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audio applications

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audio applications

Postby weroflu » Wed Nov 09, 2016 3:41 pm

Can I use the 2000 or 3000 series to do basic testing of audio signals from mic level to line level. I was told that these are not good for p/s troubleshooting, but maybe they would be somewhat useful for lower order harmonics?
Also I was told that the probes might not work properly and I might need third part probes, is this accurate?
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Re: audio applications

Postby Gerry » Mon Nov 14, 2016 2:11 pm

Hi weroflu,

The answer to your question depends upon exactly what you need to see in the signal in order to perform your testing. I'm assuming that by p/s you mean power supply (PSU) in which case the PicoScope 2000 and 3000 series should be fine for at least some PSU trouble shooting (if you have a PSU problem) but may not be a good choice for trouble shooting audio problems caused by PSU's (where, for instance, you need to see the detailed effect of PSU noise or harmonics induced onto a low level audio signal)

A major issue is that the resolution of the PicoScope 2000 & 3000 series PicoScopes is only 8-bits, while the lowest input range (excluding the entry level scopes) is +/-20mV, giving you 256 steps at a step size of 0.16mV. This is too large a step size to be able to look at low-level audio signals. For instance, if we look at Mic level, the microphone signal varies depending upon the type (and sometimes model) of microphone that you are using but a typical value would be about 1 mV RMS or 2.83mV pk-pk (-58dBU or -60dBV). So, you would only have 2.83 / 0.16 = 18 steps to represent the audio waveform (which is just over 4-bits, and doesn't account for noise). This would be a very poor representation of the audio waveform.

Signal levels for semi-pro audio (e.g. for SPDIF) are -10dBV (or 316mV RMS or 894mV pk-pk) which is enough for 7-bits of resolution (also accounting for noise), but if you then want to look at lower level artifacts in the signal such as induced harmonics, which will be at a much lower level, you will struggle to get any detail (and may even miss much smaller, but still audible harmonics).

So, if you are looking at mic level signals then you really need the PicoScope 4262 which is a 16-bit scope that, from our range of PicoScopes, would give you the maximum detail (and would also give you the benefit of very low noise on the input). Alternatively you would need to first amplify the signal to line level. If you going to only work with line-level signals then you could get away with a 12-bit scope such as the PicoScope 4224 for looking at harmonics and artifacts on your audio signals (again depending upon how much detail you need to see).

Regards,

Gerry
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