Princeton Reverb Problem

Matt Steindl · Post by **Matt Steindl** » 17 Jan 2004 2:04 pm

I am having problems w/ a SF Princeton RVB. It is overdriving at extremely low levels. If I have the amp volume set at 2 and the volume on my Les Paul at half, it is already overdriving. Any ideas?

Before anyone asks about the speaker, I have already resolved that that isnt the problem. I have used 2 different 10"s w/ the same result.

If it is a tube problem, would it more likely be the pre or power tubes? The power tubes are actually marketed by Mesa Boogie, so maybe they are supposed to overdrive it.

Any help would be greatly appreciated.

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Mattman in "The Big Sleazy"-:
S-10 Dekley, Suitcase Fender Rhodes, B-bender Les Paul

Matt Steindl · Post by **Matt Steindl** » 17 Jan 2004 2:10 pm

Oh yeah, it seems a lot louder than it used to(and no, the push/pull boost knob isnt pulled!)

Jon Light (deceased) · Post by **Jon Light (deceased)** » 17 Jan 2004 2:19 pm

just checking---the power tubes are 6V6 as they should be, yes? (I don't think of Mesa/Boogie when I think of 6V6).

Matt Steindl · Post by **Matt Steindl** » 17 Jan 2004 2:34 pm

Yup, 6v6 GTA. Thats all Guitar Center had, so I got em.

What should the rest of the tubes be?

I Have 4 12ax7's in a row. Thought there was supposed the 4th tube was supposed to be something different.<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Matt Steindl on 17 January 2004 at 02:37 PM.]</p></FONT>

Matt Steindl · Post by **Matt Steindl** » 17 Jan 2004 2:47 pm

Found a whole mess of 12AT7's in my tube box, thought I remember people telling me I would get more clean headroom w/ those as opposed to AX7's. Any truth to that?

Also, I cant find a 7225 which is supposed to be the furthest tube to the right, what would putting a different tube in that slot do?

Jon Light (deceased) · Post by **Jon Light (deceased)** » 17 Jan 2004 2:57 pm

Pretty sure you mean 7025. It's my understanding that 7025 and 12AX7 are interchangeable. And yes, 12AT7 is lower gain, greater headroom than AX7. I believe that only the Reverb recovery tube is spec'd for AT7. I'm not certain which of the four that is. There is no harm to be done by any mix/match of AX7/AT7. Just sonic and gain differences. But it doesn't sound to me like this is where you solution is going to be. The results of preamp tube changing are going to be a bit subtler than the "breaking up at 2" that you describe.

Matt Steindl · Post by **Matt Steindl** » 17 Jan 2004 3:42 pm

John, thanks for the help! Don't know what I did, but I seemed to tame it down a bit. I put(left to right) 3 AT7's then a AX7 where the 7025 was supposed to go, and its sounding better.

Think I need to drop it off at my local amp tech, but am sooooo broke w/ the new baby that it might be too much of a luxury right now.

Donny Hinson · Post by **Donny Hinson** » 17 Jan 2004 3:42 pm

The second small tube from the jack-end (reverb send/return) should be a 12AT7. A 12AX7 in that spot might cause the distortion problem, since it's gain is higher. The other three small tubes should be 12AX7/7025. The 12AT7's have a lower gain, so they will reduce power when used in place of the 12AX7's, and actually lower your headroom.

Of course, since you've only got 15 watts to work with, clean headroom will be pretty scarce!

Jon Light (deceased) · Post by **Jon Light (deceased)** » 17 Jan 2004 3:50 pm

Man, I get so confused about the gain/headroom thing. BTW, Matt, check out the recent thread about the Princeton Reverb.

Matt Steindl · Post by **Matt Steindl** » 17 Jan 2004 4:01 pm

That was it, put the AX7's back in except for the 2nd from the right(AT7) and it is still good, but louder.