Does anyone really use digital Vari-Speed ?

[jdbakker]

Hi all,

As the title says: does anyone really use vari-speed?

Context: I am working on a DIY PLL to sync (DIY) AD/DAs to incoming word clock, and I am trying to judge how many people really need to be able to support a continuously variable sample rate. It would be much easier to just focus on getting the best performance out of a fixed-frequency PLL for 44k1/48k/88k2/96k/176k4/192k sampling, both for me as a designer and for anyone who would want to build it.

I have never felt the urge to use Vari-Speed. I know that older ADAT tape drives would Vari-Speed to deal with the fact that tape can't instantaneously get from zero to full speed, and there are CD drives out there with speed controls which also affect their digital output sample rate. To me such situations, if they do occur, call for an ASRC to get the variable rate locked to studio sync, and studio sync should be as rock solid as possible.

Yet many commercial converters and master clocks still support it. Is this in response to actual user demand, or just one of those pesky legacy requirements that are so hard to get rid of?

Thanks,

JDB.

 

[emrr]

here's an example. ADAT tapes recorded with BRC controller set to 44.1K; required formatting tapes at 48K if displays were to read the same. Original ADAT never officially supported 44.1K, as it was still borderline 'illegal' in the USA, being very close to the era of the grey-market import DAT machines. BRC never supported 44.1K, other than through vari-speed.

Now, try digitally importing ADAT masters recorded this way, and you get files with 'incorrect' header data concerning sample rate. Without vari-speed, one must manually re-write the data headers fo each track, one at a time. Any system allowing rate based vari-speed makes it easy.

But that's just an example. There's nothing nicer than vari-speeding up or down a step or two for recording effect, and for those times the singer can't quite hit the note as it's slightly too high or too low for them. It's a real shame to not have that option. And a damn pain in the ass to manipluate things into place via tedious DAW methods.