were absolutely terrible from day one. I really mean it, they suck - so much so that I haven't even played my tube amp for over a year.
    Anyway, I decided it was about fucking time I replaced them and started using my amp again! I don't want to make the mistake I made last time and go for average quality tubes because like I said it was a TOTAL waste of about US$50! So, are Groove Tubes the best? They are double the price but are they double the quality?

    Also, if I change from 5881s to EL34s is switching the bias switch on the back over to "EL34" enough? I've heard you guys talking about redoing the internal bias but is it *really* necessary. A mate of mine changed from 6L6s to EL34s without even changing the bias at all and it didn't fuck up his amp at all (tubes didn't last long though! )

    Thanks guys!

    BTW, I have a Carvin MTS3212 (100w 212 w/ 5 12ax7s and 4 5881/6L6s) if that matters in any way.
    RD<br /><br />"Rock 'n' Roll is my second favourite thing in the whole world" - DLR (1983)<br /><br />"We don't go for perfection, we just go for spirit." - EVH (1981)

  2. #2
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    03.30.13 @ 09:28 AM
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    I've always used groove tubes, but they come from different parts of the world so make sure you know where they're from. The code on them will usually tell you or you can visit their site and get the details.
    http://www.groovetubes.com/
    Man, I agree with you on those Sovteks. I had a different tech outfit my amp with them telling me they've improved. A mistake on my part. I went back to groove tubes.
    If you're gonna switch to el-34's it's probably a good idea to internally bias your amp once, when you first make the switch. It shouldn't hurt your amp if you don't, but if the bias is too hot it'll burn out your tubes quickly and if it's too cold it'll sound distorted and mushy, with a loss of sustain, and you'll also lose a lot of high end.

  3. #3
    Eruption
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    12.31.69 @ 04:00 PM
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    Thanks mate. I've often wondered if the internal bias was for the health of the amp's sake or the tone's sake. I think its worth getting the good tubes - especially after the Sovtek saga.

    Is it hard to change the internal bias? Will it cost much?

    Also, this is kind of a stupid question but will my amp sound more marshally with EL34s or what? Will it just be a bit crunchier and tighter?

    All the reviews of people who have changed to EL34s on the Harmony Central site have raved about the better tones etc.

    Thanks again for your help! I can always count on you guys to help out! [img]smile.gif[/img]
    RD<br /><br />"Rock 'n' Roll is my second favourite thing in the whole world" - DLR (1983)<br /><br />"We don't go for perfection, we just go for spirit." - EVH (1981)

  4. #4
    Eruption
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    12.31.69 @ 04:00 PM
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    just a little update, I checked the manual, this is what it said about the bias:

    "The internal P11 bias trim control can be set by a qualified technician. To set the bias, measure the current across the terminals of the STAND BY switch (set this to the off position when the amp is on). Set the idle current to 100mA for all tube types."

    Does "Set the idle current to 100mA for all tube types." mean that if my internal bias is currently correct (ie 100mA) then I don't need to change it for EL34s?
    I don't want some tech to charge me $100 for opening the amp up and telling me it didn't need any altering!
    What do you reckon?

    I'm getting pretty excited about changing these tubes - can't wait!!!
    RD<br /><br />"Rock 'n' Roll is my second favourite thing in the whole world" - DLR (1983)<br /><br />"We don't go for perfection, we just go for spirit." - EVH (1981)

  5. #5
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    03.30.13 @ 09:28 AM
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    If the manual's refering to the el-34 bias at 100ma, then it seems to sound right.
    You'd probably have to put in the el-34's and then set the bias with the proper tubes installed.
    If you use a different grade of tube next time then you'd have to reset the bias for the grade of output tube.
    Again, make sure the manual's refering el-34's for biasing at 100ma.
    Biasing by a tech shouldn't cost you more than 20. though, and please make sure you have a reliable amp meter, and know what you're doing bud. There are some serious voltages in the power section of an amp.

  6. #6
    Romeo Delight strangegrey's Avatar
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    06.05.17 @ 08:59 AM
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    I gotta jump in here....

    I have a carvin MTS head...and I recently went through a tube change...

    #1 - DO NOT BUY GROOVE TUBES. They will not offer an improvement over your Sovteks. Reason? Groove Tubes simply buys sovteks and chinese tubes in bulk...and relabels them with groove tubes logos. I suggest that you give Bob at eurotubes.com a call or email him. He's good people and he'll steer you right.

    #2 - If you replace the powertubes, you will NEED to rebias. If you are electrically capable and you have a multimeter, you can do it yourself..I have..it's not too difficult. But if you're a little timid with the idea, bring it to a technician.

    #3 - Carvin's recommended 100ma is a very cold setting for the amp. The reason they do that, is that it greatly reduces the amount of returned amps. Its almost cold enough for the amp to be in crossover distortion...If you get good EL34s, you can go as high as 132ma or 135ma without too much trouble....if you get good 6L6's (the JJs from eurotubes are the bets production 6L6 being made) you can probably go higher, maybe to 140-145..... regardless, get that amp running a little higher and you will get more life out of that amp than you ever thought possible.

    Good Luck,

    Frank

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    03.30.13 @ 09:28 AM
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    The only thing I'll add to that is that the the groove tube site clearly states which tubes are russian and which are chines, U.S., etc..
    The order no. signifies the make and location of manufacture.

  8. #8
    Eruption
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    12.31.69 @ 04:00 PM
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    Jeez, thanks for the extra bits of info fellas! Now I don't know what to do!!! lol

    I'll check out that site Frank - thanks for that. My only concern is that maybe the availability of some tubes will not be that great. I'll try though. Its interesting to hear an opinion from an actual MTS owner. Do you have el34s or 6L6s in your amp?

    Finally, when you said that I'm not gonna get tubes that are better than Sovteks, you can't be serious!!!! My amp ABSOLUTELY sucks with those tubes in it. Is it possible that all 5 tubes were duds? I don't know if I want to risk buying more of the same type. What are ruby tubes like? They seem to be everywhere in Australia! Some people love 'em and some people hate 'em.

    Tribb, so what you are saying is that all I really need to check is that the tubes are from Russia and not China - yeah?

    What I haved heard is that all the tubes are made in the same factory but then graded into different quality levels - GT buys the good ones and Sovtek and the like buy the not so good ones. Would that be a fair comment?

    Anyway, thanks for the help fellas. [img]smile.gif[/img]
    RD<br /><br />"Rock 'n' Roll is my second favourite thing in the whole world" - DLR (1983)<br /><br />"We don't go for perfection, we just go for spirit." - EVH (1981)

  9. #9
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    03.30.13 @ 09:28 AM
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    RomeoDelight, no.
    Sovteks are russian tubes.
    Russian tubes all seem to have a gritty sound to them, with crappy distortion characteristics. I'd stay away from russian tubes period.
    Tubes from the Chek. republic are good.
    The best tubes I've found were US tubes, or Mullards, but both are hard to get.
    Groove tubes are good, but stay away from the russian stuff.
    Chinese tubes really aren't bad, but they wear out more quickly and have quicker breakup characteristics.
    I have it from a very reliable source that Ed's early preamp tubes were chinese.
    He used those big coke bottle output tubes that were 6ca7's from what I've been told.

  10. #10
    Eruption
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    12.31.69 @ 04:00 PM
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    Originally posted by tribb:
    I have it from a very reliable source that Ed's early preamp tubes were chinese.
    He used those big coke bottle output tubes that were 6ca7's from what I've been told.
    I've seen an old pic of the back of his amp in the early days and you're right - they were coke bottle lookin' things! Most people assume they were EL34s!

    Anyway, I'm thinking about ordering a full set of JJ tubes - 12AX7s and either 6L6s or EL34s. What do you think of JJ preamp tubes? Are they US made? Most people say their power tubes are good but I haven't heard much about their 12ax7s.
    RD<br /><br />"Rock 'n' Roll is my second favourite thing in the whole world" - DLR (1983)<br /><br />"We don't go for perfection, we just go for spirit." - EVH (1981)

  11. #11
    Hot For Teacher Trennasol's Avatar
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    01.15.07 @ 05:34 AM
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    I don't think that tubes are made in the US anymore. IMHO, JJ's are the best tubes out there.
    Give them a try. They're a hell of a lot better than the relabeled Groove Tubes.

  12. #12
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    03.30.13 @ 09:28 AM
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    6ca7's are replacements for el-34's, but US tubes can still be found. Most are NOS, but there are still plenty of them around if you know where to look. JJ's are good tubes too. It depends what you're looking for.

  13. #13
    Romeo Delight strangegrey's Avatar
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    06.05.17 @ 08:59 AM
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    Romeo,

    Here's what I have in my MTS.

    4 Svetlana EL34s

    and 5 JJ 12AX7s

    But I swap in an electroharmonix 21ax7 once in a while, if I want a little more grain and distortion.

    The JJ preamp tubess are quite clear and they lack a miniscule amount distortion and gain. But they are nice and warm....

    I don't think I really like what the EL34s have done to my amp. I am quite curious to hear what the JJ 6L6s will do to my amp....since I hear that they are the best overall 6l6 that you could buy without spending rediculous amounts of money.

    -F

  14. #14
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    03.30.13 @ 09:28 AM
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    EL-34's will tend to break up and distort faster than a 6L6, so if you want a cleaner gain with better articulation go for a 6L6.
    If you want more gain then substitute your 12ax7's for ECC-83's.

  15. #15
    Hot For Teacher
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    10.06.12 @ 06:27 PM
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    Originally posted by strangegrey:
    I gotta jump in here....

    I have a carvin MTS head...and I recently went through a tube change...

    I suggest that you give Bob at eurotubes.com a call or email him. He's good people and he'll steer you right.

    Frank
    Yes indeed Bob is the man to talk to.BTW the JJ EL34S are great as well.I put a quartet in my Marshall JCM800 and it's never sounded better.
    Originally Posted by vanzefflin
    This configuration cancels noise or cyclical hum. Hence, the name humbucker. It bucks hum.

 

 

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