Enough SET Power for Rock and Roll

I had a set (pardon the pun) of SET 45s. My speakers are 98 db. There was no-where near enough power...

So I built up a set of type 45 push-pull amps just for fun. Instead of about 3/4 watt, now I get something more like 5. So about double what I got out of my 2A3 SETs that I also had. One thing is for sure: the P-P 45s sound a lot better than either SET did before, regardless of volume- deeper bass, more extended highs, far more neutral and engaging in the midrange (nevertheless my 30-watt OTL took it to task immediately but that is another story).

DHT (Directly Heated Triodes) have a lot of linearity, but I don't see people comparing P-P to SET much in this realm, mostly because P-P DHT amps are somewhat rare. But I would consider it- you always want the amp to have essentially unlimited power regardless of the speaker for best result. With the Klipsch (depending on the room) that might mean 15-30 watts to really never be pushing the amp hard.

The problem with SETs is if you need power, the more power the amp can make the more the bandwidth is limited. By the time you get to 7 watts, most of them don't have much bandwidth below 30Hz (if they do then there will be no really high frequency extension...). This means that there will be colorations translating to lack of impact up to about 300Hz. But getting well below 15 or 20 Hz is no problem for a P-P amp, even if it makes 60 watts (and you can still have the HF bandwidth).

Now usually SETs are more transparent than many P-P amps, but if we are to compare apples to apples that P-P amp really should be using DHTs. If its a pentode amp *of course* the triode amp is going to be more linear...

The nice thing here is that with the Klipsch you pretty well can run whatever you want- its friendly to all known amplifiers.

you'll find yourself turning it down to 50-60 decibels and about 2-3 watts per channel,

There is a reason that it appears that you don't need the power if you have SETs. It has to do with how they distort and how the human ear/brain system uses higher ordered harmonics in order to gauge how loud sounds are.

SETs don't have measurable distortion at low power levels (the source of their 'inner detail'); as power is increased the 2nd, 3rd and 4th come into play (the source of their 'warmth' and 'bloom') and after about 20% of full power is reached the higher ordered harmonics come into play (at full power most SETs make about 10% THD; if anyone claims less its either because they spec the power at a lower level or because they are running feedback. Because our ears use the higher ordered harmonics as loudness cues, the amp might appear to be more 'dynamic' (since the loudness cues or excess distortion is on the transients where the power is) or it might sound 'loud' simply because of this distortion.

If you take away that distortion it won't sound loud anymore and you will naturally turn up the volume, perhaps by as much as 15 db or more depending on the amps and speakers! Note also that by me telling you this, you will now be aware that distortion is why the amp sounds loud and dynamic so the experience might not be as pleasant as it was before. The cerebral cortex is funny that way. So I might have ruined it for you.

FWIW, about 90% of the time audiophiles are talking about 'dynamics' (and usually the plural not the singular) they are really talking about distortion, and as a result the word 'distortion' can safely be substituted into the sentence without changing its meaning.

Since it really is about high end audio sounding real, the solution is of course either more power or more efficiency or both. The thing is, the real challenge is bass (the holy grail of both SETs and high efficiency loudspeakers), which lacks more as the amplifier power is increased. The bigger the amp, the less bandwidth. That's why the 300b was king 20 years ago, but by 15 years ago the 2A3 supplanted it (sounds better due to greater bandwidth in the output transformer) and finally that got supplanted by the 45. IOW there is an economy of scale! The result is unconvincing bass (I played string bass in several orchestras for many years- I'm hard to please in that regard) and no way around it. The smaller amps play bass better but the speaker efficiency you need to really show off what the amp does means you can't have any bass. This is excluding the use of a subwoofer of course.

but I rarely hear those loudness queues you are speaking of. Even on very dynamic orchestral music I hear power and it even seems that there is additional headroom to spare.

The way you would notice them is if the system sounds loud.

The use of a powerful subwoofer system can help out an SET quite a lot!