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Message started by Donnie on 08/17/26 at 16:16:49

Title: Tube degradation
Post by Donnie on 08/17/26 at 16:16:49

I'm going to ask a very simple question that I think has a very complex answer that probably has many variables attached to it.

When should you replace the tubes in your amplifier?

Variable one would be what tube? I know that some tubes last longer than others.
Another variable would be is a new built tube, a NOS tube, a used tube from your stash?

I know as a tube degrades you get used to how it sounds.
Probably why when you change the tube out you are amazed on how good this new tube sounds.
I guess the variable on that is if the tube actually sounds better than the last tube or if the last tube had degraded into sounding bad.
So I guess if I take this thought even further is your new wonder tube just in a better place in it's life span than your last tube?

Then I could ask the question of how each tube interacts with the other tubes in the amp, and where the other tubes are in their life cycles?

This line of logic is making my brain hurt.

Title: Re: Tube degradation
Post by armstdav on 08/17/26 at 16:27:04

That way madness lies! If you try to science all those variables you'll drive yourself crazy.

For me the answer to your simple question is also very simple: if I swap in a new tube and it sounds better, it stays. That's true whether I'm tube rolling for fun or my tube tester reveals a possible weak link.

Title: Re: Tube degradation
Post by Steve Deckert on 08/17/26 at 16:54:49

It's a great question. As tubes age, they loose power, and they get smoother/softer sounding. That right there can be problematic. Output tubes almost never last more than 5000 hours in our amps, the SE84UFO being an exception, often going double that. Input tubes on any amp we make generally last longer than output tubes. Rectifier tubes go between 500 ~ 5000 hours depending on if Father Murphy likes you or doesn't.

Title: Re: Tube degradation
Post by Dominick on 08/18/26 at 04:55:18

Donnie….to make things even more complex….i have always thought about the speed and tone of a given tube, and how its placement in the signal chain changes the sound.

Scenario 1: is it better to place slower tubes in the beginning of the signal chain, and then speed it up as it progresses towards the amp and speakers or vice/versa. Or do you deliberately mixed it up as a combination creating a constant balance throughout.

Scenario 2: if you start with tubes in the beginning of the signal chain ( like the ZRock) that are more lush in the midrange and bass, to then lean it out with tubes that emphasizes top end later in the signal chain…and/or vice versa as it hits the amplifier. Is there a preference and does it matter how you approach this philosophy…or does it not matter at all.

My approach thus far has been that if I like a tube for certain characteristics, and I decide to keep it in the signal chain, I would then listen by ear to determine where I want the sound to go, and then start swapping out other tubes to the find the sweet spot.

Just some food for thought.

Title: Re: Tube degradation
Post by Kamran on 08/18/26 at 05:25:30

We have to give Donnie a new hobby. He’s pontificating a bit too much lately.

Title: Re: Tube degradation
Post by Lon on 08/18/26 at 11:39:59

Dom, that's a nice little snack for thinking.

I don't have a definitive conclusion on that. I think both ways have been determining factors in my tube journey particularly with the SEWE300B. If I had slower inputs I needed faster driver tubes, and if I had faster inputs I needed slower driver tubes so to speak. Now. . . I have an input tube and a ZROCK3 tube that is really neither fast nor slow and driver tubes that are just a bit "fatter" if not really slower--works really well and I haven't changed them in some time. These work really well with my regulation and output tubes which are perhaps a bit slower, beefier for sure, than others--and in cooperation with the dynamic calrity of the Dynagrid Jr.

The Dynagrid Jr.'s character has really determined how all the others interact. That has been a great addition to my system.

Ultimately I think it may not matter, 1 or 2, and like you I fit a tube in with other tubes. I used to have the rectifier and output tubes as the "anchor" tubes I worked around. Now there are no rectifiers in the system, and the Dynagrid Jr. and the output tubes are the ones that don't change.

Title: Re: Tube degradation
Post by Donnie on 08/18/26 at 13:41:57

Kamran,

Yeah, my mind needs to be more occupied, pretty soon I will start back on my manifesto, that never ends well.

Wait until I start pondering the age of capacitors and wiring!
Don't get me started on how old my speaker wires are!

Title: Re: Tube degradation
Post by Kamran on 08/18/26 at 16:38:32

LOL