|
|
|
|
|
Need Pro Sound or Pro A/V gear? Call Daniella or John Karr 888 545 8271 Most Major Pro Audio Brands! International shipping! Great Prices! Looking for a Rat Sound Hoodie, stickers, shirts of more, check out the Rat swag |
![]() |
Wednesday, March 25. 2009Seeing Things As They Really AreTrackbacks
Trackback specific URI for this entry
No Trackbacks
Comments
Display comments as
(Linear | Threaded)
Im really glad someone is getting to the bottom of this, regarding the word clock issue. Ill look forward to seeing what the PM5D looks like. Regardless I think you hit it right on the money. Is the word clock in the the Yamaha desks good enough for them? Is it really that big of a deal. What if any is the audible improvement?
Also it would be really kewl, if yall could add one of those nifty links similar to Digg, Facebook, Deliceous, Stumbleupon.... Just like the BBC does. .... Just a thought.
Josh "stuck in a sand storm" Evans
Dave--
i dig the first rat for the skateboard design. He looks more like a rat versus a mouse. The second mousy looking one seems like he's streamlining his shape in order to crawl into a hole. That said, the first rat looks like he's alert and creeping like a rat creeps-- but clearly looks like he needs to find a hole, for obvious reasons that i can see.
Also recommend you go old school shape on the skateboard. I'm too old and my feet are too long for the the new style boards. Besides, a rat is only supposed to have one tail anyway...
-scott noteboom
The curve of the Yamaha word clock graph shows that it was not terminated correctly. If it is terminated correctly with 75ohms, it will be as good a square wave as the other devices. Note that many Yamaha products (including PM5D and PM1D) have terminate switches on them for word clock input. M7CL has a kind of automatic termination for receiving word clock. The oscilloscope obviously does not have the correct impedance at its input. You could redo the test with a t-connector at the osc input, and another cable returning to the M7CL word clock IN (but keep M7CL set to run on internal clock). That will provide correct termination and a nice square wave.
It's not so much the shape of the signal that influences the quality of the clock, but the regularity of the leading edge (rising line). Even with the M7CL un-terminated signal, this is very regular and very well defined. This is the key.
Lots of discussion, my Q is sample rate or clock... Really the coolest thing, is that this testing is going on! Smaart visuals will be great as well. But you know, hearing is believing. Balls Out!
Hey Dave,
One test which you don't mention running: Check the clock versus an external input signal rather than an internally generated one. I can't recall ever spending much time listening to the onboard tones but I usually spend lots of time listening to mic and line inputs :-) Maybe take an external tone generator and see how much change there is?
I'm also curious to see if Petri's suggestion of properly terminating the clock fixes the problem.
Balls, yes. It's pretty crass and I like it. As for scoping the waveform, it would be interesting to hook the clocks up to an actual dedicated jitter scoop and see what the real variation in edge timing/stability is . I have scopes for that here at my day job to do that, alas no Yamaha digital desks. The scopes here are capable of high data rate jitter measurement for HD TV as well, so they can really give you accurate readings of several significant digits. Gotta love the expensive toys...
I can provide PM5DRH, M7CL48 and LS9-32 but you'd have to come to Finland with your scope... ;)
(PS I have a nice sofa)
How is the M7's clock measured?
Are you connecting the M7's word-clock output directly into the 'scope input?
The clock that's actually important is the ADC modulator clock, which typically runs at 128, 256 or 512 times the sampling frequency (so for 256x 48kHz, that clock is at 12.288 MHz). When synching to external word clock, a PLL generates the modulator clock. This means that the console's internal PLL determines the final result. A good PLL can help clean up jitter from a crappy external clock. A fabulous external clock can help ensure that a marginal PLL design stays somewhat happy (less likely to lose lock) though the PLL jitter is what it is.
A good question to ask someone at Yamaha is: when running off of the internal clock, is the PLL still in play, or do the converters clock directly off of an internal crystal oscillator?
-a
|
Links to Things of CuriousnessCalendarQuicksearchArchivesCategories
|