Denon X3700H and Amp? (nothing but hum)

[Tony Cardenas]

Dear audioholics forum - I have a Denon x3700H that I am looking to get working with an Outlaw 500x amp. Ideally I'd like to power the Front, Center, and Surrounds with the Outlaw and let the Denon handle the sub and 4 height channels. It would be a 5.1.4 (single powered sub - hopefully will be able to add a 2nd sub in the future).

Here's my problem - no matter what interconnect cables I use when the amp is connected - all I hear is a pretty loud (I think 120Hhz?) hum from the channels powered by the amp. Audio sounds muted too. I can't find a way to specifically enable/disable the internal amps in the Denon (I've dug throuth the manual several times). I called Denon tech support and after a long wait they indicated all I needed to do was simply connect the amp to the pre-outs and that was it (in other words the Denon is smart enough to detect the amp I guess).

Once I disconnect the Outlaw and let the Denon run the 5.1.4 setup - all sounds fantastic - absolutely no hum/issues whatsoever. Reconnect the amp - hum and terrible audio. I did try the following to no avail:

- different interconnect/RCA (good quality cables used - short 1.5ft lengths)
- different A/C cable for the Outlaw
- tried plugging the Outlaw into a different A/C circuit in the house

The closet where the A/V equipment is in has its own dedicated 20A circuit. The home wiring is all to code/new <5 years old).

I'd be beyond thankful and appreciative if someone could point me in the right direction or might have experience with this configuration.

Thanks!
Tony C.

 

[TLS Guy]

Dear audioholics forum - I have a Denon x3700H that I am looking to get working with an Outlaw 500x amp. Ideally I'd like to power the Front, Center, and Surrounds with the Outlaw and let the Denon handle the sub and 4 height channels. It would be a 5.1.4 (single powered sub - hopefully will be able to add a 2nd sub in the future).

Here's my problem - no matter what interconnect cables I use when the amp is connected - all I hear is a pretty loud (I think 120Hhz?) hum from the channels powered by the amp. Audio sounds muted too. I can't find a way to specifically enable/disable the internal amps in the Denon (I've dug throuth the manual several times). I called Denon tech support and after a long wait they indicated all I needed to do was simply connect the amp to the pre-outs and that was it (in other words the Denon is smart enough to detect the amp I guess).

Once I disconnect the Outlaw and let the Denon run the 5.1.4 setup - all sounds fantastic - absolutely no hum/issues whatsoever. Reconnect the amp - hum and terrible audio. I did try the following to no avail:

- different interconnect/RCA (good quality cables used - short 1.5ft lengths)
- different A/C cable for the Outlaw
- tried plugging the Outlaw into a different A/C circuit in the house

The closet where the A/V equipment is in has its own dedicated 20A circuit. The home wiring is all to code/new <5 years old).

I'd be beyond thankful and appreciative if someone could point me in the right direction or might have experience with this configuration.

Thanks!
Tony C.

Clearly connecting the outlaw amp is causing a ground loop.

A ground loop is caused by a resistance between grounds. This results in grounds being at a different potential (voltage). This causes current to flow in the ground plane, resulting in hum.

So we need to know all the equipment you have connected, and which ones are grounded and which not. In addition we need to know in great details about your TV/cable and Internet connections. The latter are a potent source of ground loops.

 

[Tony Cardenas]

Hi TLS Guy,

Thanks so much for the time in responding to this. Here's everything in 'the stack:'

-Cox tv DVR. The coax is coming from a 1:2 splitter in a different room of the house. The other side of that splitter goes to a cable modem. The main coax line coming into the house is grounded at the 'demarc' point at the side of the house. It is grounded to the earth ground (bonded to the rest of the home wiring I believe.
-Xbox
-AppleTV
-Denon X3700H
-Outlaw 5000x
-AC Infinity top mount component fan

Everything in the stack is connected to a Monster Power HTS 3600 MKII power center. Monster power center is connected directly to the 20A outlet (which is a dedicated circuit directly back to the main panel).

Interestingly I just realized the only 3 prong A/C device is the Outlaw 5000x.

Internet in the house is also Cox cable. All networking gear is in a different room of the house and powered by a different 15A circuit. I do have the Denon connected to a wired internet connection though.

Thanks again for the assist on this.

 

[Kleinst]

On the outlaw, if you can temporarily try a cheater plug from Home Depot (3 prog to 2 prong conversion) if the hum goes away, buy one of these

https://www.guitarcenter.com/Ebtech/Hum-X-Hum-Exterminator.gc

don’t use the cheater plug with normal use. dangerous

 

[Tony Cardenas]

Thanks Kleinst - I will give that a shot 1st thing in the morning. I did see a couple of threads where others were suggesting something similar - man if that works I'll be beyond thrilled. Then again - I'd best not jinx it till I test.

Appreciate the advice! Have a great night,
Tony

 

[VMPS-TIII]

1. I would try plugging the amp into the same surge protector as the receiver.

2. If #1 has no effect I would try disconnecting the Cox cable coax from the wall and turn the amp and stereo back on and see if the hum still exists.

3. If both of these failed to give a hint of the issue I would call Outlaw. They have a long list of trouble shooting procedures for hum in all of their manuals and are experienced with this issue with their amps.

 

[lovinthehd]

On the outlaw, if you can temporarily try a cheater plug from Home Depot (3 prog to 2 prong conversion) if the hum goes away, buy one of these

https://www.guitarcenter.com/Ebtech/Hum-X-Hum-Exterminator.gc

don’t use the cheater plug with normal use. dangerous

Is it dangerous if you never touch the amp case?

 

[Tony Cardenas]

Thanks VMPT-TIII - much appreciated. I actually have the Outlaw and the Denon into the same surge protector. I also tried separate but that didn't change anything.

I tried unplugging the Cox set top box from the wall (didn't disconnect the coax/hdmi though). I can try that tomorrow too and will post back if there's any change. Much appreciated and cheers!

 

[TankTop5]

I’m just jumping in out of left field but I thought grounding to water was better than grounding to earth. Run an extension cord from your Outlaw to an outside GFI and see if the problem goes away. I could be full of crap, I’ll defer to others on the forum...

 

[Tony Cardenas]

Thanks TankTop5. That was a great thought to check - I was mistaken - looks like the installer installed the ground from the grounding block at the demarc point to the cold water line. I visually confirmed - Cox plastic tag still there too! I did try running a short extension to another outlet but I could certainly try one further away in the panel.

All in all - I'm really hoping a 2:3 conversion works. Thanks for everyone's input on this - much appreciated!

 

[lovinthehd]

In my last place I lived the cable installer had created a second ground which I only noticed after introducing some amps using 3-prong grounded outlet and hunting down the culprit. I used a cheater plug for a while but problem solved by moving a bit later....

 

[Tony Cardenas]

In my last place I lived the cable installer had created a second ground which I only noticed after introducing some amps using 3-prong grounded outlet and hunting down the culprit. I used a cheater plug for a while but problem solved by moving a bit later....

Thanks lovinthehd!

 

[lovinthehd]

Thanks lovinthehd!

I did mean my question earlier about just how dangerous use of a cheater plug is. I never had to touch the amps (separate on/off mechanism) but that's my understanding, if you touch the case of something you're using a cheater plug on is the danger.....but not sure what other potential danger it may bring.

 

[Tony Cardenas]

I did mean my question earlier about just how dangerous use of a cheater plug is. I never had to touch the amps (separate on/off mechanism) but that's my understanding, if you touch the case of something you're using a cheater plug on is the danger.....but not sure what other potential danger it may bring.

Very good point. I was noticing that the Outlaw has a chassis ground - I guess I could ground the Outlaw to the ground post on the Moster power center?

 

[Tony Cardenas]

Very good point. I was noticing that the Outlaw has a chassis ground - I guess I could ground the Outlaw to the ground post on the Moster power center?

This is what I was thinking.

 

[lovinthehd]

Page 5 of your amp manual suggests using that post to ground to the pre-amp or avr in the case of ground loop hum....

 

[Tony Cardenas]

Page 5 of your amp manual suggests using that post to ground to the pre-amp or avr in the case of ground loop hum....

Yeah buddy - I'm ashamed to admit I completely overlooked that! "To eliminate ground loop hum use this post..." Wow - wouldn't that be amazing. I'll actually try this 1st in the morning. Appreciate the tip. This forum rocks!

 

[TLS Guy]

Yeah buddy - I'm ashamed to admit I completely overlooked that! "To eliminate ground loop hum use this post..." Wow - wouldn't that be amazing. I'll actually try this 1st in the morning. Appreciate the tip. This forum rocks!

I suspect the Outlaw may be overloading that Monster unit. It is not actually a good idea to connect power amps to external power supplies or UPS devices. Plug the outlaw into the same outlet as the Monster unit, but do not plug it into the monster unit.

If you still have hum, then see if the hum stops if you completely disconnect your system from the cable system and the Internet.

If the Outlaw amp is the only unit grounded, then you should not have hum. Cable systems are renowned for causing ground loops and are always suspect number 1.

 

[Tony Cardenas]

I suspect the Outlaw may be overloading that Monster unit. It is not actually a good idea to connect power amps to external power supplies or UPS devices. Plug the outlaw into the same outlet as the Monster unit, but do not plug it into the monster unit.

If you still have hum, then see if the hum stops if you completely disconnect your system from the cable system and the Internet.

If the Outlaw amp is the only unit grounded, then you should not have hum. Cable systems are renowned for causing ground loops and are always suspect number 1.

Thanks TLS Guy - I did try plugging the Outlaw into another surge protector separate from the Monster PS. It didn't seem to make a difference. I will try to completely disconnect the Cox STB tomorrow though - I did try unplugging it and that didn't make a difference (although the RG6 coax was still connected to the STB and HDMI was connected from the STB to the Denon). Either way - I have several great options to test out:

1. use 3:2 converter (non grounded amp).
2. fully disconnect coax/unplug coax STB
3. confirm amp powered on separate outlet(s) with coax/STB disconnected
4. ground amp to avr(?) per Outlaw manual on p5 - not sure the best way to do this as there's no dedicated ground terminal on the Denon

Thanks again everyone.

 

[TLS Guy]

Thanks TLS Guy - I did try plugging the Outlaw into another surge protector separate from the Monster PS. It didn't seem to make a difference. I will try to completely disconnect the Cox STB tomorrow though - I did try unplugging it and that didn't make a difference (although the RG6 coax was still connected to the STB and HDMI was connected from the STB to the Denon). Either way - I have several great options to test out:

1. use 3:2 converter (non grounded amp).
2. fully disconnect coax/unplug coax STB
3. confirm amp powered on separate outlet(s) with coax/STB disconnected
4. ground amp to avr(?) per Outlaw manual on p5 - not sure the best way to do this as there's no dedicated ground terminal on the Denon

Thanks again everyone.

Then the problem has to be in the cable/Internet system, if the Outlaw is truly the only other grounded unit. One ground can not give you a ground loop, it takes two or more grounds to cause trouble. The Outlaw will be grounded to the receiver by the screens in the interconnecting cables.