I have a Bruno Underground 30 head which I love. I am currently using NOS Tesla power tubes in it. It is starting to lose some if its sparkle and headroom. I am wondering if I am starting to wear out the power tubes. I have some questions for you folks who know about these tubes. I have read that they wear pretty fast in these cathode biased amps. I have had them in my Bruno for about 6 months. I probably play about 8-10 hours a week. Is this normal wear for El-84's in this type of amp? How can I tell if my tubes are starting to get worn out? How often do you have to replace yours? And lastly, what kind of tubes do you use? I am leary now of using nos tubes in EL-84 amps, Mike at KCA states that some of these amps will wear out any tube fairly quickly compared to some other types of power tubes. Has anyone tried JJ's and how do you like them? Thanks, Tim
Before I start I should say that I don't use new production tubes at all, anymore, by choice. Now, JJ EL84's along with the JJ E34L and the 6L6GC are the only three JJ tubes that I could tolerate and even liked in some amps. I won't go into a cork sniffing description of the JJ EL84 but all in all, they are decent tubes for new production in the tone area if you get a "good sounding pair or quad" and my experience is that they have what seems to be more output than any EL84 I have ever used. They are plain loud compared to other EL84's that I have experienced. Now, all that aside, I have also experienced inconsistency in tone between one matched pair to the next and with JJ overall, I am approaching between 20% and 25% failure rate which includes microphonics, some only under hard vibration but still. I expect my out of the box unusable rate is around 5%. All of this experience however, was sometime ago. Maybe 2 1/2 to 3 years ago before I decided to spend my money on good vintage tubes at all times.
are you running the Bruno full out? With a master volume? Attenuator? The hotter/harder you run the tubes the faster they wear out. 25X10 is 250 hours if youre running the tubes hard I would expect them to show some wear. I was using nos ges in a bad cat cub with an attenuator, after a while I pulled them to save what was left and ran jjs most of the time. I put the ges in when I wanted the max sound quality.
This amp breaks up nice at that volume, I also use a hot plate as the amp is loud. But I usually use the hotplate only on one or two clicks of attenuation. I am noticing the sound is starting to get a little thinner, with less chime. It is also starting to sound a slight, very slight bit harsh. Sounds great when first turned on but goes downhill from there. I guess the Teslas are getting worn out. Thanks, Tim
Check this link http://kcanostubes.com/content/estore_list.asp?category=32&catname=6BQ5/EL84/7189A Generally, EL84 amps run their power tubes beyond the maximum power dissipation for the tubes. In these amps, ALL EL84s will have shorter life than if run within spec.
Sounds like new power tubes to me. I gig with el84 cathode-biased amps, and tubes last me nearly a year. However, I never have the amps much past 10:00 and I never use an attenuator. When the amp sounds weak, flat, etc., new power tubes do the trick. I typically use JJ's from Bob at Eurotubes. No problems.
That sounds like about the lifespan of EL84s if you're pushing it even at all. Reeek, thanks for the comments on the JJs. I DO find them to be louder than some others. I really need to replace mine with something else.
I am surprised that you got a solid six months from the tubes if you are gigging that much per week. Interestingly, I have been using EL84-based TopHats for the past 7+ years solid. I always use current production tubes, and simply replace them every 3-4 months or so. That way, I know pretty much for certain that my amp won't crap out in the midst of a gig or band practice. I have used JJ's, Ei's, EH's and Sovteks. The JJ's sound pretty girthy and punchy in the midrange area. Ei's are pretty glassy - but a bit lifeless sounding to me. The new EH's are not bad - pretty smooth sounding overall. I have bought tubes from both Doug's Tubes and Bob at Eurotubes. Both have been good to deal with. At this point, i use Doug exclusively. While I have not tried NOS Teslas, I simply decided that I dig the JJ's enough to use them. Due to the fact that these tubes tend to last for about 6 months at best, it just did not seem logical to put out $55 for a matched pair or $110 for a quad. The JJ's, when matched with good preamp tubes, sound more-than fine. Plus, you'll save a bunch of dough over the course of a year if you swap out your power tubes 3-4 times.
I got an old console radio that was full of original Telefunken tubes, including two EL84s. I took out those Telefunkens and tried them in an EL84 amp I had. They sounded good, but no better than the JJs I had been running in that amp. Shea
Get some NOS GE's, they are the best bang for the buck NOS EL-84 out there. Can be had for $50 a pair, works really well in my Top Hat.
The oval plates I find them to have a slightly lower output than most EL84's I play with but they are super sweet. Something tells me a nice dual EL84 Class A amp with GE oval plates and a tube rectifier and a Celestion Blue comes to mind as an etheral mix
To me, JJ's sound good for maybe a few weeks, then they sound wrong, harsh...EH's I think sound better at first, last much longer and don't seem to thin out untill the last of their life...I have had a larger failure rate out of JJ (3 out of 8) than EH's (1 out of 8, and that one I am told is unusual)...... But I am also a old tube snob....my favs are GE's, and am in persuit of Polams (asked Santa for a quad) or Tungsrams...would also like to hear some Herleen Amperex's.............
Mike, I've been waiting to read your reveiw of the Telams since you mentioned you were getting/had them... $45 is a great price for a matched set.....
I actuallt took the plunge and got some NOS Mullard EL-84's for my Top Hat. Between those, the nos pre-tubes and a Heritage G12M that is one nice sounding amp. Perfect for small clubs.
