Transporter External word clock

[mashley]

I might be getting someone to build me a battery powered external word clock for my Transporter and have been asked at what frequency?

Also is the one above freq able to handle all the different files I'll inevitably be feeding?

And to this I'm feeding the signal from the Transporter to a modded Behringer Ultramatch which the has it's own clock, before feeding my Ref 7 dac. Which then does it's own thing with jitter reduction

So, would I actually benefit from a word clock at the Transporter, or will it just be negated by the rest of the chain?

[Archimago]

Good question and one I've been curious about (simply because the plug is there :-).

I can imagine with a complex studio setup, wordclock sync could be very important... But for a straightforward playback chain, I'd love to read any articles advocating this.

Here's an interesting article from a pro perspective:
http://www.soundonsound.com/sos/jun1...sterclocks.htm
Looking at the writeup and charts, doesn't look like a master word clock helps in many cases - looks like the tests are ADC performance though.

[Mnyb]

Is not the idea to slave the transporter to the DAC clock ? So there are DAC's with clock output, not many but. They do exist, or you can have the DAC modded to have it.

This would then reduce jitter as the data is feed to the DAC by a rate dictated by it's own clock, piont is not absolute o'clock precision but that it really is the same clock in transport and DAC .

Also I think external clock generators are a necessary evil demanded by a typical layout of a audio or video studio with a multitude of devices needed to run on the same time base not necessary a way to improve quality .
in video you want the frames to be in sync between devices .

I have a hunch that keeping the clock close to the DAC chip on pcb level is an advantage , but let some of the forums electronic engineers improve on that argument

[JohnSwenson]

When you feed an external wordclock into a Transporter it has to use a PLL to generate the high frequency "master clock" used inside the TP. This PLL is going to have much greater jitter than the crystal oscillators already in the TP.

The ONLY reason to use a wordclock with a TP is if you already have a DAC which has very good internal oscillators AND both reclocks the incomming data with those clocks, and outputs a wordclock based on those oscillators. For this and ONLY this case is the external wordclock input useful. It allows the TP to synchronize it's output to exactly match the clock already in the DAC. The data from the TP gets reclocked by the very low jitter clock in the DAC so the extra jitter added by the wordclock PLL in the TP is irrelevant.

And for reference the wordclock has to change for every different sample rate, so using an external wordclock can get very tricky since you have to tell the DAC what the sample rate is so it can send the appropriate wordclock to the TP, but the TP runs at whatever rate it gets from the wordclock, sort of a chicken and egg problem.

So using an external wordclock JUST into the TP is either going to do nothing or make things worse, so I don't see any point to even try it.

John S.