How can I listen to the input; after hitting the “click to start monitoring” button, the meter scales show the input signal but there is no output signal. The input can be recorded and played back but how can I listen to the input signal. Why isn’t there a “monitoring” reference in the index?
There is a way to do this, but it may not always be as helpful as you think.
Audacity > Edit > Preferences > Recording > [X] Playthrough > OK.
Yes, that’s useful if you’re recording a turntable or cassette machine, but not if you’re overdubbing or recording a live microphone. Even if you’re routing the Playthrough to your headphones, it’s going to be late with an echo. I challenge anybody to sing this way. It will drive you nuts.
You didn’t say what you were recording.
What are you recording?
Koz
Older or some extremely expensive computers might let you unmute mic and Line In inputs of the built-in sound device in the Playback side of the sound card’s control panel (this may be exposed in the Windows Sound Control panel too). If available, this is hardware playthrough and has no appreciable latency.
Gale
Yes, that worked fine. I’m recording a guitar through a behringer usb UCA200 interface, and now use Audacity to play through as well as record. The audio latency was as you said not useful, but with WASAPI drivers and setting the priority to high it works fine. I think it could be better if ASIO4ALL drivers were incorporated but I haven’t figured out how to do that yet. My Audacity is installed on an i7 3GHZ HP laptop running win10.
Audacity cannot use ASIO4ALL drivers unless you compile Audacity with ASIO support. ASIOALL is not ASIO but a wrapper for non-ASIO API’s, so ASIO4ALL can never be faster than those API’s.
Audacity’s Software Playthrough is at fixed latency, so reducing Audio to buffer in Audacity’s Recording Preferences (which also affects playback) won’t let you reduce software playthrough latency that way.
Windows’ version of software playthrough (called “Listen to this device”) is usually a little faster than Audacity’s software playthrough, at least when using MME or Windows DirectSound host in Audacity.
Gale
I think it could be better if ASIO4ALL drivers were incorporated but I haven’t figured out how to do that yet.
ASIO4ALL will NOT work with Audacity… Audacity (as distributed) is not an ASIO application.
ASIO4ALL replaces part of the Windows driver stack to allow regular Windows hardware to work with true ASIO applications, but it doesn’t work the other way around… ASIO4ALL does not work with non-ASIO applications.
ASIO was designed for low latency, but from what I understand WASAPI can be just as good or better (but ASIO may be is easier to set up for low-latency).
Just a note in case you’re solving a problem you don’t have, the UCA-202 is one of the devices I certified for perfect overdubbing—zero latency show mix in your headphones. The trick is to listen to the UCA-202 instead of the computer. It’s totally possible the UCA-200 will do this trick.
I think the set up is still available in the on-line manual.
http://manual.audacityteam.org/man/tutorial_recording_multi_track_overdubs.html
Basically, switch the UCA to “monitor” and set the UCA as one of the Audacity playback devices. Turn Off Playthrough!
To be clear, you are required to set Recording Latency when you do this. The object is to “tune out” the difference between when you think you should be playing the chord and where it’s actually supposed to go in the song. That’s the latency you can adjust.
The headphone connection is not a flame thrower. It will only get as loud as 5 volts will go, so it’s possible you may need a booster or amplifier for actual performances. That should be a piffle compared to the other recording problems.
Koz
From the tests we did a few years ago, you can’t get WASAPI latency in Audacity below about 70 milliseconds (ms) for physical or stereo mix inputs on most machines, because Audacity’s Audio to buffer setting usually has no effect for WASAPI. WASAPI loopback latency could be about 30 ms. Windows 10 is supposed to have some WASAPI latency improvements so it might be good to retest.
The fastest non-ASIO API is WDM/KS but current Audacity does not support it. With WDM/KS and “Audio to buffer” reduced down to a few ms, you can get latencies of only a few ms, almost comparable to ASIO at a few ms buffer. The other Windows API’s won’t record at a few ms buffer.
Gale
The last Audacity version with WDM/KS support (2.1.0-alpha-jan 12 2015) is working just fine on my Windows 10 x64 system. Realtek integrated audio. 
2.1.0 alpha (audacity-win-r13705-2.1.0-alpha-06-dec-14) with WDM/KS on W7 worked fine on my external USB soundcard (Edirol UA-1EX), but not with the on-boad Realtek card. See this Bugzilla report:
http://bugzilla.audacityteam.org/show_bug.cgi?id=651#c5
I no longer have that alpha build or access to a download for it so I can’t test on W10 (unless we ever experimentally re-enable it for alpha builds)
Peter
If it’s of interest to you or anybody, I have uploaded “audacity-win-r13879-2.1.0-alpha-12-jan-15.zip” to Google Drive: audacity-win-r13879-2.1.0-alpha-12-jan-15.zip.
Also I would love to be able to test a new experimental alpha build with WDM/KS support…
Alpha builds should not be used for production work. If anyone wishes to use 2.0.4 release that included WDM-KS you can obtain it here: https://code.google.com/archive/p/audacity/downloads.
Please be aware that several hundred users reported that 2.0.4 with WDM-KS crashed their computer, especially with Realtek devices having HDMI outputs. Thousands of users downloaded a replacement 2.0.4 without WDM-KS that was posted, so there is a risk.
Gale
I just tested 2.0.4 (I still have a copy) with WDM/KS under W10.
I get exactly the same symptoms as I got previously on W7 as reported in the Bugzilla report - so no change in gounf grom W7 to W10
Peter