Amplifier Hummmmmmm

[K-daugh]

Just picked up an Adcom 7605 nice amp....hardly used...not a scratch on it ....when there is no music or ht playing but everything is powered on there is a slight hum coming from the speakers.....Even when im watching tv you can still hear the hum....is this normal? Is it the rca's , could it be the speaker wire?? ....I didnt have this problem before the addition of the amp so i dont think its the speaker wires...Please Help

[falconcry72]

Just picked up an Adcom 7605 nice amp....hardly used...not a scratch on it ....when there is no music or ht playing but everything is powered on there is a slight hum coming from the speakers.....Even when im watching tv you can still hear the hum....is this normal? Is it the rca's , could it be the speaker wire?? ....I didnt have this problem before the addition of the amp so i dont think its the speaker wires...Please Help

if the loudness of the hum gets louder as you turn the volume up, then it's likely a ground loop hum. You can alleviate it by trying to plug the amp into to a different outlet, using a cheater plug (3 prong to 2 prong), or the best option, getting a decent power conditioner/surge protector.

I used to have to use cheater plugs on every single piece in my rig: my computer, computer monitor, amp, preamp, dac, and sub. It worked but made me feel uncomfortable. I got an APC power conditioner, and now it's all good with no plugs.

edit: hey we have the same sub! I love that thing for music!

[K-daugh]

nice currently i have it plugged into the wall i do have everything else plugged into a monster power conditioner ...Ill try that

[newrival]

I would bet it's your cabling. If you weren't using an amp before, or perhaps a less revealing piece of equipment, you likely wouldn;t have heard it before. Especially if its in the IC's between your AVR and the amp. Also if the wire is too long, looped, coiled, etc, this can all give you interference. Or if you're cables are unshielded and running behind a tv. Also, Are you using a power strip?

[K-daugh]

ok did that its not as bad its still there though my power conditioner is nothing special its a monster HT700 ....maybe i should invest in a better power conditioner

[inspiredsports]

Is the Amp's power cord terminated with a 3-prong male? If so, try one of those gray 3 to 2-prong cheater plugs and let us know the outcome.

If that quiets things down, it's a ground loop problem.

If you have cable TV, that is typically the source.

[K-daugh]

bingo that was it ....now how do i fix it obviously i have the adapter on for now but permantly how do i take care of it

[K-daugh]

Would this work http://www.amazon.com/VSIS-EU-Cable-...=cm_cr_pr_pb_t and if so do you put it near your ht or do you put it in your basement where the main cable line comes in

[inspiredsports]

Would this work http://www.amazon.com/VSIS-EU-Cable-...=cm_cr_pr_pb_t and if so do you put it near your ht or do you put it in your basement where the main cable line comes in

I'm not an expert, but I will share what I learned.

First, Im not positive this is true, but I have heard that those isolaors definitely work, but may slightly cut the signal level to do so. I stubbornly did not use one and chose to find the grounding problem because I didn't want to risk signal loss, especially from my FM tower.

As I understand it, all grounds are not exactly equivalent and while your cable installer probably grounded the cable installation, it's not grounded in exactly the same manner as your breaker box. If not equal, there is a differential in grouding (voltage? /current?) that shows up as hum.

My breaker box is grounded to both my water line and TWO separate 1/2" X 8' copper grounding rods driven 7'-10" into the ground just outside of the foundation where the breaker box is located.

In order to get rid of my cable induced (and later rootop FM antenna induced) hum, I had to hook both the cable installation grounds and antenna mast grounds to the water pipe plus both 8' rods to keep everything equal. This took some runs of heavy gauge copper grounding wire from the antenna mast and cable grounds that were not in exactly the same location as the breaker box.

There were also rules about crossing past AC lines in walls with the grounding cable, and how to properly route the ground cable around the outside of the foundation, etc. that I don't exactly remember.

When completed, I had absolutely no hum left.

Someone with even more knowledge should chime in.

[K-daugh]

where would you install the isolator downstairs in the basement before my nice electroline 8300 8 way cable amp or upstairs where the cable line comes out of the wall

[ibewbrother]

There are many variables to consider....How old is your house? What else is on the circuit? Is the house ground still good? Loose wire on a neutral somewhere in the circuit? Other appliances inducing noise?

I intend to run a plug circuit dedicated for just my rig....I haven't got around to it yet, but I figure it'll be the best way to insure I get the best power my service (built around 1966 with a sub panel added 2002) can provide.

As an Electrician....I say that there could many causes. If you live in an apartment or subdivision your electrical system in general may have been just thrown in.

Good Luck

[inspiredsports]

where would you install the isolator downstairs in the basement before my nice electroline 8300 8 way cable amp or upstairs where the cable line comes out of the wall

There's no wrong answer. It seems street side (before your 8-way amp/splitter) would make the most sense. On the other hand, if there is not a problem on any of the other cable runs that you use, the single run where you are now having trouble would be fine.

[K-daugh]

There are many variables to consider....How old is your house? What else is on the circuit? Is the house ground still good? Loose wire on a neutral somewhere in the circuit? Other appliances inducing noise?

I intend to run a plug circuit dedicated for just my rig....I haven't got around to it yet, but I figure it'll be the best way to insure I get the best power my service (built around 1966 with a sub panel added 2002) can provide.

As an Electrician....I say that there could many causes. If you live in an apartment or subdivision your electrical system in general may have been just thrown in.

Good Luck

Well theres one major problem that i should probably address....im a carpenter/everything by trade and most of my house i wired myself as i added rooms then added more rooms then more rooms then a garage ....but currently im building a bunch of walls in the basement and i got the electric panel like half ripped apart ....gonna re do the whole panel once i get the walls built...but i just went downstairs and realized the panel wasnt hooked up to the ground anymore....could this be the route of my problem also how would you differentiate noise with the electrical and noise with the cable...

[ben62670]

Any dimmers or fluorescents on the same circuit? Was the amp and the power conditioner plugged into the same outlet? Is it just the stock power cord on the amp? If it is just grab some diagnal cutters and pull/cut the ground pin out of the cable. You shouldn't plug an amp into a power conditioner.

[Zaigrith]

Any dimmers or fluorescents on the same circuit?

Would having a dimmer or fluorescent cause additional noise on the line? I have a low end power conditioner that I have been thinking of upgrading and this could be my justification.

[tonyb]

bingo that was it ....now how do i fix it obviously i have the adapter on for now but permantly how do i take care of it

I've had a cheater plug on one amp or another for over 7 years now. Why not leave it as is ? Also agree with Ben, don't plug an amp into a power conditioner.

[Zaigrith]

You shouldn't plug an amp into a power conditioner.

Also agree with Ben, don't plug an amp into a power conditioner.

Why not? Would one use just surge protection then? Are you referring to preamp as well or power amp only?

[On3s&Z3r0s]

Why not? Would one use just surge protection then? Are you referring to preamp as well or power amp only?

The reason not to is that surge protectors/power conditioners want to keep a nice, smooth, well-regulated supply of power going to your components. Basically, a surge protector's only function is to keep "extra" power from being delivered to your equipment. That's good if the power is coming from the pressure side because it keeps a potentially damaging surge from being delivered to your gear. But it can be bad if the amp is trying to draw extra power to handle a loud or complex musical passage. Having a surge protector prevent the amp from getting all the power it wants deadens it sonically, especially in the bass range.

So, cheap surge protectors are the worst things you can plug your amp into. Some power conditioners are designed to have amps plugged into them. These will have special outlets that treat the amp differently than the other components on the system. Some may even have extra capacitors so that they can maintain their own power reserve for the amp to draw from. These work to varying degrees depending on the quality of the power conditioner. Some manufacturers might just label an outlet "amplifer" on a surge protector but have it wired the same as all the other outlets in the device.

Basically, if you don't have a power conditioner where the manufacturer specifically says that the amplifier outlets function differently than the others then you should probably plug the amp directly into the wall if you want the best sound.

To answer your other question, this only applies to the power amp, not the pre.

[inspiredsports]

The reason not to is that surge protectors/power conditioners want to keep a nice, smooth, well-regulated supply of power going to your components. Basically, a surge protector's only function is to keep "extra" power from being delivered to your equipment. That's good if the power is coming from the pressure side because it keeps a potentially damaging surge from being delivered to your gear. But it can be bad if the amp is trying to draw extra power to handle a loud or complex musical passage. Having a surge protector prevent the amp from getting all the power it wants deadens it sonically, especially in the bass range.

So, cheap surge protectors are the worst things you can plug your amp into. Some power conditioners are designed to have amps plugged into them. These will have special outlets that treat the amp differently than the other components on the system. Some may even have extra capacitors so that they can maintain their own power reserve for the amp to draw from. These work to varying degrees depending on the quality of the power conditioner. Some manufacturers might just label an outlet "amplifer" on a surge protector but have it wired the same as all the other outlets in the device.

Basically, if you don't have a power conditioner where the manufacturer specifically says that the amplifier outlets function differently than the others then you should probably plug the amp directly into the wall if you want the best sound.

To answer your other question, this only applies to the power amp, not the pre.

I know this is not perfectly related to the OP's question, but I think we've helped him out so I'll ask since we are somewhat derailed.

If the power conditioner (low cost APC H10 in my case) is used on the amp and the transformer/capacitor capacity is less than what the amp needs, I understand that high current bass passages can be starved. NOTE: that doesn't seem to be happening as I rarely pull even 20% by it's front panel indicators.

However, what could typically happen (damage-wise) to components in the amp in extreme surge or extreme brownout conditions if I take the APC out of the loop?

[On3s&Z3r0s]

...but i just went downstairs and realized the panel wasnt hooked up to the ground anymore....could this be the route of my problem also how would you differentiate noise with the electrical and noise with the cable...

Don't you have the neutral bus connected to ground? Why would that have been disconnected? Messing around in a panel without it grounded sounds like a recipe for a life insurance payout!

Anyway, it seems odd that you would have ground loop hum without a ground on the elecrical mains. Your only ground would be on the coax cable jacket.

... Sorry it just occurred to me that you might have been saying that your panel enclosure has a separate ground jumper, so the load center is grounded but the panel enclosure isn't. If that's the case, then that by itself couldn't be causing a ground loop... still scary though.

[jinjuku]

Why not? Would one use just surge protection then? Are you referring to preamp as well or power amp only?

You don't need a power conditioner for the amp because it already has it's own conditioner designed into it.

[inspiredsports]

You don't need a power conditioner for the amp because it already has it's own conditioner designed into it.

So are you thinking an amplifier is less prone to surge/brownout damage?

[On3s&Z3r0s]

...If the power conditioner (low cost APC H10 in my case) is used on the amp and the transformer/capacitor capacity is less than what the amp needs, I understand that high current bass passages can be starved. NOTE: that doesn't seem to be happening as I rarely pull even 20% by it's front panel indicators.

However, what could typically happen (damage-wise) to components in the amp in extreme surge or extreme brownout conditions if I take the APC out of the loop?

I like APC's stuff. I believe that even the H10 falls into the category of conditioners that filter differently for the high-current outlets even though they aren't very specific about what exactly they are doing differently. I was talking more about the sub $100 Monster power strips. I have one of those and noticed problems when plugging my amp into it. The same problem doesn't exist at all with a Furman PC I have.

If it was me, I'd try it both ways and if I didn't hear a difference when I was paying attention, I'd leave the amp plugged into the H10 for the extra peace of mind and for the convenience of being able to control everything easily. (I like the delayed start feature for amps so the amp doesn't get input after it's already hot to the speakers.)

But I also agree that a well-built amp isn't as fragile as a lot of other electronics and is doing its own "power conditioning" as part of its job. Saying an amp needs a power conditioner is kind of like saying a magnifying glass needs a light filter. I think if you don't run it during brownouts and unplug it during electrical storms you're golden.

[k0tuynh]

Would this work http://www.amazon.com/VSIS-EU-Cable-...=cm_cr_pr_pb_t and if so do you put it near your ht or do you put it in your basement where the main cable line comes in

It worked for my parasound amp.

[jinjuku]

So are you thinking an amplifier is less prone to surge/brownout damage?

Yes, I do believe that. Most manufacturers recommend a direct connection to the wall socket and have built in adequate ac protection measures.

If you have a surge strip that is rated to handle what the amp can demand in dynamic draw moments then go for it. For 23 years I have had my amps plugged directly into wall outlets and zero issue. YMMV.

[aboroth00]

From what I've gathered you have a hum from your CATV. If this is the case, this may due to most likely, different grounds used for your house (equipment) and the ground used for your CATV. If they shared a common ground there would be no voltage difference and thus no hum. The cable guy usually just grounds it to any ground such as a water pipe that goes below instead of the common ground for your house. To alleviate this, people most often buy a CATV isolator as I have. This has mostly resolved any hum coming from my speakers or amps. I purchased the Holland ground loop isolator.

A ground loop hum will hum at the SAME volume at any volume you set your amp or pre/pro. Another cause of amplifier hum is the transformer humming, this may be caused by DC current being present in the AC line (your socket). This WILL cause your transformer to hum. More commonly though it's just a ground loop. But do NOT, I repeat DO NOT use a cheater plug, it is only a temporary solution. While many on forums say, they've been using it or doing that for many years, you never know in your case whether that ground comes lose. That ground (3rd prong) is there for a reason.

As for power conditioners, damned if you do, damned if you don't sorta thing. Higher end conditioners claim to keep the current, but IMO anything that is between your amp and the wall will only diminish the current, (to what extent who knows?) RGPC, PS AUDIO are all big EXPENSIVE names in the game.

[inspiredsports]

From what I've gathered you have a hum from your CATV. If this is the case, this may due to most likely, different grounds used for your house (equipment) and the ground used for your CATV. If they shared a common ground there would be no voltage difference and thus no hum. The cable guy usually just grounds it to any ground such as a water pipe that goes below instead of the common ground for your house. To alleviate this, people most often buy a CATV isolator as I have. This has mostly resolved any hum coming from my speakers or amps. I purchased the Holland ground loop isolator.

A ground loop hum will hum at the SAME volume at any volume you set your amp or pre/pro. Another cause of amplifier hum is the transformer humming, this may be caused by DC current being present in the AC line (your socket). This WILL cause your transformer to hum. More commonly though it's just a ground loop. But do NOT, I repeat DO NOT use a cheater plug, it is only a temporary solution. While many on forums say, they've been using it or doing that for many years, you never know in your case whether that ground comes lose. That ground (3rd prong) is there for a reason.

As for power conditioners, damned if you do, damned if you don't sorta thing. Higher end conditioners claim to keep the current, but IMO anything that is between your amp and the wall will only diminish the current, (to what extent who knows?) RGPC, PS AUDIO are all big EXPENSIVE names in the game.

Agreed, but as in post #9, I believe anything that filters at the cable level diminishes the signal level available to your equipment so correcting the ground is the best way to do it.

[aboroth00]

A power conditioner, new cabling will not help a ground loop hum. Plugging your amp into a different outlet than the rest of your equipment is not recommended. It is BEST to plug all of your equipment into the same outlet to avoid a ground loop hum. The only way to test whether you have a ground loop hum is using a cheater plug.

It is true unshielded cables, and bundling your cables into a loop will introduce RF interference. However, if it's very noticeable hum, it is usually not RF interference.

[aboroth00]

Would having a dimmer or fluorescent cause additional noise on the line? I have a low end power conditioner that I have been thinking of upgrading and this could be my justification.

Solid state dimmers can cause hums. Typically power conditioners will NOT help with these sorts of hums. The best thing you can do is replacing your solid-state dimmers with variable transformer dimmers.

[inspiredsports]

A power conditioner, new cabling will not help a ground loop hum. Plugging your amp into a different outlet than the rest of your equipment is not recommended. It is BEST to plug all of your equipment into the same outlet to avoid a ground loop hum. The only way to test whether you have a ground loop hum is using a cheater plug.

It is true unshielded cables, and bundling your cables into a loop will introduce RF interference. However, if it's very noticeable hum, it is usually not RF interference.

My APC H10's Power Conditioner's cable filter "CATV In / CATV Out" feature did in fact completely cure my ground loop hum until I properly grounded my Time Warner cable installation and FM antenna mast.

After properly grounding the antennas, I stopped using the APC's feature as it reduces some percentage of the initial signal's strength.

FM signal strength as displayed o my Onkyo T-9090's dbx display meter was as much as 10% less going through the APC.