Hi All,
I have two monoblocks of Lynn's Amity amplifier which use JJ ECC99 dual triodes to drive PP 2A3s.
When I plug brand new ECC99 tubes, the amplifier sounds fantastic. However, after about a year or so of normal use sound changes and becomes "grainy" (meaning it is distorted). $30 spent on new tubes brings things back to normal. I have replaced driver tubes each year for three years now.
Measured parameters for new JJ ECC99 tubes are according to specs. However, when I measure same tubes after several months the same parameters are off significantly.
Here is my question: is it normal for JJ ECC99 to have such a short lifespan?
please share your experience with this tube. Thanks.
I have two monoblocks of Lynn's Amity amplifier which use JJ ECC99 dual triodes to drive PP 2A3s.
When I plug brand new ECC99 tubes, the amplifier sounds fantastic. However, after about a year or so of normal use sound changes and becomes "grainy" (meaning it is distorted). $30 spent on new tubes brings things back to normal. I have replaced driver tubes each year for three years now.
Measured parameters for new JJ ECC99 tubes are according to specs. However, when I measure same tubes after several months the same parameters are off significantly.
Here is my question: is it normal for JJ ECC99 to have such a short lifespan?
please share your experience with this tube. Thanks.
Nothing extraordinary.
Ua=145V Ia=18-20mA (per section).
Here is the schematics:
http://www.nutshellhifi.com/IT-Triode-Amp.gif
BTW, power tubes are three years old and going strong (EH 2A3s).
I just started using the ECC99 two weeks ago so I am unable to answer your question (yet). I am using the ECC99 as CF's to drive the output stage of my dc coupled PP amp, so far they are performing really well. I will let you know if I find them degrading over the next couple of months.
I don't see a specific reason for using the ECC99 in your application. The main advantage of the ECC99 is it's current handeling capability. In my situation I chose them because I needed a twin triode capable of delivering enough current to drive the screen grids of my output stage. In your situation I expect a 'lower-current' twin triode could also do the job.
Have you tried to replace the ECC99 with a different twin triode? The ECC82 immediatly comes to mind because the pinout is the same. Personally I would try if a 6CG7 (noval version of the 6CG7 with a mu of 20) works for you.
I don't see a specific reason for using the ECC99 in your application. The main advantage of the ECC99 is it's current handeling capability. In my situation I chose them because I needed a twin triode capable of delivering enough current to drive the screen grids of my output stage. In your situation I expect a 'lower-current' twin triode could also do the job.
Have you tried to replace the ECC99 with a different twin triode? The ECC82 immediatly comes to mind because the pinout is the same. Personally I would try if a 6CG7 (noval version of the 6CG7 with a mu of 20) works for you.
I think the grainy sound comes from the tubes losing their section to section matching. I had to go through several to find a pair that matched well. I am using them in 2a3 amitys as well. As I am sure you know, the drive requirements are such you need a pretty ballsy tube. I use ecc99 as a directly coupled voltage amp/phase splitter in a pp el84 amp, and they have worked very well for quite a long time.
This is not a good alternative.
The amplifier is interstage transformer coupled, and hence the Rp of the driver tube is something to consider.
The ECC82 (or 6CG7, or 6SN7) have plate resistances (7k or higher) which does not make them a good choice for this application; it would require transformers with very high primary inductances, requiring many turns which leads to high winding capacities, in other words a no-go thing.
When the ECC99 is not reliable for life endureance, better try a 5687, E182CC or 6H30.
I totally agree with you. Another remote possibility is that the driver stage starts to oscillate. I need to check for that too.
IMO you can not generalize.
In my experience within each brand there are good types and lesser ones.
Hi, Tesla was very good especially EL34 tube. These tubes were branded for Mullard. Today are very expensive and rare / brown and black socket /. Pieter Sorry, no offense. Regards Dinkers
Pre "JJ" Tesla tubes have a very good reputation. Don't dis Soviet military production tubes, many of them are very good.
jeff
Irakli, about how many hours of use are you talking in an average year? At this operating point I would not expect them to last much over 1000 hrs and conceivably much less, they're being run very hard indeed. The 5687 may be a reasonable alternative, but will require some wiring changes to accommodate, and might not last any longer..
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