Why line-level input is a better option than usb?

Hi everyone,

I have read the great Audacity tutorial How to Connect Your Equipment. Thank you a lot for the work. However, I wonder why line-level input is a better option. I believe I have an integrated sound card. I heard the video signal may introduce noise into the recording using the 3.5mm input jack. A direct usb input bypasses the sound card so the recording quality will be better?

Right now I have a dynamic microphone connected to the input on a mixer. The mixer has aux RCA outputs so I connected those to the computer line-level input (blue) on the back of the computer as indicated in the tutorial.

Another question is: can I just use an RCA to USB cable to connect the aux output on the mixer to the USB on the computer? Or, I definitely need some adapter like the U-CONTROL UCA202 for Audacity to work, or to achieve better results?

Please advise, thank you.

I’m confused, I just read that Manual page and I can’t see where it says line input to the PC is to be preferred over USB input. It does say:
“Users with high-grade equipment may prefer to use the source device’s “aux out”, “tape out”, “line-out” or “record” output (if so equipped), since those bypass an unnecessary stage of possibly low-quality amplification, and standardize the signal at a fixed (non-adjustable) level of approximately 1 - 1.5 volts, resulting in a higher quality recording”

Basically if you feed a signal to the line input of a PC (if it has one, my laptop doesn’t) then it will be fed to the PC’s on-board soundcard for ADC (Analog to Digital Conversion). If you use an external USB soundcard that device is normally with a line-level signal and then the ADC takes place on that soundcard and converted into a USB signal for transfer to the PC. By and large most external USB soundcards are better quality than on-board soundcards - plus you take the ADC process away from the “electrically noisy” environment of a PC/laptop.

If you let me know exactly what is confusing you on that page I can take a look at trying to improve it.


I changed the following sentence to read:

If you choose this approach, you will need a cable that has dual RCA red/white plugs at one end (for connecting to the “aux out”, “tape out” or “record” jack of the device) and a stereo 1/8 inch (3.5 mm) plug at the other end (for connecting to your computer’s line-in port or to the line-in inputs on a USB soundcard).

The full page in the alpha 2.0.7 Manual now reads thus:
I can’t go back and edit the 2.0.6 Manual

Thanks for this catch by the way, that was useful :sunglasses:


Thank you, WC.

I might have taken some content out of context and read between line. It is the second green box that confuses me, which reads like this:

"If there is no way to record at line-level, add a line-in by adding a sound card or interface that connects to the computer via USB.

Examples such devices known to work with Audacity:

Behringer UCA202 (left and right RCA inputs/outputs)
Roland Duo Capture UA-11 (jack 1/8" & 1/4" inputs and 1/8" mini-jack output)
Griffin iMic (standard 1/8 inch input)"

It kind of implies “via USB” is used only when “there is no way to …” , not as an equally preferred option. But probably it implies only “line-level” is the easier way, not necessarily a better one.

I am new to recording and have no idea how ADC looks like. I took your answer to my second question as: an RCA to USB cable is not an adapter with ADC built in it so it won’t work and devices like UCA202 (a box with ADC) will work and eliminate interference that usually happens on the PC sound card during ADC. Am I right? The reason I asked this cable vs box question is I have a USB to RCA cable coming with a digital camera (with both audio and video RCAs). I never used it to connect the camera to TV. I thought if it could function as ADC, I may put it in some good use - with a mini-usb to ubs converter of course.

I have to throw in two other questions.

1)You mentioned the different line-level outputs - I probably have them all on my mixer. Please see the two attached photos. I got this mixer second-hand. It was made by some DJ service company a few decades ago so it is impossible to find a manual - the DJ service is still there but they don’t make mixers any more. There are two sets of “tape in” and two sets of “tape out” in the middle of the back panel but I am not sure if two “out” are for recording in a computer because there are “record” and “dubbing” buttons on the top panel - can’t assume anything as I have no idea how they are supposed to work together. Could you please enlighten me? There are also four sets of other line-level outputs on the left of the back panel. The two sets on the top (“I” and “II”) have “2.0v” next to them - I suppose they have amplified signals for two amplifiers - I connected my receiver/amplifier to one of them. The left on the bottom (“III”) has “1.5v” next to them. The fourth is the Aux on the bottom right. I assume the bottom left one (III) creates signal weaker than 2.0v but stronger than Aux, therefore, it is also used for recording (with EQ saved in this case unlike the Aux)?

  1. Currently I use the MIC one input (XLR) on the top panel. If I have another 1/4" microphone plugged in the Mic II input on the back panel, I will have two voices recorded on two channels (stereo), right? What if I add a background music? Which channel will the music be recorded on?

Too many questions at a time. Thank you very much for your time, patience, and help!
mixer top panel.JPG
mixer top panel.JPG

BTW, the audio/sound on my PC is

Integrated audio is not available if a sound card is installed.

Built-in High Definition 7.1 channel audio
Audio codec: IDT 92HD89E

Posts of all new users are moderated. The message after you post says that. Please
be patient and do not double post.


Yes, it follows on from the text above it:

Always try line-level input first, and only use a microphone input if you cannot otherwise get adequate recording volume. You can buy modestly priced, decent quality USB interfaces with line level stereo input if needs be.

I agree it would be better to mention at the top of the page that using a USB interface is an option instead of line-in (on the grounds there may be less noise). However most entry level computers these days have no line-in, hence the slant of that page.

USB is not always quieter. RF transmission noise from USB can leak backwards into the analogue stages and contaminate the analogue signal during the sampling process.


I set a P2 editornote in the Manual to update that page before 2.0.7 in the light of this discussion.


The images you posted are identical.

Yes, if those are left and right inputs and you set Device Toolbar in Audacity to record in stereo.

If you mean recording into Audacity, that recording will by default be in a new track, which is the best place for it. If you want to record from a particular spot, say 2 minutes in, then click to place the cursor there, then Record will record from there into a new track.

Also there is an Auto Duck effect you may be interested in which can duck the background when the voice comes in: Audacity Manual.


Thank you for the information, Gale. It is good to know that USB interface is not always quieter than line-level inputs. I will try to cancel my order of the UCA222 and first determine if the line-level is too noisy on my PC before adding and trying a new device. Cheers.

If you do end up acquiring one you will find that you will have a device that should work on any or all computers that you own.

My Edirol UA-1EX sound card is now on it’s third PC :wink:


Hi, Gale, I posted that reply twice with slightly different texts and the second one had two different pictures. I attached the picture of the back panel here again for your reference. Thank you.
mixer back panel.JPG

Yes, WC, you are absolutely right. I am thinking maybe I can use it with my laptop, which has no line-in, in another room, which is quieter!!

Thanks - yes your second reply was assumed to be a duplicate rather than substantially different so was deleted.

I suggest you use the output that gives the best result with your line-in, but there probably won’t be much difference.

If you need an output where you can control the level sent to the computer, you can use the headphones output unless you are already using that to monitor yourself.


Thanks, Gale, I tried with audacity yesterday. Strange enough, only the 1.5V output works. The Aux and tape out can’t record anything except hiss - I think I tried to press the “record” button as an option - doesn’t work either. Guess I have to keep trying. With the 1.5v output, the best result comes when I push microphone volume to maximum and mater volume lower than 3/10. I use headphones for monitoring, yes. When I get the external sound box, I will see if it is better.