Tube life?

[HipKitty]

The standard 12ax7a will work fine in the v4 position. The v4 in that amp is the phase inverter tube, which "drives" the output tubes. It's rare that these fail, but they do sometimes. Usually they get noisy or microphonic. If you replace it and still have no output, that means something greater has happened. Let's hope it's just the 12ax7a. If not, let us know.

Regarding using Mesa's 12ax7a, you certainly can! You don't need the spax7a (the high grade 12ax7a) in that position, just the standard. Or you can get a pre-tested 12ax7a (like Groove Tubes, Ruby, TAD, etc.) and use that, it doesn't have to be Mesa's. You might be able to get a 12ax7a cheaper elsewhere...that is if funds are an issue. Stay away from the EI brand though! Also Electro Harmonix has been having issues over the last 2 years with their 12ax7a's.

Good luck!

 

[estring]

actually I know its V4. I swapped them out one by one with some old marshall tubes I had and V4 was the culprit. The amp was shipped from canada so maybe something happened in transit.
Anyway thanks for the response. I'll probably just order a new Mesa tube. The amp itself is only 7 months old.

On second thought...how much does V4 affect tone????

 

[HipKitty]

The phase inverter tube doesn't really affect tone. It can, however effect the response of the amp in terms of gain. some 12ax7a's have lower gain characteristics, while others have higher ones. The chinese tubes and the Tung Sol brand tubes are among those that have the higher gain characteristics. With higher gain 12ax7a's, this typically ends up with the amp sounding fatter, more distortion, some slurring between notes and a warmer overall sound. Whereas, you take a JJ brand tube, depending on which one, it will generally have a brighter, more "sharper" focus...which is why a lot of Marshall owners love them....very fitting to those amps.

 

[estring]

So wait a minute...you say that V4 does not affect tone. But all the characteristics you describe in changing V4 are all tonal qualities..???

 

[HipKitty]

Actually, no, not exactly. I don't mean to be confusing, but tone response effects treble, mids and bass frequencies. "Fatness", slurring, and distortion are descriptions of tube response that occurs to the signal that can seem to have a smoother response...often referenced as a "warmer" sound...even though the amp's frequencies are not being effected.

 

[HipKitty]

Also, in referencing the JJ brand tubes, they don't exhibit the same qualities as the Chinese and Tung Sol 12ax7a's....the "brighter" reference is perceived by the limited slurring/distortion. They have more clarity, therefore, sound more focused in their response.

 

[estring]

Lets say I replace V1 and V2 with Tung sols. Should I get it rebiased?

 

[Rocky]

Mesa amps have a fixed bias in the power amp section so you dont bias them.

Preamp tubes never need biasing

 

[stokes]

Mesa amps have a fixed bias in the power amp section so you dont bias them.

Preamp tubes never need biasing

That is providing you use Mesa or GT's or power tubes that are pre-screened to match the bias of your amp.Cant use NOS power tubes without a bias adjust or at least a check to be sure they fall into the proper range.Pre-amp tubes are a different story and generally need no bias check unless there is a problem with the amp.

 

[Rocky]

That is true, Groove tubes has JJ tubes. They tack an 'S' to the end of the tube designation.....Mesa color codes correspond with GT hardnesses of 4 to 7.

 

[gonzo]

FWIW---

i took my boogie for it's once-every-26-years-tuneup 2 wks ago...

(picking it up tomorrow)

and as a side issue, i took in my collection of power tubes from the last 10 years....

the amp tech has both high and low voltage bench testers, so we were looking at the extremes on my power tubes..

the newest tubes (all branded mesa tubes, supposedly matched) were clearly out of spec.

guess which ones were the best out of the bunch (5 sets, 10 tubes total)?

the oldest ones.

i even had one of my oldest pair of 12ax7's (circa 1984) which saw 6 nights a week gigging, for probably 2 solid years...

and they were still in spec.

the brand new 12ax7's?

no better.

 

[Murphy Slaw]

I rest my case.

Thanks Gonzo.

Good tubes are good tubes. Age doesn't have anything to do with it.

 

[gonzo]

you're quite welcome.

 

[phaboo]

I rest my case.

Thanks Gonzo.

Good tubes are good tubes. Age doesn't have anything to do with it.

Yes, testing one batch of tubes proves it for all tubes on the planet.

:roll:

I wouldn't be surprised that the newer tubes tested out of spec--it's getting harder and harder to get quality tubes. Making the things is half art and half science.

I change power tubes every six months, and I ALWAYS get an improvement in tone with the new batch. In spec or out of spec doesn't matter--it's what it sounds like that's important.

And that should be the test criteria--what does it sound like? If your old tubes sound great to you, then rawk on. You'll never really know if your amp is sounding its best, though, unless you swap with another set to A/B test it.

If you're using any power amp compression/clipping for your tone, the the tube being in spec isn't going to tell you anything about tone. Pushing a tube that hard is CLEARLY out of its intended design parameters (we guitarists LIVE to abuse tubes!), so just being in spec doesn't tell you what it's going to sound like. Again, A/Bing is your friend.

It also depends on the tone you go for. If you lean more towards the cleaner side of things, or have a more rounded crunch (less highs and lows), you probably won't notice much difference with a tube change. The sound loss over time seems to be in the lows and presence. If you like a lot of presence (as I do), you'll find yourself changing tubes a lot.

The rest of your setup can also affect your satisfaction with tube life. Once I switched over to EMGs from passive pickups, I got used to hearing every little thing I did with the pick. As the power tubes age and start losing even a little definition, it drove me crazy. I never noticed it with passive pickups--the definition in the source just wasn't there.

So, the moral is, "your mileage may vary."

 

[gonzo]

Yes, testing one batch of tubes proves it for all tubes on the planet.

no, it only proves it for this one batch of tubes, and only underscores the bigger picture..

that there are no rules to tube usage and worth.

and to simply say 'if this happens, then this occurs' is somewhat misleading.

i simply provided a case for balance.

the ears are always the final say so, but honestly, this is a given....

or at least, should be.

 

[212Mavguy]

Wow! great posts appear here on this particular subject. Getting back to the original question, depends on how well the tubes were designed and built, how hot the tubes were biased, how many hours they were used and also how much they were or were not thrashed in operation.

The comments of Hipkitty and Murphy Slaw stand out to me as both being correct, despite what appear to be conflicting statements. My hat is off to both of them.

Murphy speaks from the common sense viewpoint of if it sounds good don't fix what isn't broken, if it sounds good it's good, and his long use of the same tubes in His heavily gigged Class A (hot bias) Blue Angel stands in good testimony. Anybody who had gigged as long and as often as he has has got to have valid opinions for sure.

Hipkitty is a great resource and in this topic writes from the technical side, displaying a great grasp of vacuum tube theory. His opinions are well backed up by solid knowledge and lots of experience as well.

Here's my two cents:

If I'm not mistaken the LSC is a pretty powerful amp. The power tubes probably have not been pushed all that hard, and if the amp was not run for more than in the hundreds of hours since its creation the power tubes are probably still in great shape, especially if they were biased on the cold side. New tubes might sound a little brighter on top and provide slightly more harmonic detail.

Maury, I'd listen to what Hipkitty AND Murphy Slaw have said. If it was Hipkitty's amp I'm sure he'd obtain replacement tubes. I agree, purchase a complete set of replacements for every type tube in the amp, falling within Mesa specs if not the actual Mesa units. Personally, I have a pretty decent collection of tubes accumulated for my various amps...

I'd also listen to Murphy's pragmatic sounding viewpoint, paraphrasing, if it sounds good to your ears, it is good, play great music, and don't try to fix what isn't broken...

Despite my posts regarding voicing amps by adjusting bias, changing out various tubes, transformers, resistors, capacitors, and speakers, once I finish the weenie-ing out and have an amp of mine dialed in, I pretty much leave it alone. Peace.

 

[fishyfishfish]

FWIW, I experimented with all kinds of pre and power tubes with my LSC, and finally just put in the original Boogie tubes back in and let it rip, couldn't be happier! There was some WOW factor with the different brands, but the end result was the amp still sounded the same as when I bought it. The one tube that did make a difference was the JJEL34L, on the clean channel, but as far as tubes and Boogies go, unless you get a bias mod, tubes are just a tone hunt with no end...

 

[212Mavguy]

Hi fishyfishfish,

I like what you said in your post. I applaud your having done the work of science in experimenting with different tubes in your LSC. In trying to stay on task both to the original question posed at the beginning of this topic and also to your most recent post here, I humbly offer:

1) It is my opinion based on owning different amps that the simpler the amp's circuit is, the more the differences stand out from tube rolling.

2) Your amp was designed to work with new production tubes. There is nothing wrong with being happy with original tubes sound, after all it was designed to do exactly that, so the engineers got it right for your ears. Great! However, as you said in your post, it does respond to tube rolling. Not all amps respond the same to changes in a given tone variable.

3) Tone chasing is fun, especially if you know where you are going for a final result. The more a user experiments in a given variable the more they have control of their tone from that variable. I'm confident from "science project" results smelling the solder fumes, rolling tubes and speakers that there is more effect on tone from the output transformer , then the speakers, then the tubes.

4) Eventually all tubes change in the sound they transmit through the circuit, and eventually wear out. Some do it faster than others in the same type. Older production vintage stock tubes tend to last longer than the new ones produced today.

5) The result of experience in tube rolling provides more certainty in knowing what will happen sound wise at tube replacement time when choices need to be made.

Finally, on a side note, I'm glad for the mostly real attempt to help attitudes present in the Boogie forum. Caring and sharing is better than dissing and pissing. Peace.

 

[212Mavguy]

The very last part of my previous post is meant to be directed at all, not a particular individual. Hope this helps.

 

[Murphy Slaw]

I agree. The final decision on tone is with ME!

It never fails, some nights in clubs I'll have 2 or 3 "wannabes" come up and want to give me tone tips. Turn up, turn down, add gain, less gain, whatever. If they knew what the hell they were talking about they'd be gigging, and not stumbling around my stage! I work very steady, thank you.

Best of luck.

Murph.