Most desirable vacuum tubes for SET amps

Generally, I think the 300B is probably the most popular, and therefore sought after option for a SET.  That being said, I personally prefer the 845 in a SET as I love the soundstage it delivers.  It also give you a touch more power and has a bit more flexibility than a 300B.  

My second preference is the PX25 as it provides a middle ground between the 2A3(ultra detailed) and the 300B(ultra lush).  It has a velvety detailed sound that is awesome with Avantgardes.

I don’t know the GC33C or GM70.  

Other candidates would be:

45
PX4
T100
EL34

other 300B derivatives
300B XLS
320B XLS
520B
1605

full disclosure, I import a line of SETs and am a dealer for KR and Emission Labs.  

2A3

http://whammerdyne.com/

The most desirable tube is the one that works best with your speakers. 

The best sounding SETs are the ones with the least amount of power. This is due entirely to the output transformer- the differences people talk about between the various tubes has more to do with the output transformer than the tubes themselves. Once you get over about 7-8 watts of power it gets extremely difficult to build an output transformer that has full frequency bandwidth- and as a result many have compromised bass response on that account.

So back in 1990 there was a mystique around the 300b; by 2000 the 2A3 had ascended the throne and these days its the type 45.


If you really want to hear what any SET does, that will best be done with a set of loudspeakers that are efficient enough that the amplifier is never asked to make more than about 20-25% of full power. This is to prevent distortion, in particular the higher ordered harmonics, from showing up on the transients present in all music. The ear uses the higher ordered harmonics to sense sound pressure, so when they show up on transients it tends to make the system sound 'dynamic' but its really distortion masquerading as dynamics.