Crown Com-Tech 410 and Yamaha P2050 hum help.

[Jess]

Hello! First of all, sorry if this is the wrong forum - I've been trying to search for the answer to my problem before posting and haven't had much luck.

I have two Power Amps.
Crown Com-Tech 410 and a Yamaha P2050.

My set up is immiting a very bad hum, here is how its set up currently:

My Source is from the Computer > Standard Stereo 1/8 mini jack to RCA cable > RCA extension to either the Crown or the Yamaha (I'm not trying to use both, I tried both to see if the hum would magically vanish) > Speaker Wire > Pheonix Gold ISM8 8 Zone Speaker Selector > Speakers.

If you are not familiar with either of these amps, they are both rack-mounted amps, and I do not have either on a rack - I believe rack mounted amps ground through the rack? We tried grounding both amps and while it reduced the hum some, it far from eliminated it.


Some Details:

The speaker wire from Amp > Switch is "Honeywell Genesis Oxygen Free Home Theater/Pro Audio 16/2 (UL) C1L3" ALL of our Speaker wire is that, or a 14/4 version of the same wire. It is very good wire, but it is not Shielded.

The RCA cable from Source is unshielded as well, but it does not run near any power lines. As far as I know, there is no power lines near the speaker wire either, other than whats coming out of the Amps. I do however, have a pair of Monitor Speakers on the switch that are only on 3ft of wire not near any power and they still have the hum.

Both Amp's are plugged directly into the wall.


The Switch's product discription:

"8 zone, low profile speaker distribution system with individual on/off selectors distributes stereo speaker level signal to each zone, manual protection switch, handles 140W without protection and 70W with, engages 10ohm/15W resistors wired in parallel, three per channel, accepts up to 12 gauge cable, daisy chain output terminal."


My feeling is that these Amps don't like the computer output and that I'm missing something.

Any advice would be great, Thanks!

Jess

 

[WmAx]

You have a ground loop.

The easiest solution is to get a Samson S-Convert. This will both remove the loop and convert the low voltage unbalanced output from the computer's sound card to pro level voltage to drive the amplifiers properly. I would not consider this hardware optional.

-Chris

 

[Jess]

Thanks for the response Chris! I picked up the S-Convert but it doesn't appear to be removing any hum. Like, 2 days after I ordered it we found the Mixer that my Dad got with this Yamaha (he forgot he had it and the garage has been a disaster since moving in until the last two weeks)

It is a Yamaha PM-180. Finding it was a good thing because we are having a 100 guest family reunion this coming weekend and we needed a mic, which this has inputs for.

Anyway - At the moment, I only have one XLR cable (a 50ft we got for the Mic, Radio Shack is a rip off and they only had 25ft-50ft cables so to hook the Mixer and the P2050 together I'm using RCA to Mono Phone Jack Adapters for the Computer cable and two straight Mono Phone Jack cables to use between the Mixer & Amp.

I have tried the following combinations, anything with the XLR cable was just using the left or right channel to see if it worked.

RCA/Phone > PM-180 > Phone to P2050

RCA/Phone > PM-180 > XLR to P2050

RCA to S-Convert > XLR to PM-180 > Phone jack to P2050

RCA to S-Convert > XLR to P2050

I would like to try RCA > S-Convert > XLR to PM-180 > XLR to P2050 but I'm thinking that is not the problem?

If I have a ground loop and the S-Convert isn't fixing it, how else can I fix it? I have tried messing with the input/output levels on the Mixer and the Amp and can't seem to reduce the hum without the volume of music being to low.

I shortened my cable lengths and made sure my output cable from the computer did not run along any power lines - however it is coming out of the computer so it runs near the computers power supply.

I have an Onkyo A-8087 Receiver and plugging from the computer directly into that results in no hum, the reason we are not using it is the left channel is blown

 

[highfigh]

Hello! First of all, sorry if this is the wrong forum - I've been trying to search for the answer to my problem before posting and haven't had much luck.

I have two Power Amps.
Crown Com-Tech 410 and a Yamaha P2050.

My set up is immiting a very bad hum, here is how its set up currently:

My Source is from the Computer > Standard Stereo 1/8 mini jack to RCA cable > RCA extension to either the Crown or the Yamaha (I'm not trying to use both, I tried both to see if the hum would magically vanish) > Speaker Wire > Pheonix Gold ISM8 8 Zone Speaker Selector > Speakers.

If you are not familiar with either of these amps, they are both rack-mounted amps, and I do not have either on a rack - I believe rack mounted amps ground through the rack? We tried grounding both amps and while it reduced the hum some, it far from eliminated it.


Some Details:

The speaker wire from Amp > Switch is "Honeywell Genesis Oxygen Free Home Theater/Pro Audio 16/2 (UL) C1L3" ALL of our Speaker wire is that, or a 14/4 version of the same wire. It is very good wire, but it is not Shielded.

The RCA cable from Source is unshielded as well, but it does not run near any power lines. As far as I know, there is no power lines near the speaker wire either, other than whats coming out of the Amps. I do however, have a pair of Monitor Speakers on the switch that are only on 3ft of wire not near any power and they still have the hum.

Both Amp's are plugged directly into the wall.


The Switch's product discription:

"8 zone, low profile speaker distribution system with individual on/off selectors distributes stereo speaker level signal to each zone, manual protection switch, handles 140W without protection and 70W with, engages 10ohm/15W resistors wired in parallel, three per channel, accepts up to 12 gauge cable, daisy chain output terminal."


My feeling is that these Amps don't like the computer output and that I'm missing something.

Any advice would be great, Thanks!

Jess

How far is the computer from the system? If it's in another room, it's probably on a different breaker, and the other phase of the electrical service. If you have an extension cord that's long enough, plug the computer into it and plug the cord into the same power management as the system. I'd bet that it will get better, if not go away.

 

[Jess]

In the same room, but its on an outlet on the other side of the room. I'll try it, thanks!

 

[Jess]

Hmm, it did not do anything noticable. With or without the S-Convert. I noticed if I plug my Mic into one of the inputs of the Mixer its crystal clear until I plug the computer into the Aux of the Mixer, then the hum goes over the mic.

 

[TLS Guy]

Hmm, it did not do anything noticable. With or without the S-Convert. I noticed if I plug my Mic into one of the inputs of the Mixer its crystal clear until I plug the computer into the Aux of the Mixer, then the hum goes over the mic.

The problem is likely your Internet connection to your computer. How is it connected? If you are connected to a phone or cable system, that will be the source of your ground loop, it nearly always is.

 

[Jess]

It's connected via the on board Ethernet with Cat5e. I unplugged the cable and it didn't do anything. I was able to reduce the hum some by swaping out a crappy headphone extension cable that was connected on the back of the computer to make swapping headphones/speakers on the desktop easier. But it is still pretty loud.

Using the S-Convert still does nothing. (With the Cat5 unplugged)

 

[TLS Guy]

It's connected via the on board Ethernet with Cat5e. I unplugged the cable and it didn't do anything. I was able to reduce the hum some by swaping out a crappy headphone extension cable that was connected on the back of the computer to make swapping headphones/speakers on the desktop easier. But it is still pretty loud.

Using the S-Convert still does nothing. (With the Cat5 unplugged)

So that is part of the problem. If you computer has a three prong mains plug, then get one of those two prong adapters, and place that between the computer mains plug and the wall socket. Let us know what happens.

 

[Jess]

Hrm, I'm confused - you mean a 3 prong power cable? So get an Adapter to a 2 prong power cable to plug in the wall?

 

[TLS Guy]

Hrm, I'm confused - you mean a 3 prong power cable? So get an Adapter to a 2 prong power cable to plug in the wall?

Yes, lift the ground for a test. These common ground loops occur because equipment that is interconnected has a potential between grounds. AC current then flows in the grounds of cables connecting equipment inducing hum. We need to track down the source of your ground loop. Ideally there should be only one ground in the whole system. You get rid of ground loops by removing or interrupting grounds.

 

[Jess]

I see. Well I used a 3>2 converter and it didn't do anything other than make the hum sort of "wavey" (If i wiggle the power cable the sound sort of decreases and increases in volume) but that may be because the converter is rather old and cheap feeling. Maybe I should mention. To avoid moving the computer, I used a power strip, the power strip is plugged into the Unswitched plug in the back of the Mixer, the Mixer and the Power Amp are both plugged into the same wall outlet.

 

[TLS Guy]

I see. Well I used a 3>2 converter and it didn't do anything other than make the hum sort of "wavey" (If i wiggle the power cable the sound sort of decreases and increases in volume) but that may be because the converter is rather old and cheap feeling. Maybe I should mention. To avoid moving the computer, I used a power strip, the power strip is plugged into the Unswitched plug in the back of the Mixer, the Mixer and the Power Amp are both plugged into the same wall outlet.

Now you need to go to one ground. Ground the power amp only. Lift the other grounds and see if you have no hum. If you have hum then, then the computer has an internal ground loop due to problems with its ground plane. This is not uncommon with computers.

By the way while doing this test, pull the cat 5 and any other cables connected to a cable box or satellite.

 

[Jess]

I tried doing this just now:

Skipped the Mixer and went into the S-Convert and went out directly into the Amp, there was still a hum. I skipped the S-Convert and the hum is pretty much gone. You can hear it if you stand next to the speakers and the volume is up.

Plugging the Mixer in brings the hum back to its original loudness.

Edit: Unpugging the LAN did nothing.

 

[TLS Guy]

I tried doing this just now:

Skipped the Mixer and went into the S-Convert and went out directly into the Amp, there was still a hum. I skipped the S-Convert and the hum is pretty much gone. You can hear it if you stand next to the speakers and the volume is up.

Plugging the Mixer in brings the hum back to its original loudness.

Edit: Unpugging the LAN did nothing.

What mains plug is on the mixer? Make sure the amp only is grounded and there is nothing plugged into the mixer. You add connections one by one, to find the source of the ground loop, or loops. If you have hum, you have more than one ground. You must get to a situation of only one piece of equipment in the whole set up being grounded and that should be the amp.

 

[Lordoftherings]

Maybe I should mention. To avoid moving the computer, I used a power strip, the power strip is plugged into the Unswitched plug in the back of the Mixer, the Mixer and the Power Amp are both plugged into the same wall outlet.

^^^ Try different connection alternatives by using extension cords. Use only the three-prong ones. I'm talking about the one for the power strip, in particular. You got nothing to loose by trying.

Regards,
Bob

 

[Jess]

Hey guys, thanks so much for the help! I really appreciate it. The hum is now 100% gone.

Here's what I tried:

I got an extension cord and plugged the power strip into it. The Computer, Mixer and Amp all into the power strip. I noticed the hum was still present while the computer was off which made it easier to move plugs around. First thing I did was lift the ground to the computer, and I noticed immediatly the hum getting louder when the computer was unplugged. Plugging the computer into the 2 prong adapter didn't do anything, so I lifted the Mixer as well, it didn't do anything either.

So, then I put the Mixer and Computer back into the power strip so nothing was lifted (which also resulted in the least amount of hum) and unplugged the power strip and plugged it into a different outlet and the hum was 100% gone. It is crystal clear.

Unfortunately the outlet I was using was built into the cabinet where we are going to tuck these things away, so I'm going to have power cables hanging out of the cabinet doors. But, I don't really care, the hum is gone - I'm happy lol.

Any ideas why the amps and stuff like this other outlet more? Just more AC/noise running along the cabinet's outlet wires?

Again, thank you guys for the help.

 

[Lordoftherings]

Thanks to let us know. I'm very happy for you.

* It's all about where things are connected, some places are bad, some others are the right ones. And you just use the wrong one (too much stuff running from the same wrong outlet). It's like an illuminated Christmas tree, you don't want to keep adding extension cords from the same outlet.

You have a beautiful and illuminated day,
Bob

 

[TLS Guy]

Hey guys, thanks so much for the help! I really appreciate it. The hum is now 100% gone.

Here's what I tried:

I got an extension cord and plugged the power strip into it. The Computer, Mixer and Amp all into the power strip. I noticed the hum was still present while the computer was off which made it easier to move plugs around. First thing I did was lift the ground to the computer, and I noticed immediatly the hum getting louder when the computer was unplugged. Plugging the computer into the 2 prong adapter didn't do anything, so I lifted the Mixer as well, it didn't do anything either.

So, then I put the Mixer and Computer back into the power strip so nothing was lifted (which also resulted in the least amount of hum) and unplugged the power strip and plugged it into a different outlet and the hum was 100% gone. It is crystal clear.

Unfortunately the outlet I was using was built into the cabinet where we are going to tuck these things away, so I'm going to have power cables hanging out of the cabinet doors. But, I don't really care, the hum is gone - I'm happy lol.

Any ideas why the amps and stuff like this other outlet more? Just more AC/noise running along the cabinet's outlet wires?

Again, thank you guys for the help.

Congratulations on your persistence. I suspect that the AC socket that hums, has the live/neutral wires switched. You can check this with a voltmeter, or get a device at home depot that will detect it.

If there is a switch it should be corrected, as it is hazardous.

 

[Lordoftherings]

Well, he's the man above, right? So,... he's thee man.

Pard my sense of humor, I hope you can see it like I do, with friendship and happyness.
Truly, TLS Guy is a man of great knowledge that demands respect and loyalty. I'm 99.9%* with him.

* The 0.01% missing must be from Bi-Wiring.

Thank you TLS guy for all you do here, I greatly appreciate it, and I'm very glad to get to know you. It is an honor sir, and a great pleasure.

Sincerely,
Bob