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#1 mikeyciccarelli

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Posted 16 May 2011 - 09:42 PM

Hi,

just purchased an XLS 1500 from a local retailer (guitar center) and did some initially testing and am not too happy so far. I have an onkyo tr-sx806 receiver and I'm using the sub pre amp out... I have an additional existing 12" sub with built in amp that I'm comparing against. When I used the subout and did bridged mode and connected to a sub I hear a horrible hum.. Also I seem to have to crank up both the output on the amp and the output on the onkyo to get any decent sound out of it. When I do this the amp's hum is horrible and unacceptable. I plugged the amp into a different wall outlet (could be on the same circuit) and stll had a bad hum.

so 2 problems
1) hum.. I guess if I have to run another circuit in my house I will return amp as none of my other peices of equipment have this problem
2) I have to turn the gain on the amp all the way to 10 (and I wish it had 11) to get any results compariable to the other sub. Also when doing this the other sub becomes waay overpowering (because onkyo has +10 db on the sub output).

Edit: I did a little more testing.. if I enable the low pass filter the buzz goes away. If I enable high pass it comes back and if I leave it bypass i also hear it still.

Any ideas? Is this amp just that underpowered??

thanks,
Mike Ciccarelli

#2 Kevin Heber

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Posted 17 May 2011 - 09:37 AM

As far as the hum, does the amp still produce a hum when you remove the audio input?  If not, then it's not the amp, it's most likely a ground loop.

As far as not playing loud enough, this topic may help:  http://www.crownaudio.com/forums/index.php?showtopic=3839


#3 mikeyciccarelli

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Posted 17 May 2011 - 11:04 AM

Kevin,

awesome thanks for the great info... I'd be open to maybe getting a converter (they don't look to be too cheap, but not horribly overpriced, just something I didn't figure on). Doesn't seem like something I can buy at a local retailer or where I bought the amp from. Not sure who to trust online (the places I found that sell them look kinda questionable).

I'd pay crown good money if they came up with a rca "booster" solution that got rid of ground loops and obviously boosted the signal. Or have a switch on the amp that has a boost for signal just on rca. I'm guessing I'm a small percentage of users that would be requesting this and it wouldn't happen....

For now I think I understand why not to use pro amps for household use. From what I've read I think it's going to be incredibly hard for me to debug the ground loop. Or would something like this also remove ground loops?

http://www.mcmelectronics.com/product/555-...0570992#reviews

Doesn't specifically say so I'm at a loss. Hoping going to balanced output would get rid of hum?

thanks,
Mike Ciccarelli



QUOTE(Kevin Heber @ May 17 2011, 10:37 AM) View Post
As far as the hum, does the amp still produce a hum when you remove the audio input?  If not, then it's not the amp, it's most likely a ground loop.

As far as not playing loud enough, this topic may help:  http://www.crownaudio.com/forums/index.php?showtopic=3839



#4 Kevin Heber

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Posted 17 May 2011 - 11:19 AM

Make sure your gear is all plugged into the same AC outlet, and if possible, make it so all the metal chassis are coupled (like mounted in a rack or otherwise stacked).

The MCM piece you found will do the job and may help the ground hum.  In general it takes trial and error to get rid of these.  At home I have a particular lamp (touch-on/touch-off) that induces a hum into my system.  So it could be coming from a number of things.

#5 mikeyciccarelli

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Posted 17 May 2011 - 11:53 AM

Kevin,

with the noise I was hearing.. I could plug any rca cable into the crown input and get the hum.. the other end didn't even have to be plugged into the output of my onkyo.. Would this still happen if it was a ground loop?

How come this seems to happen more with pro audio? I have a bunch of other home equipment and never had a ground loop hum...

thanks,
Mike

QUOTE(Kevin Heber @ May 17 2011, 12:19 PM) View Post
Make sure your gear is all plugged into the same AC outlet, and if possible, make it so all the metal chassis are coupled (like mounted in a rack or otherwise stacked).

The MCM piece you found will do the job and may help the ground hum.  In general it takes trial and error to get rid of these.  At home I have a particular lamp (touch-on/touch-off) that induces a hum into my system.  So it could be coming from a number of things.



#6 Kevin Heber

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Posted 17 May 2011 - 01:45 PM

I'm betting the converter box will fix this.  The cables are probably acting as antennae and picking up the hum from the air.  Home audio equipment typically has a higher input impedance which prevents this.

#7 mikeyciccarelli

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Posted 18 May 2011 - 10:17 AM

Kevin,

converter box is on order... I got a different model simply because it was one of the only one available from the retailer I'm buying most of my stuff from. The one converter box I purchased supposedly has a bad response at lower frequencies.. guess it is a slight tradeoff.

http://www.guitarcenter.com/ART-CLEANBoxPr...589-i1519782.gc

Since I'm just trying this out I wanted the option of using 1 vendor incase I needed to return everything.

Could you honestly push the idea of having an RCA input that is "ready" for home use? Something specifically desgined to accept lower input levels from home receivers and also something built in that helps with the grounding issue over RCA? There aren't many options for home audio amps that run greater than 1,000 watts that cost less than $1500.00 .. Not sure if this is a niche market not worth dealing with?

thanks,
Mike

QUOTE(Kevin Heber @ May 17 2011, 02:45 PM) View Post
I'm betting the converter box will fix this.  The cables are probably acting as antennae and picking up the hum from the air.  Home audio equipment typically has a higher input impedance which prevents this.



#8 Stephane

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Posted 19 May 2011 - 07:42 AM

QUOTE(mikeyciccarelli @ May 18 2011, 11:17 AM) View Post
Kevin,

converter box is on order... I got a different model simply because it was one of the only one available from the retailer I'm buying most of my stuff from. The one converter box I purchased supposedly has a bad response at lower frequencies.. guess it is a slight tradeoff.

http://www.guitarcenter.com/ART-CLEANBoxPr...589-i1519782.gc

Since I'm just trying this out I wanted the option of using 1 vendor incase I needed to return everything.

Could you honestly push the idea of having an RCA input that is "ready" for home use? Something specifically desgined to accept lower input levels from home receivers and also something built in that helps with the grounding issue over RCA? There aren't many options for home audio amps that run greater than 1,000 watts that cost less than $1500.00 .. Not sure if this is a niche market not worth dealing with?

thanks,
Mike

QUOTE(Kevin Heber @ May 17 2011, 02:45 PM) View Post
I'm betting the converter box will fix this.  The cables are probably acting as antennae and picking up the hum from the air.  Home audio equipment typically has a higher input impedance which prevents this.


Also other common problem with noise like this can be track down to the cable box receiver, i know in your case you only had a wire plugged in your amplifier but just saying. I do have 6 pro amplifier in my rack and 0 issue of noise. Many people out there are using pro amp in their surround sound already with 0 issue as well. It always suck when it does happen to you but like Kevin mentioned most problem can be solved by '' Grounding'' all your components together.

#9 Kevin Heber

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Posted 19 May 2011 - 12:07 PM

Yes, we have lamented for years about Crown missing the opportunity to make $$ on a simple home-to-pro preamp.  The RCA inputs on the XLS Drivecore are a nice feature, but they only work really well with DJ mixers that produce very high "line-level" output.

#10 mikeyciccarelli

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Posted 20 May 2011 - 10:55 AM

Once I get the rca->xlr converter box (today hopefully) I will test it out. I've read online to determine what could cause ground loops and tried to read up on them a bit. I don't have a cable box at all. I use the built in cable turner on my TV.. so not sure how to work around that. Also my receiver is an onkyo.. not sure where or how to ground that device. I know old receivers used to have a ground for turnables.. I will have to see if there is a ground on my onkyo. If I have to buy a rack to house my onkyo and pro amp that's just more cost to figure into the entire investment. If I find that I'm spending more money than just buying a nicer (more expensive) home audio amp then that is a deal breaker for me.

I have read of several success stories using proamps for home theater. This is why I figured I'd try it out. I've also read of a couple of failures (gound hum, not enough output from amp, etc). Overall It's been fun testing out new equipment and learning more about audio equipment..

Stephane, what preprocessor/mixer/preamp are you using and do you have it grounded or racked with your proamps? If you could provide more detail maybe it would help me debug my problem...

thanks,
Mike



QUOTE(Stephane @ May 19 2011, 08:42 AM) View Post
QUOTE(mikeyciccarelli @ May 18 2011, 11:17 AM) View Post
Kevin,

converter box is on order... I got a different model simply because it was one of the only one available from the retailer I'm buying most of my stuff from. The one converter box I purchased supposedly has a bad response at lower frequencies.. guess it is a slight tradeoff.

http://www.guitarcenter.com/ART-CLEANBoxPr...589-i1519782.gc

Since I'm just trying this out I wanted the option of using 1 vendor incase I needed to return everything.

Could you honestly push the idea of having an RCA input that is "ready" for home use? Something specifically desgined to accept lower input levels from home receivers and also something built in that helps with the grounding issue over RCA? There aren't many options for home audio amps that run greater than 1,000 watts that cost less than $1500.00 .. Not sure if this is a niche market not worth dealing with?

thanks,
Mike

QUOTE(Kevin Heber @ May 17 2011, 02:45 PM) View Post
I'm betting the converter box will fix this.  The cables are probably acting as antennae and picking up the hum from the air.  Home audio equipment typically has a higher input impedance which prevents this.


Also other common problem with noise like this can be track down to the cable box receiver, i know in your case you only had a wire plugged in your amplifier but just saying. I do have 6 pro amplifier in my rack and 0 issue of noise. Many people out there are using pro amp in their surround sound already with 0 issue as well. It always suck when it does happen to you but like Kevin mentioned most problem can be solved by '' Grounding'' all your components together.



#11 Stephane

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Posted 21 May 2011 - 08:13 AM

I do have an older AVR HK (Harman K), made my own RCA to XLR cable or 1/4 TRS jack where required(good quality cable and plug) to 2 Beri DCX2496 then going to sub power amp QSC MX3000A, bass front QSC RMX1850hd, mid front QSC Serie 3 3350, hi front Crown CSL460, center QSC USA360 and Rear Crown XLS402B. all my components are mounted in an Middle Atlantic rack if this can help you.

For grounding issue you can use a piece of wire long enough and try to bound it from any of your AVR screw on the case to your amp and see what gonna happen.

Now for your cable plug directly to TV if end up be the culprit, you will need something like a Jensen filter for cable which is usually a little expensive or try to electrically isolate your TV from AVR ( RCA to optical converter).

When trying to figure out what is causing you these type of problem, always plug your cable or component one at the time and check for problem and so on.

Also you did mention with only a cable plug to the amp you were getting noise, i suspect you are using cheap cable and or damaged shield. Check place like monoprice they do sell nice RCA to XLR cable properly made.

#12 mikeyciccarelli

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Posted 23 May 2011 - 11:09 AM

Well the Art Cleanbox Pro did fix all of my problems (input level being too low and also the hum). I have a JL audio 10" sub I was using for testing and the thing was going nuts at 5 to 15 Hz (was nice to see that it all came together).

I was thinking of getting the rca -> xlr cables instead of the art cleanbox but I don't think this would have addressed the output level from my onkyo. I think if I had the proper cabling it would have fixed the hum, but with this boost in the line level output the amp really shines... Using the cleanbox pro also will allow me to use a normal 12" home theater sub in addition to whatever I finally hook up to the crown xls...

The only negative is having to purchase another 90+ dollars worth of stuff to integrate with my home audio, but after briefly testing it I can't complain at all..

thanks for the support!
Mike


QUOTE(Stephane @ May 21 2011, 09:13 AM) View Post
I do have an older AVR HK (Harman K), made my own RCA to XLR cable or 1/4 TRS jack where required(good quality cable and plug) to 2 Beri DCX2496 then going to sub power amp QSC MX3000A, bass front QSC RMX1850hd, mid front QSC Serie 3 3350, hi front Crown CSL460, center QSC USA360 and Rear Crown XLS402B. all my components are mounted in an Middle Atlantic rack if this can help you.

For grounding issue you can use a piece of wire long enough and try to bound it from any of your AVR screw on the case to your amp and see what gonna happen.

Now for your cable plug directly to TV if end up be the culprit, you will need something like a Jensen filter for cable which is usually a little expensive or try to electrically isolate your TV from AVR ( RCA to optical converter).

When trying to figure out what is causing you these type of problem, always plug your cable or component one at the time and check for problem and so on.

Also you did mention with only a cable plug to the amp you were getting noise, i suspect you are using cheap cable and or damaged shield. Check place like monoprice they do sell nice RCA to XLR cable properly made.