Wouldn't a drop amp have capacitors that last longer than that? I thought even cheap capacitors lasted 10-12 years nowadays.
As for the changes, I didn't notice the problem getting any better or worse, cause it wasn't much of a problem before I switched amps. My old McIntosh had no earth ground prong on the plug. I switched recently to the Crestrons, and they are both grounded on the AC, so that may be part of what triggered (but not caused) the problem. As I said, the Crestrons have a rep. for being very very low-noise and well-grounded, and they are both dead silent if the antenna system is detached.
As for the changes, I didn't notice the problem getting any better or worse, cause it wasn't much of a problem before I switched amps. My old McIntosh had no earth ground prong on the plug. I switched recently to the Crestrons, and they are both grounded on the AC, so that may be part of what triggered (but not caused) the problem. As I said, the Crestrons have a rep. for being very very low-noise and well-grounded, and they are both dead silent if the antenna system is detached.
Detached from what specifically? Everything on the antenna or a specific component? You're staring right at the solution.
Hi All
Ground loops can cause several problems, VIDEO HUM BARS & AUDIO HUM. My AV system had both and I needed the cable company to install a GALVANIC ISOLATER inside the outside drop box this reduced the VIDEO HUM BARS to almost none. I them had to add another GALVANIC ISOLATER @ the inside cable box and the VIDEO HUM BARS completely disappeared. My system connects to a distribution amplifier and several other boxes and TV’s. The AUDIO HUM was still there and I had to add audio isolation transformers to the TV. Now is all OK.
It is important that you identify the real problem(s) and remove each one. I started by using my clamp on amp meter it showed 1.2 amps @ the cable entrance after they installed the GALVANIC ISOLATER it was zero. My internal cable to the AV had 30ma and none after I added the second isolator. I want to let you know that my system has full GROUND protection and the isolators only open additional ground paths.
The Jensen VRD-1FF IsoMax Digital RF Isolator is a great coax GALVANIC ISOLATER and costly. I have used others @ less than half the cost and they work. Amazon has several types of the isolators.
Duke
Ground loops can cause several problems, VIDEO HUM BARS & AUDIO HUM. My AV system had both and I needed the cable company to install a GALVANIC ISOLATER inside the outside drop box this reduced the VIDEO HUM BARS to almost none. I them had to add another GALVANIC ISOLATER @ the inside cable box and the VIDEO HUM BARS completely disappeared. My system connects to a distribution amplifier and several other boxes and TV’s. The AUDIO HUM was still there and I had to add audio isolation transformers to the TV. Now is all OK.
It is important that you identify the real problem(s) and remove each one. I started by using my clamp on amp meter it showed 1.2 amps @ the cable entrance after they installed the GALVANIC ISOLATER it was zero. My internal cable to the AV had 30ma and none after I added the second isolator. I want to let you know that my system has full GROUND protection and the isolators only open additional ground paths.
The Jensen VRD-1FF IsoMax Digital RF Isolator is a great coax GALVANIC ISOLATER and costly. I have used others @ less than half the cost and they work. Amazon has several types of the isolators.
Duke
To be sure, I appreciate the help, folks, but how about reading beginning at the first post. I don't feel like repeating the same things I've already posted 3 times, and we are not narrowing down the problem to the antenna system. We have already established that some part of the antenna system is likely the problem.
We also have talked about 5 or 6 different coaxial ground hum isolators, so you don't need to mention the most commonly found ones. All in my first post.
Thanks
We also have talked about 5 or 6 different coaxial ground hum isolators, so you don't need to mention the most commonly found ones. All in my first post.
Thanks
"As soon as I connect the TV output to the Passive Pre, I hear what sounds like ground hum, big time, but only if the antenna coax (RG6, IIRC) is connected to the TV. If I disconnect the antenna coax from the TV, the hum seems to disappear."
If you just touch the coax cable to the TV input and it HUM'S, install the COAX ISOLATOR DEVICE.
Duke
If you just touch the coax cable to the TV input and it HUM'S, install the COAX ISOLATOR DEVICE.
Duke
Could the problem be that each Crestron amp is being grounded by its power cable as well as by the ground connected antenna screen via the TV? That would constitute a ground loop which could be broken by inserting an isolator at the TV antenna input as has been suggested.
The fact that your old McIntosh amp was not grounded via its power cable and didn't experience the hum seems to reinforce this supposition. The McIntosh would have been grounded via the antenna screen only i.e. at one place and therefore no ground loop.
The fact that your old McIntosh amp was not grounded via its power cable and didn't experience the hum seems to reinforce this supposition. The McIntosh would have been grounded via the antenna screen only i.e. at one place and therefore no ground loop.
Well, I picked up the cable isolators recommended by Stratus46 today. I plugged one in, firmly and...the hum is better, but still there. Another interesting effect is that since I inserted the isolator, the volume on the system is much louder, given the same volume setting on the passive pre. That's a nice thing. Can anyone explain why?
So I'm wondering, what does that mean that there's still a little hum? Does it mean that there may still be bad caps in the antenna amp? Should I try better interconnects between passive pre and amplifier?
Tomorrow, I will remove passive pre from circuit just to see if that further reduces the hum.
So I'm wondering, what does that mean that there's still a little hum? Does it mean that there may still be bad caps in the antenna amp? Should I try better interconnects between passive pre and amplifier?
Tomorrow, I will remove passive pre from circuit just to see if that further reduces the hum.
You do realize those isolators are intended for an RF feed like an antenna or cable TV feed. Used that way there is no conceivable way the audio level could change. If you are using the isolators as prescribed AND you're in fact getting an audio level change there is something WAY WAY odd in the setup.
G²
Sorry, I'm not clear what you meant here:
I installed the isolator at the end of the antenna cable output on one end, and the other end screwed directly onto the TV. I don't believe the isolator is designed to have anything screwed into its output end. Also, if you're implying doing so would change the sound/signal somehow, I don't see how that is possible.
I installed the isolator at the end of the antenna cable output on one end, and the other end screwed directly onto the TV. I don't believe the isolator is designed to have anything screwed into its output end. Also, if you're implying doing so would change the sound/signal somehow, I don't see how that is possible.
Hogwild, I think we were all just trying to confirm that you've correctly inserted the isolator at the TV antenna input. You have now clarified that this is the case.
How is the TV connected to the passive pre? Is it via line level RCA outputs on the TV?
Have you removed the passive pre from the circuit as an experiment yet?
How is the TV connected to the passive pre? Is it via line level RCA outputs on the TV?
Have you removed the passive pre from the circuit as an experiment yet?
Okay, I finally managed to test the system without the passive pre connected. It's hard to tell if taking the pre out reduces the hum or not. The main reason is that without the pre, I have no volume control. Without a volume control, the TV input is up at full blast, so things are so loud, I doubt I'd hear the hum over that.
I tried switching to a TV channel that plays classical music and sometimes has quiet passages. I still couldn't tell.
What do you all suggest as a next step?
I tried switching to a TV channel that plays classical music and sometimes has quiet passages. I still couldn't tell.
What do you all suggest as a next step?
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