Questions about Preamp Tubes

The only problem with tubes is you might get the bug and try different types of tubes to play with the sound. I now have 5 sets of 12ax7/cv4004 and 4 sets of 12au7/5814a tubes and having a blast :)

"Tubes in preamps normally last 5000 to 10000 hours of playing time"

It makes sense to me that tubes in a pre-amp would have greater reliability than in power amps.

But is it all or nothing? In other words does the system sound the same for this long and suddenly die?

Or do subtle changes for better or for worse occur in the sound as the tubes age?

My guess would be the latter, but I do not know for certain.

Some high end tube vendors like VAC even offer automated health monitoring systems in their products to address this. IS this a frivolous feature that does not add value or the real thing? I suspect the latter.

The first case would not concern me much. The second would, in particular if many tubes are involved. I want to spend my time listening, not having to constantly check tube health if I think something does not sound right.

After the initial breaking in period (of the preamp), the sound will be fine for 5000 - 10000 hours of playing.
When the tubes are nearing the end of their life, you will hear them fade away (more noise).
Replacing them after a few years won't cost you a fortune.

15 years ago I owned a Audio Research LS-2b preamp (only one tube inside). The tube did survive the upgrade to a LS22, 3 years later.....

"My understanding is that it becomes very, very hard to differentiate between tube/SS in high-end products; however, is this the case in lower-end models?"

This is a very good question. I think you are on to something here.

I've noticed that the better tube systems I've heard that cost upwards of $10000 do not sound all that much different from some SS products that may cost 1/4 as much. SS products from Musical Fidelity, Classe, and Krell I've heard come to mind.

Even the late 80's vintage Carver SS pre in my system that provides a tube emulation voiced output is not too far off from what I've heard.

Any thoughts on this?

Mapman, Whether it sounds different to you depends, IMHO, more on the developement of your listening skills than anything else. When the differences are very subtle they can be missed by most anyone except the most attentive and especially by those who are looking for the wrong things.

If you look for the difference in frequency response linearity, often referred to tonallity, there often is little or no difference at all. Either can be warmish, brightish, fast or dull. Although many feel that warmth is automatically obtained by getting tubes, in fact some tube pre-amps might actually brighter than some ss pre-amps.

What I hear when I listen to a tube component, as compared to a ss component, is the tube component lacks what I would call 'grain'.

I suspect that this difference is in the quality of the signal - which I see as one of 'liquidity' which I think has its origins in the treatment of rise time and corresponding decay time which are more reminiscent of live music. Especially the latter (decay). Too short a decay and the sound lacks 'body', too slow and it becomes dullish. Too fast and the signal becomes unnatural, brightish, and ultimately (to me) fatiguing.

Now some folks see this fast decay as additional resolution of detail becauce without the 'tail' you can hear the next signal as being more clean, clear, resolved. I think SS tends to err's on the lack of a more natural decay.

An analogy would be to hear live sound in outdoor open air where the notes might decay naturally but there would be no room effect from a room where we always hear music and think thats where it is most natural. This music wouldn't have much 'body'. I think of this as SS sound. Live music in a great concert hall which has great acoustics and allows a natural decay with some reinforcement. I think of this as tube sound. Live music in a lesser concert hall where its construction emphasizes or guts parts of the sound spectrum - usually to much decay or or in 'modern - show' halls too much glass or other reflecting surfaces. I think of this as either format 'gone bad'. Ever notice the difference between a live recording and a studio recording the principle difference in sound is often only exists because in one you have a audience to absorb sound and the a studio recording the effect of the audience is missing and the sound seems artificial only because we never hear it that way when we go to the hall. Or live music in an echo chamber, YUK

Hope that makes sense. It's not something I think a lot about............