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Is It A Tube Problem?


cw0401
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And there are techs like me who deal with both,... and radio station transmitters as well.

Sorry, which exact parts of the processor board get damaged by jj's again??? And you say it is due to the fact that their curve doesn't quite match the eh's..?

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That and other things.

As for what's on the board,... can't get into that.

 

Klystron is a special kind of tube used for power amp outputs at

hi wattage commercial radio stations. Also used in microwave communications.

 

Oh, and,...  in certain situations the oil can are used as coolant for the tube.

 

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I love what happens when Marty strums his first chord!  I think it's in every guitarist's DNA, a kind of racial memory peculiar to six-string slingers to be blown backwards by the blast of your amp, so seeing it with my own eyes on the silver screen was enormously gratifying--and riotously funny!

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ease up man...I do not know this for sure, but I think actual Line 6 employees cannot give any public DIY advice in regards to technical procedures or IP. He is saying all that he is allowed to say. If what he says scares you, then you should take your amp to a shop...It means you don't know enough yet to do it properly and safely...THESE THINGS CAN KILL YOU....It would not be cool to get killed by your amp while working on it....

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Years ago there was a time when information could be had if one asked the right person with experience and knowledge. Over time this has dissappeared due to people getting hurt, ending up in the hospital fighting for their lives or dead in the end. After that the lawsuits start up which cause law to change and it changes the people who have the busineses and knowledge forever after. Add on top of that knowledge is gained by experience and experience is the reult of hard work, some of which never get paid for. Knowing this, knowledge becomes a very important and valuable tool for years to come.

 

For instance, the cars of today are more complicated to work on than say cars from the 60's. Knowing that the 60's conveyances were not as complicated they didn't require as much technical information laid out on paper to make up a service manual or manuals. Cars of today have a library for a service manual, a stack of books that are difficult to carry, lol. More information more valuable.

 

At times, 24 years ago If I needed a small amount of infromation to fix a car and couldn't buy the service manuals 'cause of cost, I would be charged a fee for the tid bit that I needed, lol.

 

Yes, just like Melissa Francis says, "Even when they say it's not, it's always about money".

 

In the end it's about CYA.

Edited by Brazzy
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I've been running TADs STRs for about a year no problem.  In fact a just ordered a new back up set about month ago just before I read this thread.  After reading all of this I decided to get a new matched set of EHs per psarkissian's advice.  I bias and install the tubes myself so for roughly $25 I wanted to see how a new set would compare.  My thought was if there wasn't any huge difference I would run EHs and move on (I only have one other backup amp left!!).  What I found was that a new set of EHs sounded really really good.  I've had them in about two weeks and played through rehearsal last night.  I'm not going back - I'm going to take psarkissian's advice and run matched sets of EHs from now on.  I guess the only reason I'm writing this is that I wonder if you compare any set of EL84s that are brand new to a set that has been used and pushed hard for a year or more - the new one would sound better.

 

Take it for what it's worth.  So much goes into a tone (the person playing, guitar, pickups, strings, tubes, preamp tubes, speakers, cabs, pedals or POD, signal strength, PA systems, microphones for cabs, the room, what your band is playing, style of music, etc.) this is just one aspect of all of that.  I think the amp sounds absolutely wonderful - I'm sticking with EHs.

 

thanks psarkissian!!

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Just this past time I was comparing a new matched set of EHs to a new matched set of TAD STRs.  In the past I tried JJs, Gold Lions, Tung Sol and then obviously TAD STRs.  I'm not saying any or all of those are bad sounding tubes at all.  I'm not an amp tech nor do I understand all the curves, etc.  So if I can get great tones with the EHs I decided to go back to be safe.  The main issue I had with them in the beginning is that it seemed to get "harsh" very quickly especially when over driven.  The ones I got in there now sound fantastic.  I'm glad I tried a new set to compare apples to apples.  I'll probably change them out about once a year now - I think I let the original stock EH tubes go too long.

 

The PI spot I've tried a bunch of tubes and keep going back to the Sovtek LPS.  I've tried the JJ 803, JJ 83, Mullard 12X7 (which I think is the same tube as the Sovtek LPS), Tung Sol & the Tung Sol 12AT7.  Lastly I just tried the Northern Electric 12AX7.  I keep going back to the Sovtek and will probably just run that for a long time.
 

Hope this helps.  Good luck!!

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  • 1 month later...

 

Just play the amp, don't mod it or do anything strange to hot rod the hot rod.

Can you comment on the modification of having a bias trim pot and probes mounted on the chassis back? I am seriously wanting to do this. I would pay a tech to do the mod, after which point I would start swapping and biasing tubes myself. I have the DT25 COMBO and the bias pot and test probe location necessitates a chassis removal anyway...

Really appreciate any and all info on this.

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"The Wall of Sound was comprised of 586 JBL speakers and 54 Electrovoice tweeters powered by 48 MacIntosh 2300 Amps (48 X 600 = 28,800 Watts of continuous (RMS) power."

 

who's the band? it looked like the Grateful Dead at first, but there's only one drum kit...

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Tube amps should be dealt with by a Line 6 authorized service center.

They will have access to service manual and service info. There's more

to the bias procedure than adjusting a trim pot. Specified tubes should

be used.

 

I see too many amps come across my bench because someone tried to

hot-rod an amp that's already hot-rod. It's a hybrid amp with a digital section

and with multiple gain loops and amp classes. Using non-spec tubes will

create problems. Using incorrect bias will create problems, bias is not a

"one size fits all" proposition.

 

These aren't our grandfather's Marshall or Phase Linear tube amps.

Leave it to the guys with the service info access. Besides,... it really hurts

when you touch the wrong thing and get zapped!

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"The Wall of Sound was comprised of 586 JBL speakers and 54 Electrovoice tweeters powered by 48 MacIntosh 2300 Amps (48 X 600 = 28,800 Watts of continuous (RMS) power."

 

who's the band? it looked like the Grateful Dead at first, but there's only one drum kit...

 

 

Definitely The Grateful Dead! My guess would be, if only one drum kit, then it is during the time Mickey left the band after his Dad, Lenny Hart ripped the band off for a large amount of $$$.... Eventually they reunited with Mickey, but stuff like Europe '72 was all Kreutzmann.

 

Gotta love descriptions that start off like this!!

 

"After Owsley "Bear" Stanley got out of prison in late 1972, he, Dan Healy and Mark Raizene of the Grateful Dead's sound crew, in collaboration with Ron Wickersham, Rick Turner, and John Curl of Alembic combined six independent sound systems using eleven separate channels, in an effort to deliver high-quality sound to audiences. Vocals, lead guitar, rhythm guitar, and piano each had their own channel and set of speakers. Phil Lesh's bass was piped through a quadraphonicencoder that sent signals from each of the four strings to a separate channel and set of speakers for each string. Another channel amplified the bass drum, and two more channels carried the snares, tom-toms, and cymbals. Because each speaker carried just one instrument or vocalist, the sound was exceptionally clear and free of intermodulation distortion."

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  • 5 years later...

Dear Psarkissian,
 

Could you help me out with a problem I'm having with my DT25. I had it serviced here in the Netherlands (at Hanex, an authorized Line 6 repair centre) 
because one of the EL84's was "red plating", after I played the amp for about 20 minutes at a moderate output level. Suddenly a "hum" occurred  which 
I took as a signal, to switch the amp back in standby mode certainly after I noticed the "red plating" tube... 
So I took it to the repair centre. They have changed the  EL84 tubes (matched pair...) and re-biased the amp. Yesterday I got the amp back from them and
tried it out.... After about 20 minutes of playing it.... Same problem occurs. :(  Loud hum, one "red plating" brand new EL 84.
Could you give me some advise please, to handle this issue?
I bought this amp (sec hand) from a friend, who has used it for years, without any problem. I don't want to spend a fortune on it. What is wisdom in this case.
They charged me about $170,-- for this fix. I bought the set(amp + cabinet) for about $400,-- Anyway, I will contact them about it tomorrow.
As a youngster I used to build and fix amps myself, but after your post I decided to take the "official road". :) 
Thanks in advance for your reply!

Yours sincerely,
Ron Pluijm.
(Netherlands)

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