query about speakers + two amps (not used at same time)

[denti alligator]

So I had my SEX amp *and* a Denon A/V receiver hooked up to my Klipsch Forte IIs for years. I never had the two amps on at the same time. When the SEX was running music, it sounded great. When the Denon was doing 5.1 movies, it was fine.

I added a projector to my system in December, and ever since then there was a hum coming from the Denon amp. This was not audible before. Honestly, I didn't care enough, because during movies you couldn't hear it, and the SEX on its own still sounded great.

Now I have the Stereomour in place of the SEX. It sounds great! The Denon now does not hum, but it sends out a slight bit of white noise. When I unplug the Stereomour from the speakers, it's gone.

Two questions:
1) is this harmful to my amp and/or speakers?

2) if not, what can I do to "disconnect" the Steremour while using the Denon surround receiver? Manually doing this would be a pain.

[2wo]

What is happening is when you run your Denon with the Stereomour attached, the poor Denon is seeing the very low impedance of the Stereomour output transformer in parallel with the speaker. Close to a dead short, this would kill a lot of amps. You need to build of buy a switch box, if you are building you could use a relay that switches when one amp is turned on.

Another thought, you could try adding a power resistor on each + speaker leed from the Denon and see how it sounds. Might be good enough for TV. Try 4-8 ohms or so...John       

[denti alligator]

Wait, so is it dangerous for my Stereomour?

[denti alligator]

I guess I'll build a switch. Two inputs, two outputs. Any suggestions on what parts to use? I have no clue, other than a box and four sets of speaker lugs.

[2wo]

You need 2 inputs and one output. You can get a double pole double throw switch at Home Desperate and the like. Switch the + and connect the  - together for each channel...John

[[email protected]]

Hi
I do the same as you, I use a dual amplifier switch. It is a break before make and keeps all P/N separate , ( total isolation is best between two amps) you can use it as a a/b selector on the fly w/o worry.It is mounted on a PCB with terminal strips and is very high quality, you can either let the wire hang out the back of the box or make up a nice looking project box with 12 binding post for a clean looking device and easy connect / disconnect. The Mgf. slips me as of now but they are readily obtainable through Amazon or host of others. I paid about $40.00 and it is much better than any double pole double throw Switch that you will get at H D.

Happy Listening

[Paul Birkeland]

Though it's not the most safe and/or proper recommendation, disconnecting the wires from each black binding post on the Stereomour that go to the chassis ground lug will likely remove the noise you describe.

Though the secondary of the output transformer is very low in DC resistance, it should have sufficient inductance to not completely overload the receiver.

Having said all this, however, the switch box is the proper method of accomplishing what you're looking for, and you may find that your receiver ends up sounding quite a bit better.

-PB

[SammyJ]

Hi
I do the same as you, I use a dual amplifier switch. It is a break before make and keeps all P/N separate , ( total isolation is best between two amps) you can use it as a a/b selector on the fly w/o worry.It is mounted on a PCB with terminal strips and is very high quality, you can either let the wire hang out the back of the box or make up a nice looking project box with 12 binding post for a clean looking device and easy connect / disconnect. The Mgf. slips me as of now but they are readily obtainable through Amazon or host of others. I paid about $40.00 and it is much better than any double pole double throw Switch that you will get at H D.

Happy Listening

Got a link to a point me in the right direction? I was unable to find anything of decent quality...

Thanks!

[[email protected]]

I bought one from crutchfeild a while back, I do not have the info on it, you can find it through the search engine


Don