Noise floor: Toshiba laptop

[Line In]

Hi,

I just got an old Toshiba laptop, a Satellite 1135 series, that I plan to use for some mobile recording. Running WinXP SP2. I'll be adding a USB interface but in the meantime I've been experimenting with the  onboard sound (Avance AC97 Audio) and Audition 1.5.

The noise floor with no input is bad (no surprise) but quite different on each channel............a fluctuating -58db on one and a rock steady -40db on the other. I can live with the lower one but I'm puzzled about what might be causing the other to be so different. This is with Line In selected on the Windows Mixer recording control. If I choose Stereo Mix I get different numbers, -65db  and -54, both fluctuating slightly.

I suspect some of this is due to the onboard sound picking up noise but I'm not really too familiar with the Windows Mixer, particularly what control to use for line recording. If anyone has any suggestions or can point me in the right direction I'd appreciate it.

Thanks.

G.

I just got an old Toshiba laptop, a Satellite 1135 series, that I plan to use for some mobile recording. Running WinXP SP2. I'll be adding a USB interface but in the meantime I've been experimenting with the  onboard sound (Avance AC97 Audio) and Audition 1.5.

The noise floor with no input is bad (no surprise) but quite different on each channel............a fluctuating -58db on one and a rock steady -40db on the other.

Basically, my advice would be not to waste any more time on this! In my experience, the rock steady 'noise' reading is often caused by the soundcard having a DC offset on one or both channels. You may be able to remove this via the AA 1.5 options, but I've had machines where the DC offset changes with the mixer level or input selection settings. The cheap laptop I'm typing this on has apparently random hum problems on record as well as the DC offset. It works fine with a usb interface, though.

The Windows mixer "Stereo Mix" just feeds the output of the Windows playback mixer as an input to the record mixer. If the machine has a line input, it ought to be better to select that unless you want to record multiple sources or, say, from an incoming internet feed. The trouble is that, as is obvious, laptop designers don't seem too competent with audio design, and have been pushed away from using separate audio hardware, so it's anybody's guess which source to the Windows mixer will work least badly.

Basically, my advice would be not to waste any more time on this! In my experience, the rock steady 'noise' reading is often caused by the soundcard having a DC offset on one or both channels. You may be able to remove this via the AA 1.5 options, but I've had machines where the DC offset changes with the mixer level or input selection settings. The cheap laptop I'm typing this on has apparently random hum problems on record as well as the DC offset. It works fine with a usb interface, though.

I can absolutely confirm that having a typical laptop soundchip feeding Audition will screw with the meters. Fortunately, you can make a much better estimate of what the BG noise level really is without actually recording anything, by right-clicking on the meter scale and selecting 'adjust for DC'. Usually this has the effect of lowering the apparent noise floor quite considerably, and generally evens the channels up. And yes, all laptop-recorded sound is excruciating.

Thanks for the responses. I'm very new to laptops and I appreciate the explanations and advice. I'll be picking up a USB interface soon. Actually I'd been considering the Zoom H2 flash recorder, which, according to the documentation should do double duty as a stand alone recorder and a USB interface for inputing other audio directly to the PC.

Thanks again.

G.

Actually I'd been considering the Zoom H2 flash recorder, which, according to the documentation should do double duty as a stand alone recorder and a USB interface for inputing other audio directly to the PC.

Yes, the Zoom will do this - but you have to remember that as a direct interface it's only 16-bit, despite inherently making 24-bit recordings. Works fine, though - as long as you can actually see the display!