Hello All,
Hopefully someone on this list has some experience with the
ISD audio recording/playback chips. If so, has
anyone been successful recording to one of these chips directly using the
headphone output from a stereo or computer, rather than using a microphone as
input?
The circuit example that come with the datasheet
for the 1400 series shows a microphone input, though it also says that
"...if the desired input is derived from a source other than a microphone,
the signal can be fed, capacitively coupled, into the ANA IN pin
directly."
Following this advice, I've hooked up the
negative headphone output from the stereo to the circuit ground, and have the
positive signal going through a .1uF capacitor and 100K pot (in series) to the
ANA IN pin on the 1400. When I attempt to record to the chip, I hear a loud
"hum" coming from the speaker. When I try to play it back, I don't
hear any audio, other than a "click" when it reaches the EOM
marker.
Does anyone see anything wrong with this setup?
BTW, since I'm not using a microphone for input, I don't have anything connected
to the MIC, MIC REF, or ANA OUT pins, nor do I have anything connected to the
~RECLED pin other than a resistor and LED. (The application diagram shows this
pin also connected to the microphone components). I do have the AGC pin
connected to a resitor and capacitor as shown in the diagram.
Any advice (or a pointer to a working circuit
diagram) would be greatly appreciated!
Thanks,
Mark