...I am going to make this Rotel system hit if it kills me!!!!

Here is the system....

I implemented a T3/RP6/RM433 to control a Rotel stereo receiver driven 2 zone system via 232. Tivo series 3 (emitter), Denon DVD (direct IR input) and Apple TV (emitter) run through a Gefen 4x1 HDMI switcher (232) into a Pioneer Elite 1130 (232) utilizing a media receiver. All audio is analog stereo through the receiver.

My issue...

Before I implemented the HDMI switcher I had encountered 232 signal crosstalk in the audio system when controlling the receiver. It was especially evident when ramping the volume. I found that I could reduce this crosstalk substantially by connecting a ground wire between the ground pin of the RP6 and the lug on the receiver. After I implemented the HDMI switcher a high pitched noise entered the system. After troubleshooting I discovered that If I disconnected the ground wire between the processor and RP6 or if I disconnected the HDMI cables from all of the components or if I disconnected the 232 connection from the HDMI switcher. I tried many grounding schemes with no luck and found that as long as the control system, switcher and receiver were interconnected, the high pitched noise was present. I pulled the ground to the receiver and the client and I agreed to "make lemonade out of lemons" (his words) and revel in the fact that we had audio feedback of the volume control (Crestron move over!).

Any ideas?
Any experience out there?
Rotel anyone?

I would love to kill the crosstalk if at all possible.

I can see some comedian out there getting ready to tell you: Noise? Filter it out! just hang a 100 microfarad capacitor across each audio input!

Call Rotel and raise hell. It is entirely unreasonable to have to connect a separate ground cable between an RS232 controller and the device it's controlling. If that were necessary, they would provide a pin for it in the cable. Actually, there IS a ground wire in the cable, so what the heck?

But also check for parallel runs of anything near anything that could be inducing that noise.

What happens if you ground the switcher to the RP6 but not to the receiver? This makes no sense but you should try it.

Does any of this noise show up as artifacts on the screen? What happens if the screen is off, or better yet not connected? Does the screen have a three-prong power plug? And, of course, its media box? Maybe if you ground the RP6 to the TV media box instead of to the Rotel....

Just the usual rack spaghetti.


when I remove the ground from the receiver the high pitched noise dissapears so I did not even bother grounding it at the switcher.


I tried grounding it to every component with the same result.
No effects on the video whatsoever.

I thought about mucking with the EQ adjustments on the gefen switcher. I know nothing about that EQ circuit but hey, I can always fiddle with knobs!

I was also going to explore ground lifting the devices one at a time to see if I could tackle the crosstalk without supplemental device grounds. Now that I recall, I think the Gefen tranformer may use a grounded plug. The rack mounted power distribution is hard to see in the rack and I may have just assumed that it was a two pronger. Its not like I have not had power supply issues with Gefen before.