Adjusting input volume for USB turntable

[samliden]

I have an iMac with OS 10.6.8, and recently bought a Sony PS-LX300USB turntable. The input volume is very low on the Audacity transport display (less than 0.1) and I am not able to adjust the input level. The turntable does not have a level adjustment. What can I do?

Sam Liden, Phoenix, AZ

[kozikowski]

The instructions say that low volume can be caused by the analog connections being set wrong. Are you using both analog and USB connections? Does the turntable work with the Sound Forge Audio Studio LE that came with it?
Koz

[samliden]

The turntable comes with an anolog output as well as a USB output. Only the USB is connected and the the Audacity input is set to USB Audio CODEC. The Sound Forge Audio Studio CD that came with the turntable only runs on a Windows PC.

[kozikowski]

Oops. Missed that.

Yes, USB systems tend not to have adjustments and everything works perfectly until you need one. You can fix it in post production. That is probably one of the steps in the Vinyl to CD tutorial.

http://manual.audacityteam.org/help/man ... to_cd.html

The stand-alone technique is select the whole track (click on the track left panel) and Effect > Amplify > -1dB.

You should be careful about doing these steps out of order because if you intend to "clean up" the music later by filters land effects, some of those tools can interfere with each other.

If it's going to be wrong, this is a good way. Wrong the other way -- too loud -- gives you immediately unusable recordings.

Koz

[samliden]

When I select USB Audio CODEC for input, the input level slider becomes disabled. WHY??? This seems to me to be a design flaw. I bought a USB turntable to be able to digitize my extensive LP collection. When I use the analog output from the turntable (line level) with Built-in Input selected, the input level slider is enabled, but I have to set the level a maximum to get a reasonable-looking waveform. Could you explain why your program can't adjust the input level with USB input, and if there is a disadvantage (loss in quality) in using the analog line from the turntable?

[Gale Andrews]

When I select USB Audio CODEC for input, the input level slider becomes disabled. WHY??? This seems to me to be a design flaw.

Correct. It's a "design flaw" in the Mac OS X operating system that it does not permit the volume of USB audio devices to be controlled. You can use Windows instead, which does permit this.

if there is a disadvantage (loss in quality) in using the analog line from the turntable?

It may be your only choice if you want to use Mac. On a fast machine USB is often preferable as the Analogue > Digital converter may be better than that in a built-in sound device, without the likelihood of transmission hangups.

USB can still be noisy, but hiss and hum rather than the electro-mechanical noise the built-in sound device can pick up.

If the turntable analogue output also drives speakers, turn the switch from phono to line.



Gale

[kozikowski]

You didn't say which Mac you have, but all but the newer ones have a very good stereo analog input. That's how I digitize all my old vinyl. Conventional turntable > Hafler preamp with phono preamplifier > directly into the Mac Stereo Line-In. Terrific work. If you already have a top quality music/turntable system you might very seriously consider doing it this way. "Throw Them Out When You're Done" USB turntables frequently have shortcomings in quality that affect the music.

But yes, a simple adapter cable into your Mac should do it -- depending on the Mac.

http://kozco.com/tech/audacity/pix/RCAMiniStereo.jpg

Koz

[PGA]

USB can still be noisy, but hiss and hum rather than the electro-mechanical noise the built-in sound device can pick up.

That statement implies that USB can add noise, just like analogue can. Any noise coming from the USB device is being generated "upstream" of the USB socket. A USB signal comprises only binary ones and binary zeroes. If they represent noise, the noise was either added by the analogue-to-digital converter or already present in the analogue signal going into the converter. USB is the most perfect implementation of "garbage in - garbage out" I know of. Give it garbage and it will transmit it onwards with 100% faithfulness. Give it a good, clean signal and you will be forever in HappyLand!

[Gale Andrews]

USB can still be noisy, but hiss and hum rather than the electro-mechanical noise the built-in sound device can pick up.

That statement implies that USB can add noise, just like analogue can. Any noise coming from the USB device is being generated "upstream" of the USB socket. A USB signal comprises only binary ones and binary zeroes. If they represent noise, the noise was either added by the analogue-to-digital converter or already present in the analogue signal going into the converter. USB is the most perfect implementation of "garbage in - garbage out" I know of. Give it garbage and it will transmit it onwards with 100% faithfulness. Give it a good, clean signal and you will be forever in HappyLand!

I am not implying that digital transmission pre se creates noise, but it would be very misleading to suggest that using a USB device will always give quiet results (a common misconception). USB transmission can add noise before finally reaching digital (and I would say often does with cheap USB devices). Just think too of all the noise sources at the computer end of the USB cable. See http://audacity.238276.n2.nabble.com/Ex ... l#a5722453 .



Gale

[kozikowski]

I think that's a little slippery. Yes, certainly, USB is half-duplex. It only works one direction at a time and putting a busy USB hub in the system is just begging for trouble. The audio tries to change directions and it has to wait for the keyboard, mouse, and printer to finish. It's one of the reasons the video people stayed with FireWire with bleeding fingers. No negotiation problems.

But that results in very serious breakup and noise, not a slightly "hissier" show than normal. It results in forum postings, not slightly degraded performances.

We are experiencing audio problems at work by extending USB too far. That one is seriously magic. Move the conference sound unit from one side of the conference table to the other -- bend the cable -- and it starts breaking up. Again, that's not a minor problem. We have to cancel talks over it, but it's caused by us intentionally abusing the USB standard. Plugging a US desk lamp into the UK mains will result in a very entertaining error. But neither UK mains nor the lamp are broken should they be properly used.

The only other "USB" damage I ever saw was the famous iMic I put in the car park. In that case, the ratty battery supply from the computer got into the analog amplifier, it wasn't strictly a USB problem.

Just think too of all the noise sources at the computer end of the USB cable.

I am and I don't think there are any. That message thread is yards long. Is the upshot that one person has a broken USB connection? It seems to be as far as I read. That's different from everybody picking up hard drive whine noise in the digital connection. Doesn't happen with a healthy computer. If your computer 5 volt rails are sinking below 2-1/2 volts on occasion, you got a lot worse problems than gaps or noise in the audio. Your computer is heading for dust bin certification.

So I would not assume USB is natively noisy. It's frequently broken, yes, and it's easy to install wrong, I'll certainly give you that. But that doesn't mean USB sound is automatically noisy or defective after it becomes digital.

Koz