[sdiy] Oscilloscope question

[Derek Holzer]

With some sound cards, defeating the high-pass filter is as simple as 
shorting the input capacitors. I did this on the output channels of an 
RME Hammerfall (admittedly a pretty high-end card) in order to get a DC 
output. Several MOTU sound cards come DC coupled out of the box, as long 
as they have 1/4" jacks.

Other soundcards may have filtering at the ADC level, which unless you 
want to write new drivers and/or firmware for them would make them 
pretty useless for this application.

There is a huge thread on the Muffwiggler forum about soundcards which 
pass DC at the outputs at least:

http://www.muffwiggler.com/forum/viewtopic.php?t=2904

I imagine many of these would accept DC inputs as well.

Best,
Derek

Tom Wiltshire wrote:
> Watch out if you're recording LFO waveforms into a computer to view in a 
> sound editor.
> 
> I once wasted a couple of hours trying to find out what the hell was 
> wrong with an LFO circuit I had on the breadboard before I realised that 
> the audio input on the computer (the clue's in the name..) was losing 
> everything below 50Hz or so and acting as an effective high-pass filter 
> for my LFO waveform. That was the cause of the distortion that had been 
> troubling me.
> 
> Other sound cards may vary, obviously. (OSCMV? New internet acronym?)
> 
> T.
> 
> 
> On 21 Feb 2010, at 18:31, David G. Dixon wrote:
> 
>>> A PC with a sound card will work, just about any of the audio recording
>>> software could be used.
>>> Gold Wave is a good package that allows changing sample quality and
>>> modifying playback rates.
>>
>> Yes, of course!  I've used Cakewalk to look at scope patterns.  I'd
>> forgotten about that.
>>
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-- 
::: derek holzer ::: http://macumbista.net :::
---Oblique Strategy # 177:
"What is the reality of the situation?"