Best Tube Amp for High Sensitivity Speakers: 45, PX25, or 300B?

Great question - great idea for a thread.

I previously used a vintage (Cary Audio/Dennis Had designed) AES SE-1 300B stereo amp, from the ’90s. It sounded great and I loved it with my 93dB sensitive/efficent/whatever JBL studio monitors.

Then I had a chance to compare it to a pair of Alan Eaton 45 monoblocks, that put out somewhere around 1.5 watts. The Alan Eatons were better - deeper bass, clearer, lovely treble, richer tone, more beautiful sound. Note - this is in my room, with my listening preferences. I typically listen in the near field below 75dB, so I am just using a fraction of a watt. The Alan Eatons are simply coasting.

A couple months ago I also picked up a pair of Altec A7 Magnificents. ~96dB.

I learned about these amps on the Glow in the Dark audio website. I love that website for the photos, the writing, the descriptions of the various amps and tubes.

Also, as I have previously done, I humbling suggest you download a simple app for your smartphone so you can check what volume you normally listen at. I use decibel X-Pro. It was not expensive and works great. I use it frequently. No, it is not the best SPL meter in the world but it will tell you what you need to know.

Personally I think the 45 tube is where it’s at and these simple, simple circuits with minimal parts count and highly efficient speakers.

Your 96dB speaker requires 8+ watts to sound reasonable for full scale music.

If you insist SET using DH tubes,  PX25 or 6336A is the way to go.  paralleled 6336A ( Using both sections of single tube for one channel)  could provide 15W pure class A output with 2 windings of primary per channel.  2A3, 300B, much less 45 has to be used in push-pull fashion to produce enough power for your speaker.

Sound wise, as I posted in "300B lover" thread, 45 is the most balanced DH power triode. However, all the commercially available DH amplifiers not using DH driver tubes have bottleneck at their driving stage, so the amp sounds what driving stage sounds, output power tube sound signature are not most impactful.

The best sounding low power SET amp I built using 71A (shunt regulated) to drive VT25A/801A, producing most seductive 2w pure class A output when driving my JBL horn system.

Hi Gregjacob,

Some nice and great responses to your inquiry on quality flea-watt tube amplification for your efficient speakers. I have had tube amplifiers in the past and for the past 12 years, I am the proud owner of a BorderPatrol S20 parallel 300-B tube amplifier with dual power-supplies. I have heard a few tube amplifiers on my system and all of them sounded good with of course their own sonic signatures, but my mind was made up when I heard the BorderPatrol amp. Not only did this amp sound more dynamic especially in the bass area, but articulation, frequency response and clarity of the music really drew me in to each performance. Also, vocals especially female take on a very realistic presence. With this amp, the music on the whole seemed to have for lack of a better word, more body. I, also own three solid-state Class-A flea-watt amplifiers all of which sound great on my system. While they all have their own sonic signatures, I keep on coming back to my two favorites, the BorderPatrol S20 300-B amp and the First-Watt SIT-2. I wish you well on your tube-amp journey.

Regards... John

@gregjacob 

I think you're going to have to try some different options in your system. while i appreciate the opinions of those who have a strong technical understanding, my experience is that things that should not work DO work for me in my system. 

Again, my system, my room, my preferences. 

liquidsound  John:  That BorderPatrol is a beautiful unit.  Out of my current budget but could be a bucket list amp one day.  Thanks for sharing.

Markusthenaimnut:  I think you are right.  I failed to give proper disclosure from the beginning of the thread:  exact speaker specifications, exact room dimensions, exact distance to speakers and, finally, average decibel listening of what genres of music.  I know all that could / would affect answers and opinions here.  

At any rate, the wealth of information continues to grow.  Thanks everyone. Your participation is being heard and it's a help to many!