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Explain A-B selector on a receiver (1 Viewer)

Philip Hamm

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I found and fixed one problem.

Some kind of electromagnetic interference.

After more toubleshooting I found that if I hooked up my speakers to my Integra home theater receiver they sounded sweet and clean. (One trips the protection if I crank it up, the other does not. More information on this in later posts - see below) If I hooked them up to either the old JVC or the H/K receivers it sounded like ass. The only thing common between the H/K and the JVC receivers was the location.



This is an old photo of the back of my home theater rack and my patch bay and rack for structured wiring under the stairs.

In LOCATION 1 you can see my old JVC receiver at the bottom of the rack. There is a lot of stuff there including an amplified distribution system for an antenna in my attic. I can get great local reception of TV and HDTV. The big old Crown amp taking up five rack spaces is my vintage 1970s Crown DC300A which powers my Infinite Baffle sub. This amp has never had a problem with interference that I could detect (but now it may move as well). Above the old JVC stereo receiver is a Harman Kardon amp I was using for 7.1 in the theater. That amp is gone as is the amp on the box on the floor. I ditched the separates and went back to a receiver about a year and a half ago.

I moved the the box with the amp on it between LOCATION 1 and LOCATION 2 over the LOCATION 2 and put the JVC receiver on top of it. Same problem. I then moved the JVC receiver to the top of the home theater rack which opens into my movie room, to LOCATION 3. All interference is GONE.

It seems my entire problem with distortion for the last two years has been electromagnetic interference from the location of the receiver. I think the big old CROWN amp can filter and handle the interference. It was built to be in a rack with all kinds of other unpredictable stuff. The JVC receiver and my HK3270 (which is a -great- powerful stereo receiver - still for sale here in the for sale forum) were not shielded.

I can't believe it was so simple. It definitely makes me want to get my house tested for Radon I can tell you that. I don't think the antenna distribution machine should cause such havoc with electrical signals.

So now I'm going to reinstall my old volume controls and see how everything works. I'll bet everything is going to work great! I'll follow up.
 

mylan

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Hmmm, you're not anywhere near the island on "Lost" are you? Seriously, it is good to get to the bottom of things. I have been toying around with the idea of using two Niles hubs to wire two speakers into one and the other two into the other, provided I can figure out that set-up that Scotty was talking about so maybe have more power to each (two) pairs.
 

Philip Hamm

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The set up Scotty described is very simple and I would do it if I had an old 5.1 receiver with 5.1 input. You'll need Y-connectors to split a stereo signal to L/R FRONT and L/R REAR for your receiver. Set your receiver to 5.1 channel in and you're good to go.

When I was running 7.1 I never noticed a problem with the rear channels. The interference was not messing with my amplifiers, it was only messing up the preamps built into my receivers. TOTALLY Wacked out I tell you. The strangest audio eff-up I've ever experienced, and I've experienced a few.
 

mylan

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Do you ever get the impression that you and I are the only ones on this thread? Yes, my Yammy is 5.1 with inputs. Lots of good info here from your trial and error. I'll try it once I get time :emoji_thumbsup:
 

Philip Hamm

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I can't even believe the bad luck. Thanks Mylan for inspiring me to finally set my stuff up again. Revisiting my broken whole house audio. Bad luck abounds. First I have the problem with my reciever being in an interference zone. Very difficult to find, but once I did, I had another problem once I set it up.

One of my speakers was only giving me one side stereo. The other side was either a broken wire or a short in the wire someplace. This was causing my volume controls to constantly trip the protection circuit in my receiver with anything but extremely modest volumes. Again, very difficult to figure out - I had to wire the dining room solo and pull the speaker down and try both side wires into both sides of the speaker. Bad news. One side of stereo gave me only barely audible sound the other was fine. And the hookups were direct.

So I have a bad wire built into my house. Great. I don't know if I can re-run the wire or what I can do. It's in an exterior wall loaded with insulation. Snaking a new wire is almost unthinkable.

However, the good news (particularly for you) is that once I figured out that problem and got the bad wire out of the circuit, my in-wall volume control to one speaker works like a charm for the one speaker. I think if you can run your wires without any major shorts or problems you should be gold. I, on the other hand, am screwed. The only thing I can do is run new wires in my walls for the one that's shorted or broken. I'll bet this has been like this since the day the installers put it in. Some nail holding the wire to a stud went through the shielding and shorted the one side. The effed up wire going to the dining room was what was causing the short.

Doesn't matter. Your ides inspired me to get up off my ass and get cracking on my system.

So I have one room working. If I was just going to get audio in one room I'd be better off with a stereo in that one room. :frowning:
 

mylan

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Thanks, I appreciate the fact that I inspired you and hope you can resolve your wiring problems without many headaches. My house was also pre-wired during construction and I have noticed while up in the attic, they did use those wire braids to hold them in place, dear God, I hope they didn't punture the conductor! My greatroom works so one down and three zones to go. On the VC's, I think I will need to use the 4X multiplier setting even though there is no 4th VC. My thinking is that the receiver is going to be the fourth (volume control).
I don't really think you are screwed, maybe you can pull another run, custom installers do it all the time. All you need is access to the attic if the wiring is going on the floor directly underneath. Thank you (and to Scotty, wherever he is) for letting me bounce ideas off of you, this is much better than the $1,200 Tweeter wanted for installation, now I just need to get going on the actual work part of this thing. The way my work schedule is running it may be a week, i'll let you know how it turns out.
 

mylan

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Ok, i've started and I must say, even with 16g wire it is hard to get it into the connectors on those Niles VC's. More to follow....
 

mylan

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Update: After much interruption, I have begun moving the receiver upstairs after having installed the in-ceiling speakers, and I have an idea and a question for you experts: Instead of using a hub and reducing the wpc to 25, why not run each pair to the front left/right, surround left/right, and leave the center in "phantom" mode. I would always have to have surround engaged but this seems like it just might work. I would set my VC's to 1x and get almost 100 wpc this way to all speakers. Would this work?
 

Philip Hamm

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Jan 23, 1999
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If you are playing stereo music and have some kind of "five channel stereo" mode on your receiver this should work nicely. Very much like Scotty's suggestion actually.
 

mylan

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No, my receiver only has DD but does have other DSP modes. I wonder if straight DD will work, maybe turn all delays to their minimum setting.
 

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