I've been a long-time user of Stereo Tool (plug-in version) (thank you again for the wonderful piece of software), and using a transmitter with it's own on-board hardware stereo coder. This setup has worked well for me, except that it doesn't support RDS.
Based on a suggestion given in this thread
, I recently bought the Asus Xonar U5 USB box as I need it to work with a laptop PC (which I'm guessing standard PCI cards are not an option for). I modified my transmitter by installing a direct MPX input jack and a switch to switch back & forth between the jack and the output of the unit's hardware coder... making this my first foray into directly driving a transmitter with ST.
The problem I'm having is atrocious stereo separation (maybe 10dB at best). I've made sure the Xonar card's audio "enhancement" features are all turned off, and I've tried tweaking the volume, phase-shift, and tilt adjustments in the FM calibration section all to no avail.
With my oscilloscope connected to the Xonar card's output, I discovered that the card seems completely incapable of properly reproducing a square wave of any frequency, and it's the same whether I generate the wave using Stereotool, or with another (separate) audio editing software.
(I was going to attach pics of my 'scope patterns but I'm not seeing an option here for it, so I'll try to describe:
The Xonar U5 card:
Output pattern looks like a squiggly line (like sine-waves of different frequencies mixed together), with an extremely thin spike where each square-wave transition from hi to low would otherwise be. There is completely no resemblance whatsoever to an actual square wave.
My PC's onboard sound card on the other hand:
Output pattern clearly looks like a square wave, except that the tops & bottoms have some slant to them (and is what I assume the "tilt correction" feature built into ST would normally be used for). Unfortunately the onboard card is not 192kHz-capable.
Does the OP of the thread I linked above or anyone else here who is familiar with the Xonar U5 card know what I am doing wrong or maybe have overlooked? Or is this card actually is not usable for this purpose? (or is it defective? Listening to normal audio through my speakers it seems to sound fine)
If it matters, I'm using ST 7.50.
Thanks for any insight on this (sorry for the length, I figure the more details though, the better).