zx81 save failure

[Rich Moore]

I tried using audacity to save a program from my zx81. The 'save' tone only lasts about 3 or 4 seconds before the signal drops to a very low level. Does anyone know what might be causing this?

[1024MAK]

The signal level from a ZX81 Mic socket is very low. Well below the normal audio ‘line level’.

The socket on a ZX81 is a mono type. Are you using a mono plug?
The socket on your PC/laptop will almost certainly be a stereo type, so needs a stereo plug. What lead are you using, only the contacts on a 3.5mm stereo plug are in different positions to that of a mono plug.

Mark

[XavSnap]

Hi,

The saved signal on the PC computer may be right (2/3 of the max level).

But the sound output from the PC computer or a MP3 player can be voiceless...
You had to put a mono or a stereo amplifier between it and the zx81.

You can use a LM386 amplifier, too. (unsoldering the R1 resistor on this module! *drive the level multiplier... must be x1*)



aliexpress.com

Or use a speaker amplifier.

Just use one channel (the right or left) and don't join both outputs together ("Y" link).
The "Y" link is used to merge right and left signals, but it reduces the dynamics and quality of the signal.