Sound loop back, please help

[giossoj]

I am trying to do an audio loopback with BurnInTest V6.0 pro to test the microphone input and the speaker output.

How do I do this?
My tech built this loopback cable (See picture) he said he got this info off the net, though I do not know where.

This does kind of work, but I get a lot of destortion and flakey results.
Is there a better way of doing this?

Thanks!

[Ian (PassMark)]

I don't know about your test circuit. As I understand it, the mic in signal is amplified (when compared to line in). Maybe you can reduce distortion by simply turning the volume down on your line out.

[giossoj]

Audio loopback

I did try that, and that does help but I am still getting some random distortion that fails my bit test.
Is there a way to test the mic input? Maybe I can separate the two.

[David (PassMark)]

We just used a straight audio cable, and it works OK for us once the levels are adjusted.

[patrickshaw]

sound failure

We are seeing the same results using a realtek and IDT sound card. The output waveform is jittering and appears corrupted. We have run the passmark 6.0 using soundcheck instead and the signal is stable.

I have included copies of the waveforms

[Ian (PassMark)]

I couldn't see the waveforms you mentioned, so if you could link to those I can take a look.

If you have line out conencted to line in, and you have distortion (and it is OK in soundcheck) then the most likely cause is that the volume is too high. Try changing the line out volume while the test is running.

[Ian (PassMark)]

Further to my post, I see you have sent the waveform images via email. I have them now.

I assume this is line out to line in and not line out to mic in. Can you please send me your configuration file (e.g. LastUsed.bitcfg) showing what other tests are running and at what duty cycles they are running. You have my email address.

[giossoj]

Audio loopback

If you are just going from line in to line out BIT seems to work fine. Unfortunately I did not have a line in on the unit I am testing, only a Mic in and speakers out.
I found a web site that talked about an audio attenuator. http://www.epanorama.net/circuits/line_to_mic.html I think this is what my tech was trying to do above, but just had the wrong values.
I used the 40db PAD schematic and turned the Mic and master volume way down, but not off.
This worked great! I have been running for 2 days with no errors logged with a threshold of 5%.
Just make sure you tie the R2 resistor to the speaker + side of R1.

[Ian (PassMark)]

giossoj: Thanks for posting the information.

patrickshaw: Just to document the results of this issue in this forum post: It seems a change to the sound loopback test resolved this problem. Please use the latest version of BurnInTest where possible (in this case at least V6.0.1013).