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

I am looking to change / upgrade my tube amp.  I have a good, all-purpose Primaluna EVO 400.  It employs the EL34's and has a nice sound, especially in the ultralinear mode. Other components:  streaming from Innuos Zenith MKIII to Lampizator Atlantic DAC.  Everything playing through Daedalus floorstanding speakers with a 96-97dB sensitivity. Currently, my office / listening room is on the small side: 12'L x 16'W x 8' H, but I'm building a new listening room on our farm where I will later upgrade some components to fit a larger room.  Now, here are the tube amp options I am looking at:

Audion Silver Night PX25  8 Watts.  Very popular among some, touting a slightly more balanced, dynamic sound over the 300B.

Swissonor 45 SE  or  Tektron TK One 2A3 / 45 i   The 45 is the low wattage (2.5W) but sweet tone alternative. Considered by many to be one of the most musical out there. Of course, its low power makes it more restrictive, only efficient with high-sensitivity speakers and in more small-to-moderately-sized rooms.  It might be great in my current office but would have to work harder in a larger one later.

300B Integrated Amp, Make / Model not yet determined.  8-10 watts.  Of course, the 300B is making a big comeback and has wonderful characteristics, especially in the midrange and especially with certain genres of music such as acoustic, vocals, jazz, etc.  I heard one opinion from someone with a history of work in sound production, "The 300B is great if you just want to listen to a female vocalist with a guitar." One take on it.

Adherents of the PX25 and 45 tend to regard the 300B as a nice-but-limited cousin. I honestly have no experience with any of these three tubes.  I moved from SS to tube with the PrimaLuna, a well-built amp that I have increasingly felt carries some limitations that other tubes--more focused specifically on higher sensitivity speakers--would open up the sound in the lower frequencies and some tone qualities all around.

Any opinions would be welcome.

 

gregjacob
ltmandella's avatar
ltmandella
152 posts
 

There is a 300B based OTL amp available in kit form.  If you don't want to build it, announce on the manufacturer's forum that you would like someone to build it for you.  You will have to compensate the builder but it is the best 300B amp money can buy.

medium_grade
87 posts
 

Personally, I love my Elekit 8600 300B amp. Even if you get someone to build it for you, the price is fantastic and you won't have to wait nearly as long as you will for a new Decware amp 🤮

nrthomas2
39 posts
 

I love my Yamamoto 2A3. Hand crafted beauty with soul. Plenty of power with my 96dB speakers. There are 45 and 300B options as well.

markusthenaimnut's avatar
markusthenaimnut
371 posts
 

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.

byang12's avatar
byang12
39 posts
 

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.

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