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  1. #1
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    01.23.09 @ 11:26 AM
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    Peavey XXX amp came with EL34's stock, guitarist switched them to 6L6. Pros/cons? I use EL34's in my amps for guitar, but does it really make all that much of a diffeence in your tone? I dont hear anything drastic

    [ March 08, 2002 at 06:21 AM: Message edited by: SMUDGE NYC ]</p>
    Plstrcast everywhere else, Smudge NYC here.. so kiss my arse!<br /><br /><a href="http://www.cdbaby.com/cd/smudgenyc" target="_blank">http://www.cdbaby.com/cd/smudgenyc</a>

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    03.30.13 @ 09:28 AM
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    You should hear a difference Smudge, but a lot of it will depend on the preamp too cause the power section's only amplifying the preamp signal.
    If both preamps are set up with exactly the same settings you should notice more of a difference at louder volumes. Put them both on clean settings and then see if you can hear the differences. There's a difference in voltages and power between the two types of tube, but the EL-34 has a little more raw sound with more breakup at an earlier stage, where a 6L6 tends to have a bit more bottom, smoother sound and will ususally stay clean longer, depending on it's power rating. A Groove tube 6L6 for instance, with a rating of 1-4 will break up just as quickly as an EL-34, but the sound will still be different. EL-34's have a rating system too and can be rated to breakup quickly or very little. I had some EL-34's at one time that were rated at 10, and I couldn't get those suckers to break up at all. I keep my EL-34 rating at 6-7.
    A 5150 uses 6L6's, but the preamp is so hot that it's hard to tell. A marshall uses El-34's in most amps, but their preamps are not as hot. A big part of what gives a marshall it's classic sound, besides the output transformer are the El-34's.
    If you listen to a Fender amp with 6L6's you can hear the true tone of them(6l6's).
    Once you find the right tube then it's a matter of finding the right rating for the amount of breakup you like, again depending on your preamp.
    Not too confusing huh.

  3. #3
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    12.31.69 @ 04:00 PM
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    Originally posted by tribb:
    You should hear a difference Smudge, but a lot of it will depend on the preamp too cause the power section's only amplifying the preamp signal.
    If both preamps are set up with exactly the same settings you should notice more of a difference at louder volumes. Put them both on clean settings and then see if you can hear the differences. There's a difference in voltages and power between the two types of tube, but the EL-34 has a little more raw sound with more breakup at an earlier stage, where a 6L6 tends to have a bit more bottom, smoother sound and will ususally stay clean longer, depending on it's power rating. A Groove tube 6L6 for instance, with a rating of 1-4 will break up just as quickly as an EL-34, but the sound will still be different. EL-34's have a rating system too and can be rated to breakup quickly or very little. I had some EL-34's at one time that were rated at 10, and I couldn't get those suckers to break up at all. I keep my EL-34 rating at 6-7.
    A 5150 uses 6L6's, but the preamp is so hot that it's hard to tell. A marshall uses El-34's in most amps, but their preamps are not as hot. A big part of what gives a marshall it's classic sound, besides the output transformer are the El-34's.
    If you listen to a Fender amp with 6L6's you can hear the true tone of them(6l6's).
    Once you find the right tube then it's a matter of finding the right rating for the amount of breakup you like, again depending on your preamp.
    Not too confusing huh.
    Good descriptions of the two tubes, I've also found that the EL34s compress more than the 6l6's. However the main reason you don't get any power amp characteristics from the 5150 is because it has a cold fixed bias, some stock 5150's have tested at about 10mA of plate voltage going into the power tubes. This puts the amp in what is called "crossover distortion", similar to the way a solid state power section amplifies the preamp. In order to get the amp out of crossover distortion, the plate voltage needs to be at or above 30mA, and adjusted to no higher than 42mA(this is a really hot power section). I'd say ideal get some nice power tube break up is at about 35-38mA, that keeps you running pretty hot but not too hot. Fortunately the 5150 can have a trim pot installed(for about 50 bucks, by just about any good amp tech), in place of the stock fixed bias resistor, and this allows the bias to be adjusted out of crossover distortion and actually incorporate power tube break up into the 5150 sound. Tribb is correct though, that if you run the preamp to high it will cover up the dynamics of the power tube section, kinda like running a a dimed fuzz in front of a Marshall. You can however keep the preamp gain down at about 2-3 to stay around the 3rd gain stage, and that will give you a good mixture of preamp and power amp breakup resulting in a nice dynamics, without the trademark 5150 preamp buzz, and lack of power amp dynamics. You also want have to crank the amp nearly as loud to get the buzz out, as the power tubes get to work really quickly, with the proper amount of plate voltage going into them.

    I heard a while back 5150 that a lot of you who aren't fans of the 5150 would love. It had the bias mod($50), and the guy had Bob at Eurotubes match him an integrated quad of JJ EL34s and 6l6s(same price as a quad of 6l6s), and it yeilded the best sound I've heard out a 5150. It had the EL34 bite and compression, with the 6l6s smoothness and bottom end.

    Smudge, I also think that the XXX is a fixed bias amp(i could be wrong). That's why you're not able to tell much of a difference between the 6l6s and the EL34s.

  4. #4
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    01.23.09 @ 11:26 AM
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    yes, it's fixed bias... YOU GUYS ARE GREAT!
    Plstrcast everywhere else, Smudge NYC here.. so kiss my arse!<br /><br /><a href="http://www.cdbaby.com/cd/smudgenyc" target="_blank">http://www.cdbaby.com/cd/smudgenyc</a>

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    09.05.15 @ 12:20 PM
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    I think a 5150 can be made to sound very good stock. It take a bit knob turning, and some earplugs, but it can be made to sound smoking. The problem is for me it does that one sound and that's it.
    A few of the local boys up here swear by them, Devin Townsend is one, and live he gets a killer tone, but it's just a balls out metal amp. If that's all your doing, then they work great.

    SMUDGE NYC, what do you think of the triple x? I heard one for the first time a few weeks back, and when you clean em up, they almost sound like the most recognizable boggie tone that's so popular these days, just a bit cold. I can't believe how much gain some of these amp have, it's nuts, who the hell would ever use that much gain?

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    12.11.05 @ 03:08 AM
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    Hi folks....I've had my 5150 combo for a year now and very pleased with it too.. [img]smile.gif[/img] so its about time for a re-tube
    I'm gonna go with Bobs recomendation, and get some matched JJ tubes for the pre & power amp, I found a supplier here http://www.watfordvalves.com/mainindex.htm
    Do ALL 7 valves have to be matched together? Or the pre & powre amp done seperate (2 & 5)?
    Will usin' the JJ tubes make a big difference?
    I'm not really technically minded so I'm probably best gettin' a pro to do it for me

    Cheers folks [img]graemlins/thumb.gif[/img]

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    03.30.13 @ 09:28 AM
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    The power amp section should be rebiased for the 2 new power tubes, but the preamp section will bias itself.
    When you take it in for the power amp tubes just have a tech install the preamp tubes for you as well.

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    01.23.09 @ 11:26 AM
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    I LOVE the sound the xxx gets! To me, it's a Recto-clone all the way
    Plstrcast everywhere else, Smudge NYC here.. so kiss my arse!<br /><br /><a href="http://www.cdbaby.com/cd/smudgenyc" target="_blank">http://www.cdbaby.com/cd/smudgenyc</a>

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    12.11.05 @ 03:08 AM
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    Originally posted by tribb:
    The power amp section should be rebiased for the 2 new power tubes, but the preamp section will bias itself.
    When you take it in for the power amp tubes just have a tech install the preamp tubes for you as well.
    Cheers Tribb...

  10. #10
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    12.31.69 @ 04:00 PM
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    Originally posted by tribb:
    The power amp section should be rebiased for the 2 new power tubes, but the preamp section will bias itself.
    When you take it in for the power amp tubes just have a tech install the preamp tubes for you as well.
    You must have skipped my post because it was so long? The 5150 can't be rebiased, because it has a fixed bias, which means its not adjustbale. The fixed bias is conveniant for replacing power tubes, but it's what give the amp the cold, sterile feel to it. So Kamikazee if you're tech charges you for a rebias on a 5150, consider it a tip, because it can't be done on a stock 5150.

  11. #11
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    12.11.05 @ 03:08 AM
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    Originally posted by LarryJ:
    </font><blockquote>quote:</font><hr />Originally posted by tribb:
    The power amp section should be rebiased for the 2 new power tubes, but the preamp section will bias itself.
    When you take it in for the power amp tubes just have a tech install the preamp tubes for you as well.
    You must have skipped my post because it was so long? The 5150 can't be rebiased, because it has a fixed bias, which means its not adjustbale. The fixed bias is conveniant for replacing power tubes, but it's what give the amp the cold, sterile feel to it. So Kamikazee if you're tech charges you for a rebias on a 5150, consider it a tip, because it can't be done on a stock 5150.</font>[/QUOTE] So wots this bias mod that Bob from Eurotubes does on 5150's ??

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    03.30.13 @ 09:28 AM
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    5150's can be rebiased as well as modded to tone them down a bit. My tech., who's name is Bob as well (no relation), has done both to 5150's.
    The result is quite a difference from the original sound. I don't care for it, even with the rebias and mod, but the guys that are die hard 5150 users have no complaints.
    A big part of the sterile sound of those amps are the sheffield speakers. If you don't believe me put your marshall, or peavey, or mesa head through a set of sheffields and see what it sounds like. [img]graemlins/yell.gif[/img]

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    12.31.69 @ 04:00 PM
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    Originally posted by tribb:
    5150's can be rebiased as well as modded to tone them down a bit. My tech., who's name is Bob as well (no relation), has done both to 5150's.
    The result is quite a difference from the original sound. I don't care for it, even with the rebias and mod, but the guys that are die hard 5150 users have no complaints.
    A big part of the sterile sound of those amps are the sheffield speakers. If you don't believe me put your marshall, or peavey, or mesa head through a set of sheffields and see what it sounds like. [img]graemlins/yell.gif[/img]
    Yep, I'm not a fan of the Sheffeilds at all. I like my 5150 tons better with my 4x12 with Celestion V30s. You're right, the lack of speaker breakup as well as power tube break up is what makes it sound sterile.

    In stock form there's no way to rebias a 5150, as the plate voltage is controlled with a resistor. But once you have the resistor replaced with a trim pot you can rebias. I don't think "tone down" would be the right thing to say, as the average plate voltage going into the power tubes on a stock 5150 is about 10mA , that's a horribly cold sterile bias, and the amp isn't out of crossover distortion until about 30mA, and you start getting good power tube breakup at about 35-38mA.

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    12.31.69 @ 04:00 PM
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    [/QUOTE] So wots this bias mod that Bob from Eurotubes does on 5150's ??[/QB][/QUOTE]

    It's a very simple mod, any amp tech can do it for about $50-$60 US. The resistor that controls plate voltage going into the power tubes is replaced with a trim pot, which allows you to adjust the plate voltage(adjust the bias) on the amp. It warms the amp up a lot, and takes away a lot of the sterile feel the amp has.

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    03.30.13 @ 09:28 AM
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    I spoke to my amp tech this evening. The bias is something that a trim pot will take care of, but the internal mod he does has nothing at all to do with the bias.
    Biasing will allow you to use different rated 6L6 tubes to control breakup to an extent, but has nothing to do with the actual tone of the amp.
    From what I'm told as well, the bias is more than just adding a trim pot because of the output circuitry.
    The mod for tone, has nothing to do with bias.
    He changes a no. of characteristics of the preamp circuitry by rewiring the preamp itself.

 

 

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