Puzzled: TI sample size?

[GrooveNinja]

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?

[Timo]

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).

[GrooveNinja]

Originally Posted by Timo

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

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?

[Timo]

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.

[Crossfire]

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?

[Timo]

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.

[Crossfire]

Thanks for clarifying that.

And great idea!!

[GrooveNinja]

Originally Posted by Timo

... 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:-

That is exactly what I would like! Good idea!