Problem trying to add new tracks to existing project

First, the hardware and software configuration:

Dell Inspiron 530 with built-in Realtek sound card;
Electronic keyboard connected to an external mixer channel;
Mics connected to mixer channels;
Mics are switched to off;
Volume sliders on mixer are at zero except for keyboard and master;
Multi-chanel mixer output connected to Line-in on sound card;
Line-out on sound card to stereo amp;
Speakers connected to stereo amp.
Stereo amp is NOT connected to multi-channel mixer;
Windows XP 32-bit with Service Pack 3;
Audacity 2.0.2 installed with installer;
Software Playthrough checked,
Overdub not checked.

We are trying to add a separate track to an existing project. Overdub adds the new track, but it mixes it with the original track.

With the setup as described above, we get a loud oscillating feedback in Audacity when output VU meters are clicked and when Record is selected.

I’ve seen a number of entries that say DO NOT check Software Playthrough. However, we need the new track to be completely separate from the original. In fact, we would like to add several separate tracks and mix them as the last step. That seems to be what Software Playthrough provides. However, with this problem, it is useless.

I hope someone can help us out here. Thanks.

That is correct.

No, that is what “Overdub” provides.

“Overdub” needs to be on (selected)
“Software Playthrough” needs to be off (not selected).

A critical point in the setup is the “Device Toolbar” settings:
The input (recording) device must be set to the actual input that you are using (Line In) and not to “Stereo Mix”, “What U Hear”, “Mix” or similar.

There are lots of variations depending on the mixer, but a typical set-up might be:

Instruments / mics into the mixer.
Mixer “2 track” (tape) out to line input of sound card.
Line output of sound card to mixer channel that is NOT routed through to the 2 track output, but IS routed through to the headphone/control room mix.
Then either use headphones plugged into the mixer, or the control room out to the the monitor amp. Note that monitor speakers should not be used in the same room as any microphones. For mic recording, always use headphones.

If you still have difficulty, please tell us the exact make and model of the mixer that you are using.

Thank you for the prompt response.

We tried adding a track with Overdub checked and Software Playthrough NOT checked. What we got was a new track with the original track (vocal) with the keybooard mixed together. So we had the vocal track and the new track that had the vocal plus the keyboards. We observed this by muting the original track and playing the new track. The new track had the vocal present in it. What we need is a vocal track and a keyboard track, where the vocal track has only the vocal and the keyboard track has only the keyboard.

We had the Output device set to Line-out and the Input device set to Line-in.

The mixer is a Radio Shack Three Channel Stereo Sound Mixer. There is no model number, but the catalog number is 32-2057. I have a PDF document that shows the fron and back of the mixer. I’ll upload 2 png files showing back and front.

What were we doing incorrectly?

That’s helpful. That mixer is really designed more for DJ type use rather than as a recording mixer, but I think that we should be able to get this working.

I presume that the mixer is connected to the computer sound card with a lead something like this:

As a test, disconnect the two RCA connectors from the mixer and make a recording.
It should record nothing, right?
I’m guessing that any existing tracks are still recorded onto the new track.
So which is it?

I think this problem is covered in One Recorded Track, Unitentionally Recording To Another. located at
I had the same problem but solved it by assigning recording & playback devices.