Topic: 744t: Recording a 24 bit and 16 bit signal

[baustin]

Plugged my 744t into my Tascam DA-20 mkII yesterday and the signal locked on to 24/48. Hmmmm....

Looked on page 16 of the manual under Digital Inputs - AES3id (S/PDIF), didn't realize that the 744t only locks to sample rate and not bit depth.

Trying to figure out what this means.
-I'm pretty sure the 744t will only accept 1 digital signal, correct?
-Can I record my analog in at 24/48 and also accept a 16/48 signal for shits and giggles?

Input?

-ba

[MattD]

Plugged my 744t into my Tascam DA-20 mkII yesterday and the signal locked on to 24/48. Hmmmm....

Looked on page 16 of the manual under Digital Inputs - AES3id (S/PDIF), didn't realize that the 744t only locks to sample rate and not bit depth.

Trying to figure out what this means.
-I'm pretty sure the 744t will only accept 1 digital signal, correct?
-Can I record my analog in at 24/48 and also accept a 16/48 signal for shits and giggles?

Input?

-ba

I think all four tracks record at the same bit depth. That means your scenario would be possible, but you'd have to chop the last 8 bits from each sample of the 16/48 file, which should all be null. I don't know about accepting more than one digital input.

[mmedley.]

I am fairly certain you can. I noticed this as well at a recent show with the 722. Patched out of the house CD burner and it locked onto a 24/44.1 signal. Thought that was strange...and to top it off Wavelab showed a true 24bit signal in the bit meter! I am curious to know how this is handled as well and what is going on.

[ghellquist]

Nothing odd really. It is your settings.

1 - you set the file bit depth to 24 bits. This means that anything coming in will be recorded as that. Of course if the input has only 16 bits of true info, the last 8 bits will probably be zeroes.
-- an advantage of this,  on the 744 you can have 24 bit resolution on the analog ins even if you simultaneously record a 16 bit digital in from another source
-- only issue with this is that you waste a bit of hard-disk space. Generally there is plenty anyway
2 - the digital input is smart and tries to lock to whatever you send in there. This is most sensible really, saving a lot of hassle. 16, 20 or 24 bits it will simply lock (20 bits used to be rather common)
3 - the sampling rate is "overridden" by the digital input. I am not sure about how large the locking window is. Assuming your external equipment is nominally 48kHz but really runs at 47kHz. This, in this respect, very large difference may be locked to or not, I am not quite sure. With normal "errors", say less than a percent the SD recorder locks fine (in my limited experience).

So all in all, nothing odd is happening, the machine simply does its best at doing what you ask it to do.

Gunnar

[mmedley.]

Nothing odd really. It is your settings.

1 - you set the file bit depth to 24 bits. This means that anything coming in will be recorded as that. Of course if the input has only 16 bits of true info, the last 8 bits will probably be zeroes.

I know it was on 24bit and the last 8 should be 0. The last 8 bits are not zero though according to Wavelab and my tests. That is the odd behavior!

[ghellquist]

I know it was on 24bit and the last 8 should be 0. The last 8 bits are not zero though according to Wavelab and my tests. That is the odd behavior!

Agreed. Maybe you should ask at the source, there is a forum for registered Sound Devices owners which the actual developers seems to be responding to at times.

Gunnar