Audio Interface – Low Latency Performance : Part 1

There are a wide and varied range of audio interfaces available, all with their strengths in regards to specifications and features. The current market is crowded with new interfaces coming online cramming more and more features at pricing even more affordable than anytime in the past , which on the surface seems like a win/win for those looking at dipping their toes into the pond, and for many it is just that.

However for those that place higher demands on their systems, the cracks start appearing very quickly when these interfaces are driven to lower latency, and as that becomes more and more important , a lot of the gloss of the extra features pales when the performance of the drivers do not hold up to the demands of the low latency working environments that many of us require. Now while a lot of these interfaces will perform well for the majority in less critical working environments , the performance variable can become quite dramatic at the lower latencies, and that is what I am specifically going to be focusing on

Hardware Buffer Setting v Actual Latency :
All audio interfaces have their respective hardware control panels where adjustments to buffer /latency settings can be made. The buffer settings in most case have little correlation to what the actual latency achieved due to various factors including added sample buffering for both the Input and Output streams and also added sample delays associated to the AD/DA conversions. Its also worth noting that simply having the latency value available, doesn’t guaranteed that the interface will work reliably at that latency.

The actual latency can be measured in numerous ways, one method is to use the RTL ASIO Latency Test Utility which will test round trip latency for both Digital and Analog Streams ( Analog taking into account the AD/DA ) , the other is by using a DAW application that accurately reports the actual Digital Input / Output latency reported by the ASIO driver. In this instance Cubase 5.x, but that is not infallible as mixing and matching say a PCIe card with an AD/DA from another manufacturer can result in the AD/DA delay not being reported to the ASIO driver.

To further complicated things, some mixers with added FW interfaces that are becoming more popular do not even report the actual latency to the host DAW, only the theoretical value for respective buffer settings, which could cause synchronization errors. To say that there is a wide and varied range of reported latencies across the interfaces is an understatement, and some developers have also chosen to have double buffers on playback to help loosen the reigns so to speak.


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