Small Tube Amp - What Kind of Tubes?

For the 12AX7 I was told to try the tubes that have the biggest plates and wound filaments, in order to get more gain and less hum, less noise.....

So I tried it and that is exactly what I got, less noise less hum and more gain.

I bought Sovtek 12AX7LPS and JJ Tesla ECC803 hi-gain from TubeDepot, because they have pictures and I could see which ones had the biggest plates for under $20. As soon as I put them in, I could tell the difference.

Might work out the same for you.....

Of course, you can always just try to match what is in it now...
 
IF you're reall looking for a cleaner sound, lower gain 12Axx tubes will get there. You might consider 12AU or 12AT series tubes. Be sure to check on compatability with the manufacturer of your amp but generally these are interchangable. 12AX7 tube is generally the highest gain pre-amp tube available...they come in different flavors...some higher or lower in gain than others but if you move down in the family...12AT, 12AY and 12AU have lower gain characteristics and will drive the next stage less hard which results in less break up and/or distortion.

See these sites;

http://www.thetubestore.com/tubeinfo.html
http://www.tubedepot.com/12ax7reviews.html
http://cydathria.com/fdm/12AX7_sub.html
http://www.kcanostubes.com/content/newsletter_details.asp?ArticleID=4
 
soundchaser59 said:
For the 12AX7 I was told to try the tubes that have the biggest plates and wound filaments, in order to get more gain and less hum, less noise.....
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Ouch!

That is completely bad advice, for a number of reasons.

If you want to replace preamps tubes in a combo amp, you DON'T want a typical longplate design, as they will become microphonic - or fail - in short order.

The Sovtek 12AX7LPS is a perfect example of this. It is an excellent tube (if you have a good one) and my personal favorite for vintage bass heads, but it will not last in combo amp with the vibration to which it's subjected. The design is just too fragile. If you have a low-wattage combo that's never cranked up and is in a stationary application, it might work, but it's not a great choice. In something like a touring Twin, wow, just say goodbye.

It's no accident that the typical OEM tube was for years the Sovtek 12AX7WA, which is an extremely short-plate design. There is one reason for that, alone: It is rugged enough to survive the warranty period in a gigging combo amp.

I know an engineer in NYC who does amp prep for the biggest names in the business, the superstars. What preamp tubes does he use? Specially selected Sovtek 12AX7WAs.

Not terribly distinguished sound, no, but they work and they last and they don't go microphonic.

A good compromise for combo guitar amps is a JJ ECC83S or a real vintage Mullard or the essentially identical Dutch Amperex.
 
bongolation said:
Ouch!

That is completely bad advice, for a number of reasons.

If you want to replace preamps tubes in a combo amp, you DON'T want a typical longplate design, as they will become microphonic - or fail - in short order.
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I understand what you are saying, but maybe next time you can try not to slap me down quite so hard. I think I left some hair on the concrete. Everything you said makes sense for a guitar amp, and it's a great point......but it makes me wonder then....

what about the same question for a tube mic preamp? Most of the low voltage mic pre's use the same 12AX7 breed of tube, would the large plate wound filament advice I got be ok for a mic pre?? There must be a reason why they make them, what are they good for?
 
soundchaser59 said:
I understand what you are saying, but maybe next time you can try not to slap me down quite so hard. I think I left some hair on the concrete.
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I certainly apologize, I meant that you had received bad advice, I was not blaming you for it. :o
what about the same question for a tube mic preamp? Most of the low voltage mic pre's use the same 12AX7 breed of tube, would the large plate wound filament advice I got be ok for a mic pre?? There must be a reason why they make them, what are they good for?
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Those starved-plate "tube" preamps are a whole different discussion, but the bottom line relative to this thread is that they are not in a situation where high vibration and shock are problems. From the standpoint of sheer hostile electronic environment, a combo amp is hard to beat. That's why that Fender, for example, had OEM so-called "5881" power tubes that in fact are rebadged Soviet-era avionics relay circuit tube designs that are not even technically audio tubes, and sacrifice not only tone but about 30% output efficiency. They can take the brutal environment.

Longplates like the 12AX7LPS tend to be used by Hi-Fi tube enthusiasts in stationary, fairly pampered applications. There are some old longplate Telefunken designs that are supposedly less damage-prone, but they are too expensive for me.
 
If you like the sound of a full 100% preamp tube,.... .... that is what other types are measuered from.....

the 12AX7 is the one,..... highest gain from any preamp tube,....


at least from current amp designs,....


after that you can vary the flavor a bit by making it different,...WA, or WT,.. or any of several designations from different manufacturers....


The others are 12AU7,12AT7,12AY7,12AV7,12AZ7, 12DT7,12df7, 5751, 7025,6057,6681,7729,6L13, B339, B759, E83CC, ECC83, M8137,.......and yet many others that would work,..... such as the 12DW7, it is actually an AU, and an AX in the same bottle...

In a single ended low wattage tube amp the usual circuits that are used, use only 1/2 of the tube for the preamp stage anyway,... and the other half on the power stage,...

How you achieve your 'PERFECT' tone is up to you,....


Read your manual, and ask a tech to be sure, but usually there is no problems with the sort of amp you have,.....does it have a solid state rectifier stage???

If so, you should be sure to use the standby switch, it turns on the heaters in the tubes to warm them up before full power is put to them,... that happens when you go from standby, to full ON...

If your amp does not have a standby switch,.... be sure to warm up the amp when you move it in cold weather,..... otherwise,.... you will, at the VERY least shorten the life of the tubes,....

find somewhere to try some used tubes to get some idea of different sounds,..just by putting a different type or brand in that Pre slot....


the power tube on a single ended, usually can be changed to the same numbered tube with no dire results, but that tube is sometimes not for an inexperienced person to mess with,..... that should be researched for your own amp,.... it is different for an A/B amp as it is very important to have them balanced in those designs,... Push/Pull,......


if the experimenting is not an option for you,.... I would suggest any (I prefer NOS RCA) brand of 5751,... it has tons of tone,....only about 70% of the gain of a 12AX7,... are built VERY rugged as they were designed for military applications,.....

If it can be dropped from a plane, sort of ruggedness,.....I think it would be OK in most any amp.....

GE has a nice tone too,... a bit brighter,... but in my single ended amp it is a bit piercing so I like the RCA,.... better mids and a little darker sounding,.... ringing highs,.. but not piercing,.... find one, and Eme, I will send you a brand new GT12AX7WA and you will hear the difference a cheap russian tube will sound like....you can keep the GT,......Sovtek,.....as a backup.......

Steve


the above is only an opinion, and your safety cannot be guaranteed if you do not seek professional help with any major modifications,...especially when it pertains to your attitude,.....
so put down the dube, splif,blunt,bud,........put,.... and be safe......

THE ABOVE MESSAGE IS BROUGHT TO YOU BY<<<<<<<<<<<>>>>>>>>>>







you know,.......









them......... :confused:








<<<<<<<<<, over there<<<<<<<<











:eek:








Yup, Knowing that ,.... how could you even,...... :p
 
One caveat I try to remember to bring up when these preamp tube discussions appear is that one of the things you have to look out for is wearing out the tube sockets (to the point they have to be replaced) by swapping tubes in and out testing the comparative sounds. They lose their grips pretty fast and this is a problem when they are downward-oriented and don't have spring-loaded covers on them. Most cheaper amps don't. I've seen amps in which the tubes vibrate loose and fall out in use because of this.
 
those are really great replies everyone, thanks for the help thus far.

two questions come to mind... 1) this may sound stupid, but I can't figure out what NOS means in reference to tubes. Is it "New Old Stock" or something like that? and 2) what about the 6L6 tube? will changing that out make any type of difference? any suggestions? or is my tone more based on the 12AX7 tube?

At the moment I think I might try out a 5751..
 
I would do just the preamp tube for now,... and experiment with that for a while,.... as for the 6L6, it is the power tube,.. and in applications such as this,..... it also would be ok to change,....as long as you stick with the same number, and brand,....if not, and you want to use something else,... unless you know what your doing,.... you should ask the place you bought your amp,... they usually have a tech that can advise you there,... but the preamp tube is ok ....change away man,... and do be aware of the advice of those who know,... too much ,..... and you may just .... well,... you know,....


what he said.......



:rolleyes:
 
I found a used Sylvania I can send you,... you must return it at the fest,.....


unless you like it,... in which case,.....


hey, I know it works,.. I just tried it out for the last half hour,... an it sounds great,......


PM me your snailmail addy,.... an it'l be on it's way,....


Steve
 
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Thatupstateguy said:
I would do just the preamp tube for now,... and experiment with that for a while,.... as for the 6L6, it is the power tube,.. and in applications such as this,..... it also would be ok to change,....as long as you stick with the same number, and brand,....if not, and you want to use something else,... unless you know what your doing,.... you should ask the place you bought your amp,... they usually have a tech that can advise you there,... but the preamp tube is ok ....change away man,... and do be aware of the advice of those who know,... too much ,..... and you may just .... well,... you know,....


what he said.......



:rolleyes:
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Excellent idea...the pre-tube(s) will impact the sound much more dramaticaly than the finals will besides...they're cheap.
 
mshilarious said:
You had it right before, new old stock. It means tubes that were manufactured years ago, but supposedly have not been used.
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Please note the important use of that term, "supposedly."

In any case, I think (like most people who take vintage tubes more seriously than I do) I would prefer to have a vintage tube that has had some mild use as a satisfactory audio piece and as tested out showing lots of remaining life. Then, as now, an awful lot of brand new tubes weren't much good out of the box and got tossed or reserved for non-critical use. This is the pool from which a whole bunch of those NOS tubes spring. ;)

It is not uncommon for raw new stock (vintage or current) tubes to have sonic defects in half or more of the examples. Seriously. That's why you want to buy your tubes from specialty resellers who have burned-in and tested the tubes in actual audio devices prior to sale.
 
Thatupstateguy said:
I would do just the preamp tube for now...
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I agree. In my amps, I rarely change out more than the V1 tube as the others have relatively negligible effect on the sound to my ear at the volumes at which I work. As many people have pointed out, most home amps will probably never reach the volume levels needed to experience power-stage breakup anyway. And in gigging amps nobody will be able to appreciate the finer audio points in the typical venue. There, I've said it :p
 
bongolation said:
As many people have pointed out, most home amps will probably never reach the volume levels needed to experience power-stage breakup anyway.
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Ahhhhhh.......my amp kicks so much ass. ;)
 
now I also have a Fender Hot Rod Deville. it has 2 6L6's and 3 12AX7's. Could I buy 3 NOS 12AX7's to put in there.. and still keep my old GrooveTube 6L6's in there? is it better to switch out both power and pre-amp tubes at once... or not really?
 
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