User guide

MS-DMT Guide v1.04
Released 05-30-2014
58
The test program Check Sample Rate (CheckSR.EXE) from MixW is the simplest way to test
sample rate error on both input and output. However making use of HF reception of WWV using
various software programs is the most accurate way to test your RX sample rate error. Once
your receive sample rate error is known, you can then perform a loop back test to determine
your TX error.
When using a USB port based sound device, do not go through a hub unless the hub is one of
the expensive TXCO or GPS referenced types (e.g. Maestro-GS22 and Maestro-iS22, see
http://www.fiberbyte.com/maestro_home.htm) as the hub will likely introduce additional
sample rate error. Check all USB ports directly on the PC to determine the port with the lowest
sample rate error. If you still have a high sample rate error check the USB sound device on
another PC if one is available to determine if perhaps it is the device itself that has the issue.
Allow 20 minutes of sound device warm up. Be sure that all latency causing processes are
mitigated, in other words always below 1000us, preferably under 500us on latency. Then with
and no sound device software running, not even the Windows sound panel and no audio input
to the sound device, with any screen savers disabled, suspend and power saving modes
disabled. Start the test and just leave the PC alone after starting the test, do not even move your
mouse. Run the CheckSR.EXE at least 30 minutes before clicking on stop.
NOTE: Windows Vista and later sound card inputs are only detected when a cable or
microphone is plugged in.