el34 and rectifier tubes

[greg_moreira]

Hi Folks.

Still sorting out my options for an EL34 retube, and I see that it says that I must run this thing in the vacuum tube position if used with an EL34, or the tube life(power tube) will be short lived if used in diode mode.

My question is....is it safe to upgrade to a "stiffer" rectifier tube when using the EL34? The stock rectifier tubes are just too saggy for my tastes. I can deal with some sag, but not quite this much. I read that the reason is because a rectifier tube is going to provide less plate voltage than the diode mode, which is good for EL34 tube life. BUT....I also read that the less saggy rectifier tubes provide more voltage than the stock rectifier tubes. With that in mind....is a less saggy tube just as bad as the diode mode, or still not quite as bad? This is for a 3 channel triple recto by the way.

Lastly(out of curiousity)....how many of you EL34 guys are breaking the rules and running it in diode mode anyways, and what kind of tube life are you seeing?

Thanks!

 

[mikey383]

My question is....is it safe to upgrade to a "stiffer" rectifier tube when using the EL34? The stock rectifier tubes are just too saggy for my tastes. I can deal with some sag, but not quite this much. I read that the reason is because a rectifier tube is going to provide less plate voltage than the diode mode, which is good for EL34 tube life. BUT....I also read that the less saggy rectifier tubes provide more voltage than the stock rectifier tubes. With that in mind....is a less saggy tube just as bad as the diode mode, or still not quite as bad? This is for a 3 channel triple recto by the way.

You can basically run any type of 5 volt rectifier tube in these amps. A lot of people like the GZ34/5AR4 rectifier tubes. They're said to be similar to diodes but with tube sag. Yes, a stiffer rectifier tube will supply more voltage.

Here is a list of compatible rectifier tubes. http://www.nostalgiaair.org/tubes/5u4g.htm

Here's an article about swapping rectifier tubes too: http://www.guitaramplifierblueprinting.com/rectifiers.html

Lastly(out of curiousity)....how many of you EL34 guys are breaking the rules and running it in diode mode anyways, and what kind of tube life are you seeing?

I would be one of those guys. I ran a set of JJ E34Ls in diode mode for nearly 3 years with absolutely no problems. To top that, they were running very hot, at about 93% dissipation (typical Mesas run around 45%). I only stopped using them because I went to KT77s. I still keep them as a backup set.

 

[greg_moreira]

Thanks for the quick reply! That rectifier tube type is the type Id be interested in if I decide to change, so this is good info here. Another quick question.....I was peeking around on the eurotubes site, and its reccomended to upgraded the fuse if using this tube type(as opposed to the stock rectifier tubes).....but this doesnt quite make sense to me. If ultimately, the silicon diode provides the most voltage.....why would those rectifier tubes, albeit hotter than stock rectifier tubes, but still not as much as a diode need an upgraded fuse when the diode works just fine with the stock fuse? Just didnt quite make sense to me....... Im also usually not leaning on the volume very hard that often, so Im not sure how much of a consideration this is either way.

The EL34 tube im currently considering is the tung sol EL34b. I like what I hear about it still retaining good headroom for the cleans, and having some 6l6 qualities as well in the distortion channels. I wonder though.....does it retain the 6L6 flavor because its a colder tube? If so....I may not have the same luck you did trying to run this particular EL34 tube in diode mode.

Thanks for putting up with all of the questions!

 

[mikey383]

No problem.

I don't have a clue why Bob would recommend upping the fuse size. I thought at first it may have something to do with heater current, but after looking up the specs on both tubes, the 5U4 actually draws 1.1A more than a GZ34. It doesn't make any sense to me either, unless it has something to do with the GZ34 having an indirectly heated cathode compared to the 5U4's directly heated. :?: I would try using the stock fuse size first and change it only if it doesn't hold up.

I don't know much about the Tung-Sol tubes. I've heard good things about them, but never personally used them. If I remember right, there was a thread here not too long ago where someone was having trouble with their TS EL34bs....they kept blowing them up.

If you're looking for a EL34 that still has 6L6 qualities, you may want to check out either KT77s, or JJ E34Ls. The KT77 is kinda like a hybrid between the two...lows and low-mids of a 6L6, and the sweet upper mids and highs of EL34s. I just put a quad in my DR and really like them. The E34L is great too. For being an EL34, they still have a lot of low end, and I thought they had more low end than the 6L6s I used to run.

 

[greg_moreira]

Thanks again!

I did some digging, and it took a little bit, but I actually was able to find the thread you mentioned, and yes...it was the EL34b tung sol tube. He mentioned that he had gone through three sets in a year and a half.

I also did a little more reading about this tube, and its said that the reason for the EL34 qualities is because the plate impedence is manipulated. Im wondering if this might be part of the issue, having frankensteined the tube to act more like a 6L6 than you would typically expect from an EL34....and it just cant take the voltage?

It makes it a tough call, because some folks have good luck, and some have bad luck. My gut tells me since I want to either use the diode setting....or use a more potent rectifier tube....I might be one of the guys having bad luck with this tube.

And realistically, this head(the triple rectifier) has so much power on tap, I assume Id have ample enough headroom with any tube. For now...I think Im back to the drawing board, and am going to look around at some other EL34 options before I jump the gun on anything just yet.

Thanks again for the info, as you may very well have prevented me from getting involved in an unsatisfying and costly endeavor!

 

[mikey383]

You're very welcome.

That's interesting about the Tung Sols. Would you mind posting the link to where you found that info at please? I would like to read up on it.

Realistically, unless you're playing un-mic'd large venue gigs, the Triple has more than enough headroom with pretty much any tube. I haven't had headroom issues with my Dual, and I've played some pretty loud gigs with it before.

Like I mentioned earlier, you may want to look into KT77s or JJ E34Ls. A lot of Recto users here really like the E34Ls.

 

[greg_moreira]

I actually found that info on thetubestore in the review section for the EL34's.

http://thetubestore.com/el34review.html

They are not making the claim themselves that the impedance is manipulated, but rather stating that the manufacturer makes this claim. They do not go into much detail beyond that, so at least with this resource...I didnt see any sort of data that would be useful for tech purposes.

Those tubes you mention are on my radar for sure. Another one Im heavily considering is the Winged C EL34. Once I make a choice and buy some new bottles, I'll let you know how it turned out.

Thanks!

 

[mikey383]

Thanks. I've never bothered to check out their reviews before.

The Winged Cs are on my list to try. I was going to try a set of them the last time I retubed, but I found a great deal on KT77s instead, so I had to go that route.