[nocat]

Latency is the one thing that will make or brake your aspirations as a home recording
enthusiast... There are 4 factors that affect latency. In order of importance...

1) Your sound card
2) Your processor (cpu)
3) Your recording software
4) Your system's memory

lcjones is absolutely correct in comparing analog to digital recording...

When you record on tape (analog) there is no latency when monitoring your playing. What goes into your input comes out of the output instantly. The same is true for digital, but only while monitoring... The real difference is after you recorded a track...!!! In an analog system this is not a factor. The signal is read from the tape and played instantly. However, when you record a track to digital, a few things happen. The analog signal has to be changed by a transducer (microphone, pickup etc.)to an electrical impulse. Once it gets into your sound card, it must again be changed into a series of 0's and 1's or a "digital signal". That digital signal now has to be read by your recording software and sent to your cpu for processing. Once the cpu is done with it, it gets stored in your ram, so that your recording program can access it and send it to your sound card, where it gets changed again into an electrical pulse which gets sent to your speakers...

Your sound card plays a major factor in all of this. Different sound cards will have different latencies at different sampling rates -- the higher the sampling rate, the lower the latency. In that sense, the latency occurs in numbers of samples, dependent on the number of samples that need to be put into a buffer before monitoring begins. Because the latency in samples is fixed or defined by the card, then the faster the sampling rate, the quicker a fixed number of samples will pass through the buffer. Hence, faster sampling rates = lower latencies. Often, a buffer size can be set in the sound card's control panel, and a lower buffer size = fewer samples that need to be buffered. As long as your system can handle the lower buffer size, lowest is best.

Your processor (cpu) must be able to keep up with the billions of calls that the software is imposing on it to "process" the numbers and return them to the sound card's buffer, while also maintaining your operating system and all its processes. So, you can see how a powerful cpu is essential. If the processor can't keep up, information is dropped, and you notice this as clicks and pops in your sound, some times to the point of distortion... (very unpleasant...!!)

Your recording software comes into play when you are monitoring in a "tape type" fashion, which is essentially monitoring through the program. While you have the program in 'input,' you hear your instrument from the inputs of the program much like a pro tape deck. If you 'roll tape,' or rather put the program into play, you no longer hear the instrument until you punch in, again, like a pro tape deck. All of this, unlike a pro tape deck, occurs with a bit of latency between what you're playing and what you're hearing through the program.
Some say that 11 or 12 milliseconds of latency is acceptable. You can be the judge. At higher sampling rates, 3 ms latency might be possible. If you desire this type of monitoring, which is a fairly normal and accepted way of recording, then this may be the best that hard disk recording has to offer.
ASIO is a standard for audio device drivers. As much as possible, ASIO bypasses the Windows or Mac operating system, creating a more efficient communication between the audio device and the software, thus lowering the amount latency in the audio..!! Windows latency can be as high as 50 or 75 milliseconds, so that 'tape type' monitoring is not feasible using only MME drivers. Waiting 50 or 75 ms is a heck of a lot of time to hear the monitoring signal of something you've just played. That's similar to the timing you'd use in a slapback delay...!!!

Your system's memory must be adequate enough to contain all the information required by the recording program with out having to create a paging file, or, virtual ram on your hard drive. Even the fastest, most efficient HD will not be able to keep up.
If the track you just recorded won't fit on your system's memory, it will get written to your hard drive, which will later have to be recalled and move something else out so it can occupy it's place... This slows the whole process down, and although it won't affect the sound, it will affect your system's performance and put even more of a load on your cpu...!!!

I hope this helps you guys... If you have any questions or need further explanations, I'll be more than happy to help...!!!

Cheers...!!!

Ben