I put the current mirror on a board and it does sing. (to well actually)
The test board worked so well I added the jacks, switch and a volume pot.
The problem is it is to sensitive. I put a pair of back to back diodes across the input to limit the drive. With a wire clipped to the input it sounds like a radio between stations. With a tank on the input I could tune it and select a station from the mix. We have a local low power day time station about 12 miles from us. This mourning I turned the amp on and could hear it. Low in the background but there. With a test lead clipped to the input it is an easy listening level. So it's back to the drawing board. The simplest way to reduce gain is to reduce stages.
This is the amp as built. With the 2.2K resistor in series with the earbud it is still to high gain.
Here is the final version. I bypassed the middle stage. I have two resistor representing the earbuds. The red graph is one and the yellow is across both. Much better but it could still use a gain control.
With a 10K pot adjusted from 100 Ohm to 10K Ohm in 100 Ohm steps, this is what the output looks like.
So I replace the gate resistor for the output fet with a 10k pot and bypass the second stage.
I think a new build is in order. I can use the one I have as a signal tracer. I need to make a probe for it. Another project to add to the list ;).
*** I did the new build with two stages and I'm using 8 Ohm headsets. I connected a DBM and picked up AM1160. It is a low power (1 KW) in Dallas Texas. That's about 600 miles.
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