Audacity might do that if it loses contact with its recording device. It starts searching for a device that’s still alive—usually built-in microphone. If you disable the microphone in System Preferences, Audacity may just crash.
You’re not using your entertainment system and a USB interface are you? Chances are good you’re using an Affordable Home USB Turntable. When you transfer the last record, you’re doing to put the turntable in the trash, right? We may have reached the trash stage a little early.
As I understand it the NAD amp is just there for listening - the turntable connects to the ProJect USB interface which then connects to the Mac via USB.
Go to Apple (menu) > System Preferences > Input and select the ProJect USB interface. Play an album. Does the input level meter bounce? Let it play for a while. Does the interface remain connected?
Under Sound I have two options: iMac Microphone & USB Audio CODEC. Selecting the latter it states Settings for the selected device: the selected device has no input controls. I’m playing an LP now and the input level is registering it as you would expect. I have played the whole side of the LP and it’s fine all the way through.
That’s not normal. Suppose you were recording a live interview with the Governor? We expect Audacity to continue recording unless you intentionally stop it or it runs out of resources.
delete a recording after exporting and try to make a new recording.
How do you delete the first recording? Press the little [x] to the left of the track? Audacity doesn’t just forget the first recording when you do that. It saves it up in case you need to Edit > UNDO the closure and get the first track back.
Audacity forgets all those housekeeping chores when you close it.
…runs out of resources.
The symptoms are screaming running out of memory or other overload condition. I predict (holding fingers to forehead) nobody else is going to be able to duplicate your failures. Your machine isn’t big enough to do your jobs.
I used to regularly get the Film Editorial Manager out of trouble by closing the hundreds of apps he left running in the background. Does this Mac still have little lights or dots or something under the Apps that are running?
How many dots do you have?
Carefully save all your work and Apple > Shut Down… > Shut Down. Not Restart. If you never do this, it may take a while to close everything. Watch for a little spinning daisy as it goes.
Make sure it’s dead (make coffee) and then start it. Macs don’t Chong any more, right? I miss that confirmation tone. I wonder if you can put it back.
Start just Audacity and see if the problem changes.
Just made a two minute recording via USB and it switched to microphone after about 60 seconds. Deleted the recording, started recording again, error message, shut program, reopened it and made at the recording via USB for 90 minutes without a problem. Random. I have restarted the Mac numerous times. And I have tried shutting down programs. I guess from your responses I’m just going to have to live with it… Thanks for your interest in this problem and the suggestions.
Can you record using Quicktime Player? After opening it you can select File > New Audio Recording. Click the downward-pointing arrow next to the record button and choose maximum quality. Then click the record button and start your LP. This should save as an AIFC file. You can then import that file in Audacity to do your editing.