Hello everyone, and welcome to Black Lion Audio’s Blog. We would like to invite you to read our weekly Q&A blog. Here’s our first one. Enjoy!
Q: What is Jitter?
A: A very broad definition of jitter could be something like this: Any variation of the frequency, amplitude, or phase of harmonics within a given clock or data signal. There are actually two types of jitter: Random Jitter and Deterministic Jitter. Without getting too complex, Random Jitter is jitter that appears randomly from the signal generation. It’s caused only by errors within the crystal oscillator and not by any outside force. Deterministic Jitter is the opposite in a sense. It’s caused by an outside force acting upon the behavior of the crystal oscillator.
For the purpose of audio applications, jitter would be more narrowly defined as any unwanted and unrelated artifact that appears within the lower half of clock signal–a form of Deterministic Jitter. Typically, measurement equipment will place the most emphasis on frequencies between 0Hz on up to approximately 1/2 the clock signal frequency. So if we use a 44.1kHz signal as an example, we will mostly look for jitter between 0Hz and roughly 22kHz. Imagine for a second that we look at our 44.1kHz signal on a piece of test equipment. We’ll see the 44.1kHz fundamental as well as harmonics that extend upward in frequency. But then imagine that we also see something else: a 13.26kHz signal roughly 80dB lower than our 44.1kHz fundamental. This 13.26kHz signal would be an example of jitter. It bears no true relationship to the 44.1kHz fundamental, and is there because of some interference from an outside source, like power supply noise, switching harmonics, etc.
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Great explanation! I really appreciate you spelling it out in a simple and straight-forward description! Every one else I’ve spoken with either skirts the issue or spews too much technical mumbo jumbo.
can’t wait to check out your Micro Clock! Can’t believe it’s less than $500!
Peace,
–Teddy McGridle
Hey guys,
OK, I recently got the scheduled a signature mod and its actually on the way to Chicago from New York as we speak. My box is a Digi 003R+ and I know that the Micro Clock comes with this mod as opposed to the internal clock mod.
So here is my concern, I own a Mytek ADC 96 which has an internal clock that is damn good. Does it make sense to use the Micro Clock, an external clock, when I have this hi-end ADC + clock to sync the 003R+ to?
And if I can use the Micro Clock in this setup, what is the best application possible for its use?
If I recall correctly, the Mytek and the Micro Clock actually have similar published specs in terms of jitter (under 10 picoseconds). Our published spec is based on measured jitter at the output, but I don’t know exactly where in the circuit Mytek’s measurement is derived. The phase noise performance sets them apart significantly though, and this is a difference that is quite audible (there are published phase noise specs on our website, something that no other clock manufacturer provides). Add to this the fact that when the 003 is locked externally to the Micro Clock mk2, measured jitter performance at the converter is about 3 picoseconds (it measures exactly the same as our internal clock). There are Bode plots available on the website that show this; click on the Micro Clock mk2 page and scroll down.
Have you heard the A/B clips we tracked using our Signature Series and the Mytek ADC96? They’re also available on our website. Click on the ‘audio’ tab, then click on the ‘signature series’ link. I think you’ll be pretty impressed with the performance of Micro Clock mk2 when compared to the Mytek clock. Try using the Micro Clock mk2 as a master for both units.
OK, thanks… I will.
Best,
Why use an external clock with the Signature Series? I had the 002 SS mod done about two months ago. I haven’t had a chance to really check it out, but I thought this would be the only clock needed. Maybe I’m missing the point.
Hello–
I’m not sure I understand your question. There’s no way to use an external clock with the 002 Signature…there’s no word clock input.