mtreehugger

I reactivated another thread with the bench tech who says "only use EH." It's bumped toward the top of the list of threads in this forum. He just wrote today that Sovtek is the same factory as EH, but they scrutinize the EH to match (Bogner's) tighter tolerance requirements (not his exact words, but read all this guys posts) and paint the EG logo on the glass. He also says that other tubes would need to be biased to a different voltage, which would to me indicate that if you have a tech with a sine wave generator and an o'scope you could probably use other tubes. However, that is not recommended by this gentleman. My take is that if you're swapping tubes and biasing yourself, stick to EH. Geez, I SURE hope the EH tubes I'm getting are quiet compared to the dull roar I'm getting now!!!

You almost make it sound as though the EH EL34 pair I ordered from MF would not meet the same requirements that the OEM tubes meet. That can't possibly be, can it?

Do FW updates to the DT ever fail? Mine went like a dream, Monkey saw through my interface right to the DT without me even needing to select anything, and the process showed no signs of glitches. However, I notice no difference in my amp. I still get loud pops when changing patches unless the voicing, class, and pentode remain unchanged. It's like the updated failed, but monkey sees my DT at the latest FW level. THANKS!

Thanks for the prompt reply! There is a Q&A in the Knowledge Base by Line 6 Tony (http://line6.com/support/page/kb/_/amplifiers/dt50dt25/dt50dt25-faq-r144) where he says that the DT25 ships from the factory with Sovtek, not EH, power tubes. Another owner, inovine, reports that his DT25 was originally equipped with EH Tubes. (http://line6.com/support/topic/12006-dt-tubes-is-there-only-one-choice/) Your assertion that only EH tubes can be used, does that pertain only to the DT50, or are you referring to both DT50 and DT25? (Did Tony make a boo boo?) Also, the EH EL34 comes in soft, medium, and hard matched pairs, with soft saturating the earliest, hard the latest, etc. From your perspective, are these 3 "flavors" essentially the same thing? Do they all meet spec, or is only one flavor recommended? If so, which? Finally, do you know which flavor ships from the factory? (I would assume medium, but we all know what happens when one assumes, as is evidenced when we phonetically dissect the word into its components for analysis...) : ) THANKS!!!!

I tried swapping my inverter and boost tubes and the white noise seems to have ramped up. I was testing presets, and when I went from NFL-III the noise got really loud. When I went back to NFL II the louder noise remained. I suspect, without any knowledge of the circuit, that the inverter tube and the boost tube are unaffected by gain and volume knob adjustments. (So then my symptom of having a relatively constant white noise roar regardless of volume and gain knob positions would be consistent with noisey tubes.) Just making sure here--Is that correct? The noise is now killing me. I think it may be getting worse every day, but having only owned the DT50-112 for a week, and due to the complexity of HD POD+DT et. al. and my experiment yesterday, I can't quite be certain of that. I've ordered a GT balanced inverter, a mullard for the boost, and a matched pair of EH "medium" EL34s. In the meantime, would it be advisable for me to pull my lone 12AX7 from my '70s-era Dual Showman and try it in either the boost or inverter positions of my DT50? I'm caught between my obsession with the tone potential in my DT and a fear that such an experiment might harm this elderly vintage tube.

I wouldn't draw any conclusions yet. Innovine says his DT25 came with EHs, and he had JJs fail. Also, we don't know for sure what to make of the conflicting statements from the Line 6 employees.

FOUND IT! I believe he's talking about DT50 only. http://line6.com/support/topic/2998-is-it-a-tube-problem/

Question: you're talking about the DT50 only, right? DT25 ships with Sovtek power tubes, correct? Can you tell me which of the available 3 "flavors" that the Electro-Harmonix EL34 tubes come in--soft, medium, and hard--are shipped in the DT50? Can we use any of these 3 choices, or are we limited, and to which "flavor?" THANKS!

here's a great post from Line 6 Tony. Apparently it's only the DT50 that comes with the EH power tubes, and the DT25 comes with Sovtek. Q: What tubes ship in the DT50/DT25 amps? A: DT50: Electro-Harmonix 12AX7 preamps tubes (2) and Electro-Harmonix EL34 power tubes (2). DT25: Chinese-branded 12AX7 preamp tube (1) and Sovtek EL84 power tubes (2). Everybody who hasn't already should read the entire post: http://line6.com/support/page/kb/_/amplifiers/dt50dt25/dt50dt25-faq-r144 This leads me to believe it's only the DT50 where, reportedly, it must be EH power tubes. **********I STILL WOULD LOVE TO KNOW IF LINE 6 SHIPS SOFT, MEDIUM, OR HARD TUBES WITH THE DT50, AND IF ANYONE HAS EXPERIMENTED WITH THESE "FLAVORS" OF EH TUBES**************

What specifically did they repair/replace? What were your symptoms originally?

Brazzy, you definitely deserve some recognition for your efforts here! Thanks!!!

Good to hear from you--I saw your earlier posts on this subject in an earlier thread, and have been wondering how your tubes are faring. So your noise floor got better swapping in tubes. Sorry I'm not familiar with DT25. Are you referring to the the little ones (PI and boost?) and not the power tube(s)? Have you ever replaced the little tubes? I think they're 12AX7's in your amp as well as mine... Spaceatl points to these as the noise culprits. I just ordered a GT balanced inverter and a mullard for the boost. I'm expecting a very noticeable difference, but through Amazon, who knows how long it'll take. Also, I'm tempted to try something other than EH power tubes, but still wary... I have to find that post from the Line 6 guy where he says only EH can be used for the power tubes (but so far no luck).

Thanks for the hardness clarification, Brazzy! My guess is that Line 6 installs the mediums and it's okay to go with soft or hard as long as it's EH. Anybody have any info on this? Anybody want to talk about which they prefer and why?

So THAT's where I got the (wrong) idea about EL84!!! Very much looking forward to your report! From what I read, the JJs will sound better than the stock EH's, but lifespan may vary. But that's just a few cases, hardly definitive.

"Quiet" can be subjective, but I doubt anybody would say mine's quiet. It sounds like I have a fuzz box (i.e. distortion pedal, for all you young-uns) hooked in and running. I did read that aging tubes can cause this. I have no clue how old these are, but they look very new. I also read that the EH tubes are noisey, so I curious if there is an alternative. Also wondering about the soft/medium/hard options EH provides for these tubes. Anybody have any insight here? THANKS!

THANKS! That woulda s_cked, as I was confident enough it was 84 that I probably wouldn't have double-checked.

As I write this, I'm listening to the whoosh of my DT50-112. I should be hearing less of that, or nothing at all, I believe. And I'm ready to try some new tubes, even though I don't actually need them at the moment. From what I've seen here in this forum, the EH tubes from the factory are the culprits, but folks trying JJ tubes and other makes have experienced premature failure. There was a post from a Line 6 tech who said that the el84s <EDIT--he did not cite EL84s, I believe he was speaking only of EL34s, which go only in the DT50> MUST be the EH tubes due to narrow tolerances required by Bogner's design, and that EH was the only tube known to be in compliance with the stricter standards. <EDIT see below for the link to this quote> Further confusing to me is the lack of discussion about the EH tube choices in the el84. <EDIT--SHOULD BE EL34 FOR THE DT50> If you look at MF or Amazon, you'll see that they come in 3 flavors: soft, medium, and hard. Which ones do the DTs ship with from the factory? One poster opined that replacing the inverter tube and the other little guy (12ax7s if memory serves) helped with the noise floor. Does anyone else concur with this? Apparently any ole 12ax7 will work for these. Should I stick with EH or is another brand better? So what do you, oh community of DT players, have to say? Care to share? THANKS!

That's reassuring, Zap. Thanks! I was kinda thinking biasing myself, but you're right--why do that without new tubes? I'm still worried about the electronics, though. The chassis (i.e. metal box) gets hot enough that you couldn't keep your hand on it for more than a few seconds, even while playing at the aforementioned low levels. In a vintage amp all that's in there are caps, resistors, and wires, mostly, and those items aren't known to be vulnerable to heat. But in this thing there are semiconductors and God knows what all (maybe a smartphone). Has there never been a heat-related failure to the non-tube electronics in a DT? In particular, the combo amps where the tubes are below the electronics...?

I fired up my old Dual Showman Reverb, which has like 20 tubes in it, and it got hot, but not as hot as the DT50, which as you know has just 4. That has me wondering. Also, because all those electronics are sitting above the hot tubes, it's got me worried. And I'm just running low power mode with the master at 4 in class AB--it's not like I'm pushing the thing. In fact, the tubes are kinda dimly lit, not bright at all. And they look brand new!

Radatats, that's just too friggin funny!!!!

I've been googling, and among gear heads there's somewhat of a debate about cooling fans. One guy says they cause the tubes to work harder in order to maintain their operating temp, and claims that amps with fans have more tube failure, and further that the tubes closest to the fans failed more than the ones farther away. Another guy talks about the heat causing his circuit board to warp. Brazzy, if your head has the chassis at the bottom, below the tubes like a Marshall, you probably don't want a fan. In my case, I can't ignore the threat to the electronics that are sitting directly above the tubes (even if I could ignore the heat issue with tubes all by themselves).

Thanks, zap! So how hot should my DT be running? I have another thread on this. I know now the heat isn't coming from the transformers, but I have no basepoint so I'm not sure if I have a problem or not.

So you can pick any reverb as long as you can send it the MIDI command, eh? I'd guess the same would apply to the amps, except you'd be without deep edit parameter adjustment. I wonder If I can do that with what I've got. It's not MIDI notes, it's something else, correct?

I finally got smart enough and courageous enough (my amp's in an awkward-to-reach location) to touch the transformers. The one furthest from the tubes was actually cool to the touch. The one on the other side was a bit warm, due to proximity to the tubes, I assume, So it can't be coming from the transformers. Even in low power mode, even with the covers off, that chassis still heats up, unlike yours, Brazzy.

Zap, is it possible for you to read my OP in a different thread and weigh in on my heat issue? Brazzy has been very helpful, and after comparing notes we know that his DT50 head runs much cooler than my DT50-112. Can my problem be due to a bad transformer ala TSB-059? Am I just being overly-protective? is my prized DT destined to be a boat anchor? should I start getting Techs and Line 6 involved? There aren't many who know amps like you do, so your thoughts here would be invaluable. My OP is here: http://line6.com/support/topic/11927-how-hot-should-my-dt50-get/ Thanks!