How do you know when your tubes are going home?

[Primalsea]

I've been into hifi and audio electronics for quite a while now but it occurred to me the other day unless there is an obvious failure I dont really know how to tell when valves are coming to the end of there life.

Anyone??

Is it something you can hear or do you have to swap in another set when you think its about time to see if they sound remarkably better than the older ones?

[DSJR]

Swapping in new for old is what I'm going to be doing shortly on the Croft's power supply and phono stage valves...

You know when a valve amp gently fades the sound away when switched off? My ancient experiences with our Bush table radio from the mid fifties (and Dad's Deccalian 88 record player) was that the sound goes a bit "weak" and lacking in "drama" over its re-valved counterpart. In the case of my preamp, the bass rolloff in the phono stage changes as the ECC83's go down, making the sound currently brighter than the tuner and CD inputs (!!!!!). The ECC82's supplied on the line stage (I very much doubt by Glenn) sounded incredibly "tired" and rather washed out. Putting in the 5841a's transformed it, although I've a sneaking suspicion they're over-egging the pudding a little.

Once I have the short-plate Mullards in the phono stage (and a new one in the power supply, which uses three valves including an EL86) I'll report back. I didn't like the long-plate Mullard ECC82's I tried, as they sounded too lush for my tastes, but we'll see..

Do these comments help at all?

P.S. I forgot that my Tube Technology Genesis amps ate their EL34's in around a year (500 hours). The sound went dull and bland from hard but "fast" in this time. The one amp that took to the Groove Tube replacements sounded fantastic straight off, although the other amp couldn't be biased low enough and had to be returned for fettling. I sold them straight after.

[Marco]

Hi Paul,

I've been into hifi and audio electronics for quite a while now but it occurred to me the other day unless there is an obvious failure I dont really know how to tell when valves are coming to the end of there life.

Anyone??

Give them to someone with a proper valve tester, such as Anthony TD, and get them measured. If they test fine, then they are fine. This is one area where measuring things gives a definitive answer

I had all mine done recently

Marco.

[The Grand Wazoo]

From The Grave