I hope I could get right answer as soon as possible here. For this procedure, VAC 4.09 (4.90) was used.I wrote the following question in other forum space but some MSFT guy told me to try this forum for my question.

There is a demo version of VAC but it can not be used because the demo version corrupts the audio I/O with a pre-recorded voice telling you it is demo software, essentially making it crippleware.

It must be purchased from the authors web site. The benefit of VAC is that the audio exchanged between PowerSDR and WSJT stays entirely in the digital domain resulting in high dynamic range signals and there are no wires to introduce RF into the software defined radio system. VAC makes PowerSDR 'look' like a sound card or Windows audio device to WSJT. Download, install and configure the Virtual Audio Cable software (VAC) VAC is a program that transfers the RX audio from PowerSDR to WSJT and subsequently transfers the TX audio from WSJT to PowerSDR without using a physical interface between the radio and a computer sound card. For this procedure Com0Com 2.1.0.0 was used. You can download the virtual com port software from the Com0Com SourceForge project page. Download, install and configure a virtual com port software Com0Com for PTT Control Although there are two different free software packages for enabling virtual com ports, I have chosen Com0Com because it provides better control over the com port configuration, the configurator works under Vista(vCom does not) and comes in a 64-bit and 32-bit version. Download and install the latest version of WSJT You can download WSJT software from the WSJT home page. This procedure was developed using the FLEX-5000, so it is important that you have the latest Firewire driver and firmware loaded for your radio as well. In this procedure we are assuming that you have your software defined radio and PowerSDR properly communicating and are using the most current versions of PowerSDR. Configuration Overview and Required Software Configuring WSJT for PowerSDR is a five (5) step process. The configuration of WSJT's parameters other than the audio and PTT are out side the scope of this article. How to Configure WSJT with PowerSDR and VAC How to Configure WSJT with PowerSDR and VAC System Dependencies Minimum PowerSDR Version: 1.14.0 Applicable Hardware: All transceivers Content provided by: Tim, W4TME The intent of this article is to describe in detail the setup and configuration of WSJT with PowerSDR.

Virtual audio cable 4.09