SET amplifier recommendation

How different is the sound between 300b and 805 (LM 508AI, etc)?  

With SETs, the bigger the amp the less bandwidth. 300b is about as powerful as an SET can get and still be considered 'hifi' as far as bandwidth goes.

With SETs, the bigger the amp the less bandwidth. 300b is about as powerful as an SET can get and still be considered ’hifi’ as far as bandwidth goes.

That’s an interesting point, Ralph, which I presume derives mainly from the bandwidth limitations imposed by output transformers when they are used in SET configurations.

Would the bandwidth limitations you refer to apply to the small signal bandwidth as well as to the bandwidth at or near full power? Or just to the latter?

Thanks. Best regards,
-- Al

300Bs and other lower powered tubes vs. 805s - 845s - 211s - T100s have pretty significantly different sound profile. 

The 300B, 2A3, PX25 has this lush midrange that borders on addictive.  It is amazingly musical and is what most people think of when they here a SET.  

805s, 845s, 211s, etc... have a different sound profile.  It is less lush and more dimensional IMO. Delivers tighter bass and a less pronounced midrange even compared to and EL34.  As someone who has an 845 SET and 845 Push Pull and use less sensitive speakers (current pair in my system has an SPL of 84dB paired with Push Pull) I am a fan of its sound profile. To me, there is far more difference between tubes than there is going from Push Pull to SET using the same tube.  

The Line Magnetic you are talking about is an interesting amp in that it is 3 stage instead of 2 stage and there are 300B Driver Tubes to help deliver a more lush sound.  I did a ton of reading on it today for a customer or mine.  It is lovely out of the box but can be improved by rolling in just the right tubes. 

Also, high SPL speakers are a completely different animal.  They can sound great.  Klipsch are wonderful.  Depending on the model, some require being place in a corner.  The Cornwalls are great speakers, work in most rooms and are wonderful with a 300B.  Zu also makes some great speakers and Tekton, assuming you like larger units, has some great units.  

If you really love your 805s, I mentioned above.  You might want to look at a push pull with a different tube compliment.  

So I have made the entire journey across 30 years from SET to High Power and back to SET.  I do own the Coiencident Frankenstein Mk-II's and must concur with those above regarding the poor match to the B&W 805's which I use in a separate surround system driven with significant power.  

I recommend that you determine the sound priorities your are looking for and start matching from there.  In the world of SET the speaker options are somewhat limited and need to match your priorities.  This does not mean limited volumes or dynamics or base extension but has to be carefully thought through to wisely use the ~8 watts available.  My fife can run me out of the house on our system listening to rock at 100db.

Do have fun with the journey!

That’s an interesting point, Ralph, which I presume derives mainly from the bandwidth limitations imposed by output transformers when they are used in SET configurations.

Would the bandwidth limitations you refer to apply to the small signal bandwidth as well as to the bandwidth at or near full power? Or just to the latter?

The issue of bandwidth becoming more limited as the total output power is increased happens with any amplifier with an output transformer. In SETs this issue is exacerbated. To give you an example, a Harmon Kardon Citation 2 which makes 60 watts has bandwidth at full power from 10Hz or so to well past 60KHz; a 300b SET which makes only 7 watts can't go as low or as high. This is why lower powered SETs like the 2A3 and the type 45 have gained ascendancy-  they have more bandwidth. But speakers with the efficiency needed to bring out their qualities are considerably more limited- you need well over 103 dB in most rooms to make amps like that work. Even with a 300B I would not be using a speaker of less than 99dB for the simple reason that if you use more than about 20% of the total amplifier power the distortion becomes unacceptable (that increased distortion is responsible for that 'dynamic' quaility for which SETs are known).