18 February 2009

Return of S-5 Electronics K-12 Tube Amp Kits

The most common questions we get from our website visitors are about the inexpensive and simple K-12 Tube Amplifier Kits by S-5 Electronics. These little tube amp kits have generated a lot of interest over the past few years, but for a little over a year now the question has been ... "The K-12 tube amplifier kit is no longer available - can you suggest a comparable kit?" Back in December 2007, Bruce tried out the new S-5 Electronics K-8LS Tube Amplifier Kit to see if it would make a suitable replacement for the K-12. Unfortunately the performance of the K-8LS was poor. So for over a year, we have not been able to suggest a simple to build and inexpensive tube amplifier available as a kit.

A couple of days back, Lofton posted a message on the DIY Audio Projects Forum letting us know that the S-5 Electronics K-12G Tube Amp Kits are once again available (Thanks Lofton). Well, this is great news and now we have an answer to a very common question that we get.

The photo below shows the contents of the recent K-12G Tube Amplifier Kit.

S-5 Electronics K-12G Tube Amplifier Kit Contents
The contents are very similar to the previous kits which came with the 10GV8 tubes. One thing that I did note is that the power transformer appears to be larger than the one which came with my K-12M Tube Amp Kit. This should be an improvement as my K-12M power transformer runs hot, but in fairness, has not failed even after several years of use. The K-12G kits are modestly priced at $189.95 and available from Tube Depot. Right now (Feb 2009) Tube Depot is offering a free 3.5mm to dual RCA cable that you can use to connect the tube amp to your portable music player. It's not clear if this is a limited time offer.

Please note that these kits do not come with an enclosure. Instead they come with a pine board which will allow you to mount all of the parts and put together a fully functional amplifier. However, this will not be practical and possibly unsafe for most environments. There is high voltage present on the board and the tubes get very hot, so you don't want little fingers or paws poking around the amplifier. So be prepared to construct or buy a suitable enclosure for the kit.

Update March 2009: Here is a finished photo of Lofton's K-12G Tube Amplifier Kit.

Finished K-12G Tube Amplifier Kit

If you do pick up one of these simple and fun tube amp kits, here are a few links that will give you some enclosure and modification ideas.

S-5 Electronics Tube Amplifier Kit Resources:
If you do build one of these kits, please send us photos so we can share them with our readers.

What's Playing: Steely Dan - Aja (LP)


  1. I've been trying to find a k12 or k502 kit for a while now.

    Thank you!


  2. Here's a quick add to Gio's comments on the K-12 G kit. The OTs are the same as used in the K-8, and it appears the PT is the same as well. If you plan on using the "breadboard" (versus chassis) build, go get a bigger piece of wood. The poplar board supplied with the kit doesn't allow tinkering with transformer positioning. Lofton

  3. This is really great news as I need something simple with a board and low cost. Please report back with the final results.