HN Labs Noguchi 2A3/300B

The 2A3 and 300B are two of the most iconic and most popular triodes in use today. Both tubes date back to the early 20th century, with the 2A3 being used in radios, church organs and other consumer products, while the 300B saw use mostly in industrial applications like long distance telephone and theater amplification. Both tubes are capable of extreme hi-fidelity, and both are readily available today in old stock and new production. To date, I’ve had a pile of amplifiers based around both tubes, and am always pleased, and although I do feel that the 300B is overpriced for its performance, it sure sounds wonderful on this amp.

Here then is an amplifier that runs both tubes optimally, a rare bird indeed and pure pleasure in use. Labeled HN Labs, this amp is well made, with superb parts quality, but it does still feel like a one-off project. A Japanese build, this amp features top-quality transformers made by Noguchi; very desirable and rare hand wound power and output iron. In fact, this is the only amp I’ve ever seen for sale with these fine transformers. Underneath, the wiring is exceptionally well executed, and overall this is a top-shelf build that is a serious performer.

With the flip of a switch, this beautiful amp transforms between the 2A3 and the 300B; in the case of the 2A3 it is AC heated and the 300B is DC heated. Readers of this site won’t be surprised that I prefer the 2A3 here; I like the sound of the tube better and always prefer AC heating if I can get it. AC heating can be a bit noisier, but the wide-open and effortless sound quality is worth it. 300B still sounds very good here, rich and harmonic and somehow “romantic” in a way the 2A3 doesn’t quite approach, but like seemingly all 300B amps I eventually tire of the over the top chocolate syrup-like sound. I usually prefer the more incisive 2A3, and that is also the case here.

With dual built in volume controls, this amp is a one-stop solution, and although I did try it briefly with both an Eastern Electric Minimax preamplifier and my trusty Paul Birkeland 6AV11 preamp, I used this amplifier mostly as an integrated with the onboard volume controls. It has plenty of gain and had no problem driving every speaker I have on hand with ease. Both the 2A3 and the 300B make enough power for most single driver/wide band solutions, which of course make up the vast majority of my speaker stable in my small single ended room.

So how does it sound? Very, very good of course. As stated I prefer the 2A3, but both tubes are extremely satisfying through this amp. Strangely I did not feel any real power advantage from the 300B here, in fact from a perceptible volume standpoint they performed almost the same, with only a very small increase in volume through the 300B. All music sounds good through this amp, and talk radio/spoken voice is exceptional. The Noguchi transformers are high-pedigree parts and they are certainly make this amp sing. An added bonus was no objectionable hum or other noise through either tube combination. Driven by the 6SN7, there are many choices and flavors available to further tailor the sound, but I have used only a pair of narrow gap RCA here and have been quite pleased with the results.

This is an unusual amplifier in several ways; being a convertible platform is a huge advantage, and of course the superb boutique parts play a big role in the performance and presentation. Japanese hobby-built/low production amps like this have become my favorite single ended solutions, and as of this writing I have several on hand from illustrious names like Yamamoto, Kurashima and Feastrex, but this HN Lab amp holds its own. I have not encounters a 2A3/300B convertible amplifier before, and its been a lot of fun getting to know this one. Its hard not to be impressed with the wide range of output and the flexibility this platform offers. Like most everything that comes through the doors here, this one will be going back out into the world soon, and I know that its new owner will be thrilled. Hats off to HN Labs!

This amp has very classic lines, and I always like a nice wooden base. The front switch is power, and the center switch changes between 2A3 and 300B.

Its hard to understate the importance of the output transformer to a low powered single ended amplifier, and these Noguchi are top quality.

The narrow gap 6SN7 are real sleepers and these RCA did a great job for me on this amplifier.

Sophia’s Royal Princess 300B are among the very best of the type that I have tried. I would have liked to give a set of Elrog’s a try, but so far have not owned a pair.

Triad monoplate 2A3 from the early 30's. These are incredible tubes!

Plain old vanilla RCA 2A3 sound excellent as well. These are from the 50's I think.

The Super TNT mesh plate 2A3 are probably the "best" sounding 2A3 I’ve experienced, eclipsing even the monoplates for my taste.

And the Sophia Royal Princess 300b. Extremely good sounding tubes!

Here is an extremely unusual modern tube, the S300B by Stradi in South Korea. This is sort of a remake of the German Ed, a telecommunications tube from the 1930’s which is vanishingly rare now. The Ed had similar characteristics to the 300B, and in the S300B Stradi has made a plug and play version for use in 300B amplifiers, with construction faithful to the German original. In the HN Labs amp the Stradi S300B sounds really nothing like a 300B, if anything it has a 2A3 sound; drier and airier but very clean and precise. Its not lush like the Royal Princess tubes are, the S300B is very even handed. Percussion in particular has a pop and snap with the S300B that can be startling, and it manages to re-flavor yet again some of my most familiar music.

Above is the Stradi S300B (Ed) tube in relation to the Sophia Royal Princess 300B and the more conventionally shaped Sovtek 300B.

Here with a few from the current Japanese stable. These are all superb amplifiers!