Spam ? - Re: Soft Rock exciter update

Frank Gentges metavox at
Mon Oct 2 10:57:26 CDT 2006


At first glance this looks like a good choice from several viewpoints. 
The USB interface to isolate the A/D circuits has the potential to 
improve the S/N.  The price is right.

At some point I want to try one of these out but at the moment, I am not 
sure how I would test it to the limits we expect.  Perhaps a super clean 
source of two audio tones as input and a FFT package on the digital 
output to see the intermod products and noise levels.

We can generate super clean tones using a pair of simple oscillator with 
a passive L/C bandpass filter on each one.  The filter outputs should be 
added resistively if the oscillator output levels were high enough so in 
the end the composite tone signal were at the required line level.

We could just use the sound card under test to write out a file.  If we 
use a .wav format, the samples would be limited to 16 bits if I remember 
correctly.  An FFT package should be sitting somewhere out there on the 
shelf that would suffice for this testing.  We need to find it.

I don't see a Linux driver on the M-Audio web site.  A quick Google 
search finds some talk on the Ubunto Forum and it appears to work well 
but needs some grooming to work.  AMRAD could help make this better if 
we want to put this card on our "good" list.

Thanks for steering everyone to this nice card.


Robert E. Seastrom wrote:
> "Mike O'Dell" <mo at> writes:
>> one of the things to look at closely are firewire audio
>> interfaces. they are outboard pods so they can be shielded
>> much better up front and they need it less because they
>> are outside the RF Soup that is inside a modern PC.
>> several of the SDR experimenters are using firewire interfaces.
> I've got an M-Audio Transit; it works fairly well for audio stuff.  It
> has the advantage of being comparatively cheap (found it for $80) as
> external hardware goes, and it runs on USB.  I have had it apart once,
> don't remember what shielding was like (it might have just been spray
> on stuff inside the shell) but it has the advantage of not having
> *any* controls on it and being small enough that it can be easily put
> inside a metal box.  Get some short cables, strip out the outsides, etc.
> If someone would like to temporarily borrow mine for eval purposes, I
> can bring it to Tacos (not this weekend or next as I'm going to be off
> on a plane).
>                                         ---Rob
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