Koch Classictone SE 6

Cool low wattage single ended Class A amp that has more options than typically found on similar amps.

Here are the amp‘s details from Koch’s website:

The Koch Classictone SE 6 was designed to please the more demanding guitarist who loves a no-nonsense “all about tone” approach to guitar amplification. The Classictone SE 6 has a single-ended 100% Class-A all-tube amplifier design. It was our goal to use as few components as possible to create an amp which would be very dynamic, super responsive to a guitar player’s playing style and type of guitar, while allowing the vacuum tubes to naturally color the sound.

The beauty of the single-ended design of the Classictone SE 6  is that players can experiment with different tube types in order to get even more different sounds from the amp. For example, when using the EL84 tube, the amp will deliver (tube) tone as it was meant to be. With single coil pickups you will have nice chimey and sparkling clean tones with humbuckers the sound will be slightly darker. The overdrive is smooth. The tubes have just the right amount of compression to track with the overdrive and keep it beautifully controlled while blooming nicely as the note fades out. This produces a very nice organic sustain.
On the other hand, with the EL6V6 tube it has all the classic tone you want, plenty of gain and very little noise. With this tube, the amp sounds great, period. You will get clean with smooth,  clear high end, but on the other end of the spectrum it will deliver big fat bass notes that are well- defined and have a piano-like quality. Crank up the gain, and you will get everything from a nice crunch to an all-out screaming distortion - and not just mush, but a very controllable, musical distortion -. 
The built-in auto-bias circuit enables you to exchange various tube types without the need to rebias the amp. With the Classictone SE 6 you can keep on creating new sounds on the fly by utilizing the single Tone control in combination with the three voicing switches (Mid-boost, Bass-cut & Gain-boost) and with the Gain and Volume control.