danb20@pro-graphics.cts.com (Dan Bachmann, SubOp) (02/05/91)
In-Reply-To: message from v078p6g8@ubvmsb.cc.buffalo.edu
This is a fixed version of the Audio Digitizer: The other file works,
but the change involved in this file reduces the high frequency noise
introduced into the sample due to the digitizer. The fix is simple if
you already have one built: cut the "link" between pins 3 and 5, and
move the wire from the DB25 Pin 10 to pin 5 and solder another wire from
pin 3 on the A to D chip to pin 1 on the DB 25.
This is a simple two chip Audio Digitizer for the Amiga (specifically the
500, but the DB25 pinouts can be changed for the other models). The parts
list is:
Qty Item/Desc Value
1 Resistor 1k
1 Pot 100k
3 Caps .1uF,47pF,10uF
1 Mini Plug or RCA plug
1 Connector DB25
1 A/D converter ADC0804 (Heathkit usually has these)
1 Audio Amp LM386N (Radio Shack)
This circuit will work with the program from the Perfect Sound digitizer
with one small exception--it won't digitize in stereo.
All the Vcc's (Pin 20 on the ADC0804 and Pin 6 on the LM386N) can be
powered from the printer port (at least it is working for mine with no
power supply problems!).
Use the monitor signal level option in the Perfect Sound program to adjust
the pot to the correct level (NOTE: If the circuit is hooked to a line
level--e.g. to the Audio Out of a VCR or stereo--the pot should be turned
WAY down, just listen to the "monitor" and you'll see what I mean).
I do have this circuit built and running on my Amiga so I know it works.
(I just hope you can read the diagram!)
Jamie C.MUELLER (GEnie)
----
ok, now the new version...
[30m Use More to read this file c
[32m[3m[4mAudio Digitizer for the Amiga 500/2000[0m[31m
I got a copy of a file called [1mADC.arc[0m[31m ([3mAnalog to Digital
Converter[0m[31m)
It worked ok but I found that the opamp it used had a problem with the
output voltage. On an LM386 the output would only go from +1.5 up to +3.5
above ground. [1mThats only a 2 volt swing![0m[31m The real problem is in the
fact
that there is no bipolar supply (-12v & +12) from the Parallel port for the
opamp to work properly. The only easy solution was to use an LM358 which
will give an output from 0v to +3.5 which is a little better. If anyone
knows of a better opamp please let me know.
Another big problem was with the [32mADC0804[0m[31m chip. This chip has a
110 us
conversion time. Quick enough for up to about 20,000 samples per sec. but
with the new software you can do up to over 44,000. I found another ADC
that is 40us but I have not tried it yet. It has the same Pin config. as the
ADC0804 and you don't need to use the cap and resistor to set the clock for
the chip! It's an [33mADC0841[0m[31m. So omit R1 and C1 from the plans if
your able to
get a hold of one.
If your using the [32mADC0804[0m[31m tune POT R1 so you get the best
speed with
out getting any noise or pops. POT R2 is for centering the output. Play
with it in the monitor mode to get the best results.
I'm sure this circuit will work with the Amiga 1000 but you need to
rewire the DB25. I don't have an A1000 to test it on so you'll have to
figure it out your self.
[1m[33mGood luck building it![31m[0m [3mGlen
Aidukas[0m
Parts List:
[1m IC1[0m[31m 1 [33mADC0841[0m[31m or [32mADC0804[0m[31m ([3mAnalog
to Digital Convertor[0m[31m)
[1m IC2[0m[31m 1 [33mLM358[0m[31m ([3mopamp[31m[0m)
[1m R1[31m[0m 1 [33m5K POT[31m[0m ([3mTrimer pot[31m[0m)
[1m R2[31m[0m 1 [33m10K POT[31m[0m ([3mTrimer pot[31m[0m)
[1m R3[31m[0m 1 [33m100k POT[31m[0m ([3mVolume control
pot[31m[0m)
[1m C1[31m[0m 1 [33m.1 uF cap[31m[0m ([3mcoupling
cap[31m[0m)
[1m C2[31m[0m 1 [33m47pF cap[31m[0m ([3mclock cap[31m[0m)
[1m J1[31m[0m 1 [33mRCA Phone or Mini Jack.[31m[0m
[1m J2[31m[0m 1 [33mDB25 connector[31m[0m ([3mMale[31m[0m)
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