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I have my Bogner Duende since September 2009.
Never changed a tube in it.
I'm using the clean channel most of the time... but today tried to put a little gain.
I noticed that the gain is not like it was. But I also changed guitar (I now have single coil).

After 4 years would it be preferable to bring it to a tech to verify the tubes?

Depends how much and how hard you play it. A noticeable loss of output and/or gain could def be a sign that the power tubes are bad but very likely due to the switch from HBs to singles. How do the tubes look when they're running? What color? All uniform or does one look off from the rest?

I've never noticed a power tube going bad in terms of sonics. They've always just blown on me unexpectedly. That's where fuses save the day.

How often you guys changes tubes?
Four years should they be verified?

Here what I have in the amp right now:
V1 to V2: TAD 12AX7-C (The Sovtek have been replaced due to microphonic noise in 2009)
V3 to V5: Sovtek 12AX7LPS
V6 to V7: ARS 6V6GT (it’s written Tesla/JJ on one of them)
V8: ARS 5AR4/GZ34
The V6 6V6 look a bit paler compared to the V7.
Never really got any light on those Sovtek... thats normal.

I change tubes when they go bad--some people are much more religious about it.

It couldn't hurt to have a tech give it a once over--have you tried/can you try using a guitar with the same output as your original?

I only have the tele at the moment.

One thing you can do is bring it in to your tech to have it retubed, biased, and given a once over, but make sure that the tech doesn't throw the old tubes away--ask him/her to save them for you.

That way you'll end up with sparkly new tubes and a clean bill of health (not to mention peace of mind), but also an extra set of tubes for backups.

Could be tubes. Could be the bias slipping/shifting.
Unless I'm completely wrong (feel free to correct me, anyone), 6v6s are a little like el84s in that you shouldn't expect too much life out of em, they just don't last forever.
A lot of new 12ax7s just don't "light up". Its all good.
Drop those sovteks and get some tung sols or EHXs though. You'll thank me later.
I dunno much about rectifier tubes, mayhaps they're on the way out and attributing too much "sag" to your sound???
I imagine they're a pretty hard working tube, like the PI.

If you do end up needing new power tubes, best to swap the rectifier tube out at the same time.

I will think about it... a tech is expensive.

Maybe I should replace those Sovtek-LPS for some TAD or some Tung-Sol to start.

I'm all about leaving em in till they fail. Checking bias if it isnt fixed and making sure the caps are good is a better route, but that's just, like, my opinion man.

AxAxSxS wrote:I'm all about leaving em in till they fail. Checking bias if it isnt fixed and making sure the caps are good is a better route, but that's just, like, my opinion man.

I don't know how to check the bias.

http://www.youtube.com/results?search_q ... n-GlsS2MWM

U shud git lurned.

I'd go over it but I'm not really that smart and I'm drinking and I dont want anyone to get shocked because I'm not making sense

Yeah, Ax has a point. Pres generally go on for a long time before failing. I just don't like Sovtek 12s. I have some 6l6WXT+ in my amp though and they ain' too shabby. But i needed tubes that could cope with 600=V of plate voltage, so, you know..
And biasing ain't hard. Even I can do it....and that is saying something. I didn't wanna mention as I know some people just do not want to fuck with their amp. I can understand that. I used to be like that.

Today everything sound great again...