I am digitizing LP records using a USB turntable, and have a clipping problem. The turntable has no volume control, and Audacity has no input level control when using the ‘USB Audio CODEX’ input, the only one I can find that connects Audacity to the turntable.
I am guessing
the clipping happens during the analog to digital conversion,
that has to happen in the turntable if I use USB, which is digital,
therefore I can’t use the USB output.
Are these solid conclusions or should I check something before continuing?
Best solution seems to be to use the RCA line-out connectors from the turntable. I have no computer with line-level inputs, just USB and mic-in connectors. So what do I need to buy?
Technical Info:
iMac late 2013
running Mojave 10.14.6
Innovative Technology USB turntable model ITUT-201SVR
outputs: USB, line out
Audacity 2.3.1
input: USB Audio CODEX
level meter: pegged red
waveform: worst clipping, 11 samples in a row; guess max level 1.8
On your Mac, choose Apple menu > System Preferences, click Sound, then click Input. = apple icon
Select your USB device in the list of sound input devices.
All sound input devices available to your Mac are listed.
To adjust your sound input settings:
Adjust the input volume: Drag the volume slider.
If you’re recording sound through your computer’s sound port, you can adjust the input volume to compensate for the sound source being too loud or quiet.
For example, if you’re recording loud music, lower the input volume so the recorded sound isn’t too loud or distorted. Or if you are recording someone who is speaking softly, increase the input volume so your Mac can better capture the person’s voice.
the clipping happens during the analog to digital conversion,
that has to happen in the turntable if I use USB, which is digital,
therefore I can’t use the USB output.
That can happen with some USB turntables and some records. Some records are louder than others but clipping should be rare. There is one popular USB turntable with “famously low” output, allowing plenty of headroom.
Best solution seems to be to use the RCA line-out connectors from the turntable. I have no computer with line-level inputs, just USB and mic-in connectors. So what do I need to buy?
You can get a USB audio interface with line inputs. Don’t buy a regular “USB soundcard” because they are like laptops with only mic-in and headphone-out. The Berhinger UCA 202 and UCA 222 are popular and inexpensive but they also don’t have recording level controls so there is still a chance of clipping the ADC. Behringer and other manufacturers make audio interfaces with switchable mic/line inputs and recording level controls. The ART USB Phono Plus has switchable phono/line inputs and a level control.
Thanks to all for your input. I consider this thread answered.
I tried updating Audacity and then comparing recordings made before and after. The clipping was unchanged. Interestingly, the turntable speed varied by 0.12% between the two recordings (which, if I am correct, is about 2 cents pitch change, on the edge of noticeable). Cold room maybe.
Maybe the Innovative Technology turntable is unusually hot, but I have tried four different records and they all clip about the same amount. Seems silly not to put gain control on these animals.
Hey Doug, where can I get Boney M’s “Dancing In The Streets” (45 rpm, 1978) on CD?
Bill, thank you very much for your input. I don’t know much about macOS (but I do try to do my homework before posting). Anyway - that is why I am here - to learn.
Help me learn. You are on Catalina, ILove2Sing is on Mojave. I found these instructions, documentation for another USB input device, specifically for Mojave which shows how apple Mojave can adjust the input volume on a USB input device. Did apple change the Mojave’s behavior? What am I misunderstanding?
Preliminary setup with MacOS Mojave
If you are using MacOS Mojave, you must enable software access to the microphone, using the security and privacy settings.
Connect the ATR2100x-USB microphone to an open USB port on the Mac (Type A or Type C).
Open the system preferences by clicking the Apple logo in the upper left corner of the menu bar and selecting System Preferences. Alternatively, you can click on the gear icon in the dock. Click the Loudspeaker icon to open the sound preferences.
By default the Mac selects the internal microphone as the sound input device. When the ATR2100x-USB is plugged in, the Mac assumes that it is the desired input device and automatically selects it.
Verify that the ATR2100x-USB is highlighted.
The input volume for the microphone can be adjusted by moving the input slider and watching the level meter while speaking into the microphone. Setting the level too low will not provide enough input signal to your recording application. Setting it too high can overload the input to the recording application resulting in clipping or distortion.
What I meant was that the “input volume control” in Sound Preferences is disabled for USB audio input devices on Mac. This also means that Audacity’s recording volume slider is disabled and set to maximum.
Yes, some USB input devices have a hardware volume control, including some USB turntables. I looked up the manual of the turntable in question and it said nothing about an output volume control.
You are correct that some USB microhpones can have the input level control active in System Preferences. The same applies to my AT2020-USB microphone. This appears to be a “real” volume control, not just scaling of the digital signal.
However, I have never seen a USB turntable, cassette deck, or other interface (such as one of the Behringer adapters) with the input volume control active. They usually show up in Sound Preferences as “USB Audio CODEC”.
If you buy an interface like the UCA 222 with no level control and you get still clipping you use fixed inline attenuators but then you have to guess the amount of attenuation or buy more than one pair, and they are a little pricey. I have one of [u]these variable attenuators[/u] (which I bought for a different purpose).
> System Preferences, click Sound, then click Input. 
