Re: TX image rejection problem with SB Live! 24-bit USB
- Thanks Alan. I do have the Creative driver, but not any applications. With this setup, the button certainly does something, and I can see it very clearly on the scope. I have been able to null the image (with the CMSS off).
I think CMSS is an attempt to generate surround sound from stereo.
I searched the registry and found some SB-related keys where CMSS was set to 1, so I set it to 0. Hopefully this will tell the driver to disable CMSS.
--- In email@example.com, "Alan" <alan4alan@...> wrote:
> ----- Original Message -----
> From: "Sivan"
> Subject: [softrock40] Re: TX image rejection problem with SB Live! 24-bit
> > Actually, by pressing the CMSS button on the front of the USB sound card
> > box, I can get rid of these problems! The output are about balanced when
> > the sliders at the 0 position.> The remaining problem is that I can't tell
> > if the CMSS feature (which I think is causing the problem) is on or not;
> > it's LED is never on. Perhaps this is because I am using just the
> > sound-card's driver, not any other software that came with it.
> If you have not loaded any Creative software the CMSS button will do
> nothing. (I do not know what it is supposed to do. All sound effects should
> be OFF) Without Creative software I do not think the device will be able to
> use 21 bits or 96KHz. BUT you will not be able to use 96KHz with RX/TX, it
> is only USB 1.
> This device needs the "Shift Right Channel Data" correction. I do not
> remember, but it needs + or - 1 to be entered in the box. One way the image
> will dissapear if everything else is correct.
> 73 Alan G4ZFQ
> > So I guess I can get balanced output, but without a scope (or a receiver
> > to monitor the image), it's hard to know whether I'm in the "good" state
> > or the "bad" CMSS state.
> > Any hints on this? Thanks, Sivan
> > --- In firstname.lastname@example.org, "Sivan" <sivan.toledo@> wrote:
> >> I am trying to align the image rejection on an Ensemble RXTX using Rocky.
> >> With a SB Live! 24-bit USB, I am not able to get rid of the image. I am
> >> using the phones output. After trying for a while I connected the outputs
> >> of the sound card to a scope, to try to do the coarse alignment this way.
> >> What I discovered is that on Point 1, I can get the two channels to have
> >> similar amplitude, with the x100 slider at 5.16dB (almost at the end). On
> >> Point 2, there is no point where the amplitude is the same; even at -6dB
> >> (the max), one is higher than the other.
> >> Two other weird things: (1) when I connect to the "front" output (there
> >> is no simple line out), there's a big amplitude difference that can't be
> >> corrected with the sliders. (2) moving the amplitude slider in rocky
> >> changes not only the amplitude, but also the phase, and there is one
> >> point (around 1dB) where the phase actually jumps from one output leading
> >> the other by about 90 degrees to tailing by about the same amount.
> >> All of this happens not with one such card, but with two. Same behaviors.
> >> When I test the TX I/Q balance using the output of my laptop's built in
> >> sound card, the amplitude is about balanced without touching the sliders
> >> at all. I didn't try to null the image, but I guess it's doable.
> >> I may end up with the laptop's output, but it's really strange. Anybody
> >> has this card and has any advice on using it?
----- Original Message -----
Subject: [softrock40] Re: TX image rejection problem with SB Live! 24-bit
> Thanks Alan. I do have the Creative driver, but not any applications. With
> this setup, the button certainly does something, and I can see it very
> clearly on the scope. I have been able to null the image (with the CMSS
> I think CMSS is an attempt to generate surround sound from stereo.
> I searched the registry and found some SB-related keys where CMSS was set
> to 1, so I set it to 0. Hopefully this will tell the driver to disable
Thank you Sivan,
I did not know about that.
And I am wrong about the "Shift Right Channel Data" correction. This is one
Creative that does not need that correction, well, certainly not with the
basic Windows "USB sound device" driver.
73 Alan G4ZFQ