Test & Measurement interface for Soundcard

Thanks a lot!

One left as of now...

I thought I had blown up my SoundBlaster Live in the system in the shop by not using a resistor divider on the output of my amp with AudioTester when I first tried to set it up.

However, I changed to another sound card and get the same results, which is I see no change in the FFT when I unplug the cable from the line in (no active components, just a stereo cord from line in to line out).

Same configuration in the den and I see the first harmonic drop from -70dB to -110dB when I unplug the Line in plug (simple loopback with no active components).

Now I'm thinking I have something configured wrong in the shop.
 
This happened to my power supply in my server a week or two ago.

It's was not a cheapo either...it was a nice $200 PC Power and Cooling unit.
 

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Fortunately I had a spare power supply. I am beginning to find more blown stuff. The TV antenna has proper lightning protection and is actually plugged into a HD Homerun unit which goes into my router. Both af them are fine.

The ham radio antenna coax runs through the same bundle of wires that many of the computer and TV wires go through. The radio was disconnected. and I was at work (yeah both Saturday and Sunday). I got home at about 5PM today and the PC wouldn't turn on. After fixing that I have discovered that one channel of my $39 2.1 PC audio system is dead, and a VCR in another room is dead. It was connected to cable TV.
 
I bet that let the Majik Smoke out!

Looks like the Soudnblaster Live is indeed died. I tried another el-cheapo sound card I had in my computer drawer and it works after a Passion. At least the FFT shows some peaks, and they go away when I pull the stereo Line In plug. The SBlive card just shows floor noise at -90dB. No change when the Line In plug is pulled.

I'm replacing the PS in the son-in-law's computer. Here is what caused his problems...
 

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Lightning can do weird things...jumping from one circuit to the next..blowning up some things and not others.

I'm not sure what caused the failure on this one. The exploded trace was after the rectifier. I have plenty of power supplies...just annoyed that it was one of the "good" ones.

Gimp...what's all the crud from? Doesn't look like normal dust.
 
Lightning can do weird things...jumping from one circuit to the next..blowning up some things and not others.

I'm not sure what caused the failure on this one. The exploded trace was after the rectifier. I have plenty of power supplies...just annoyed that it was one of the "good" ones.

Gimp...what's all the crud from? Doesn't look like normal dust.

SIL is a heavy smoker and smokes at the computer. My best guess is the tars from the smoke combined with all the dust in the air and really gunked up all the filters. His power supply looked just as bad inside. His computer booted up when I took the PS out of my computer and used it to test the system, so I ordered a new PS for it. I just hope he hasn't damaged anything on the motherboard due to heat buildup. New power supply should be in this week. adn I'll have to let it run for a day to see if everything else is ok.
 
I took the BOM over to Digikey, they are out of stock of the capacitors that are the DC blocking capacitors C2 and C3. Any recommendations for a capacitor that will work well and fit?

You could use a Panasonic part from Digi-Key, EF4105-ND. Or a CDE DME4W1K from Mouser. Or you may find others... pretty much any 1uF 400V film cap that has a 22.5mm lead spacing will work.

Pete
 
Hi Pete,

I expect I ought to be able to figure this out, but no luck yet... Can the INA134AP take an unbalanced signal from the SC output? I looked at the datasheet, but it wasn't so obvious that even I couldn't miss it.

EDIT: Okay, I looked at the datasheet again, and elsewhere, and it looks as though an unbalanced source is okay but CMRR will be degraded, depending on the impedence of the SC output. Is that correct?

Thanks. Looking forward to building up my board over the holidays.

Regards,
John
 
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I got mine in the mail today. Looks good, but I won't have time to build it until next year. If enough of these get out there, they could become a "standard interface" such that the DIY community can accurately compare measurements. I am not sure if that is a good thing or a bad thing though.
 
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