Puzzled: TI sample size?
 

I am rather puzzled by the various references to the sample sizes on the Virus TI. From what I have gleaned from postings on this board, the inputs and outputs of VirusControl are 16-bits. The DACs and ADCs are 24-bits, though, so if I am using the Virus as a "soundcard" to input and output from/to these inputs via the USB connection, are the samples 16-bits or 24-bits? It would seem futile to use the Virus as a soundcard if it is only 16-bits. Finally, what is the sample size for the S/PDIF input and output?

Anything that travels over USB in the Virus (including soundcard usage) = 16-bit depth.

USB = 44.1KHz @ 16-bit
6 x balanced jack outputs = 192KHz @ 24-bit D/A

Not sure what the bit-depth of the digital S/PDIF outputs are, but the sample frequency rate is 44.1KHz/48KHz.
S/PDIF connections are usually 20-bit, or 24-bit (depending on the hardware), but can be made to run at 16-bit by way of truncation. So I'm unsure as to what bit-depth Access have set them to run at.

Separately, the 2 x balanced analog inputs use 24-bits A/D (unsure as to the sample frequency rate for these).

That is quite disappointing. It seems that any decent sound card will do 24-bit audio into the DAW, so why bother with the TI thing? Was the TI not intended for serious audio recording? I have a sound card with 192kHz 24-bit balanced inputs, so is my best option to use the TI's analog outputs into this card and forget about the TI's USB inputs?

I think it may be more to do with the limitations of the hardware that Access implemented elsewhere.

There are three different types (speeds) of USB v2 chipsets:-

1) Lo Speed = 1.5 Mbit/sec (187.5 KByte/sec)
2) Full Speed = 12 Mbit/sec (1.5 MByte/sec)
3) High Speed = 480 Mbit/sec (60 MByte/sec)

Access chose to use the Full Speed chip. So the TI's USB connection is limited to 12 Mbit (1.5MByte/second) - for everything.

Streaming a mono track at 44,100 Hz 16-bit would require 86 KByte/second.
(16-bits = 2 Bytes, therefore 44100 x 2 = 88200 Bytes = 86.13 KBytes).

Access allow six audio channels, so 6 x 86 KB = 517 KB/second (0.5 MByte/second).
Factor in streaming MIDI, Virus Control, VST automation data, Remote control, and error correction, and it'd probably not be far off from using up most of the 1.5 MByte/second bandwidth available.

That said, streaming a mono track at 44,100Hz 24-bits would only require 129 KBytes/second.
(24-bits = 3 bytes, therefore 44100 x 3 = 132300 Bytes = 129.2 KBytes).

Six channels of 24-bit would need 775 KByte/second. Which is only 258 KByte/sec more than six channels at 16-bit.

I'm unsure as to how much bandwidth MIDI, VC, VST, Remote, and error correction require.

If it were me, I'd try plumbing your Ti into your 192KHz/24bit soundcard for recording at 44.1KHz/24-bit, and use the TI's USB for MIDI/VC purposes. You can always try it yourself and see if the added fidelity of that setup is noticeable or not.

What about if you use the Virus as the sound card and record the Virus back into itself to utilise 192khz/24bit converters in and out? Does it still get bounced down your DAW at 44.1/48khz/16bit and defeat the purpose of trying to do this?

I think although the Virus' inputs are 192KHz/24-bit, the data only remains 192KHz/24-bit while it stays inside the Virus, or gets passed to the 192/24 audio jack outputs....

... HOWEVER, wouldn't it be great if Access gave a software-switchable option of using either 4 channels of 24-bit, or 6 channels of 16-bit, over USB? Either would use identical bandwidth, as shown:-

6 channels of 16bits: 44100 x 2 Bytes x 6 channels = 517KByte/sec
4 channels of 24bits: 44100 x 3 Bytes x 4 channels = 517KByte/sec

Would be ideal for those (the vast majority of us) who don't need to use 6 channels of Virus, but want higher quality sound via USB.

Thanks for clarifying that.

And great idea!!

That is exactly what I would like! Good idea!