mtreehugger

I do not know what that means. Sorry. They're made in Russia. I bought some replacement EH EL34s for my DT50, and even though they're a matched set there are numbers on each individual box that are dramatically different, suggesting that my matched pair comes from different lots--but who knows? One other complexity is that EH tubes are often offered in differing sub-variations, soft-medium-hard, which has to do with how easily they break up into distortion (soft = more distortion). We have no further info, though we're in the process of trying to find someone, anyone, who has experience or knowledge. Your tubes will need to be biased. Line 6 will tell you that only a Line 6 authorized service center can do this. These amps are "hot-rodded," and apparently if the new tubes don't match, your amp could wind up on a tech's bench. (seems this happened mostly involving tubes other than the EHs)

Amazing that Line 6 won't say what they put in! Thanks for the info, Colonel! You know, it just occurred to me that since I have a pair of EH EL34's I should look at the markings on them. So I did, but can't say that I see anything. And I can't compare them to my DT since it's in the shop. The tubes' boxes have some kind of nomenclature on the individual labels that's beyond me. Looks like there might be a lot number on each box, which is discomforting as the tubes are then from different lots if that's what it is. There's also one label slapped across the 2 boxes which says "EL34EH Pair Med Green." That could have been put on by MF or anybody (I kinda think it was MF).

You might ask them if the Tungsol tubes fall within parameters (requirements/specifications) of the EH tubes. To put that another way, can these tubes be swapped into an amplifier that is designed to use only EH tubes, and would the DC bias voltage spec for that amp with the EH tubes be the same if Tungsol tubes were substituted?

Thanks for the info!

I would just like to know which variation, soft, medium, or hard, Line 6 installs. That much should be easy to learn. It would also be very nice to know, given Bogner's stringent requirements, whether these minor variations could have a negative impact on the DT. Since we're being told that we can't just replace tubes, that they must be the exact tubes that Bogner specifies and they must be biased only by a Line 6 certified service center, it does seem theoretically possible that, for example, a soft EH power tube would fall outside the Holy tolerance range. Maybe it wouldn't sound as good in the DT, or wouldn't last as long. Or it could sound better than stock if you're going for a bit of dirt (like most of us). So far there is zero feedback on this that I'm aware of.

Brazzy, did David read you the riot act about biasing your own tubes? He did so with me at the merest suggestion that I might be leaning that way, even though I never said such a thing.

I have a scope too. Need a sine wave, need a test point, then adjust the pot until the "notch' is gone. Due to the electrical shock hazard and dummies biting off more than they can chew, don't expect the needed info to be made available.

+1 to that!

There's no adjustment for anything other than bias, is there?

I totally wouldn't take out the tubes if they're working fine. Did you bias these yourself? If so, then that's different, as articulated by Partev Sarkissian (Line6 tech) in response to my earlier query. I believe (but don't have proof so be wary) there are amp techs that are putting JJ and other tubes successfully into the DTs, and because they use a signal generator and oscilloscope they are able to bias the tubes correctly. The DC voltage arrived at would be different from that of the EH tubes. --wait--I just re-read your thread and you said a repair center put them in. I think a discussion is appropriate here. If they're any good, they did not simply follow the DC voltage spec but use the proper techniques to make the JJs work (assuming that this is possible, which I and others who know more than I believe). As for the 12AX7s, those can be any 12AX7 that you like. it's the power tubes that are critical. The Tube store doesn't seem that affordable to me. I bought a backup matched pair of EH EL34s for $34 with free shipping from Musician's Friend. I got a GT balanced inverter 12AX7 and a Mullard 12AX7 for the boost position (DT50's have a 4th tube) from Music 123. via Amazon for about the same. When I first saw the price at the Tube store, I wondered if that was for a single or the pair, since the pair option was selected. (I didn't put the tubes in yet because my amp has some issues and is in the shop for a diagnostic)

Never heard of "Ultra matched power tubes." Is this some kinda gimmick by a reseller? Line 6 says "only EH" and that those tubes are made to conform to Bogner's tighter specs (kinda what you said already, I know). However, I have been universally thwarted in my efforts to find out about the soft/medium/hard variations that EH offers. These variations have to do with how easily the tubes break up and distort. My guess is that any are fine, and the Line 6 installs the medium flavor, but nobody seems willing to confirm this.

Being the EH owns the brand, I think it's a safe bet that they're made in the same plant. In fact, now that I think about it, I believe I read in these pages a post from a Line 6 Tech who reported that all russian tubes are made at the same factory. The EH tubes are held to a narrower spec which works for the Bogner design. Some kind of arrangement between Line 6 and EH was implied. So there's a 50/50 chance that the tung sol tubes are simply EH tubes with a different logo painted on them. Perhaps this is true sometimes but not always--might be the tung sol brand is whatever russian tube is handy/available/overstocked at the moment. Russia and China are both that way. You must have a DT25. I wonder if the same luck can be found in my DT50, which has a bias voltage of 36mv. My guess is that higher voltage means hotter, so it could be more critical in the 50s.

how many hours per week do you play? So the stock tubes lasted 6 months, and since then you've put in EHs, JJs (one or 2 sets) and Tung Sol, correct? Do you adjust the DC bias voltage when you change tubes? Do they all seem to last about the same length of time?

Because speakers have coils but not capacitors, I think you're both essentially correct: "In electrical and electronic systems, reactance is the opposition of a circuit element to a change in current or voltage, due to that element's inductance or capacitance. A built-up electric field resists the change of voltage on the element, while a magnetic field resists the change of current."

Sure hope I get there! I dropped it off for warranty service today. The guys at the shop couldn't believe how new it looks--which it does because the original owner never played it (which I totally can't understand but oh well). It's so weird, I've owned it less than 3 weeks, but from the moment I heard it deliver that creamy articulation to my lead playing and smooth, elegant crunch to my rhythms, I've been obsessed with not letting it go despite the concerns; dating from my original post "How hot should my DT get?" to the excessive white noise thing, the ground buzz thing, and all along trying to get an answer from Line 6 (which I finally did get yesterday on the phone) about TSB 059. But as soon as the data tipped the scales for me to where it seemed clear that I must bring it in for service, a load has lifted from my shoulders! It could easily be gone more than 2 weeks (which is the absolute minimum), but the service center is one of the best in the state, so I am now confident that I won't be having these doubts after this. I mean, yeah, it's possible that my aforementioned concern materializes, but reflecting on all these symptoms which in small part are normal but in this amp are excessive, I highly doubt that something wrong isn't going to be discovered. So at that point I will be living the scenario you predict. :D Yeah, baby! Back to my HD500 for now, but I sure won't forget my DT50 anytime soon.

Very interesting, both of you! Results with non-EH tubes varies so widely. If I'm remembering it all accurately, it seems like the people who put in non-EH the tubes themselves have issues, but when a tech does it there are no problems. Some of the reasons why this may be are scattered in other threads I've posted in, so I'm gonna get lazy with the typing and not be repetitive here.

He already answered that, and yes, my amp is among those s/n's.

I'm sorry, in what scenario can I be confident I won't I experience the problem? Thanks for the advice on calling back!!!

Silverhead, thanks so much for the support! I'm sorry I wasn't clear and neither was Line 6 (David). I do not have a 30-day return or RETAILER support like Marcus 2323. His store is handling it because otherwise he would probably return it. When I found out my amp was on the list, I really was expecting the same treatment he got, and was surprised and disappointed when that didn't take place. Now I'm kind of in limbo. I did not learn much about Line 6's support beyond being told that I should bring it in to get it checked out. He did not tell me much beyond this. I wish he would have. He said that my amp "could be" affected by TSB 059, but that only a very few of those with s/n's on the list are actually affected. (???) I did tell him that my amp has 4 months' transferable warranty remaining. I spoke with a tech from a L6 service center afterward, and when I asked if he could determine if I have the bad transformer(s) as Line 6 stated, he said usually the transformers go bad in the first year. In other words, (my take on this is) they need to see failure to be certain that replacement is required. Because the guy I bought the amp from swears he only used it for 2 hours (I'm thinking 10-20 in reality), I won't have a full year's use by the time my warranty expires, so my transformers' likelihood of failure won't have been fully tested out when my warranty expires. So now I have an amp that could go belly up anytime in the next 11 months, after which I should feel more secure that at least TSB 059 won't bite me. I can understand not wanting to repair amps that might not be broken, but it seems wrong to me to be saddled with an "at-risk" amp and a wait and see approach. The amp is so versatile and sounds so great, but now I very much wish I would have bought something else that is more reliable. Edit 2-24-15: After sleeping on it, I realize I'm not so much "saddled" with an at-risk amp, it's just that I wasn't told that this was a defect and (in effect) a recall, which was what I would have expected. Instead, I got more of a seemingly reluctant concession that bringing the amp in for a diagnostic was an option for me. I was told my amp "could be" affected by TSB 059, which I found strange given that it is one of the affected serial numbers. Because it is under warranty, I am able to bring it in for a warranty diagnostic service, and as such I can't say I'm "saddled" with the problem. However, if after the diagnostic I'm told "it looks good so far so we didn't do anything..." well, then I would consider myself as being saddled because it is unreliable, at-risk, and un-repaired. I'm dropping it off for the diagnostic after work today. I do expect that some repair will be made, and will report back when the service is complete or if I have any further news.

I'll give that a try! Thanks! EDIT: I put the amp in full power mode with channel volume maxed, with gain and master volume at 70%. I heard very little coming out of the speaker, and that's with me trying to get my ear down and directly in front of it. How much hiss and buzz are you folks getting? With all volumes and gains at zero, in Voices II and especially III does it raise any red flags for you?

Marcus2323, were you told they were going to replace transformers and/or whatnot? Or are they merely checking it out? I just called today and found out that my amp, like yours, is in the s/n range where I could have the defective transformer(s). Being that I bought it used, I have no retail outlet to support me. It sounds as though nothing will be done until such time as my amp actually breaks down, which really doesn't allow me to depend on it for gigs (if and when I get gigs).

If you just go direct out on your hd500x then you can monitor the actual tone you're recording as you record it--at any volume you like, through headphones or monitor speakers! I think the Dt amps do sound better, but you can come close with the HD, and sitting in the mix it's tough to hear the difference.

Right on! Now that i've been working with preamp patches for a bit, my full amp patches will probably be tweaked all over again when i go back to studio direct...

Service centers will keep my amp anywhere from 2 weeks to 2 months, I found out. When I saw that GC was having a sale on a rackmount power conditioner at $30 (list is $100) I thought "what the heck?" But when I plugged into it, the AC noise actually got worse! More of a buzz than a hum, with a volume increase to boot. My guess here is that in conditioning the power, filtering out RFI and such, the harmonic content of the 60-cycle AC waveform is being altered. In my case the device actually dirtied it up relative to what's at the outlet. I think I'll try the comparable Furman unit, but if that doesn't fix it...

Brazzy, how long was your amp gone and how much did shipping cost?