Signal bleeding

NeilGabriel

I am running a Rotel rsp 976 pre/pro and a multi channel amp. When I change sources from DVD to CATV, I often do this before changing the inputs on the pre/pro (I don't use it for video switching). In other words, the DVD turns off and the cable turns on and then I switch the audio input on the preamp. I've noticed that I can hear the TV audio while the preamp is still set to dvd input...especially since the dvd was usually at a much higer volume than I play the cable. I have heard this in years past and I called it bleeding. I assumed that this would not happen with higher quality gear. PLEASE don't tell me I got an issue with the preamp. Should I do audio input switching before changing sources?

madmax

It happens. I haven't really studied it or anything but believe it is the signal coupling from one line to another electromagnetically. Could probably be coupled through ground currents too so I would try attaching a grounding wire between different components to see if it goes away.
madmax

billbillw

Some preamps do this, others do not.

I think its a matter of having good isolation on the signals between the RCA jacks, and the input selector. I had a B&K Pro10 that was terrible like this. I had to turn my tuner off if I was listening to CDs or LPs otherwise I'd hear the radio during quiet passages. When I took apart the pre, I found that B&K used a ribbon cable to go between the input board to the main board. I'm sure that's where it bled over.

My current Sony TA-E80ES is absolutely dead quiet on each input, no matter what is happening on the others. That's the way I like it.

If I had kept the B&K, I was going to redo the ribbon cable with discrete, shielded wiring for each channel. Never got around to it though.

Neil, if this problem really bothers you, you might want to check into that option.

NeilGabriel

Thanks. At least it doesn't sound like I need to build a coffin for the preamp just yet. Damn, you guys are good.

Systems

Units that use relays for source input switching provide better isolation between sources than units that use a mechanical switch.