Some people are probably sick of this thread, but I thought I should report on my latest experiences. Especially since it seems to be good news for a change.
At the start of this year I purchased 6 x PCC88/7DJ8 tubes to use in my ET5. These are "new old stock" tubes that were purchased untested at very reasonable prices. I am against paying a lot of money for tubes since I have had such bad luck with their longevity in the ET5.
I tested each tube in the ET5 for a very short while to evaluate their sound and to make sure they were not faulty. All were good.
Tubes are:
2 x Matsushita / National 7DJ8 / PCC88
4 x Philips PCC88. I believe this is the same tube that CJ supplies to GAT users now but I did not purchase these from CJ.
All tubes sounded good, I noted the following at the time:
Matsushita - Quiet. I actually hear very faint hiss right near the speaker as low as 1 (lowest volume) on ET5 though it stay very faint up to about 55. Gets more noticeable at 70 right near speaker. No tings changing volume.
Philips - Quiet. Very faint hiss at 81 on ET5 with ears near speaker. Noticeable above 90. No tings changing volume.
With the Philips tubes, the very faint hiss was at different volume levels for each tube. The lowest level that hiss was noticeable was at 68 for one of the tubes which is a very high volume that I never use for listening. So basically they are very quiet tubes. The Matsushita are also very quiet - just slightly noisier than the Philips.
The comment about the "No tings changing volume." is because a lot of "new old stock" tubes make a sound like a bell ting when changing volume on my ET5. The relays clicking when changing volume must really shake the tube around. This is only a problem when changing volume and is not a problem when listening. These Matsushita and Philips tubes do not have this problem.
Over the course of this year I used 1000 hours on one of the Matsushita and it still sounded good by the end of that 1000 hours. I also used 1000 hours on one of the Philips tubes and it still sounded good by the end of that 1000 hours. I noted the following at the end of the 1000 hours on the Philips:
Still sounds good. At ear next to tweeter can hear very slight hiss at 35 and above on left channel, at 1 and above on right channel. But stays pretty quiet even up to 90 on both channels.
I will continue to use both of these tubes - I just picked 1000 hours as a good amount of time*. It is 4 times longer than most tubes have lasted in my ET5. It will be interesting to see how long they last for - hopefully at least 1500 hours or more.
So I am hopeful that these tubes will work around the issue I have been having with short tube life on my ET5. With a sample of only 2 tubes (one of each brand) so far there is no certainty that all these tubes will be good but I am hopeful. While I am happy with both brands of tube, when purchasing more I will just get the Philips as they are quieter (slightly less noise) and the cost is the same.
GAT users wanting to use these Philips tubes can probably buy them from CJ. ET5 and ET3 users would probably need to find another supplier as I believe CJ has written the following in regards to the GAT2 "Additionally, the tube complement is changed to incorporate PCC88 tubes, of which we have acquired a stock that we are reserving for GAT preamplifiers."
So I tentatively recommend the Philips PCC88 tubes for people experiencing short tube life with their recent CJ preamplifiers, if you can obtain them new for a reasonable price. That may change to a full recommendation after a few years if more of these tubes last a relatively long time for me.
Anthony
* Is it sad that my expectations have lowered so much that I think that reaching 1000 hours of tube life is something to be happy about? Other people think small signal tubes should last anywhere from 1500 hours to 10,000. Oh well - regardless of that - 1000 hours is relatively a good long time so I am happy about it for now.
|