Low volume from Pro-Ject USB V Phono Box

Audacity Help Forum GNU/Linux
1

I’ve been trying to set up a Pro-Ject USB V Phono Box to my system running OpenSUSE 12.1 and Audacity 2.0.2. Even with the gain knob on the box turned up to maximum, the signal rarely gets above 0.5. Connecting the same box up to a system running Windows 7/Audacity 2.0.2 shows much more variation, with the signal clipping even when I have the volume control turned up halfway.

Does anybody have any suggestions for why the signal is so low on one but not the other?

2

0.5 on the linear (default) waveform scale is actually a good signal level to achieve (it is -6 dB) for recording. You can always Normalize or Amplify to a hgher level as your last editing production stage prior to export.

If you switch to the Waveform (dB) view in the Track Control Panel - see: http://manual.audacityteam.org/o/man/audio_tracks.html#panel
you should then see that you have a good strong-enough signal - well avoiding aby danfer of clipping.

WC

3

When I say rarely gets above 0.5, I mean even for the most massive splat of sound with the box gain knob turned right up. I’d prefer to not push the pre-amplifier to its limits and have a more mid-range setting where I would expect a cleaner sound. I’d also prefer to use the box to give a reasonably full range of resolution, since it’s delivering 16 bits and I’d like to fiddle with something that starts with a fairly good raw range.

I’m more concerned that the interface doesn’t seem to be operating uniformly. Since I would expect a USB interface to be sending samples, the difference seems a little odd.

4

Try running ALSA Mixer
In a terminal window enter:

alsamixer

Switch to the Pro-Ject USB device and check the input level there.

5

The ALSA mixer just has “this sound device does not have any capture controls”.

However, I think I have found what I need to do. I have pulse audio running. The pulse volume control shows as PCM2904 Audio Codec. The VU meter on the volume control corresponds to the phono box input. The following steps set up the card as straight digital:

  1. Start the Pulse Audio Volume Control
  2. In the Configuration tab, set the PCM2904 audio codec to Digital Stereo (IEC958) Input
  3. Start audacity using
pssuspend -- audacity

in the command line.
4. Set the input on audacity to the USB Audio Codec and the output to something like front since the default output goes through pulse, which is disabled.

If the input level is too low, then you can, instead, do the following:

  1. Start the Pulse Audio Volume Control
  2. In the Configuration tab, set the PCM2904 audio codec to Analog Stereo Input
  3. In the Input Devices tab, adjust the volume for the PCM2904 to whatever takes your fancy
  4. Start audacity using
pssuspend -- audacity

in the command line.
5. Set the input on audacity to the USB Audio Codec and the output to something like front

6

Duh! You can also do that with the digital input. I just had pasuspender running when I tried to adjust the input.