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not quite ready to throw away this old sound card (trying to fix it)

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not quite ready to throw away this old sound card (trying to fix it)

PostPosted: Tue Jul 23, 2019 8:01 pm
by mystudioneedswork
so I found a really old m-audio connectiv soundcard which has 4 in 4 out, I figured this could be useful for something now i've got asio4all installed giving me 6 mono input channels including my behringer audio interface. my studio is pretty ghetto lol but i'm wondering if I can save some money and get this old card working to a standard i'm happy with.

I did some test recordings through it and i'm getting some noise somewhere but I don't know where in the frequency range it is? I ran voxengo span which simply showed a spike at under 30hz, so I put an eq on these channels to remove that. with that gone I once again recorded silence, played the sample file in audacity, there appears to be something coming through at -50 on the volume. I uploaded the file for download here if you wanna check it out; https://drive.google.com/open?id=1y_br7 ... m_nefpZEBu

I can't hear the offending frequency or even see it? so a frequency sweep might be pointless. i've tried really boosting the audio in the blank samples then putting voxengo span on that channel to see what is going on, i then compared this to a boosted recording using my better audio interface ,the problematic soundcard is clipping like crazy whereas the clean behringer isn't at all, they both have a near identical eq curve? here is the m-audio (problem card in question)

Image

and for comparison here is the output from behringer

Image

i'd like to try to diagnose and possibly correct this with digital tools if I can, partly through being thrifty and also so I can understand recording issues like this better. any help appreciated.

Re: not quite ready to throw away this old sound card (trying to fix it)

PostPosted: Tue Jul 23, 2019 11:02 pm
by James Perrett
I downloaded your file and found that this is one of those rare occasions where you have a genuine DC offset. (Most people that complain of having a DC offset are actually only seeing waveforms that aren't symmetrical). Some software has filters specifically for removing DC offsets while with others you need to use a high pass filter set to the lowest possible frequency (something like 10Hz would be ideal).

The main issue caused by DC offsets is that you'll hear a click whenever you start and stop playback or edit between files from this card and files from another card. Some software automatically adds very short fade ins/outs to the ends of clips to prevent these clicks and can also use short fades when starting and stopping playback. It should be perfectly possible to use this card provided you are aware of the problem.

Re: not quite ready to throw away this old sound card (trying to fix it)

PostPosted: Tue Jul 23, 2019 11:59 pm
by hobbyist
mystudioneedswork wrote:so I found a really old m-audio connectiv soundcard which has 4 in 4 out, I figured this could be useful for something now i've got asio4all installed giving me 6 mono input channels including my behringer audio interface. my studio is pretty ghetto lol but i'm wondering if I can save some money and get this old card working to a standard i'm happy with.

I did some test recordings through it and i'm getting some noise somewhere but I don't know where in the frequency range it is?

Image
i'd like to try to diagnose and possibly correct this with digital tools if I can, partly through being thrifty and also so I can understand recording issues like this better. any help appreciated.


Dunno, for sure, but it looks like harmonics from something based on that picture.

Re: not quite ready to throw away this old sound card (trying to fix it)

PostPosted: Wed Jul 24, 2019 9:44 am
by Martin Walker
Hi mystudioneedswork, and welcome to the SOS Forums! 8-)

Like James, I downloaded your audio file and can confirm that it contains a DC offset sitting at about -51dBFS, as shown below:

whereisthesound.jpg



Martin

Re: not quite ready to throw away this old sound card (trying to fix it)

PostPosted: Wed Jul 24, 2019 6:46 pm
by mystudioneedswork
James Perrett wrote:I downloaded your file and found that this is one of those rare occasions where you have a genuine DC offset. (Most people that complain of having a DC offset are actually only seeing waveforms that aren't symmetrical). Some software has filters specifically for removing DC offsets while with others you need to use a high pass filter set to the lowest possible frequency (something like 10Hz would be ideal).

The main issue caused by DC offsets is that you'll hear a click whenever you start and stop playback or edit between files from this card and files from another card. Some software automatically adds very short fade ins/outs to the ends of clips to prevent these clicks and can also use short fades when starting and stopping playback. It should be perfectly possible to use this card provided you are aware of the problem.

hobbyist wrote:

Dunno, for sure, but it looks like harmonics from something based on that picture.

Martin Walker wrote:Hi mystudioneedswork, and welcome to the SOS Forums! 8-)

Like James, I downloaded your audio file and can confirm that it contains a DC offset sitting at about -51dBFS, as shown below:

whereisthesound.jpg



Martin

^ thanks for the welcome and help guys this is exactly what I needed, to put a name to the problem. now I have a way in and will look into ways to fix this! :)