300b, x45, 211, etc.

Does anyone have an opinion on the different characteristics of these tubes: 300b, x45, 211, 2a3, PX25. Thanx

Well, I can give you a reductionist, and highly subjective rigmarole based on limited experience with products sporting 300b, 211, 845, 2a3.

All tubes can be usefully operated in a no-feedback circuit. Good stability. So, basically they're VERY good amplification devices (i.e. better on paper than the best transistors for example) despite the need for output trannies. Having said this, more or less, objective piece -- here goes:

300B, good because of availability, reasonably priced tube and trannies, the worst of the lot in extension and sonics. Excellent tube for marketers, but other tubes are catching up. Reasonable linearity and some dynamics. Low power -- but still workable, somewhat (say a 112 db spl 1W/1m speaker). Basically this is a "nearly" tube: it's nearly good, nearly extended, nearly excellent sounding, nearly...
As such it lends itself to many applications -- for this very reason. I hate this tube in any application EXCEPT for powering an upper midrange driver alone. Maybe a tweet, but wouldn't know where to buy suitable output trannies.

2a3: as above for availability etc; good pricing to boot. Much better sonic attributes than the 300b even, BUT minimal power capabilities. Probably has excellent dynamics, bass trable, mid, lush and clear, veil-lifting and all that -- but given most speakrs' abysmal efficiency, you'd need an army of 2a3 to hear them. In which case of course you'd lose some of its quality attributes. Life's tough.

845: not too good availability (but improving), expensive, and variable quality trannies all expensive. Good power and extended linear region. So, so, low freq. (so what -use a mosfet instead). I like this tube -- but it's depressingly expensive in most implementations.

211: now we're getting serious. Availability starting to get better and you no longer have to be Mr Gates or similar to obtain it (but being rich remains an important consideration). Trannies still awfully expensive. High voltages. Now this is where SET leaves the whispers and enters the premier league. Good sonics, good extension and no bulls...t driving capabilities. In fact, it also has reasonably low output impedance to boot!

1610: one you didn't mention. Very serious driving capabilities, better stability with loads than 211 and capable of excellent energy swings within linear operation. BUT, very limited availability.

_______Voila___
Let me repeat that I'm personally comparing these tubes to one another -- so when I say I hate X tube it's an exaggeration and said in context -- right?
And if s/one offers me a 300B, I'll jump on it!
Cheers

Gregm thanx for a great response. I'm really surprised at your impressions though. I guess I've been infected by the marketing you mention ;^)

Have you heard a PX25? I've never even heard of a 1610 tube. Also, the 211 is a different kind of tube from the 300b right? I understand the 211 and such is a transmitting tube (radios, etc.) where the 300b was actually a repeater type tube originally created for use in amplifying phone signals travelling long distances. (In fact, I've heard that there are lots of Western Electric 300b tubes sitting on the bottom of the ocean!) Anywho...

I agree with greg except for the feedback thing - plenty of variable feedback in tube circuits, depending. Lower than solid state, but not negligible. And interesting about the 1610. However, another thing besides low power to think about with say a 2A3, despite how linear they are, they also are inherently very noisy. To which I would add: 45 tubes (even lower power than the 2A3) and the recording studio fav tube, the EL519, which is a little like the EL34 but more linear. I think only EAR makes a EL519 amp, and, well... EAR, not exactly a fan... So it's $8000 at least for an 845, a company that will irritate you in their treatment of customers like EAR, or a noisy low power tube for $2500.

Here's a great offline response I got from Dr. Chau that I'm posting with permission:

*******

First, you have to realize there are no absolute rules to the sound of a
particular tube. The end result does depend on implementation. However,
you can breakdown trends in two ways. Each family of tubes does have a
commonly accepted 'sound'. Also, many SET manufacturers have a house sound
including Cary.

300B: the most recognized SET tube. Often said to have a rich, warm and
glorious midrange. Also often said to be a bit rolled off on the top and a
bit loose in the bass. Still, it's reputation is from the glorious
midrange. The first popular directly heated tube in the US (had been
popular in Asia and Europe for much longer).

2A3: similar to the 300B but much less power (typically 3W). A bit cleaner
in the mids, more top end, and much better in the bass. The bass from a
2A3 is really good depsite the low power. This became popular in the US in
the late nineties since it was cheaper than the 300B and considered to be
cleaner sounding than the 300B. FYI-I currently use a 2A3 at home although
that will change in a week or so.

45: an even older tube than the 2A3 or 300B and even less power (2W). This
is the current hot tube in SET. Considered even more transparent than the
2A3. Supposed to be better in every way than the 2A3.

The above tubes are directly heated triodes but use an oxide cathode like
most small signal tubes. The next group of tubes are transmitting tubes
and use a thoriated tungsten heater/cathode

211: a popular transmitting tube. Can put out 12-15 W on a single tube.
I've only listened to a 211 on several occasions. I find it a bit thicker
sounding than the 2A3 and 45, more like a 300B.

845: the current hot high power SET tube. can go up to about 18 W on a
single tube. I find it somewhat less transparent than the 211. Many
commercial amps are available with this tube now.

The bass on the 211 and 845 is probably a bit bigger than the 45,2A3, or
300B but not as quick.

Other tubes:

212, 807, 811, 833A-other transmitting tubes. Some are really large like
the 212 and 833A. These can put out a lot of power (100W for a 833A) but
can be dangerous as they need very high voltages on the plate to achieve
max power. The 811 and 807 are smaller and in between the 845/211 family
and the 45/2A3/300B family.

10, 101D, VT52, etc. other small triodes in the vein of the 45. These
often are considered even better than the 45 but have really low output and
are rare. Very few commercial designs are available.

The above comments are gross generalizations and based on my own
experiences. Again, a good design can change the characteristics. A
current thread in the forums is to run the 845 at much lower than normal
voltages (i.e. lower power) which changes the sound.

Also the above tubes are all triodes. One can get good single ended sound
from pentodes and tetrodes. I just purchased a Shindo Cortese to replace
my 2A3 amps. These run a F2a pentode.

In addition to a specific tube sound, manufacturers have a characteristic
sound. Cary certainly has a family sound. Even though the first SET I
heard was a Cary and I used to own a Cary, I'm not a fan of their sound.

As to you question about moving to another tube, you will can find big a
difference even if you move to another manufacturer's 300B amp. It all
depends on what you want in terms of sound. For SET amps, I think you have
to consider the amp and speaker as one unit. This is especially true for
the lower power tubes. If you can, try to listen to a 2A3 or 45 amp since
I think you'll hear the biggest difference in these tube tubes compared to
a 300B. You can only answer you question by listening.
****