Thank you for your question.
A standard computer sound card will usually have three connectors on
the back of it - Microphone Input, Line Input and Line Output. Newer,
more advanced sound cards might have digital outputs and surround
sound connections as well. But what you are looking for is the Line
This page will give you an example of what the back of the sound card
can look like:
Here you will see that the line out appears on a 1/8" mini plug in
stereo. Radio Shack will have the cables or adapter you need to be
able to hook this up to your Cassette Deck. Either a 1/8" stereo male
adapter to 2 mono female RCA (standard stereo connectors), or a
pre-made cable with stereo male 1/8" mini connector to 2 male RCA
connectors of your desired length. Although this page is British, the
cable assembly shown here is exactly what you require and readily
available at Radio Shack or other electronics stores:
Simply interconnect in this manner and what ever you can hear through
your computer speakers can be recorded. You may need to adjust the
volume control on your computer to prevent overloading the input of
your cassette deck and if so, you will find these controls in the
Control Panel under Sounds and Multimedia. Be sure you are not
connecting your cassette deck to the SPEAKER output of the sound card,
or it will definitely be overdriven and distorted.
If you would like more technical detail on sound card connections, you
might like to view this page:
Here you will find that sound card connections are color coded and
standardized for the most part in this manner:
"Interfacing to soundcards
PC99 standard defines the following color codes to be used for PC
Pink: Microphone input
Green: Line/speaker/headphone output
Blue: Line in
For extra connections beside those the soundcard manufacturers can use
their specific extra colors. Here are colors used in popular SB Live
Black: Rear speakers output
Light green: Line out
Pink: Microphone input
Light blue: Line input
Yellow: Digital output..."
The page continues with specifications on various output connections
and suggestions for using the headphone out to drive consumer audio
gear if you do not have a line level output connector on your sound
"Audio output connectors
Line level outputs on consumer PC soundcards can typically output
signals up to 2V levels and output impedance typically from tens of
ohms to few hundred ohms (quite typical is 30-400 ohms). Those line
level outputs are designed to be connected to consumer equipments
(normal Hi-fi amplifier with -10dB nominal level line input) or
powered multimedia speakers. Just get the suitable cable in between
the computer and the Hi-fi system and you have your sound on on main
speakers. The normal line level output of this kind can normally
nicely drive up to around 5-10 meters of cable without any noticeable
effect to sound quality.
The typical 3.5 mm output jack used usually for all soundcard
connections has the following pinout on signal output: (see diagram)
In some soundcards the line output is provided using pair of RCA jacks
which are typically used for interconnecting consumer audio devices.
In any case all you need is a suitable cable (cable with RCA connector
on one end one which fits to your soundcard) to hook your PC to your
HI-FI system line level input (for example CD, AUX or TAPE audio
input). You can use the following input jacks: AUX audio, CD audio,
CD-V audio, in order to connect the Line Output of the sound card to
the Line input on the AUX function. Those inputs you should primarily
try to use for PC soundcard. If you do not have those you can try tape
inputs. Note that phono input is meant only for connecting a record
player to in and is not suitable for computer soundcard hookup.
If you happen to for some reason get some annoying humming (this
happens in some case bit not always) then take a look at Ground loop
pages to get information how to solve this problem if you get it.
Some soundcards have headphone outputs instead of line output. The
specification of headphone output could be for example 100 mW to 8
ohms. This kind of headphone output can be used to drive headphones
directly. You can used headphone output like a line output to connect
you soundcard to you HI-FI system. If you don't have a line out, a
headphone out will drive a line in of HI-FI system very nicely. Just
turn its volume down some to get the level into the right range.
Quality will usually not be quite as good as a line out would be...
...Speaker level outputs on some soundcards (not in many newer ones)
have typically around 2W of output power and can drive 8 ohm speakers
or 32 ohm headphones nicely. If you have non-powered speakers or
headphones, this is the output to use for them..."
Its a very informative page.
Sound Card Connections
I trust my research has provided you with your solution. If a link
above should fail to work or anything require further explanation or
research, please do post a Request for Clarification prior to rating
the answer and closing the question and I will be pleased to assist