sound card issues

[gill1]

I'm using a Diamond Monster MX400 sound card in an Athlon 600 machine. My problem is a slight delay in the speaker output when I use the microphone. Is there anything I can do to remedy this? I've done everything the documentation says for this card. Should I get a different sound card and if so, could someone please recommend one? Thanks.....

[Kenn LeGault]

Hi Gill1,

What you're hearing is a "normal" part of host-based computer recording. It's called input-to-output thru latency.

When an audio signal enters the input of your sound card, several things happen (which take time) that delay the signal before it comes back to the outputs. The factor that controls the amount of delay the most is the audio buffer size (set in the Setups/Hardware dialog in PT FREE).

Large buffers (like 8192) results in longer input-to-output delays. Smaller buffers (like 256) have shorter delays.

OK, then why not just use small buffer settings all the time? Well, many cheap sound cards/drivers don't work well at small buffer sizes, so larger buffers must be used. Also, on some systems other drivers (like for scsi cards, video cards, etc.) can cause problems for small buffer sizes. So, large buffers give a little more "headroom" and allow many cheaper sound cards to work reliably.

With high-performance sound card drivers, products like the Digidesign Digi001 allow you to run with buffers at 256 and even 128 on many systems. The Digi001 also has a feature called "very low-latency record monitor" that results in virtually zero latency when monitoring during recording. With buffers this small, it's possible to do record monitoring via Pro Tools without adverse effects.

There are some other companies that make decent sound cards that can run with Pro Tools FREE at smaller buffer sizes, but we have not done a lot of testing on these more expensive cards. [Also worth noting, the Pro Tools TDM systems like MIX|24 do the mixing and processing on dedicated DSP chips, so input-to-output latency is *very* low.]

If you are forced to use large buffers with your sound card, recording new tracks in time with existing tracks can be a bit tricky (you may need to "slide" the tracks in time to get them to match after you've recorded them). However, for mixing (playback only) large buffers don't pose a problem.

Most people press "mute" on the track that they're recording so that they don't hear two copies of the signal (the orignal signal plus the one coming through the sound card). If you have an external mixer, it would be best to monitor the record signal via the mixer (mixed with the outputs from the sound card) rather than using the sound card outputs to monitor the record signal.

Regards,
Kenn LeGault
Digidesign