[Elecraft] External Amp for the K2

[Lee Buller]

I am working on a project to see if I can design a "valve" amp for the 
K2.  I am following two tracks and it is really testing me.  I haven't done 
anything like this in 20 years so it has been a challenge.

First design is a single 6146 tube - grid driven - Pi-L output.  About 90 
watts with 2-3 watts for drive.  I am planning on making it selective for 
Class A, AB1, AB2, and C service.  Parts procurement is an issue, I am 
still looking for parts that are readily available.  I want to make sure 
the amp can be built easily with readily available parts from known sources.

The other track is a little more power using a single inexpensive 811A  - 
grid driven - in the same configuration as the 6146.  The only difference 
would be the plate voltage.  The 811A will give about 200 watts output in 
class AB1.  I am looking at designing different bias schemes as 
well.  Again, I want to make sure the amp can be built easily with simple 
hand tools.

I thought about putting the things together in kit form, but reading the 
FCC rules preclude any of that foolishness.  I suppose a person could sell 
parts and pieces, but the best I could do is make a list of parts, part 
numbers, and sources of those parts.  The only thing that could be in a kit 
is some sort of amplifier case with marks for drilling and punching 
holes.  I am not sure that even providing a printed circuit board would be 
legal in the sense of the rules.  So, a simple building technique has to be 
developed.  I would entertain any ideas that people on the reflector might 
have.

Currently, I am working on a the input scheme and do not like any of the 
designs I have come up with.  I would like to get away from using tuned 
inductors and move into toroids.  I am also working on developing winding 
all the coils as well.

I am also looking at designing the two amps without traditional meters but 
with a scheme of LEDs displays which allow the operator to tune the amp 
safely...ala the Alpha amps.

One other criteria is that it has to be affordable....and fun.

Anyone have any ideas....let me know....it is a intriguing project that 
uses "older"  technology (tubes) that I have not fooled with for years.

Again, we are in a design stage here and have not built one yet.

Lee - K0WA