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mtreehugger

DT Tubes--is there only one choice?

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So, here's the latest on my end of things - got in touch with the TubeStore, they are going to let me take the JJ's out of the amps and return them; no restock fee if I buy the EHX tubes from them. My amp tech also stocks the EHX tubes - and they stock the "medium". His response is:

 

"Yes we usually stock the medium and bias according to flavor"

 

 

For what it's worth; here is the most recent response from Partev:

 

"Those descriptions are rather pedestrian, but pretty much says what it is.

It has to do with what's called "the transfer function" and how linear it is, and 

operating within that linear region of the transfer curve.

 

As for what we use, I've forgotten.

 

All tubes and amps have a set of "characteristic curves" showing regions of

operations for a given set of volt vs current draw and output loads."

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Asked Tung Sol if there is a difference in quality between EH and TS, this is what I got back:

Both EL84 type are very close in quality, but the Tung-Sol EL84/6BQ5 goes through a tighter selection process.

 

Now isn't that interesting?

 

Of course I hve no idea how close they are to Bogner's magical specs :wacko: 

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Asked Tung Sol if there is a difference in quality between EH and TS, this is what I got back:

Both EL84 type are very close in quality, but the Tung-Sol EL84/6BQ5 goes through a tighter selection process.

 

Now isn't that interesting?

 

Of course I hve no idea how close they are to Bogner's magical specs :wacko: 

 

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?

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So, here's the latest on my end of things - got in touch with the TubeStore, they are going to let me take the JJ's out of the amps and return them; no restock fee if I buy the EHX tubes from them. My amp tech also stocks the EHX tubes - and they stock the "medium". His response is:

 

"Yes we usually stock the medium and bias according to flavor"

 

 

For what it's worth; here is the most recent response from Partev:

 

"Those descriptions are rather pedestrian, but pretty much says what it is.

It has to do with what's called "the transfer function" and how linear it is, and 

operating within that linear region of the transfer curve.

 

As for what we use, I've forgotten.

 

All tubes and amps have a set of "characteristic curves" showing regions of

operations for a given set of volt vs current draw and output loads."

 

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).

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I melted a EH with the BIAS on 25mv so what can I say?

What bias value will let me use jj's without them melting after a few months?
I did indeed bias them to 25mv which is the dt25 bias for eh tubes. So maybe line6 would like to let me know what value won't blow my tubes up.
 

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I melted a EH with the BIAS on 25mv so what can I say?

 

The more I hear, more inconsistencies crop up about going strictly with EH tubes.  

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I changed the EH 12AX7s to JJs. The white noise and hum improved considerably. It was only  the British Chime voicing that was really bad on my amp.

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I changed the EH 12AX7s to JJs. The white noise and hum improved considerably. It was only the British Chime voicing that was really bad on my amp.

Is that voicing II? Most folks, myself included, report the most noise in voice III, which also (not coincidentally) has the highest negative feedback. (Voice IV is a "modern feedback" which means something along the lines of certain frequencies getting more negative feedback than others, but don't quote me).

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Is that voicing II? Most folks, myself included, report the most noise in voice III, which also (not coincidentally) has the highest negative feedback. (Voice IV is a "modern feedback" which means something along the lines of certain frequencies getting more negative feedback than others, but don't quote me).

 

The chime is topo III in class A. I also heard more noise on topo III.

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I just bought my DT25 used, and it has PM Tubes EL84s in it. I have no idea where they're biased, but it sounds great and is really quiet. 

 

I did a little digging on PM, and the founder of the company used to work in the valve business in Britain, and has spent the last several decades helping tube manufacturers in other countries improve their quality. 

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Got my DT25's back yesterday from the second visit to the shop - had them take out the JJ;s and put in EH tubes.

Got them home, and one amp wouldn't make a sound!! The other was fine. Tried L6Link, and a 1/4" cord, etc.

 

Ended up pulling out the new EH 12AX7 and putting the stock Chinese 12AX7 back in, and that fixed the problem!!

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Got my DT25's back yesterday from the second visit to the shop - had them take out the JJ;s and put in EH tubes.

Got them home, and one amp wouldn't make a sound!! The other was fine. Tried L6Link, and a 1/4" cord, etc.

 

Ended up pulling out the new EH 12AX7 and putting the stock Chinese 12AX7 back in, and that fixed the problem!!

 

That ain't right. Although you got it working.

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That ain't right. Although you got it working.

 

Yeah, I had a few minutes of "Oh, Lollipop, I have to take this thing BACK TO THE SHOP AGAIN?!?"!"...

 

Tech said they jammed on them both and everything was working fine before I picked 'em up.

I suppose the car ride home could have tweaked an already faulty tube; or maybe it wasn't seating properly, I dunno.

 

Will have to compare them and see if there is any tonal difference between the DT25 with a 'stock' Chinese 12AX7 and the other DT25 with the new Russian EH 12AX7...

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Tech said they jammed on them both and everything was working fine before I picked 'em up.

I suppose the car ride home could have tweaked an already faulty tube; or maybe it wasn't seating properly, I dunno.

 

I agree, wiggling the tubes may have done the trick. Although, I've tried the wiggle thing and cleaning the contact points thing and never had success. It's been my experience with electrical things that rarely does the device just stop making noise or stop working while in use but once you power it down the next time you power it up the problems show their ugly face which usially means no joy.

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I have 6 EH 12AX7s that are all pretty crummy...All are a bit noisy...only two came out of Line 6 gear...Two are OEM from other gear and I bought two on my own...

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I have 6 EH 12AX7s that are all pretty crummy...All are a bit noisy...only two came out of Line 6 gear...Two are OEM from other gear and I bought two on my own...

 

Yeah, I would say it's safe to look at non-EH alternates to the 12AX7 slot in the DT25's - considering the "stock" tube that Line6 provides is a Chinese 12AX7B.

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Well, it's an EH12AX7 in the DT50....CHINA 12AX7 in the Spider Valves and DT-25....DT50 was so noisey with the stock EH 12AX7s....I changed them within a couple of days of it's arrival...

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Yeah, I would say it's safe to look at non-EH alternates to the 12AX7 slot in the DT25's - considering the "stock" tube that Line6 provides is a Chinese 12AX7B.

 

Seems like they did a very quick turn on your amps!  I believe that if a Line 6 authorized service center sells and installs your tubes, there's a 3 month warranty.

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Seems like they did a very quick turn on your amps!  I believe that if a Line 6 authorized service center sells and installs your tubes, there's a 3 month warranty.

 

Yes; that's another part of this thing that I messed up - I bought my JJ's tubes from the tubestore.com; who it turns out are in Canada, so the returns process is interesting to say the least! Anyhow, to get credit for returning the JJ's with no restock fee, I had to buy the EH tubes, which basically equaled out in total cost, with a few extra $$ wasted on the shipping..

 

Next time, at least now I know what to do.. :)

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Yes; that's another part of this thing that I messed up - I bought my JJ's tubes from the tubestore.com; who it turns out are in Canada, so the returns process is interesting to say the least! Anyhow, to get credit for returning the JJ's with no restock fee, I had to buy the EH tubes, which basically equaled out in total cost, with a few extra $$ wasted on the shipping..

 

Next time, at least now I know what to do.. :)

 

I have a full set of replacement tubes that I haven't installed.  When I sent my amp to the shop, I decided to let them install their own tubes if that's what they found was needed.  That way the tubes are covered for 90 days, which is about when the 1-year warranty runs out too.  The shop charges about $10 more for each tube compared to online prices, which isn't easy to swallow if you're a bargain hunter like me, but this is the least complicated route right now.

 

As for my DT50 in particular, I'm now even more convinced that it isn't just tubes, because as of Thursday they were supposed to call me Friday or yesterday and they did not.  This leads me to assume that parts are being ordered.  If they don't call me Monday, I'm calling them for another update.  

 

Will keep y'all posted!

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Got a voice mail from the shop today on my DT50-112 (after 2.5 weeks).  He says my amp is "a pretty strange one there."  Control signals are either getting mixed up by the DSP or they're coming out of the DSP wrong.  Low power mode is sometimes more like high power mode, actually (depending on the topography is what I think he meant by "sometimes").  Line 6 advised him to replace the DSP board, which is on the way and should be here in a week.  If that doesn't cure all my ills, then probably relays or...?, he said.  

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Whats actually wrong with your amp?

 

My dt25 lvm can sometimes be louder than non-lvm. I asked line6 and they said that is normal/expected in some cases.

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Nearly silent is how they should sound; just a little bit of something. Got my DT25's back from the shop, finally got to test drive them properly yesterday (after the visit to the chiropractor to fix my back from when I tweaked it loading the amps in the car to get new tubes...)

 

Anyway, JTV59 - vdi - to HD500x, linked to the two DT25's. I split the mags and models into two amp models. Basic fx; compressor and drive. 

Sounds sweet. I like the subtle slight difference between the mags and the models when they are side by side like that. Each gets it's own amp, so it's pretty easy to balance the volume difference between the mags and the models. Also makes for cool electric + acoustic when I switch to acoustic models. Overall, liking what I am hearing. Played at reasonably decent volumes; was practicing for a recording session, had the mixes going from mixer to the L2t's, and I played along with the two DT25's. Another 'L2T' sidenote, those little speakers really can crank when set vertical and used like left/right mains. At least, for home use, they sound quite tight.. WIth the band, we typically use them as floor monitors, so the sound perception is quite different. I imagine they would make nice mid-field reference monitors for doing mixing and playback. Plenty of low end, for a single 10" speaker, they get quite loud.

 

Anyway, back to the DT's, I will keep tabs on how these EH tubes do; treating yesterday as basically day one. Still need to get a replacement for that bad EH 12ax7, but as is, it's got a nearly new 'stock' chinese tube in one and the new EH 12ax7 in the other. Near as I can tell, noise floor is minimal.

 

To be honest - and further discussion of it would land in another part of the forum - the L2t's I have next to the DT's make more 'noise'. The fan turning on and off in those L2's is quite a bit louder than any noise floor of the DT25's..Though, when playing, I don't notice any noise from any of it, so it's largely a matter of microphone bleed during quite passages, or in some specific recording context - and in the home rig, I just run the two XLR's from the DT's into the mixer, and don't bother mic'ing them.

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Whats actually wrong with your amp?

 

excessive heat to the point of stinking, excessive noise, ground buzz, and it's in the range of s/n's affected by tsb 059.  apparently there was more wrong than i knew, as i didn;'t notice anhyting related to what the tech found.

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