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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: What I really wonder is WHO here can measure jitter - - - posted by AbeCollins on June 3, 2012 at 11:33:39:
I built a very inexpensive PLL circuit with the same high quality VCXO I used in my DAC. The input is attached to the clock to be measured, and the correction signal to the VCXO is bandpass filtered and then amplified, and I use the math and averaging functions on my storage scope for display. It's very sensitive, but not calibrated. I just use it as a "sniffer" type device and for comparison measurements. My main priority was getting visibility on very low amounts of data-correlated jitter, so I use it with a test CD, usually something with a worst case type signal for PCM induced jitter, such as the low level -90dB sine wave on most discs. This is the same type of method Stereophile and others used in the early days before switching to the analog sideband method. I believe there was even a construction article on a calibrated version in one of the DIY magazines way back then in the mid 90s. They all use the same general topology of extracting the correction signal, which will be mostly the jitter on the clock being measured.
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Follow Ups
- Depends how you define "measure" :) - slider 11:43:50 06/03/12 (5)
- RE: Depends how you define "measure" :) - AbeCollins 00:33:56 06/05/12 (3)
- RE: Depends how you define "measure" :) - rick_m 07:39:15 06/05/12 (2)
- RE: Excellent point ! I now want to know... - AbeCollins 10:27:11 06/05/12 (1)
- RE: Excellent point ! I now want to know... - rick_m 18:36:06 06/05/12 (0)
- RE: Depends how you define "measure" :) - Jaundiced Ear 23:03:42 06/03/12 (0)
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