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DT50 replacement EL34 matched tubes tolerances


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HI

I just got new JJ EL34 matched power tubes to install in my DT50.

When i went to bias the tubes i found out that the difference bettwen my matched pair is about 3mV.

I could set one tube to 36mV but the other would be 39mV.

Is this considered a normal tolerance for matched tubes, and will there be any trouble with my amp becouse of this missmatch?

The EHX tubes i had in the amp had a 0.3 mV difference.

Thx for your replies!

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That's a good question. I posted my findings when I bought a pair of matched tubes. I'll dig up the post later. I had a similar mismatch if my memory serves me.

I put the matched set of tubes in my DT50 after I had an issue with the sound cutting out etc. After putting them in and biasing It worked, then shortly after that no sound again. I ended up having to send it in to Line 6 to get it fixed. Ultimately I wasted my money on those tubes, biasing tool, and my time.

I hope you get 'er fixed up this amp sounds fantastic when it's right and the one I got fixed has been working great. I'll be watching your thread too.

 

On another note, just recently I put an Electro Harmonix Tube EQ in the FX Loop of the my DT50HD and Peavey Valveking II 20 Mini Head and was really impressed with how they sound with those 2 extra tubes after the preamp.

 

My findings on the biasing, the following link should take you to the specific post:

http://line6.com/support/topic/6699-dt50hd-output-suddenly-went-silent-any-ideas-why-and-more/?do=findComment&comment=61241

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This is the reason I tell people to use the EH tubes and not JJ's,

Groove Tubes or Mesa. A bias range+/- 3mV is too much. Bias distortions may

occur. Use the specified tubes. These are not tube amps from the

1960's where you can get away with tube swapping like this.

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Oh crap, I misread this thread, lol. I missed the JJ part since the topic heading had EL in it. Oh well, lol.

 

To clarify on my end. I never used JJ tubes in my DT50. I bought what was advertised as ultra matched EH EL power Tubes for the DT50 and still had a very large mismatch. So I have to question wheater I was not getting the correct tubes even though I did as much as I could to get the original replacements. I seriously think I was sold tubes that were not as advertised, buyer beware.

 

To the original poster. I seriously recommend you let Line 6 fix your amp as this is what I did.

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Oh crap, I misread this thread, lol. I missed the JJ part since the topic heading had EL in it. Oh well, lol.

 

To clarify on my end. I never used JJ tubes in my DT50. I bought what was advertised as ultra matched EH EL power Tubes for the DT50 and still had a very large mismatch. So I have to question wheater I was not getting the correct tubes even though I did as much as I could to get the original replacements. I seriously think I was sold tubes that were not as advertised, buyer beware.

 

To the original poster. I seriously recommend you let Line 6 fix your amp as this is what I did.

My amp is not malfunctioning i only wanted to replace the tubes :).

The guys i bought the tubes from said that they consider 3mV difference very well matched tubes :(.

That's why i asked what are your guys opinions and experiances.

Im gonna experiment a bit with the original and JJ tubes to see if i can see a difference in sound and hum, i just wanted to see if it's dangerous to have 'unamatched' tubes in the amp, if it can lead to malfunctions.

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My amp is not malfunctioning i only wanted to replace the tubes :).

The guys i bought the tubes from said that they consider 3mV difference very well matched tubes :(.

That's why i asked what are your guys opinions and experiances.

Im gonna experiment a bit with the original and JJ tubes to see if i can see a difference in sound and hum, i just wanted to see if it's dangerous to have 'unamatched' tubes in the amp, if it can lead to malfunctions.

 

Your right in that my amp must have been malfunctioning since I had some weird noise and pop and then intermittent sound loss. So when I put those new tubes in there that may have temporarily got things working but the real problem was still there.

 

Good Luck with your testing, If my memory serves me spaceatl has been using JJ tubes in his DT's for a long time now. I'm sticking with what Line 6 recommended since it works for me.

 

Try to let us know what you find out.

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The guy you bought the tubes from might think +/- 3mV is fine

for matched pair tubes, but it's over the bias spec for DT50's.

 

I get too many DT50's across my bench that are blown because

of using JJ's, Mesa and the occasional Groove tube. Part of that

is incorrect biasing.

 

These aren't the same old tube amps we used to have in the

1960's and 70's. Can't get away with doing the same kinds of

tube swaps we used to do back then.

 

Best stick with the EH's and have it biased correctly by a Line 6

authorized service who will have the correct test and service info.

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  • 6 years later...

I just have one question, I live in rural Wisconsin. There isn’t an electronics repair place let alone a line 6 service center within 100 miles one way. I have 2 DT 50s a head and a 212. The head wouldent be horrible to ship but the  212 is insane heavy. I’m trying to find instructions on biasing the tubes should I ever need to replace them. I don’t gig ou anymore too old. But I really just enjoy playing the 2 as a stereo setup in my small studio. I think I’d like to get 2 matched pair and put them on my shelf should I need them. I bought my w12 used from guitar center in San Francisco . They shipped it to my house in WISCONSIN for he rediculously low price of 29.00 but you get what you pay for. Thank God these amps are built like a tank. The box was totally demolished when I found it in my garage, opened what was left of the box the amp was upside down resting on the top left corner. There was a slight crack in the wood Jonny where I’m sure it landed probably falling 30k feet from a ups 747. Tough amp. Everything worked perfectly and as it is I got the amp so cheap. I’m saying I’d never want to take a chance shipping it back to line 6. I’m hoping I can find the instructions for biasing because I’ve been playing guitar since 1964 I’ve hade fenders including a 1964 black faced dual showman with twin JBL d 130 15” speakers. I’ve had ampeg PeaVey all kinds of amps. I love love the sounds I get from both my DT 50s. Can someone tell me why line 6 stopped selling the DT series. Such a winner. 

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  • 1 year later...

Update on changing tubes on dt 50, I purchased a Bias meter it wasnt too expensive, after replacing both tubes I just turned the power  on. Does everyone know there is only one pot for both power tubes? anyway I turned the pot counter clockwise and that got it close to the recomended number. ˆreplaced the preamp tubes as well and used eh tubes even though it said pre amp tubes arent brand specific, Anyway after biosing I plugged a guitae in and turned the amp on as well as standby, Man what a difference, I understand Line 6 concern about someone unfamilar with tube amps fishing around inside one, Ive had tube amps starting in 1968 with a 1964 black faced dual showman. The other guitarist in our band had a silver faced dual shoman and he did some electronics upgrades like making his amp stereo, changing a cap on the brite switch making it more a boost switch and a few other things, we did those same things to my black face, He taught me on how tubes and transformers work as well as a rectifier. It sounds more wild then actually what it does. anyway, yes if a person know enough to work in your amp know you are respomsible just like you would be if you tore your car or motorcycle apart. You wreck it or you, thats all on you. and its very easy to wreck you, I double checked my work very carefully . I had just purxhased this dt 50 212 combo as well as a dt 50 head, The conbo is super heavy and it looks like it was dropped out of a cargo door of a 747, the box was destroyed but the amp just had a scratch on the corner. Im sure that it took a bad bounce and 2 weeks later the amp was making weird whistling noises so ( turned it off. I knew it was tubes ive had that happen twice before once with a fairly new ampeg V4 I purchased new in mid 70s and a Peavey custom 212. Both made weird noises and both were fixed with tube replacement, But stick to E H tubes on the DT 50. youwill damage your amp. and Line 6 sadly denies they ever existed. Best sounding amp Line 6 or a lot of other amp makers/ I love how both mine sound. I use the L6 cable from the back of my Pod HD pro x then into one amp then out of same amp into the ther. slick as hell. I hope the helix lsts a long time, I really dont understand why they sunk the dt series, If there wAS smome rumer of it being a bad amp they simply coupl have done a public notice or something. even the original prices for what it was is reasonable. I absolutly the stock 4 tones and there is so muxh editi9ng thats avaikable, cleae as a bell the different distortion of 234 are perfect as well as the Fender Twin number 1, I think its the best amp Ive ever played. 

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