Life Span of Pre-Amp tubes?

Tim S · « **on:** 22 Mar 2004, 01:44 pm »

I've had a Sonic Frontiers Line 1 pre-amp for a year or two now and I was wondering a. how long should the tubes last and b. what are the signs they are on their way out? Just curious as my system was sounding a bit "withdrawn" yesterday and it occurred to me to wonder about the life of the tubes. Thanks.

Tim

Carlman · « **Reply #1 on:** 22 Mar 2004, 01:54 pm »

It depends on the preamp but generally a year or 2 is the norm (from what I've heard)... I have a Decware that had 4-year-old tubes in it that I replaced. I heard a minor difference... I think the tubes were/are still good. However, that's because that particular pre is designed to have its tubes last about 7 years.

I had an Audible Illusions that went through tubes about every 6 months. The way I knew the tubes were dying was that they started to make a sort of roaring noise... like chuffing wind or something. Also, they'd ring a lot when I'd tap the exterior of the preamp. Sometimes they'd sound 'microphonic' which means the vibrations would get picked up in the preamp as noise and feed it back through the speakers. It kind of made the music sound like it was in a can... or tunnel.

Replacing the tubes could help but .... could also harm it... When you put new tubes in, sometimes the new characteristics are less desirable than what you had. (Ringing, microphonics, warmth, soundstage, liveliness, accuracy, etc.) If you do some experimentaion, you should be able to find a perfect blend of characteristics you like.

I'd recommend trying some 'tube rolling' but be patient... it may take a few tries to get what's just right for your ear.

-C

Tim S · « **Reply #2 on:** 22 Mar 2004, 02:09 pm »

Thanks, that helps. The music was actually sounding like it was at the other end of a hall and the definition of the soundstage had more or less disappeared. Sounds like I may be ordering some new tubes soon. . .

Tim

meilankev · « **Reply #3 on:** 22 Mar 2004, 02:17 pm »

Tim,

My current preamp is the first tube preamp I have owned. Therefore, my opinion is not from personal experience. Like you I have had it for about 2 years now.

However, this was a question I posed to the designer, as well as the dealer (who has been in the "tube amp" business for many years). They both stated the tubes in the preamp should last for the life of the preamp. The designer said 10 - 12 years, and the dealer said he's never needed to replace preamp tubes - but he enjoys tube-rolling as a matter of principle.

Also, I follow their advice, and never turn off the power to the preamp (actually, I never turn off the power for my monoblocks, either). While the output tubes of my monoblocks will probably need replacing here soon (also owned for two years), I am hopeful (perhaps naively) my preamp will putter along for years.

Kevin

TG · « **Reply #4 on:** 23 Mar 2004, 04:52 am »

For small valves such as the 9 pin packages usually found in preamps the lifetime is, for all practical purposes, determined by how hard the valves are driven. If the filiment voltage is within +/-5% of nominal, and the valves are run conservatively (low B+) then they will last decades. If the filiment voltage is high (over +10%) or the valves are driven at the limit of their operating envelope then they may only last a year (or less).

Classic example: the GTA SEP-1 preamp is very hard on its single 6922 valve - expect about 6-12 months use (if you have a SEP-1 and the valve is 12 months old or more, check it on a velve tester - you might be in for a shock).

Without knowing the operating conditions of the valves in the SF it's impossible to estimate longevity.

warnerwh · « **Reply #5 on:** 23 Mar 2004, 05:29 am »

You may want to try asking Sonic Frontiers. My ARC tubes are supposed to last 4000 hours. It seems the different preamps stress tubes more/less depending on the design.

Tim S · « **Reply #6 on:** 23 Mar 2004, 02:01 pm »

I was intending to go through Parts Connexion if I got new ones since the guy who designed it runs that now. My guess is he might have a decent idea how long they last and what to replace them with. . . Thanks for the tips.

Tim

hmen · « **Reply #7 on:** 27 Mar 2004, 06:56 am »

Buy new tubes. Even if you find that the tubes aren't causing the problem you'll end up using the tubes eventually and knowing it's not the tubes is a good first step in tracking down the problem.

melville · « **Reply #8 on:** 29 Mar 2004, 04:42 am »

It is my understanding that small tubes like the 6922/6DJ8 family can last anywhere from 5000 to 10000 hours. Now, unless you leave the unit on all the time, or listen to an awful lot of music, that gives you several years before retubing.