Yes, 2 wires to TDA pin 4.
TDA pin 4 is ground on the uBitx.
LM386 pins 2 and 4 are both ground on the Bitx40, and thus both must be wired to TDA pin 4.
Claude has left pins 1 and 8 of the LM386 unattached, the LM386 datasheet states that
in this configuration it has a voltage gain of 20, or 20*log10(20) = 26dB.
The LM386 on the Bitx40 has a 0.1uF cap between pins 1 and 8 to increase the gain to 46dB.
The original TDA2822 of the uBitx has a gain of 40dB, so you may want to try adding a cap between LM386 pins 1 and 8
if you need more gain there.? A larger value cap (up to 10uF) would improve low frequency response.
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On Thu, Mar 1, 2018 at 10:20 am, DrZ wrote:
I note you have 2 to 4, and 4 to 4. ?Are there two wires going to the TDA pin 4?
