Single Ended 5687

Here is one of the most unique and unusual amplifiers that I have owned so far. A single ended design based around the 5687 dual triode as a power output tube, this one is a very rare bird indeed and it offers a glimpse of a sound that few have experienced. A same-drive-same approach, I believe this amp is using both sides of the 5687 run in parallel on the output tubes and singly in the driver tube, all for one watt of triode goodness. However it works, the result is pretty amazing and for its low power this one does have drive and the sense of open space that define the single ended experience.

The 5687 is a general purpose dual triode dating to the early 1950’s and was in production into the 1980s. This tube saw use in military applications and the early computer industry, and was built to be long lasting, with extreme linearity, and rugged enough in construction for cut-off or pulse duty. A tall order! In audio, the 5687 was discovered later in the game, and found a home in some of the Audio Note and Kondo stuff, as well as Modwright units, but has largely been off the radar compared the usual suspects like the 6922 and 12AU/AX7. As stated, this is a very rugged tube, with exceptional build quality that few tubes can compare to. Somewhat rare, and still fairly expensive, the 5687 is not coming back into production any time soon. More details about this cool triode can be found at both Vinyl Savior and JAC Music.

Looking to me like an elegant Nubian cruiser from Star Wars, this dense little hunk of polished chrome is quite a good sounding amplifier, and on the right speakers it offers a very clear and lit up presentation. It has a bit of pentode-like bark to it, but overall is a warm and lush sounding amplifier with all the typical triode warmth and ease. With only a single watt of output power, this amp needs a special speaker to truly appreciate. But on my 100 db/wm Lii 18 panels, the little 5687 has no problem sounding big and bold. And while my 94 db/wm Coral 8A-70 do sound clear and clean on this amp (and very pleasing overall), they don't make the same bass energy that the more efficient driver can reveal. This is a tube that was never meant to be the final amplification stage in a speaker amplifier, so I think we are lucky to have any useable output at all on less than ideal speakers.

Built by a hobbyist in Taiwan, this amplifier features 1950’s-60’s Matsushida transformers and choke, and although no one will mistake this for a factory built amp, it is clean and seems well constructed overall. The volume control knob was broken off in shipping, but I’ve been using it with my Luminous passive and a selection of tubed preamps that have come and gone in the past few months and everything has worked well with this amplifier. This amp has a sense of space that is nice and an overall transparency that is also very nice, and it presents a well balanced soundscape that doesn't lack anything except perhaps the very lowest bass register. Compared to the Gillespie Magnavox SE EL84, the EL84 has a bit more gravitas and control on a less efficient speaker, but on the Lii 18 panels this is almost equalized. The presentations are somewhat different at the core though, with the EL84 sounding a little harder and denser and the 5687 being more ethereal and open. Apples and oranges of course, and a good reason to have some variety.

So far in my hifi journey I have not seen another amplifier based around the 5687 as an output tube, so I couldn't resist experiencing it and having that sound profile in my memory. The purity of the same tube driving itself is also so appealing. This amp has been very pleasing to own; its so unique and quite good looking, it sounds great, and rolling tubes to experiment with flavor is fairly affordable compared to so many others. Being the only one I know of, I cant really recommend anything except to say, adventurous builders, the 5687 is a viable choice for ultra low power experimentation, and it sounds great to me. I’d love to see something more elaborately executed built around this tough little dual triode. Happy listening everyone!

Shiny chrome all around. It's a look I don't generally like, but on this amp it works. Classic tube amp lines in this build.

Solid, nice quality connectors, but everything looks salvaged.

The 5687 has a very powerful heater, and this results in an extra bright glow from the tubes. Very appealing to look at, especially mirrored in the chrome of the chassis.