Sample rate/frequency matching

Dick Rees

Dick Rees

Curmudgeonly Scandihoovian
Jan 11, 2011
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St Paul, MN
I have an Alesis iO2 USB pre which works well for me. Due to another use in addition to using it for a recording interface, it has come up that the sample rate (24 bit) is fixed and the frequency variable up to 48khz. Another model of the iO2 says both bit-rate and frequency are variable. That's all well and good. My question is:

How does it know?

There is no way to set rates on the unit itself. Does it "talk" to the program it's feeding and match the rate(s) set there?

Thanks.
 
Re: Sample rate/frequency matching

Dick Rees said:
I have an Alesis iO2 USB pre which works well for me. Due to another use in addition to using it for a recording interface, it has come up that the sample rate (24 bit) is fixed and the frequency variable up to 48khz. Another model of the iO2 says both bit-rate and frequency are variable. That's all well and good. My question is:

How does it know?

There is no way to set rates on the unit itself. Does it "talk" to the program it's feeding and match the rate(s) set there?

Thanks.
Click to expand...


Hard to say for sure but, I'm almost certain that its communicating with the program. The manual of the alesis unit is less than informative.

As an example Pro Tools does this with their interfaces (legacy interfaces, LE interfaces, M-powered interfaces, HD interfaces, and Avid I/O series.). This happens through standard USB and firewire connections or proprietary digilink cables. Third party interfaces may or may not need to be switched manually depending on design, or if you are using external clocking (Big Ben, etc).

Also devices that are set to clock off of digital inputs (e.g. AES/EBU) will often follow the sample rate of said input as it changes between sessions. Depending on design of course.
 
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Re: Sample rate/frequency matching

Mike Brown said:
Hard to say for sure but, I'm almost certain that its communicating with the program. The manual of the alesis unit is less than informative.

As an example Pro Tools does this with their interfaces (legacy interfaces, LE interfaces, M-powered interfaces, HD interfaces, and Avid I/O series.). This happens through standard USB and firewire connections or proprietary digilink cables. Third party interfaces may or may not need to be switched manually depending on design, or if you are using external clocking (Big Ben, etc).

Also devices that are set to clock off of digital inputs (e.g. AES/EBU) will often follow the sample rate of said input as it changes between sessions. Depending on design of course.
Click to expand...

Thanks. You're right about the manual. Perhaps for a Luddite like myself I'm just missing what is an across-the-board "given" with this technology.
 
Re: Sample rate/frequency matching

Ivan Beaver said:
Here is a link to the importance of getting "time" correct-even when the time was decades ago.

Hint-Have a good stiff drink before you read

Machina Dynamica Clever Little Clock Explanation Evolution Theory
Click to expand...

The process I'm curious about was referred to in the credits for Geoff Kate: "Frog Jump in Water Sound Tweak". That must help explain Peter Gabriel's "Kiss That Frog." "Jump in the water, come on baby get wet with me."
 
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