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12AX7 Question
- Thread starter Emian
- Start date
Tubes don't get noisier with age. That is either a connection or passive component (resistor or capacitor) that needs fixing, proably due to normal deterioration from heat over the years. Changing the tube may appear to "fix" the problem because a new tube will have a slightly different impedance and the noise might not be apparent OR it could make it worse. That preamp tube ought to be good for another few decades.
I have a Sovtek 12ax7lps in my 3500. It's not much hotter than the stock 12ax7wa, but it opens up the sound quite q bit. This tube is warm with more pronounced mids and sparkling high end. It's a very nice tube. I bought two, just in case. I have also tried a 12ax7EH (Electro Harmonix) in the amp. It was a bit hotter with a smoother tone. Also very nice.
Edit: Psycho Bass Guy, this is from the Mesa Boogie site:
"You may occasionally experience some form of tube noise or microphonics. Certainly no cause for alarm, this quirky behavior comes with the territory and the Tone. Much like changing a light bulb, you don't need a technician to cure these types of minor user serviceable annoyances and in fact, you'll be amazed at how easy it is to cure tube problems...by simply swapping out a pre-amp or power tube!"
Edit 2: Mesa also puts a life expectancy for a 12ax7 at about 10 years, though some do last longer.
Edit: Psycho Bass Guy, this is from the Mesa Boogie site:
"You may occasionally experience some form of tube noise or microphonics. Certainly no cause for alarm, this quirky behavior comes with the territory and the Tone. Much like changing a light bulb, you don't need a technician to cure these types of minor user serviceable annoyances and in fact, you'll be amazed at how easy it is to cure tube problems...by simply swapping out a pre-amp or power tube!"
Edit 2: Mesa also puts a life expectancy for a 12ax7 at about 10 years, though some do last longer.
It depends on what tube you have in there now. If it is something like a Sovtek, 10 years is a bit much to get out of a Tube like that and you can bet your booty it would be noisy (microphonic) by now.
A new Tube should fix you right up.
I suggest upon removing the old Tube, cleaning the Tube Socket with some Contact Cleaner.
For new Production I recomend the JJ ECC803.
For NOS I recomend a Long Plate Sylvania.
I appreciate the heads-up, but you need to search my past posts for "Randall Smith" to find out just how worthwhile I consider Mesa's advice on tubes. The short version is that it's a crock of it.
For me a good NOS Telefunken ECC83/12AX7 type, smooth or rib plate just about makes every preamp I've tube swapped with one, sound bigger and badder in a good way. I like the JJ's for current production and dang if I've not grown to like the Sovtek 12AX7LPS as of recent. My other vintage faves include Mullard's and Sylvania's in this class of tube type.
Where might I find the best info on tubes, then? Can you provide links? Thanks!
Also, I went looking for that thread in your past posts. I got four or five pages in before I ditched the effort.
Thumpbass1: The 12ax7LPS is the nicest sounding tube I have used, personally.
There is a wealth of info here, but you have to dig and know what to ignore and how you dig depends on what you're looking for.
If you go to the "Advanced Search" tab and search for my user name for the key words "Randall Smith," this thread is what I was talking about.
For even more fun, search for "Groove Tubes" and "Aspen Pittman."
I used the search tools properly. I was looking for "Randall" in the post title.
Thank you, sir. Interesting read; your comments and the original article. It certainly does look like he's rigged his amps to accept only his tubes, doesn't it.
Thank you, sir. Interesting read; your comments and the original article. It certainly does look like he's rigged his amps to accept only his tubes, doesn't it.
Swapping a pre tube is straightforward, and cheap. I'm thinking it very well may solve your issue, and you'll alter your tone to boot! I had a similar issue in my 7-ish year old SVT-III Pro that a tube swapped cleared right up.
Have at them toobs, homie!
Have at them toobs, homie!
If the tube is ringing like when a bass note is played or a rubber hammer is struck (gently now) to the side of the amplidier, then the tube is microphonic and all you need to do is replace the tube, if there is a popping and crackling when nothing is played, I would suspect the resistor circut biasing the tube. The first can be fixed by cleaning the tube socket and replacing the pre amp tube as Red Planet suggested, the second (resistor or capicitor replacing) should be done by a qualified technician.
Good luck to you.
Good luck to you.
If it's been 10 years just replace the tube(just for GP) and see what happens. I find that JJ tubes are probably the best value in terms of consistency(quality), tone and price. NOS tubes may sound a bit better but cost more, also keep in mind that NOS should stand for NEW old stock, I see quite a few tested, used tubes described as NOS so be careful.
While it it unfortunate that Mesa Boogie dosnt allow for setting Bias of it's Amps it is also fortunate they they made some of the Best Amps ever built.
My Mark III Simulclass , Reverb, GEQ, EV Combo is the Holly Grail of Guitar Amps and taking it to my local Tech is easy enough when replacing Power Tubes. It's simple as a resistor change. With the Boogie Simul Class Amps it is impossible to have a Bias Pot.
The Boogie Bass 400 and 400+ are very nice amps. As long as one put Tube in that are in the safe Bias Range it is not that big of a deal. You can contact Bob at Euro Tubes and can send you a Sextet or two that are matched and Pre Biased for that Amp. All you have to do is pop them in.
Now wasnt that easy?
My Mark III Simulclass , Reverb, GEQ, EV Combo is the Holly Grail of Guitar Amps and taking it to my local Tech is easy enough when replacing Power Tubes. It's simple as a resistor change. With the Boogie Simul Class Amps it is impossible to have a Bias Pot.
The Boogie Bass 400 and 400+ are very nice amps. As long as one put Tube in that are in the safe Bias Range it is not that big of a deal. You can contact Bob at Euro Tubes and can send you a Sextet or two that are matched and Pre Biased for that Amp. All you have to do is pop them in.
Now wasnt that easy?
Tubes can indeed get noisey. Some people say they go "microphonic" if they begin to howl and feedback. I've had new production tubes go after a year or two, and I've had some 40 year old tubes start to go noisey. How can I prove this? I've tried the same "microphonic" tube in another circuit and it continued to howl.
I recall Mesa telling me I had to buy my tubes from them back in the late 80s with my MkIIC. Of course, then I didn't have any knowledge of how to maintain a tube amp. Back then, though, you could have purchased from them and had a matched set you could simply pop in. It would cost you a bit more, but if you took it to a tech and they put in a matched pair it would likely have cost the same.
Today, with the interwebz, there's no reason why you shouldn't learn how to maintain your amp yourself. Techs are good and fine, especially if there is a problem that is over your head.
Swapping tubes isn't hard and no one should be afraid to do it, though. If you want to learn how to bias your amp, get a Weber Biasrite and have at it. It's so utterly simple. Check this site for some fundamentals:
http://www.geofex.com/tubeampfaq/TUBEFAQ.htm
Today, with the interwebz, there's no reason why you shouldn't learn how to maintain your amp yourself. Techs are good and fine, especially if there is a problem that is over your head.
Swapping tubes isn't hard and no one should be afraid to do it, though. If you want to learn how to bias your amp, get a Weber Biasrite and have at it. It's so utterly simple. Check this site for some fundamentals:
http://www.geofex.com/tubeampfaq/TUBEFAQ.htm
Microphony is a defect of manufacture where a tube's bracing is insufficient to keep the cathode from ringing smypathetically with vibration. ALL active devices, tube or solid state, are microphonic to some degree, but the better built ones are much less so. Exposure to vibration can make existing microphony worse, but without that vibration microphony is NOT a "normal" process of aging.
