Saturday, July 14, 2018

3 stage AF amp using the Fair radio interstage transformers

 The third line down is the transformer I wanted but I didn't want the $66 price tag, ouch!!
I shopped at Fair radio a little and found this one.
At $2 it was a deal. This is an older one with the same spec's.

This is the circuit I used for my hearing aid amp. It would be a good place to use a couple of the transformers. T1 and T2 are interstage and T3 is an out put transformer. I have a box of them I picked up for 30 cents each at a surplus sale a while back.

The output transformer is not necessary but I don't like putting my headphone in the DC circuit.
I put one on a piece of poster board to see if it was as good as I thought it might be. It was better! It needs the volume pot. Touching the input will buzz your ear.
I put my audio generator on the input and it sang with it barely off minimum output.
Time to find a box and a board for a permanent build.

This is the circuit I used before. I used GS109 and MP40 transistor with good results.

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