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Post by phatfos1 on Dec 22, 2012 13:57:11 GMT -5
Second post for today. Hello to everyone. Seems like a cool group of people.
I got the XPA-2 a couple of weeks ago. My first foray into separates. What an amp! I went from trying to power my LSI-25s with the Denon 3808 to this. The difference is shocking. I expected to get something out of the upgrade, but couldn't have imagined the improvement in dynamics and sound stage. There really is something to be said about the proverbial headroom an amp like this affords.
But to my point, I have a audible hum coming from my LSIs. It's not a group loop, as I've eliminated all connections to the Denon and the hum persists. I have also disconnected the RCAs from the Denon to the XPA (so it's just XPA-->LSIs).
I thought perhaps it was my cables, but I used a couple of other speaker runs/rca's and the hum is still there.
Customer service was great and sent me a CMX-2 to eliminate DC offset as the culprit. Still there.
Short of sending the amp back for diagnostics (and being without the amp for weeks), does anybody have a suggestion as to a possible cause?
They don't have any XPA warranty replacements at this point, and although I would love an excuse to upgrade to an XPR I just think it's overkill for my needs. And running a dedicated 20A in my current house would be a waste since we're moving in a couple years.
Thanks for any help. And happy holidays.
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Post by mgbpuff on Dec 22, 2012 14:27:27 GMT -5
You might see if a cheater plug on the powered speaker subs makes a difference.
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Post by knucklehead on Dec 22, 2012 15:00:27 GMT -5
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Post by phatfos1 on Dec 22, 2012 15:44:57 GMT -5
What does the cheater plug do? I actually unplugged the amps on the towers to make sure they were not creating a loop and the hum was still there.
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Post by phatfos1 on Dec 22, 2012 15:46:40 GMT -5
The plug for the LSI amps is not grounded.
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Post by mgbpuff on Dec 22, 2012 16:05:33 GMT -5
Sounds like the hum is truly being caused by the amp then. I'd send it back.
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Post by phatfos1 on Dec 22, 2012 17:03:53 GMT -5
Guess that's what I'll have to do.
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Post by Golden Ear on Dec 22, 2012 17:39:11 GMT -5
Second post for today. Hello to everyone. Seems like a cool group of people. I got the XPA-2 a couple of weeks ago. My first foray into separates. What an amp! I went from trying to power my LSI-25s with the Denon 3808 to this. The difference is shocking. I expected to get something out of the upgrade, but couldn't have imagined the improvement in dynamics and sound stage. There really is something to be said about the proverbial headroom an amp like this affords. But to my point, I have a audible hum coming from my LSIs. It's not a group loop, as I've eliminated all connections to the Denon and the hum persists. I have also disconnected the RCAs from the Denon to the XPA (so it's just XPA-->LSIs). I thought perhaps it was my cables, but I used a couple of other speaker runs/rca's and the hum is still there. Customer service was great and sent me a CMX-2 to eliminate DC offset as the culprit. Still there. Short of sending the amp back for diagnostics (and being without the amp for weeks), does anybody have a suggestion as to a possible cause? They don't have any XPA warranty replacements at this point, and although I would love an excuse to upgrade to an XPR I just think it's overkill for my needs. And running a dedicated 20A in my current house would be a waste since we're moving in a couple years. Thanks for any help. And happy holidays. How do you like your Polk Lsi15? |
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Post by ocezam on Dec 23, 2012 10:29:26 GMT -5
How do you like your Polk Lsi15? He's got LSi25's. Pretty big difference as the 25's have self powered woofers on board. I've got the LSi15's and can tell you I love them. Crystal clear. Open. Accurate. To me they are like Emo amps. An incredible bargain in this hobby. |
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Post by phatfos1 on Dec 23, 2012 11:20:31 GMT -5
I love the LSI line. I have the LSI 25s. I think the 15s is the better speaker. Especially when using a separate amp because they do require a lot of power. I think the LSI line offers the best speaker one can buy for under $1500. I have had many people express true astonishment when they hear them and learn they are polks. And adding the XPA truly took them to the next level. I feel my system can hold its own with setups costing two or three times the price. I have the XPA, Denon 3808 and the 25s up front with LSI 9s for surround. Very happy with it. Would buy the 15s if I was to do it again and spend the extra on a sub.
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Post by audiohead on Dec 23, 2012 15:53:34 GMT -5
I don't get why people are having hum issue's with there amps.Ground maybe?
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Post by jottle on Jan 9, 2013 20:49:22 GMT -5
I've had hum issues with my lpa-1 since day one. I ended up sending it back to Emotiva twice in three years. Their tech guys were great, and really tried hard to identify the cause. Unfortunately, they ended up claiming everything was fine with the amp and couldn't help me. I have a lot of experience eliminating hum from ground loops etc. But the low level hum in my speakers is definitely caused by my lpa-1 with no other components in my system. Even with just speaker cables and the amp connected, there's a low level hum. Unfortunately, this issue has followed me through two moves and three entirely new systems/components paired with the lpa. Sometimes I guess particular speakers are extremely sensitive to hum. Who knows. Bottom line, emotiva couldn't reproduce any humming in their test labs. So sometimes it's just a mystery. I've just come to live with the hum since I can only hear it in a completely silent room.
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Post by katjith on Jan 9, 2013 20:59:36 GMT -5
Well as you knowXPA-2 has high gain(32db) and if your speakers are highly sensitive,you are always gong to hear a low hum.What is the sensitivity of your speakers?
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Deleted
Deleted Member
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Post by Deleted on Jan 9, 2013 21:05:59 GMT -5
Well as you knowXPA-2 has high gain(32db) and if your speakers are highly sensitive,you are always gong to hear a low hum.What is the sensitivity of your speakers? Not always true. My speakers are 103db and with my XPA-1's, i get no hum. |
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LCSeminole
Global Moderator 
Res firma mitescere nescit.
Posts: 20,494
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Post by LCSeminole on Jan 9, 2013 21:27:12 GMT -5
Well as you knowXPA-2 has high gain(32db) and if your speakers are highly sensitive,you are always gong to hear a low hum.What is the sensitivity of your speakers? Not always true. My speakers are 103db and with my XPA-1's, i get no hum. I totally agree with Matt, my Klipsch Legends have a sensitivity of 100 dB @ 1 watt/1 meter and they have been dead quiet with an XPA-5, XPA-2 and now an XPR-5. |
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Post by The Mad Norseman on Jan 9, 2013 21:30:25 GMT -5
Some have tried running a insulated grounding wire from their amp (or AVR) chassis (unscrew a screw holding the cabinet casing on a little and fix it there), then running it to a grounded screw on their surge protector, and many have eliminated their hum that way.
Maybe worth a shot, as its a cheap fix/thing to try?
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Post by Cory Cooper on Jan 9, 2013 23:09:34 GMT -5
Some have tried running a insulated grounding wire from their amp (or AVR) chassis (unscrew a screw holding the cabinet casing on a little and fix it there), then running it to a grounded screw on their surge protector, and many have eliminated their hum that way. Maybe worth a shot, as its a cheap fix/thing to try? That is exaclty what I did to finally cure my ground loop hum. I had tried everything previously, and this form of star ground totally eliminated it. I made a couple of insulated wires with ring eyelets, attached one end to a screw on the side of my UMC-1 and XPA-5, the other ends to the grounding post connection on the back of my Monster Power center and the hum was gone. I recommend trying it. C |
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Post by pestilenceten on Jan 9, 2013 23:39:59 GMT -5
This may sound weird but if your tv isn't plugged into a line conditioner try un plugging it to see if the hum dissapears this worked for me. My tv and conditioner were both fighting for 0.0v
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Post by phatfos1 on Jan 13, 2013 13:40:46 GMT -5
I unplugged everything from the wall and the RCAs from the amp. So it was just the XPA to the speakers and it was still there. I contacted Nick and he sent me an CMX to see if was DC offset. Nope. Sent the whole unit back along with the CMX and got an XPR-5. No hum at all. The LSIs were dead silent. The new XPR series is pretty impressive. When I had it sitting next to the XPA it was pretty neat to see how much meatier the XPR is. That being said, I was impressed with the sound of the XPA. Just couldn't stand the hum. I guess I now have as much power as I'll ever need for five channels. I can't imagine needing more than this.
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