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Crown xti hum

T

tony3d

Active Member
Just hooked up my Crown Xti-2000 to a Crown IC-150 pre-amp, and I have a lot of hum and some buzz. The IC-150 pre-amp outputs are going into a Bose 901 eq then into the Xti-2000 with an RCA to XLR cable. The hum is ridiculous. how do I solve this? I had an Onkyo M504 hooked up to the system just before I hooked up the Crown and there was no hum at all. Can I run the amp with nothing in the inputs just to see if it's the unbalanced leads going into a balanced inputs causing the problem?
 
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does the Xti have a ground lift or ground invert switch?

You have a ground loop somewhere.

You might also try lifting the ground on the power cord to the amp, DON'T cut the pin off, use one of those little grey cheater thingys.
 
Have you tried hooking the IC-150 directly to the xTi-2000?

Unless there is something wrong with the 2000, it sure sounds like the shield on the unbalanced inputs are NOT connected to ground on the 2000.
 
Yes, you can run the amp with no inputs to see if it hums then.

I wonder if the xti is one of the components that does not follow the pin-2-hot standard for XLR inputs; if so, your adapter cable may not be right for it.
 
it sure sounds like the shield on the unbalanced inputs are NOT connected to ground on the 2000
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He says he's using rca to xlr. Pins/conductors 1 and 3 should be tied at one end or the other?
 
Some pro components use pin 3 hot also. Check your Crown amp to see if it is pin 2 or 3 that is hot. Really should be a standard, but we all know how that goes. Tie the negative and ground together at the unbalanced end. Don't use a cheater plug on the amp. If the amp develops a problem, and can't chassis ground through the signal cable, YOU will become the path to ground. If you have to you can use the ground lift switch to isolate the signal and chassis grounds.
 
What about the hum boxes like the Rolls he18 or the Art Clean box? Can I just buy that? Oh and buy the way thanks for all this help. I posted on other boards and this has been the must helpful. Unfortunately my cable building expertise is non existent.
 
The manual at the Crown web site does show pin 2 hot on the inputs and outputs, so that's not it. A hum box might be worth a try, but it is hard to know whether it will solve the problem without trying it.

This might be obvious, but have you tried changing the physical locations of the EQ and pre relative to the amp? This is a switch-mode amp, and I wonder if it might be inducing the hum just by physical proximity to one of the other components.
 
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RichPA said:
The manual at the Crown web site does show pin 2 hot on the inputs and outputs, so that's not it. A hum box might be worth a try, but it is hard to know whether it will solve the problem without trying it.

This might be obvious, but have you tried changing the physical locations of the EQ and pre relative to the amp? This is a switch-mode amp, and I wonder if it might be inducing the hum just by physical proximity to one of the other components.
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Thats a thought. I'll try that. I have Attached info on the Rolls Hum remover unit.
 
I believe the clean boxes transformer isolate the ground, possibly the entire signal. It should solve any ground loop related hum. My only thought is of the quality of those transformers, wondering if that becomes the "weak link" as far as sound quality.
 
I found the ground loop problem! It was the cable box which goes into my 62" tv then the tv goes to my Crown IC-150. Pull those off the Crown and the buzz and hum are gone. I bought the Rolls he18 hum reducer and hooked it up between the tv out and Crown IC-150 and that took care of the hum in my system and doesn't effect the rest of the system. Sounds great plus I can't get the amp hot enough to run the fans. I'm very happy so far. I have no hum or buzz the amp is very quite.*My question is why don't more people buy these pro-amps for home stereo's? This is a very clean powerful amp for $699.00. You would pay at least $1800.00 for half the power in a consumer amp. I'll never look back. I will admit the sound is a bit more analytical the best way I can describe it. I'll never run out of headroom. I have to laugh when I hear people talk about how harsh these pro amps are, I sure don't find them harsh at all.
 
Glad you found the problem, although it sounds like your cable tv ground where it enters the house is loose or missing and it was grounding through the Crown's 3 prong power cable. Your cable should ground at your home's ground rod that also serves as your electrical service ground, as well as for your telephone. Grounding these services in different locations or not at all causes ground loops like you had. Which causes currents to flow from one piece of equipment to the other as it tries to go to find ground, causing the hum, as well as possibly causing damage or potentially dangerous shock hazards. Did I say ground enough? :blah: Sorry for the ramble.
 
Did I say ground enough?
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IMO, what you said bears repeating in it's entirety.

After all, where i live the TV cable hangs just a few feet below 12.8Kv primaries, which means that in freak circumstances like a storm, tree falling, or vehicle striking a pole could cause that 12,800 volts to enter your house via the TV cable. If even for a fraction of a second, that kind of voltage will take out everything in it's path.
 
jhal said:
Glad you found the problem, although it sounds like your cable tv ground where it enters the house is loose or missing and it was grounding through the Crown's 3 prong power cable. Your cable should ground at your home's ground rod that also serves as your electrical service ground, as well as for your telephone. Grounding these services in different locations or not at all causes ground loops like you had. Which causes currents to flow from one piece of equipment to the other as it tries to go to find ground, causing the hum, as well as possibly causing damage or potentially dangerous shock hazards. Did I say ground enough? :blah: Sorry for the ramble.
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Yeah, almost :) Seriously, though, that is a very good point - it is pretty common for cable service to be poorly grounded, and there are multiple reasons for doing it right. Worth checking out.
 
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