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Message started by Archie on 07/26/20 at 22:13:17

Title: Tube life
Post by Archie on 07/26/20 at 22:13:17

About 14 months ago I bought some NOS Tungsram PCC88 tubes and put them into my CSP3 and ZMA. A couple months ago I had one go bad in my CSP3 and now I'm hearing an issue (tube rush/noise) with one in my ZMA. If I had to guess I'd say these have in the 1000 hr range of "amp on" time on them. Does this seem typical? I remember Steve saying that the tubes he supplied with the ZMA should last in the 10,000 hr range. I'm thinking it may just be Tungsrams as I don't recall issues with NOS Russian military tubes (6N1P-EV) that I've used.

Title: Re: Tube life
Post by Lon on 07/26/20 at 22:35:33

That's not at all typical, nor should these have such a short life.

Title: Re: Tube life
Post by Archie on 07/26/20 at 23:14:40

Hopefully they are outliers. But so far 2 of six in a year.

Title: Re: Tube life
Post by MrDerrick on 07/27/20 at 01:03:02

Do you have any means to test the tubes that you received or the tubes that went bad?

Not to debate Steve, he knows tubes, but I have never had a tube that sounded "good" at 10,000 hours. But that is more than likely do to how hard the tube is used and or driven

They may still function at that hour mark, but I find that 5K is about max sound quality wise. Your brain adjusts to the sound over the decline and until things get really bad, sound wise, it can be hard to detect.

They can still test strong at 5K, but they do not sound as good as fresh tubes.

Personally, I think that these are what most of the "NOS" tubes being sold are.

And except for tubes that get noisy or gassy, I call that mechanical failure vs electrical failure, that can happen at any time to any tube.

Title: Re: Tube life
Post by Archie on 07/27/20 at 01:32:24

I can't readily test tubes. The tubes I bought were NOS (never used) as far as I can tell. I push my output tubes hard in my ZMA but I don't know if that affects the input tubes. My use estimate might be off by a factor of 2 but I certainly don't have 5000 hrs on these tubes. I do think the Russian military tubes last longer in any case.

My life question is really academic since I'll use the Tungsrams until they go bad regardless -- I have 8 or 10 in back-stock. When they go I'll go back to the 6N1P-EVs. They are a nice tube, just not quite as good as the Tungsram.

Title: Re: Tube life
Post by MrDerrick on 07/27/20 at 01:57:10

I will add that unfortunately, the tubes that I generally find to be the best sounding, always seem to have the shortest life span.

Title: Re: Tube life
Post by Lon on 07/27/20 at 02:15:38

I guess I've been lucky as I haven't found that to be the case! Maybe feeding them clean power helps as I have a regenerator in each system. But I have had Amperex 7308, and 6N5P from Steve, that have been giving me trouble free long life. These are my favorite input tubes. I get scary long life out of rectifiers and power tubes too.

Title: Re: Tube life
Post by Archie on 07/27/20 at 17:00:19

I did notice the recent thread on soft start technology and possible extended tube life. I don't know if this goes for all the tubes in our amps but the sudden rush of full voltage seems to hurt tube life. I would think that the various capacitors might soften the blow though.

Title: Re: Tube life
Post by piezoman on 07/27/20 at 22:07:42

Arch, that thread you referred to seems interesting, but I worry that addi g another component in the chain might contribute to noise. But maybe not [?]

I think that as far as a rectifier goes, a directly heated one vs. indirectly heated is a salient point.

Title: Re: Tube life
Post by Archie on 07/27/20 at 23:01:03

Not sure since it's on the power end but I agree with Lon that clean power helps. I don't have what he has but I think the ZLC is a good component.

Title: Re: Tube life
Post by Lon on 07/27/20 at 23:51:59

The ZLC IS a good product, does clean up the power. It took a regenerator to replace one for me. Still have it, just am not using it now.

Also I have often used 5V4 rectifiers, and have a pair in my audio/video system again now. These have a slow start feature I believe. . . easier on the tubes. With the right complement of tubes these can sound great too.

Title: Re: Tube life
Post by paugaultierch on 09/10/20 at 05:23:27

Not sure since it's on the power end but I agree with Lon that clean power helps. I don't have what he has but I think the ZLC is a good component.