From: sleeper75se_at_yahoo.se
Date: 2001-11-29 16:45:16
Hi all,
what do you think about this design idea.
Below is a block diagram of how it could work
1. Head stage amplifier (Amplifies x 100 or maybe x 1000)
.
.
2. Lowpass filter with a rolloff to -96dB at 8kHz
a third order (single opamp) butterworth filter is sufficient.
.
.
3. Analog opto-coupler
.
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4. Analog switch or transistor that is controlled by a 9kHz oscillator
.
.
5. Buffer
.
.
6. Sound card
The idea is that in step 4, you modulate the signal by switching it
on and off. You get a pulse train that can pass through the high-pass
filter in the sound card.
Strengths:
Low part count
Very simple filtering
No digital parts that cause interference.
Weaknesses:
Needs a beefy computer and good sound card.
Unknown if analog opto-couplers are good enough.
Uses one LED per channel - power hungry.
/Andreas
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