# My tube amp is getting quieter, i dont know why???



## seedotlng (May 11, 2011)

I own a carvin x100b. I run it through a standard 4x12 cab. I recently just replaced my pre amp tubes and re soldered the resistor to the circuit board. As well i sold my guitar (mh-1000) which had active pickups and i am using a fender strat with a single duncan disaster pickup now. For some reason my amp is exponentially quieter than it used to be. I am a total noob when it comes to this. I haven't changed the power amp tubes for well over two years now, could that be whats causing it. 

Thanks!


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## seedotlng (May 11, 2011)

please help!


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## CSBen (Mar 1, 2011)

It could be for a number of reason.

- Assuming that you changed the preamp tubes for the exact same, i.e 12AX7 for a 12AX7, or a 5751 for a 5751 - so on and so forth, you could have a bad preamp tube, although it would be alot more inclinded to be microphonic.

- Power Tubes...two years, but how many hrs? I have NO clue whatsoever is in a Carvin x100b. Some type of power tubes will last quite a long time, whereas some others like EL-84s will start to go much, much sooner. It's simply the nature of the beast. Be sure to ensure that you don't need to Bias your amp after the power tube swap. I say this in reservation to it perhaps being a cathoded base amp (meaning it is self biasing).

- What kind of rectifier is in this amp? If it's a SolidState (SS), then no worries here. But if it's a tube rectifier, this could well be the culprit.

....heck I just don't know much about your rig as I had to Google what an Mh-1000 is. You're now playing a Strat, so that alone unless you have high output pickups like you did your shreddin' axe, it's a garantee you'll see a drop in the output, but seing that you used the words "exponentially quieter" makes me think it's more than just the change of geetar.

Good luck.

Ben


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## Cary (May 11, 2011)

CSben pretty much nailed it.


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## CSBen (Mar 1, 2011)

I should probably add & clarify a point about the tube rectifier.

They either work or don't. If you've been playing for hrs with that "exponentially quieter" output, then you can rule that one out. A rectifier will fade away and then…nothin'. I haven't had one that went 50%bad for days on end.


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## JimiGuy7 (Jan 10, 2008)

I would say that the power tubes are probably going as I ran into the same problem with my old Bassman. I started noticing that I was'nt as loud as I originally was and nothing in my rig had changed. I changed the old power tubes and I was back to normal. This amp does'nt have a tube rectifier, so you can rule that out. Why did you have to resolder a resistor?


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## keeperofthegood (Apr 30, 2008)

JimiGuy7 said:


> ... Why did you have to resolder a resistor?


Shot in the dark but I bet the resistor got hot. Got hot and the value went up. Bet its a plate resistor. Going from 100K to 10M will exponentially drop the volume too.


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## Jean GODBOUT (Oct 31, 2009)

I agree with JimiGuy7, the first symptom of power tubes at the end of their life is a lower output volume. Also, even if you swap the preamp tubes for the same number (12AX7 by example) each tube have is own specification so it could be the preamp tubes.


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