That infernal hum

Mon May 26 06:52:51 EDT 2008

I'm confused. What can you do with a USB sound card that has no input
connectors--as Joe said was the case with two of the three units he
saw at MicroCenter? Seems as though, without input connectors, the
external unit would have to rely on the laptop's own Mic jack to
connect all audio sources. But doesn't the laptop's Mic jack go
through a very simple preamp and then pretty much straight to the
laptop's ADC (and ONLY to the ADC)? If so, the USB sound card could
have only16-bit digital audio to work with and the data would always
contain artifacts, such as noise and distortion, that were introduced
by the laptop's ADC and mic preamp, whereas if the external unit had
its own Mic input, it could work with analog signals processed by a
higher quality preamp and digitized to 24-bit-resolution by its own
ADC. I suppose the external unit could use DSP (digital signal
processing) to up-sample (interpolate) the 16-bit data stream to 24
bits at what would appear to be a higher sampling rate, but such a
higher-resolution data stream could contain no more information than
the original 16-bit stream. I thought that lower noise and distortion
and true increased digitizer resolution were the main reasons someone
would want to use an external sound card with a laptop.

Dan Strassberg (
eFax 1-707-215-6367

----- Original Message ----- 
From: "A. Joseph Ross" <>
To: <>
Sent: Monday, May 26, 2008 12:28 AM
Subject: That infernal hum

> So I went to MicroCenter today, but of the three USB soundcards they
> had, two had only an output jack, and one had only an output and a
> mike jack.  Same problem I already have.  So I'm going to look
> online
> and see if that solves the problem.
> -- 
> A. Joseph Ross, J.D.  >

More information about the Boston-Radio-Interest mailing list