As I discussed in my last post, there is a new SET amplifier on the horizon. This SET will sit midway in power and performance between the little SETs (6CY7, 6CY7 V2, and the 6EM7) and the big 6336 SET Amplifier.
After using all four of the other SETs for a while now, I decided a nice middle ground amplifier was in order. I wanted something with a little more power and presence than the little amplifiers and something not quite as physically large and heavy (as well as hot) as the big amplifier. For my approach, I decided to simply scale back the big 6336 project a little bit. I would keep the cascaded drivers that work so well for tubes with very low power sensitivity and utilize another series regulator tube, the 6AS7/6080 dual triode.
This tube has some good properties as a power tube. It has a 13W plate dissipation so I should be able to get a handful of watts in output power. The quiescent power dissipation will also be much lower than the 6336 amp, only ≈39W total in the power tube. This means that things should run much cooler than the big amp. Also, the 6AS7 does not require the long time to come to thermal stability like the big tube. This means that this amp will be better suited to shorter listening sessions and casual usage. And finally, the plate characteristics are such that the amplifier should produce a typically rich and full tone for which SETs are renowned.
This amp did kind of throw me as to the physical layout as I discussed in my last post. But I have finally settled on something a little more open than the 6336 amp but not quite as big as the 6V6 lacewood which has an 11" by 14" top plate. Here is my layout.
The top plate here is 12" wide by 10" deep. I have also gone for a symmetrical layout that leaves ample room around the tubes for both visibility and airflow. This is close in size to both the Marblewood 12-1/2" by 9" top plate and the 6336 12-1/2" by 9-12" top plate. However, this amp utilizes smaller transformers than the 6336 so it should’t look nearly as crowded.
Now that the layout is set, it’s time to do some internal layout and try to fine an appropriate piece of wood for the case. I’ll talk more about this new amplifier as the design progresses.